scholarly journals 2'-O-Methoxyethyl Splice-Switching Oligos to Reverse Splicing from IVS2-745 β-Thalassemia Patient Cells: A Foundation for Potential Therapies

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2244-2244
Author(s):  
Valentina Ghiaccio ◽  
Alisa Dong ◽  
Irene Motta ◽  
Shuling Guo ◽  
Raechel Peralta ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Splice Site ◽  
Globin Gene ◽  
Mrna Translation ◽  
Aberrant Splice ◽  
Splice Sites ◽  
Globin Mrna ◽  
Aberrant Splicing ◽  
Advisory Committees ◽  
Intron 2

The β thalassemia trait is associated with over 300 mutations in the β-globin gene that lead to reduced (β+ allele) or absent (β0 allele) synthesis of the β globin chain. A subset of these mutations affect the canonic splicing of the β globin mRNA. Such mutations activate aberrant splice sites, which lead to an altered splicing pathway and consequently affects protein synthesis. The (C>G) IVS-2-745 mutation is common in South Eastern Europe, Cyprus, Lebanon, India, Malaysia, and Indonesia. This mutation, located within intron 2 of the β-globin gene, creates an aberrant 5' splice site at nucleotide 745 of intron 2 and activates a cryptic 3' splice site within the same intron. Portions of the intronic sequence are incorrectly retained in the spliced mutant mRNA. The mutation results in a premature stop codon that prevents proper mRNA translation and causes a β‐globin deficiency, resulting in β‐thalassemia. The IVS-2-745 allele has the functional splice sites preserved, but produces a significantly reduced level of correctly spliced β-globin mRNA and results in only marginal synthesis of HbA. Therefore, the IVS-2-745 mutation in homozygosity leads to severe transfusion-dependent thalassemia major. Taking advantage of conserved canonical splice sites in defective β‐globin genes, such as IVS-2-745, recently developed approaches show that by targeting the aberrant splice sites it is possible to circumvent the aberrant splice site and restore the normal β-globin splicing pattern. We sought to use uniform 2'-O-methoxyethyl (2'-MOE) splice switching oligos (SSOs) to reverse aberrant splicing in the pre-mRNA for the IVS-2-745 mutation. Using these SSOs, we show effective aberrant-to-wild-type splice switching. This leads to an increase in adult hemoglobin (HbA) by up to 80% in erythroid cells from patients with the IVS-2-745 mutation. Furthermore, we demonstrate a restoration of the balance between β-like- and α-globin chains, and up to an 87% reduction in α-heme aggregates. While examining the potential benefit of 2'-MOE-SSOs in a sickle/IVS-2-745-thalassemic genotype setting, we found that use of these oligos restored production of HbA and reduced HbS synthesis, which ultimately lessened cell sickling under hypoxic conditions. We confirmed increased WT β-globin expression in specimens treated with 2'-MOE-SSOs with semi- and quantitative methods (RT and Q-PCR), and further supported this evidence using a direct quantification method (ddPCR). Compared to treated specimens heterozygous for IVS-2-745 , homozygous specimens showed elevated WT HbA, reflecting the additive effect of targeting the aberrant splicing of both alleles as opposed to a single IVS-2-745 allele. In fact, while 2'-MOE-SSOs significantly reduced aberrant splicing, leading to a consequent 60% increase in HbA levels in specimens from patients with a β0/IVS-2-745 genotype, the same oligos produced a more robust effect in specimens with a homozygous IVS-2-745 genotype, resulting in an 80% increase in HbA levels. This level of increase could potentially be curative for patients with this particular genotype. Moreover, we compared the effect of 2'-MOE-SSOs treatment to a lentiviral vector carrying a WT β-globin gene. In this comparative assay, β0/IVS-2-745 cells treated with 2'-MOE-SSOs or the lentivector (with 1.13 copies integrated per genome) lead to a similar increase in HbA (50%). This suggests that the oligo-based technology is a competitive approach and a viable alternative to gene addition therapy to overcome anemia in IVS-2-745 β-thalassemia. In summary, 2'-MOE-SSOs are promising therapeutic tools for certain forms of β-thalassemia caused by aberrant splicing. Their ability to correct the underlying splicing defect offers a pharmacological treatment that is direct, specific, and accessible. In comparison, gene therapy approaches utilizing gene addition or editing are primarily available in advanced medical care environment resulting in an unfulfilled demand in regions where such conditions are not readily available. The restoration of target gene activity reported here suggests that this treatment strategy could be applicable to other forms of thalassemia resulting from mutations affecting splicing. This could have, with an effective method of delivery, potential clinical utility in helping patients reduce their transfusion dependence or even achieving transfusion independence. Disclosures Dong: Aruvant Sciences INC: Employment. Motta:Sanofi-Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees. Guo:Ionis Pharmaceutical, INC: Employment, Other: shareholders. Peralta:Ionis Pharmaceutical, Inc: Employment. Freier:Ionis Pharmaceuticals: Employment. Watt:Ionis Pharmaceuticals: Employment. Manwani:Novartis: Consultancy; Pfizer: Consultancy; GBT: Consultancy, Research Funding. Cappellini:Genzyme/Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Honoraria; Vifor Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; CRISPR Therapeutics: Membership on an entity's Board of Directors or advisory committees. Abdulmalik:The Children's Hospital of Philadelphia: Patents & Royalties: Provisional Patent. Rivella:Meira GTx, Ionis Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Disc medicine, Protagonist, LIPC, Meira GTx: Consultancy.

High-level expression of hemoglobin A in human thalassemic erythroid progenitor cells following lentiviral vector delivery of an antisense snRNA

Blood ◽  
2003 ◽  
Vol 101 (1) ◽  
pp. 104-111 ◽  
Author(s):  
Marla M. Vacek ◽  
Hong Ma ◽  
Federica Gemignani ◽  
Giuseppina Lacerra ◽  
Tal Kafri ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Lentiviral Vector ◽  
Globin Gene ◽  
Aberrant Splice ◽  
Splice Sites ◽  
Globin Mrna ◽  
Erythroid Progenitor ◽  
Hematopoietic Stem ◽  
Erythroid Progenitor Cells ◽  
Hemoglobin A

Abstract Mutations at nucleotides 654, 705, or 745 in intron 2 of the human β-globin gene activate aberrant 3′ and 5′ splice sites within the intron and prevent correct splicing of β-globin pre-mRNA, resulting in inhibition of β-globin synthesis and in consequence β-thalassemia. Transfection of HeLa cells expressing the 3 thalassemic mutants with modified U7 snRNA (U7.623), containing a sequence antisense to a region between the aberrant splice sites, reduced the incorrect splicing of pre-mRNA and led to increased levels of the correctly spliced β-globin mRNA and protein. A lentiviral vector carrying the U7.623 gene was effective in restoration of correct splicing in the model cell lines for at least 6 months. Importantly, the therapeutic value of this system was demonstrated in hematopoietic stem cells and erythroid progenitor cells from a patient with IVS2-745/IVS2-1 thalassemia. Twelve days after transduction of the patient cells with the U7.623 lentiviral vector, the levels of correctly spliced β-globin mRNA and hemoglobin A were approximately 25-fold over background. These results should be regarded as a proof of principle for lentiviral vector–based gene therapy for β-thalassemia.

scholarly journals Induction of Fetal Hemoglobin Synthesis By Crispr/Cas9-Mediated Disruption of the β-Globin Locus Architecture

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 321-321
Author(s):  
Chiara Antoniani ◽  
Vasco Meneghini ◽  
Annalisa Lattanzi ◽  
Giulia Pavani ◽  
Tristan Felix ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Genome Editing ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Genomic Region ◽  
Globin Mrna ◽  
Advisory Committees ◽  
Naturally Occurring ◽  
Total Hemoglobin ◽  
Equity Ownership

Abstract Naturally occurring, large deletions in the β-globin locus result in increased fetal hemoglobin (HbF) expression (HPFH, Hereditary Persistence of Fetal Hemoglobin), a condition that mitigates the clinical severity of Sickle Cell Disease (SCD) and β-thalassemia. Here, we integrated BCL11A and GATA1 transcription factor binding site analysis and HPFH mutational data to identify potential HbF silencers in the β-globin locus. Based on this analysis, we designed a CRISPR/Cas9 strategy to disrupt: (i) a 3.5-kb δγ-intergenic region that is specifically deleted in individuals with HPFH. This region contains BCL11A and GATA1 binding sites in adult, HbF-negative primary erythroblasts, thus representing a potential HbF silencer; (ii) a 7.2-kb region, encompassing the 3.5-kb δγ-intergenic element, which is the minimal naturally occurring deletion associated with HPFH ("Corfù" deletion; Chakalova et al., Blood, 2005); (iii) a 13.6-kb genomic region commonly deleted in HPFH, which includes the δ- and β-globin genes and putative intergenic HbF silencers. Targeted deletion or inversion of the 13.6-kb genomic region caused a substantial increase in γ-globin mRNA levels, re-activation of HbF synthesis and a concomitant decrease in HbA expression in adult human erythroid cells (HUDEP-2). Interestingly, deletion of the Corfù region or of the 3.5-kb putative HbF silencer, increased γ-globin gene transcription but failed to produce accumulation of γ-globin mRNA, suggesting a post-transcriptional regulation of γ-globin synthesis in the presence of an intact and active β-globin gene. We then tested re-activation of HbF synthesis in primary adult hematopoietic stem/progenitor cells differentiated towards the erythroid lineage in liquid and clonogenic cultures. Targeting the 13.6-kb genomic region resulted in a high proportion of γ-globin expressing primary erythroblasts, with HbF representing up to 50% of total hemoglobin. Cell morphology, erythroid marker profile, total hemoglobin levels and erythroid maturation were unaffected, consistent with the asymptomatic phenotype of adult HPFH carriers. These data suggest that this region could serve as target for therapeutic genome editing for HbF induction in β-hemoglobinopathies. Overall, this study contributes to the knowledge of the mechanisms underlying fetal to adult Hb switching, and provides clues for a genome editing approach to the treatment of SCD and β-thalassemia. Disclosures Cradick: CRISPR Therapeutics: Employment. Lundberg:CRISPR Therapeutics: Employment, Equity Ownership. Porteus:CRISPR Therapeutics: Consultancy, Equity Ownership. Mavilio:Adverum Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orchard Therapeutics: Membership on an entity's Board of Directors or advisory committees; CRISPR Therapeutics: Consultancy, Research Funding.

Nuclear pre-mRNA processing in plants: distinct modes of 3'-splice-site selection in plants and animals

1988 ◽  
Vol 8 (5) ◽  
pp. 2042-2051
Author(s):  
K Wiebauer ◽  
J J Herrero ◽  
W Filipowicz
Keyword(s):  
Splice Site ◽  
Hela Cells ◽  
Site Selection ◽  
Human Growth ◽  
Mrna Processing ◽  
Beta Globin ◽  
Splice Sites ◽  
Splice Site Selection ◽  
Consensus Sequences ◽  
Intron 2

The report that human growth hormone pre-mRNA is not processed in transgenic plant tissues (A. Barta, K. Sommergruber, D. Thompson, K. Hartmuth, M.A. Matzke, and A.J.M. Matzke, Plant Mol. Biol. 6:347-357, 1986) has suggested that differences in mRNA splicing processes exist between plants and animals. To gain more information about the specificity of plant pre-mRNA processing, we have compared the splicing of the soybean leghemoglobin pre-mRNA with that of the human beta-globin pre-mRNA in transfected plant (Orychophragmus violaceus and Nicotiana tabacum) protoplasts and mammalian (HeLa) cells. Of the three introns of leghemoglobin pre-mRNA, only intron 2 was correctly and efficiently processed in HeLa cells. The 5' splice sites of the remaining two introns were faithfully recognized, but correct processing of the 3' sites took place only rarely (intron 1) or not at all (intron 3); cryptic 3' splice sites were used instead. While the first intron in human beta-globin pre-mRNA was not spliced in transfected plant protoplasts, intron 2 processing occurred at a low level, indicating that some mammalian introns can be recognized by the plant intron-splicing machinery. However, excision of intron 2 proved to be incorrect, involving the authentic 5' splice site and a cryptic 3' splice site. Our results indicate that the mechanism of 3'-splice-site selection during intron excision differs between plants and animals. This conclusion is supported by analysis of the 3'-splice-site consensus sequences in animal and plant introns which revealed that polypyrimidine tracts, characteristic of animal introns, are not present in plant pre-mRNAs. It is proposed that an elevated AU content of plant introns is important for their processing.

Characterization of a Novel Aberrant Splice Site, 79bp Downstream of Exon 5 in the Human Factor 7 Gene Detected in Patients with Severe Congenital Factor VII Deficiency.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3481-3481
Author(s):  
Karin Wulff ◽  
Jan Astermark ◽  
Falko F H Herrmann ◽  
Günther Auerswald ◽  
Winnie Schröder
Keyword(s):  
Splice Site ◽  
Donor Splice Site ◽  
Aberrant Splice ◽  
The Novel ◽  
Splice Sites ◽  
Wild Type ◽  
Rt Pcr ◽  
Donor Splice ◽  
Naturally Occurring ◽  
Fvii Deficiency

Abstract Abstract 3481 Poster Board III-418 Hereditary FVII deficiency (FVIID) is a rare congenital bleeding disorder with an estimated prevalence of symptomatic individuals of 1:500,000. In the “Greifswald Registry FVII Deficiency” molecular defects of more than 1000 FVII deficient patients were described. By direct sequencing of the F7 genes in congenital FVIID revealed 146 different F7 gene mutations including 25 different mutations (18% of all) in the naturally-occurring acceptor or donor splice sites (Tab.1) were identified. In seven FVIID patients from Sweden and Germany the novel lesion g.IVS5+78G>A - downstream of the naturally-occurring donor splice sites of exon 5 - was identified. This variation was detected heterozygous in FVIID patients with FVII: C levels of 15%, 27%, 31%, 40% and 65%, and FVII: Ag levels between 25-50%. In two compound heterozygous patients with FVII: C levels of 1% und FVII: Ag levels of 2% and 3% respectively, one well-known causative FVII mutation is combined with the novel lesion g.IVS5+78G>A. The influence of this novel F7 gene variation on splicing was investigated by RT-PCR analysis and in vitro expression studies using exon-trap vector constructs. The total RNA was isolated from peripheral leucocytes and analyzed by one step RT-PCR and sequencing. Fragments of exon 5 and a part of the flanking intron 5 region (g.7679 –g.8073) were amplified of patients' DNA and cloned into the exon trap-vector pET01. Different vector constructs containing minigenes of the wild type (g.IVS5+78G) or mutant form (g.IVS5+78A) and the corresponding minigenes with an “optimized” naturally-occurring donor splice site in position +5 respectively were transfected into HEK293 cells. The expressed RNA was isolated and characterized. Consensus Values (CV) for all donor splice sites were calculated using a splice site detection tool according Shapiro and Senapathy (1987). The RT-PCR analysis in patients indicate that the novel variation g.IVS5+78G>A in intron 5 created an aberrant splice site in position 79bp downstream of exon 5 even though the naturally-occurring donor-splice-site of exon 5 is not abolished. An insertion of 79bp of intron 5 into the mRNA leads to a frame shift and predicts a premature termination 11 codons past the last unaltered codon. Minigenes include the naturally-occurring splice site and the variation g.IVS5+78A used exclusively the aberrant splice position 79bp downstream of exon 5 whereas wild type minigenes with the naturally-occurring splice site and the wild type form g.IVS5+78G produced normally spliced mRNA. In a following experiment the “naturally-occurring splice site” of exon 5 was optimized by the additional substitution g.IVS5+5C>G which increased their CV from 76.6 to 90.9 compared to the CV of the novel mutant g.IVS5+78A of 80.3. In presence of both mutations (g.IVS5+5G and g.IVS5+78A) only normal spliced mRNA was expressed of this minigene. In this construct the mutation g.IVS5+78G>A was without importance for the mRNA splicing. The results of the in vitro experiments demonstrated, that the Consensus Values (CV) seems to be an important factor for the selection of donor splice sites in the F7 gene. In the “Greifswald Registry FVII Deficiency” 26 different splice site variations in F7 gene were identified (Tab. 1). The atypical splice site variation g.IVS5+78G>A, +78bp downstream of exon 5 was present in 7 FVIID patients from Sweden and Germany in different genotypes. This novel F7 gene mutation g.IVS5+78G>A creates an aberrant splice site in position +79 of intron 5 and predicts premature termination. RNA analysis and expression studies demonstrated, that this novel F7 gene lesion is a type I mutation with low FVII:C and FVII: Ag levels and is the basis defect in 7 FVIID patients of the “Greifswald Registry FVII Deficiency”. Tab. 1 26 different intronic F7 gene mutations analysed in FVII deficiency patients of the “Greifswald Registry FVII Deficiency” Intron Acceptor splice site Intron Donor splice site 1b g.IVS1b-11G>A 1a g.IVS1a+5G>A 1b *g.IVS1b8del14bp 1a *g.IVS1a+6T>G 1b *g.IVS1b-3C>G 1a *g.IVS1a+8C>T 2 *g.IVS2-3C>G 2 g.IVS2+1G>A 3 g.IVS3-1G>A 2 *g.IVS2+1G>T 3 *g-IVS3-1G>T 2 *g.IVS2+1G>C 4 *g.IVS4-7T>G 2 *g.IVS2+1delG 7 *g.IVS7-10T>C 2 g.IVS2+5G>T 7 *g.IVS7-3C>G 3 *g.IVS3+1G>T 7 *g.IVS7-1G>A 4 g.IVS4+1G>A 5 *g.IVS5+78G>A 6 *g.IVS6+1G>A 6 g.IVS6+1G>T 6 *g.IVS6+3A>G 7 *g.IVS7+1G>A 7 g.IVS7+3_6 del4bp * novel mutations (HGMD Factor 7 Database, 2009 /http://www.hgmd.org) Disclosures: No relevant conflicts of interest to declare.

Pomalidomide Transcriptionally Reprograms Adult Erythroid Progenitors Independently of Ikaros Proteasomal Degradation

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 160-160
Author(s):  
Brian M. Dulmovits ◽  
Abena O. Appiah-Kubi ◽  
Julien Papoin ◽  
John Hale ◽  
Mingzhu He ◽  
...  
Keyword(s):  
Cord Blood ◽  
Board Of Directors ◽  
Peripheral Blood ◽  
Globin Gene ◽  
Erythroid Differentiation ◽  
Erythroid Progenitors ◽  
Advisory Committees ◽  
Cd34 Cells ◽  
Terminal Erythroid Differentiation ◽  
Adult Peripheral Blood

Abstract Pomalidomide, a second-generation immunomodulatory drug, is a fetal hemoglobin (HbF) inducing agent with potential implications for the treatment of β-hemoglobinopathies such as sickle cell disease (SCD). However, its mechanism of action remains unknown. Through an in-depth characterization of human erythropoiesis and globin gene regulatory networks, we now provide evidence that pomalidomide alters transcription networks involved in erythropoiesis and globin switching, thereby leading to a partial reprogramming of adult hematopoietic progenitors toward fetal-like erythropoiesis. Adult peripheral blood CD34+ cells from normal individuals were differentiated toward the red cell lineage using an adapted 3-phase culture system. At day 14 of culture, we observed a reciprocal globin gene switch at the mRNA and protein levels. These results were confirmed by high performance liquid chromatography of hemolysates (HbF/(HbF+HbA): 31.7 ± 1.4% vs. 6.5 ± 0.7% pomalidomide and vehicle, respectively). Next, we studied erythroid differentiation using flow cytometric analyses of the cell surface markers interleukin-3R (IL-3R), glycophorin A (GPA), CD34 and CD36 for early erythroid precursors (BFU-E and CFU-E) as well as GPA, α4-integrin and band3 for terminal erythroid differentiation. While there were no changes in terminal erythroblast maturation, an accumulation of BFU-E in pomalidomide-treated cultures at days 2 and 4 of differentiation was seen, indicating a delay at the BFU-E to CFU-E transition, and also, that pomalidomide exerts its effect in the early-stages of erythropoiesis. Indeed, treatment with pomalidomide during the phase of the culture system that generates erythroid progenitors led to significantly more γ-globin expression than treatment during the phase which proerythroblasts undergo terminal erythroid differentiation. At the molecular level, pomalidomide was found to rapidly and robustly decrease Ikaros (IKZF1) expression exclusively by post-translational targeting to the proteasome. Moreover, pomalidomide selectively reduced the expression of components of key globin regulatory pathways including BCL11A, SOX6, KLF1, GATA1 and LSD1 while not affecting others (e.g. CoREST, GATA2, GFI1B, and HDAC1). Pomalidomide had a transient effect on GATA1 and KLF1 expression. While shRNA knockdown of Ikaros using two different lentiviral constructs delayed erythroid differentiation, it failed to appreciably stimulate HbF production or alter BCL11A expression. These results suggest that the loss of Ikaros alone is insufficient to recapitulate the phenotype observed in pomalidomide-treated conditions. We next compared the expression levels of proteins involved in globin gene regulation among untreated peripheral blood, pomalidomide-treated peripheral blood and untreated cord blood-derived erythroid cells. We found striking similarities between cord blood and pomalidomide-treated adult cells at day 4 of differentiation. Indeed, BCL11A, KLF1, SOX6, LSD1 and GATA1 showed decreased expression levels both in cord blood and pomalidomide-treated adult peripheral blood, while the levels of CoREST, HDAC1 and GATA2 remained unchanged indicating that pomalidomide partially reprograms adult erythroid cells to a fetal-like state. Taken together, our results show that the mechanism underlying reactivation of HbF by pomalidomide involves Ikaros-independent reprogramming of adult erythroid progenitors. Finally, we found that this mechanism is conserved in SCD-derived CD34+ cells. Our work has broad implications for globin switching, as we provide direct evidence that Ikaros does not play a major role in the repression of γ-globin during adult erythropoiesis, and further supports the previously held notion that globin chain production is determined prior to or at the level of CFU-E. Disclosures Allen: Celgene: Research Funding; Bristol Myers Squibb: Equity Ownership; Onconova: Membership on an entity's Board of Directors or advisory committees; Alexion: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees.

Development of Viral Vectors for Gene Therapy of β-Chain Hemoglobinopathies: Optimization of a γ-Globin Gene Expression Cassette

Blood ◽  
1999 ◽  
Vol 93 (7) ◽  
pp. 2208-2216 ◽  
Author(s):  
Qiliang Li ◽  
David W. Emery ◽  
Magali Fernandez ◽  
Hemei Han ◽  
George Stamatoyannopoulos
Keyword(s):  
Gene Therapy ◽  
Globin Gene ◽  
Expression Cassette ◽  
Globin Genes ◽  
Internal Deletion ◽  
Globin Mrna ◽  
Retrovirus Vector ◽  
Globin Promoter ◽  
Intron 2 ◽  
Β Chain

Progress toward gene therapy of β-chain hemoglobinopathies has been limited in part by poor expression of globin genes in virus vectors. To derive an optimal expression cassette, we systematically analyzed the sequence requirements and relative strengths of theAγ- and β-globin promoters, the activities of various erythroid-specific enhancers, and the importance of flanking and intronic sequences. Expression was analyzed by RNase protection after stable plasmid transfection of the murine erythroleukemia cell line, MEL585. Promoter truncation studies showed that theAγ-globin promoter could be deleted to −159 without affecting expression, while deleting the β-globin promoter to −127 actually increased expression compared with longer fragments. Expression from the optimal β-globin gene promoter was consistently higher than that from the optimal Aγ-globin promoter, regardless of the enhancer used. Enhancers tested included a 2.5-kb composite of the β-globin locus control region (termed a μLCR), a combination of the HS2 and HS3 core elements of the LCR, and the HS-40 core element of the -globin locus. All three enhancers increased expression from the β-globin gene to roughly the same extent, while the HS-40 element was notably less effective with theAγ-globin gene. However, the HS-40 element was able to efficiently enhance expression of a Aγ-globin gene linked to the β-globin promoter. Inclusion of extended 3′ sequences from either the β-globin or the Aγ-globin genes had no significant effect on expression. A 714-bp internal deletion ofAγ-globin intron 2 unexpectedly increased expression more than twofold. With the combination of a −127 β-globin promoter, anAγ-globin gene with the internal deletion of intron 2, and a single copy of the HS-40 enhancer, γ-globin expression averaged 166% of murine -globin mRNA per copy in six pools and 105% in nine clones. When placed in a retrovirus vector, this cassette was also expressed at high levels in MEL585 cells (averaging 75% of murine -globin mRNA per copy) without reducing virus titers. However, recombined provirus or aberrant splicing was observed in 5 of 12 clones, indicating a significant degree of genetic instability. Taken together, these data demonstrate the development of an optimal expression cassette for γ-globin capable of efficient expression in a retrovirus vector and form the basis for further refinement of vectors containing this cassette.

scholarly journals Interim Results from a Phase 1/2 Clinical Study of Lentiglobin Gene Therapy for Severe Sickle Cell Disease

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1176-1176 ◽  
Author(s):  
Julie Kanter ◽  
Mark C. Walters ◽  
Matthew M. Hsieh ◽  
Lakshmanan Krishnamurti ◽  
Janet Kwiatkowski ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Board Of Directors ◽  
Research Funding ◽  
Phase 1 ◽  
Globin Gene ◽  
Advisory Committees ◽  
Cell Dose ◽  
Cd34 Cells ◽  
Equity Ownership

Abstract β-globin gene transfer into hematopoietic stem cells (HSCs) has the potential to reduce or eliminate the symptoms and long-term complications of severe sickle cell disease (SCD). LentiGlobin Drug Product (DP) is a gene therapy product containing autologous CD34+ cells transduced with the BB305 lentiviral vector. BB305 encodes a human β-globin gene containing a single point mutation (AT87Q) designed to confer anti-sickling properties similar to those observed in fetal hemoglobin (γ-globin). In two ongoing studies, subjects with transfusion-dependent β-thalassemia (Studies HGB-204 and HGB-205) or SCD (Study HGB-205) receiving LentiGlobin DP have demonstrated sustained expression of 3-9 g/dL therapeutic hemoglobin (HbAT87Q) and have shown marked improvements in clinical symptoms 1 year post-treatment. Study HGB-206 is a multi-center, Phase 1/2 safety and efficacy study of LentiGlobin DP in adults with severe SCD. We previously (ASH 2015) presented results from 2 subjects, who had 3 and 6 months of follow-up after LentiGlobin treatment. We now present data from 7 treated subjects, 4 of whom have ≥6 months of follow-up data. Subjects (≥18 years of age) with severe SCD (history of recurrent vaso-occlusive crisis [VOC], acute chest syndrome, stroke, or tricuspid regurgitant jet velocity of >2.5 m/s) were screened for eligibility. Following bone marrow harvest (BMH), CD34+ cells were transduced with the BB305 vector. Subjects underwent myeloablative conditioning with busulfan prior to infusion of the transduced cells. Safety assessments include adverse events (AEs), integration site analysis (ISA) and surveillance for replication competent lentivirus (RCL). After infusion, subjects are monitored for hematologic engraftment, vector copy number (VCN), HbAT87Q expression, and other laboratory and clinical parameters. As of July 2016, 7 subjects with severe SCD (median age: 26 years, range 18-42 years) have received LentiGlobin DP in this study. All subjects successfully underwent BMH, with a median of 2 harvests required (range 1-4). Fifteen Grade 3 AEs in 5 subjects were attributed to BMH: pain (n=10), anemia (n=3) and VOC (n=2); all resolved with standard measures. Table 1 summarizes cell harvest, DP characteristics, and lab results. The median LentiGlobin DP cell dose was 2.1x10e6 CD34+ cells/kg (range 1.6-5.1) and DP VCN was 0.6 (0.3-1.3) copies/diploid genome. Median post-infusion follow-up as of July 2016 is 7.1 months (3.7-12.7 months). All subjects successfully engrafted after receiving LentiGlobin DP, with a median time to neutrophil engraftment of 22 days (17-29 days). The toxicity profile observed from start of conditioning to latest follow-up was consistent with myeloablative conditioning with single-agent busulfan. To date, there have been no DP-related ≥Grade 3 AEs or serious AEs, and no evidence of clonal dominance or RCL. The BB305 vector remains detectable at low levels in the peripheral blood of all subjects infused, with median VCN 0.08 (0.05-0.13, n=7) at last measurement. All subjects express HbAT87Q, with a median of 0.4g/dL (0.1-1.0 g/dL, n=7) at 3 months; most subjects demonstrated modest increases over time, and the 2 subjects with the longest follow-up expressed 0.31 and 1.2 g/dL HbAT87Q at 9 months. All 4 subjects with ≥6 months of follow-up experienced multiple VOCs in the 2 years prior to study entry (2-27.5 VOCs annually). Since LentiGlobin DP infusion, 3 of these 4 subjects have had fewer VOCs, although this trend may be confounded by the short follow-up, the effects of transplant conditioning, and/or post-transplant RBC transfusions. The decrease in VCN between DP and peripheral cells contrasts with previous reports of successful LentiGlobin gene therapy in ongoing studies HGB-204 and HGB-205. The relatively low in vivo VCN in this study appears to result in the lower HbAT87Q expression seen to date. We are exploring multiple hypotheses as to the etiology of the VCN drop between DP and peripheral blood, including the adverse impact of sickle marrow pathology on HSCs, the adequacy of myeloablation, and the magnitude of the transduced cell dose. We will provide an update on study data and ongoing efforts to increase in vivo VCN in patients with SCD, such as increasing the transduced cell dose through alternate HSC procurement methods or enhancing the DP VCN through manufacturing improvements. Disclosures Kanter: Novartis: Consultancy. Walters:Bayer HealthCare: Honoraria; AllCells, Inc./LeukoLab: Other: Medical Director ; ViaCord Processing Laboratory: Other: Medical Director ; Leerink Partners, LLC: Consultancy; Kiadis Pharma: Honoraria; bluebirdBio, Inc: Honoraria. Kwiatkowski:Ionis pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Shire Pharmaceuticals: Consultancy; Sideris Pharmaceuticals: Consultancy; Apopharma: Research Funding; Luitpold Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. von Kalle:bluebird bio: Consultancy; GeneWerk: Equity Ownership. Kuypers:Children's Hospital Oakland Research Institute: Employment; bluebird bio: Consultancy. Leboulch:bluebird bio: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding. Joseney-Antoine:bluebird bio: Employment, Equity Ownership. Asmal:bluebird bio: Employment, Equity Ownership. Thompson:bluebird bio: Consultancy, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; Amgen: Research Funding; Baxalta (now part of Shire): Research Funding; ApoPharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Mast: Research Funding; Eli Lily: Research Funding.

scholarly journals Loss of Alpha Globin Genes in Human Subjects Is Associated with Improved Nitric Oxide-Mediated Vascular Perfusion

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 6-7
Author(s):  
Christopher C Denton ◽  
Payal Shah ◽  
Silvie Suriany ◽  
Honglei Liu ◽  
Wanwara Thuptimdang ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Beneficial Effect ◽  
Board Of Directors ◽  
Globin Gene ◽  
Globin Genes ◽  
Vascular Perfusion ◽  
Advisory Committees ◽  
Alpha Thalassemia ◽  
Alpha Globin ◽  
Thalassemia Trait

Introduction Absence of alpha globin genes has long been known to influence the physiology of sickle cell disease (SCD). Individuals with SCD who are missing one or two alpha globin genes have decreased rates of cerebral vasculopathy, stroke, acute chest syndrome, and leg ulcers (Bernaudin, Blood 2008; Flanagan, Blood 2011; Nolan, Br J Haematol 2006). Although there is laboratory evidence of decreased hemolytic rate in these patients (Higgs, N Engl J Med 1982), the mechanism for their improved clinical outcomes has not been identified. Recently, the alpha globin protein has been shown to be present in the endothelial wall of human arterioles, where it modulates nitric oxide (NO) scavenging during vasoconstriction (Straub, Nature 2012). In mice, pharmacological inhibition of alpha globin leads to increased endothelial NO activity, independently of NO production, and results in increased blood perfusion, reduced systemic hypertension, and increased pulmonary artery vasodilation (Keller, Hypertension 2016; Alvarez, Am J Respir Cell Mol Biol 2017). The relationship between absence of alpha globin and arterial vasodilation, and the role of alpha globin in NO-mediated vascular signaling are potential mechanisms that could explain the beneficial effect of missing alpha globin genes in SCD. Using alpha thalassemia as a naturally occurring human model of alpha globin gene knockout, we hypothesized that loss of alpha globin genes leads to improvement in microvascular blood flow in thalassemia trait subjects without hemolysis. Methods Alpha thalassemia trait subjects missing one or two alpha globin genes, and healthy controls were recruited to the study, which was approved by the Children's Hospital Los Angeles Institutional Review Board. Blood samples were obtained from all subjects to test for hemoglobin, mean corpuscular volume (MCV), reticulocyte count, plasma hemoglobin, lactate dehydrogenase, and alpha globin genotype. We assessed flow-mediated dilation (FMD) of the brachial artery following distal forearm occlusion (Detterich, Blood 2015) simultaneously with laser Doppler flowmetry (LDF) and photoplethysmography (PPG) in the fingertip. We also measured the increase in microvascular perfusion with a thermal stimulus. The maximal change in vascular perfusion after provocation indicates vasodilatory capacity. Statistical analysis was performed in JMP® version 14 (SAS Institute Inc., USA). Results Twenty-seven subjects were enrolled, including 12 controls (4 alpha globin genes), 10 patients with 3 alpha globin genes and 5 with 2. The mean MCV was lower in subjects missing alpha globin genes than in controls (p=0.0099). Importantly, hemoglobin levels and markers of hemolysis were normal in both groups. There was no detectable difference in FMD between individuals missing one and two alpha globin genes; thus, these groups were combined and labeled as alpha trait for further analyses. FMD was significantly higher in alpha trait subjects after adjusting for age (Figure 1, p=0.0357). Missing alpha globin genes had no effect on microvascular flow by LDF or PPG (data not shown). Discussion FMD is an established and specific predictor of NO bioavailability (Thijssen, Am J Physiol Heart Circ Physiol 2011), and, in addition to shear-mediated NO circulation in conduit vessels, it reflects the sum of flow in multiple arteriolar networks downstream of the conduit artery. Using this method, a difference in endothelial function between control and alpha thalassemia trait was easily detected (Figure 1). Because endothelial alpha globin is present in arterioles rather than conduit vessels (Butcher, Free Radic Biol Med 2014), we measured microvascular flow in a 1-mm3 volume in the skin using a laser Doppler sensor, and in the fingertip by PPG, but were unable to detect an effect of alpha trait. As none of the subjects had anemia or evidence of hemolysis, the significantly increased FMD associated with loss of alpha globin genes is most likely due to increased NO as a result of decreased scavenging by alpha globin. The finding reported here that lower alpha globin gene number is associated with increased NO-related perfusion in humans may explain the beneficial effect of alpha thalassemia trait in SCD and suggests that the presence of alpha thalassemia trait may also play a role in other types of vascular disease. Disclosures Wood: BiomedInformatics: Consultancy; Imago Biosciences: Consultancy; BluebirdBio: Consultancy; Celgene: Consultancy; WorldcareClinical: Consultancy; Philips Medical Systems: Research Funding. Coates:apo pharma (Chiesi Pharma): Consultancy, Honoraria; Sangamo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios pharma: Consultancy, Honoraria; Vifor Pharma: Consultancy, Honoraria; Celgene, BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees.

scholarly journals Investigating Zeta Globin Gene Expression to Develop a Potential Therapy for Alpha Thalassemia Major

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 3-4
Author(s):  
Georgia L. Gregory ◽  
Beeke Wienert ◽  
Marisa Schwab ◽  
Billie Rachael Lianoglou ◽  
Roger P. Hollis ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Globin Gene ◽  
Thalassemia Major ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Wild Type ◽  
Advisory Committees ◽  
Alpha Thalassemia ◽  
Alpha Globin ◽  
Zeta Globin Gene

Introduction: Alpha globin mutations are very common worldwide, and the severity of resulting anemia depends on the number and type of mutated alleles. While the 4 gene mutation (alpha thalassemia major, ATM) was previously deemed fatal except in rare cases, emerging evidence indicates that survival to birth and good postnatal outcomes are possible with in utero transfusions. We hypothesized that the embryonic zeta globin gene, which is expressed early in gestation prior to alpha globin, may compensate for the lack of alpha globin and that induction of zeta globin after it has naturally been silenced may become a new therapy for patients with ATM. Methods: We evaluated mutations in the UCSF international registry of patients with ATM to understand factors related to patient survival with and without in utero transfusions. We then engineered Human Umbilical Cord Derived Erythroid Progenitor Cells (HUDEP-2 cells) carrying the common SEA alpha globin deletion, in which zeta globin expression is preserved (H-SEA), as well as those on which the zeta globin genes were deleted (HBZ-/-) using CRISPR-Cas9. We evaluated the expression of alpha and zeta globins using qPCR, Western blot, and flow cytometry. We generated lentiviral vectors expressing zeta globin under the control of beta-globin promoters to examine changes in both zeta and alpha globin in a dynamic way. Results: None of the registry patients who survived to birth spontaneously (n=11) had a mutation that involves a concomitant deletion in zeta globin (such as the -FIL, -THAI, or -MEDII mutation), while alpha globin mutations extending into the zeta globin gene were found in 14 of 37 (38%) patients who were diagnosed prenatally, suggesting that the presence of zeta globin may play a role in the ability to survive to birth without fetal therapy. Interestingly, we found that H-SEA clones express higher levels of zeta globin than WT cells, as illustrated by quantitative real-time PCR (Fig 1A), Western blot (Fig 1B) and flow cytometry (Fig 1C). These cells also developed beta globin dimers due to excess unpaired beta-globin chains, as demonstrated by Western blotting with and without reducing agents, indicating that they are an appropriate cell model for ATM. We next generated HUDEP-2 clones lacking zeta globin (HBZ KO) and transduced these clones with lentiviral vectors expressing high levels of zeta globin (lenti-zeta) (Fig 1D). Western blotting revealed that increasing the levels of zeta globin in these cells resulted in decreased expression of alpha globin, suggesting reciprocal control between these genes (Fig 1E). Most importantly, we saw a reduction in toxic beta-globin dimers in H-SEA cells expressing high levels of zeta-globin after transduction with lenti-zeta, suggesting that zeta globin could functionally replace the missing alpha-globin (Fig 1 F,G). To understand transcriptomic differences in H-SEA cells that may result in increased zeta globin expression, we performed bulk RNA sequencing of wild type and H-SEA clones. We confirmed that zeta expression is significantly upregulated in H-SEA compared to wild type (log2 fold change of 4.25, p=2.24E-38). Pathway analysis of differentially expressed genes is ongoing. Conclusions: Our international patient registry suggests that expression of zeta globin may play a role in the spontaneous survival to birth in a subset of patients. Zeta globin expression is increased in the setting of H-SEA cells in vitro, and restoration of zeta expression by lentivirus results in a reduction of toxic beta globin dimers in these ATM cells. Furthermore, expressing zeta globin at high levels in H-WT cells decreased alpha globin expression, suggesting a reciprocal regulation of these two genes. This concept is similar to the relationship between fetal gamma and adult beta globins which has been exploited for therapeutic editing approaches in patients with beta-thalassemia. At this point, the natural repressor of zeta globin is not yet known, but our data suggests that a strategy of upregulating zeta globin could potentially be developed to mimic the ongoing trials of using the BCL11A repressor to induce gamma globin in patients with beta thalassemia and sickle cell disease. Disclosures Wienert: Integral Medicines: Current Employment. Kohn:Allogene Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orchard Therapeutics: Consultancy, Patents & Royalties, Research Funding. MacKenzie:Acrigen: Membership on an entity's Board of Directors or advisory committees; Ultragenyx: Research Funding.

scholarly journals The effect of disease-associated HRPT2 mutations on splicing

2009 ◽  
Vol 201 (3) ◽  
pp. 387-396 ◽  
Author(s):  
Michael A Hahn ◽  
Julie McDonnell ◽  
Deborah J Marsh
Keyword(s):  
Splice Site ◽  
Hot Spot ◽  
Splice Sites ◽  
Loss Of Function ◽  
Splice Enhancer ◽  
Aberrant Splicing ◽  
Acceptor Splice Site ◽  
Web Based ◽  
Exonic Splice

Mutations in the tumour suppressor HRPT2 occur in patients with parathyroid carcinoma, kidney tumours and Hyperparathyroidism–Jaw Tumour syndrome. Disruption of exonic splicing through mutation of donor/acceptor splice sites or exonic splice enhancer (ESE) sites leads to loss of function of a number of major tumour suppressors including BRCA1, APC and MLH1. Given that the effect of HRPT2 mutations on splicing has not been widely studied, we used an in vitro splicing assay to determine whether 17 HRPT2 mutations located in hot-spot and other exons predicted to disrupt ESE consensus sites led to aberrant splicing. Using two independent web-based prediction programs, the majority of these mutations were predicted to disrupt ESE consensus sites; however, aberrant splicing of HRPT2 transcripts was not observed. Canonical donor or acceptor splice site mutations were also investigated using this splicing assay and transcripts assessed from tumour tissue. Splice site mutations were shown to lead to either exon skipping or retention of intronic sequences through the use of cryptic splice sites comprised of non-classical splicing signals. Aberrant splicing caused by disruption of ESE sites does not appear to have a major role in HRPT2-associated disease; however, premature truncation of parafibromin as the result of canonical donor or acceptor splice site mutations is associated with pathogenicity. Functional splicing assays must be undertaken in order to confirm web-based software predictions of the modification of putative ESE sites by disease-associated mutations.

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