Deficiency Of JAGN1 Causes Severe Congenital Neutropenia Associated With Defective Secretory Pathway and Aberrant Myeloid Cell Homeostasis

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 439-439
Author(s):  
Kaan Boztug ◽  
Päivi M Järvinen ◽  
Elisabeth Salzer ◽  
Tomas Racek ◽  
Sebastian Mönch ◽  
...  

Abstract Analysis of patients with severe congenital neutropenia (SCN) may shed light on the delicate balance of factors controlling differentiation, maintenance, and decay of neutrophil granulocytes. Mutations in ELANE, GFI1, HAX1, G6PC3, WAS, and VPS45 are known to cause SCN. We here describe a new monogenetic SCN variant with biallelic mutations in the gene encoding Jagunal homolog 1 (JAGN1). We studied an index family from Northern Africa with a total of 5 children suffering from SCN. An Affymetrix SNP array-based genetic linkage analysis was performed and identified a single interval of perfect segregation with highly significant multi-marker LOD scores of at least 4.5spanning approximately 1.5Mbp from 9.52Mb to 11.04Mb on chromosome 3 of NCBI’s human genome build 36.3. This interval contained a total of 30 genes, including JAGN1 which encodes an ER-resident protein. Sanger sequencing revealed a homozygous mutation c.3G>A in exon 1 of the JAGN1 gene; this mutation leads to disruption of the defined start of translation. Systematic analysis of a cohort of 90 SCN patients identified 9 distinct homozygous mutations in the gene encoding Jagunal homolog 1 (JAGN1) in 14 SCN patients, thus accounting for approximately 10% of SCN patients. The clinical phenotype was variable and included failure to thrive, developmental delay and bone skeletal abnormalities. The only consistent finding in all JAGN1-deficient patients was SCN and partial or complete refractoriness to therapy with rh-GCSF. JAGN1 is the human ortholog of a gene originally identified in Drosophila melanogaster. Jagunal-deficient oocytes are characterized by defective ER reorganization and aberrant membrane trafficking during vitellogenesis. We found that JAGN1-mutant human granulocytes showed aberrantly enlarged ER structures and paucity of secretory vesicles. We hypothesized that that ER aberrations may be associated with defective N-glycosylation of multiple proteins in neutrophil granulocytes and found that JAGN1-mutant neutrophil granulocytes exhibited anomalous N-glycomic profiles characterized by a marked reduction in fucosylation of all their multi-antennary glycans. JAGN1-deficient neutrophil granulocytes showed increased apoptosis in response to TNFa and staurosporine, likely accounting for the lack of mature neutrophils in these patients. Additional studies in JAGN1-knockdown cells indicate that JAGN1 participates in the secretory pathway and is required for granulocyte-colony stimulating factor receptor-mediated signaling. Global proteomic analysis of the JAGN1-interactome identified a limited number of interaction partners including members of the Coat Protein I (COPI) complex (COPA, COPB2, and COPG2) which suggest a role for JAGN1 in vesicular trafficking from Golgi to ER. Taken together, JAGN1 emerges as a hitherto unrecognized factor necessary in differentiation and survival of neutrophil granulocytes and a novel gene implicated in SCN. Disclosures: No relevant conflicts of interest to declare.

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1025-1025
Author(s):  
Alexa Triot ◽  
Päivi M Järvinen ◽  
Juan I. Arostegui ◽  
Tomas Racek ◽  
Jacek Puchalka ◽  
...  

Abstract Severe congenital neutropenia (SCN) is a heterogeneous group of disorders characterized by defective production and viability of neutrophil granulocytes and predisposition to life-threatening bacterial infections. Currently, OMIM lists five defined monogenic SCN: SCN1 ELANE, SCN2 GFI1, SCN3 HAX1, SCN4 G6PC3. Here, we describe a novel SCN subtype (SCN6) caused by recessively-inherited loss-of-function mutations in the gene encoding the granulocyte colony-stimulating receptor (CSF3R). We have identified four affected children in two distinct families. Family A had a homozygous missense mutation in close proximity of the highly conserved WSXWS motif (c.922T, p.Arg308Cys) and family B had two compound heterozygous small deletions provoking frameshift mutations (p.Gly316fs and p.Gly415fs). Mutated G-CSFR p.Arg308Cys protein was characterized by perturbed N-glycosylation and aberrant localization to cell surface. G-CSF induced phosphorylation of STAT3 and STAT5 was greatly diminished. In contrast to other SCN subtypes, all patients had morphological evidence of full myeloid cell maturation in bone marrow. However, none of the patients responded to granulocyte colony-stimulating growth factor (GCSF) treatment in vivo, confirming aberrant GCSF-receptor dependent signaling. Our studies highlight the genetic and morphological variability of SCN and provide evidence both for functional importance and redundancy of G-CSFR-mediated signaling in human granulopoiesis. Disclosures: No relevant conflicts of interest to declare.


Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1402-1402
Author(s):  
Hideki Makishima ◽  
Anna M Jankowska ◽  
Valeria Visconte ◽  
Ramon V. Tiu ◽  
Kathryn M Guinta ◽  
...  

Abstract Abstract 1402 Chronic myelomonocytic leukemia (CMML) is characterized by monocytic proliferation, cytomorphologic dysplasia and frequent progression to acute myelogeneous leukemia (AML). The molecular basis of CMML is poorly defined, although somatic mutations in a number of genes have recently been identified in a proportion of patients (epigenetic regulatory genes, spliceosomal genes, apoptosis genes, growth signal transducers and others). We performed a comprehensive analysis of molecular lesions, including somatic mutations detected by sequencing and chromosomal abnormalities investigated by metaphase and SNP-array karyotyping. We have selected a cohort of 72 patients (36 CMML1, 16 CMML2 and 20 sAML evolved from CMML). Our mutational screen performed in stages (as new mutations were discovered by our and other groups) and currently reveals mutations in UTX in 8%, DNMT3A in 9%, CBL in 14%, IDH1/2 in 4%, KRAS in 2.7%, NRAS in 4.1%, JAK2 in 1%, TET2 in 48%, ASXL1 in 43%, EZH2 in 5.5%, RUNX1 37%. Based on the discovery of various spliceosomal mutations in myeloid malignancies, novel mutations were also found in CMML, in U2AF1 in 12%, SF3B1 in 14%, SFRS19 in 6 % of cases tested. Chromosomal defects were detected in 60% of patients. In particular, a high frequency of somatic uniparental disomy (sUPD) were identified 71% of patients with abnormal cytogenetics, including UPD1p (N=3), UPD7q (N=8), UPD4q (N=6), UPD2p (N=2), UPD17q (N=2), UPD11q (N=5), UPDX (N=1), UPD21q (N=2). Some of the detected mutations were homozygous through their association with sUPD as for example for 3 EZH2, 1 UTX, 6 TET2, 2 DNMT3A, 5 CBL, 1 NRAS, 1 U2AF1 mutations. Furthermore, UPD17p implies that a P53 mutation is also present in this case as previously LOH17p was shown to be invariably associated with P53 mutations. Similarly, 2 cases of UPD17q imply that homozygous mutation of SRSF2, which is one of the Serine/arginine-rich splicing factor, may be present in this location and the mutation analysis is ongoing. In over 90% of >1 mutation was found but many patients harbored multiple mutations with frequent combinations of TET2/CBL or TET2/ASXL1 as well as RUNX1 and U2AF1 serving as examples. There was an accumulation of mutations from sAML, CMML2 and CMML1 suggesting stepwise accumulation of lesions. In serial studies, some of the mutations were present at the inception (e.g., TET2, ASXL1 and DNMT3A) in some cases originally heterozygous mutations were also while other can occur in the course of disease (e.g. CBL). RAS and DNMT3A mutations were associated with a higher blasts count. In sum, combined analysis of molecular lesions in CMML reveals that similar phenotype may be a result of diverse mutations associated with seemingly unrelated pathways and that clinical phenotype may be a result of a combination of mutations which accumulate as the disease progresses. Survival analyses will require large cohorts to account for various confounding factors including the presence of multiple chromosomal abnormalities and mutations in one patient, however currently EZH2, DNMT3 and CBL mutations appear to convey less favorable prognosis. Disclosures: No relevant conflicts of interest to declare.


Hematology ◽  
2015 ◽  
Vol 2015 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Ivo P. Touw

Abstract Severe congenital neutropenia (SCN) is a genetically heterogeneous condition of bone marrow failure usually diagnosed in early childhood and characterized by a chronic and severe shortage of neutrophils. It is now well-established that mutations in HAX1 and ELANE (and more rarely in other genes) are the genetic cause of SCN. In contrast, it has remained unclear how these mutations affect neutrophil development. Innovative models based on induced pluripotent stem cell technology are being explored to address this issue. These days, most SCN patients receive life-long treatment with granulocyte colony-stimulating factor (G-CSF, CSF3). CSF3 therapy has greatly improved the life expectancy of SCN patients, but also unveiled a high frequency of progression toward myelodysplastic syndrome (MDS) and therapy refractory acute myeloid leukemia (AML). Expansion of hematopoietic clones with acquired mutations in the gene encoding the G-CSF receptor (CSF3R) is regularly seen in SCN patients and AML usually descends from one of these CSF3R mutant clones. These findings raised the questions how CSF3R mutations affect CSF3 responses of myeloid progenitors, how they contribute to the pre-leukemic state of SCN, and which additional events are responsible for progression to leukemia. The vast (sub)clonal heterogeneity of AML and the presence of AML-associated mutations in normally aged hematopoietic clones make it often difficult to determine which mutations are responsible for the leukemic process. Leukemia predisposition syndromes such as SCN are unique disease models to identify the sequential acquisition of these mutations and to interrogate how they contribute to clonal selection and leukemic evolution.


Blood ◽  
2001 ◽  
Vol 98 (9) ◽  
pp. 2645-2650 ◽  
Author(s):  
Phil J. Ancliff ◽  
Rosemary E. Gale ◽  
Ri Liesner ◽  
Ian M. Hann ◽  
David C. Linch

Abstract Severe congenital neutropenia (SCN) was originally described as an autosomal recessive disorder. Subsequently, autosomal dominant and sporadic forms of the disease have been recognized. All forms are manifest by persistent severe neutropenia and recurrent bacterial infection. In contrast, cyclical hematopoiesis is characterized by periodic neutropenia inter-spaced with (near) normal neutrophil counts. Recently, linkage analysis on 13 affected pedigrees identified chromosome 19p13.3 as the likely position for mutations in cyclical hematopoiesis. Heterozygous mutations in the ELA2 gene encoding neutrophil elastase were detected in all families studied. Further work also demonstrated mutations in ELA2 in sporadic and autosomal dominant SCN. However, all mutations described to date are heterozygous and thus appear to act in a dominant fashion, which is inconsistent with an autosomal recessive disease. Therefore, the current study investigated whether mutations in ELA2could account for the disease phenotype in classical autosomal recessive SCN and in the sporadic and autosomal dominant types. All 5 exons of ELA2 and their flanking introns were studied in 18 patients (3 autosomal recessive, 5 autosomal dominant [from 3 kindreds], and 10 sporadic) using direct automated sequencing. No mutations were found in the autosomal recessive families. A point mutation was identified in 1 of 3 autosomal dominant families, and a base substitution was identified in 8 of 10 patients with the sporadic form, though 1 was subsequently shown to be a low-frequency polymorphism. These results suggest that mutations in ELA2are not responsible for classical autosomal recessive Kostmann syndrome but provide further evidence for the role of ELA2 in SCN.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 93-93 ◽  
Author(s):  
Adrian P. Zarebski ◽  
Wojciech Pawlak ◽  
Avinash M. Baktula ◽  
Sudeep Basu ◽  
John Trent ◽  
...  

Abstract Severe Congenital Neutropenia (SCN) is a rare hematological disease manifested by a complete block in the maturation of neutrophils. The lack of neutrophils leads to recurrent bacterial and fungal infections. Most SCN patients have mutations in Ela2, the gene encoding neutrophil elastase; however, introduction of SCN-patient mutations into murine Ela2 or disruption of murine Ela2 does not recapitulate neutropenia in mice. Thus, there are no mouse models of SCN. Gfi1 is a transcriptional repressor leukemia oncoprotein involved in HSC maintenance as well as proper lymphoid and myeloid development. Mice lacking Gfi1 have profound neutropenia. We recently described four patients in which Ela2 was intact but mutant for Gfi1. The heterozygous single aminoacid substitutions were found in zinc finger 5 (N382S) and zinc finger 6 (K403R) correlating to either SCN or Non-immune Chronic Idiopathic Neutropenia of Adults (NICINA) respectively. Given that Gfi1 null mice lack neutrophils, and that people with Gfi1 mutations display SCN or NICINA, we asked whether the human mutations when introduced into murine Gfi1 are sufficient to model neutropenia in mice. To this end, we constructed murine Gfi1 cDNAs containing the SCN and NICINA patient mutations, retrovirally overexpressed them in murine Lin- bone marrow cells, then analyzed them by in vitro differentiation assays. Strikingly, cells overexpressing Gfi1-N382S produced no granulocytic colonies (similar to the profound phenotype of SCN). Whereas, the expression of Gfi1-K403R mutation resulted in a moderate reduction in granulocytic colonies (corresponding to the mild phenotype of NICINA). We have constructed a virtual model of Gfi1 zinc finger/DNA interaction to explore the molecular defect engendered by the N382S mutation. At the meeting, we will discuss the molecular basis of the profound phenotype engendered by Gfi1-N382S expression. These data demonstrate for the first time that human neutropenia can be modeled in murine cultures through the introduction of mutations in Gfi1 found in SCN and NICINA patients.


Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2264-2264
Author(s):  
Maksim Klimiankou ◽  
Murat Uenalan ◽  
Siarhei Kandabarau ◽  
Lutz Wiehlmann ◽  
Anna-Lena Hagemann ◽  
...  

Abstract It has been reported by us and others that approx. 30 % of all patients with congenital neutropenia (CN) acquire CSF3R mutations in their life time. More than 80 % of the CN patients who develop myeloid leukemia (CN/AML) harbour CSF3R mutations. This suggests that they are the first hit in leukemogenesis. However, detecting sequence changes e.g. by Sanger sequencing reveals only mutations presented in more than 20 % of the cells due to its technical detection limit. Therefore, we asked whether there is a systematic underestimation of cell clones harbouring CSF3R mutations, which might have been traditionally overlooked. We applied the deep-sequencing technology (SOLID 5500xl) to identify CSF3R mutations in myeloid cells from 158 patients with different types of neutropenia (86 severe congenital neutropenia (CN) patients with known inherited mutations (ELANE, HAX1, G6PC3), 21 cyclic neutropenia (CyN) patients, 28 patients with severe chronic neutropenia with so far unknown inherited mutations, 11 patients with SBDS-associated neutropenia) as well as a group of 12 healthy individuals. All neutropenia patients were treated with G-CSF and notably 21 CN patients developed leukemia or MDS. Deep sequencing data were processed according to our custom NGS pipeline (annotation of sequences and prediction of damaging effects on the coding sequence by Polyphen2, removal of known dbSNP variants, and accepting significant Phred-scores at the variant calling stage). Overall the read numbers ranged between 18 and 128069 (median 716), while only variants with at least two percent of the reads were accepted for further consideration (the statistically significant limit is between one and two percent of all reads). All together, we detected 92 CSF3R mutations in 42 CN patients leading to 49 distinct amino acid exchanges (38 missense and 11 stop-codon mutations). The frequency of the mutant alleles ranged from 2 to 96 %. In contrast, in CyN only five out of 21 patients harbour CSF3R mutations; interestingly, two of them in isoform IV of CSF3R (p.P752T). Most notably, whereas 18 patients displayed only one CSF3R mutation, 24 individuals had more than one CSF3R mutation (2-10 mutations, in total 74 mutations). During follow up of some patients, we could demonstrate that the number of mutations increased over time. The majority of mutations were located in the cytoplasmatic region (aa 651-831) of CSF3R, while 15 patients presented mutations within the extracellular region of CSF3R. Intriguingly, in 16 patients we detected 23 non-sense mutations, where 20 of these are stop-codon mutations affecting glutamine (Q) 768, 770, 776, and 781. This suggests that this part of CSF3R is highly instable. In two patients who did not respond to Filgrastim treatment, we detected a stop codon at aa 546 and 547, respectively, affecting the Fibronectin type-III like part of the CSF3R. Twelve patients who developed leukemia (CN/AML) had more than one CSF3R mutations (two to ten) , whereas eight with CN/AML harbored only one mutation. None of the healthy controls, only three neutropenia patients with unknown inheritance, and only one SBDS patient revealed mutations in CSF3R. Taken together, this data suggests that CSF3R is highly prone to genetic instability in severe congenital neutropenia, because more than one mutation in half of the patients was observed and various CSF3R mutations during the course of life accumulated. Once a cell clone harboring CSF3R mutation obtains a second hit (e.g. RUNX1 mutation), they are prone to undergo leukemic transformation. Disclosures: No relevant conflicts of interest to declare.


2013 ◽  
Vol 33 (8) ◽  
pp. 1403-1406 ◽  
Author(s):  
Abdullah A. Alangari ◽  
Abdulrahman Alsultan ◽  
Mohamed Elfaki Osman ◽  
Shamsa Anazi ◽  
Fowzan S. Alkuraya

Blood ◽  
2002 ◽  
Vol 100 (9) ◽  
pp. 3221-3228 ◽  
Author(s):  
David S. Grenda ◽  
Sonja E. Johnson ◽  
Jill R. Mayer ◽  
Morgan L. McLemore ◽  
Kathleen F. Benson ◽  
...  

Abstract Severe congenital neutropenia (SCN) is a syndrome characterized by an isolated block in granulocytic differentiation and an increased risk of developing acute myeloid leukemia (AML). Recent studies have demonstrated that the majority of patients with SCN and cyclic neutropenia, a related disorder characterized by periodic oscillations in the number of circulating neutrophils, have heterozygous germline mutations in the ELA2 gene encoding neutrophil elastase (NE). To test the hypothesis that these mutations are causative for SCN, we generated transgenic mice carrying a targeted mutation of theirEla2 gene (“V72M”) reproducing a mutation found in 2 unrelated patients with SCN, one of whom developed AML. Expression of mutant NE mRNA and enzymatically active protein was confirmed. Mice heterozygous and homozygous for the V72M allele have normal numbers of circulating neutrophils, and no accumulation of myeloid precursors in the bone marrow was observed. Serial blood analysis found no evidence of cycling in any of the major hematopoietic lineages. Rates of apoptosis following cytokine deprivation were similar in wild-type and mutant neutrophils, as were the frequency and cytokine responsiveness of myeloid progenitors. The stress granulopoiesis response, as measured by neutrophil recovery after cyclophosphamide-induced myelosuppression, was normal. To define the leukemogenic potential of V72M NE, a tumor watch was established. To date, no cases of leukemia have been detected. Collectively, these data suggest that expression of V72M NE is not sufficient to induce an SCN phenotype or leukemia in mice.


Blood ◽  
2007 ◽  
Vol 109 (11) ◽  
pp. 4716-4723 ◽  
Author(s):  
Marta Donini ◽  
Stefania Fontana ◽  
Gianfranco Savoldi ◽  
William Vermi ◽  
Laura Tassone ◽  
...  

Abstract The treatment of children affected by severe congenital neutropenia (SCN) with G-CSF strongly reduces the risk of sepsis by reversing neutropenia. However, SCN patients who respond to the treatment with the growth factor still have an elevated risk of succumbing to sepsis. Because the disease is usually caused by heterozygous mutations of ELA2, a gene encoding for neutrophil elastase (NE), we have investigated in G-CSF–responder and nonresponder patients affected by SCN the expression of polypeptides that constitute the antimicrobial machinery of these cells. In peripheral blood–derived neutrophils of patients with heterozygous mutations of ELA2 who were treated with G-CSF, NE was nearly absent as detected by immunofluorescence and immunoblotting, suggesting that production of the mutant protein interferes with normal gene expression. This defect was associated with abnormal expression of other granule-associated proteins such as myeloperoxidase, lactoferrin, cathepsin G, and human-neutrophil-peptide. Moreover, in one patient with partial response to G-CSF, we observed an impairment of neutrophil antimicrobial activity against Candida albicans, and, to a lower extent against Escherichia coli. Thereby, we propose that the treatment with G-CSF is not sufficient to correct all of the functional deficiency of neutrophils, and this might account for the consistent risk of infections observed in SCN patients.


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