scholarly journals Defective ribosome assembly in Shwachman-Diamond syndrome

Blood ◽  
2011 ◽  
Vol 118 (16) ◽  
pp. 4305-4312 ◽  
Author(s):  
Chi C. Wong ◽  
David Traynor ◽  
Nicolas Basse ◽  
Robert R. Kay ◽  
Alan J. Warren
Keyword(s):  
Ribosome Biogenesis ◽  
Bone Marrow Failure ◽  
Pancreatic Insufficiency ◽  
Ribosomal Subunit ◽  
Initiation Factor ◽  
Ribosome Assembly ◽  
Restrictive Temperature ◽  
Poor Growth ◽  
Shwachman Diamond Syndrome ◽  
Subunit Joining

AbstractShwachman-Diamond syndrome (SDS), a recessive leukemia predisposition disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, skeletal abnormalities and poor growth, is caused by mutations in the highly conserved SBDS gene. Here, we test the hypothesis that defective ribosome biogenesis underlies the pathogenesis of SDS. We create conditional mutants in the essential SBDS ortholog of the ancient eukaryote Dictyostelium discoideum using temperature-sensitive, self-splicing inteins, showing that mutant cells fail to grow at the restrictive temperature because ribosomal subunit joining is markedly impaired. Remarkably, wild type human SBDS complements the growth and ribosome assembly defects in mutant Dictyostelium cells, but disease-associated human SBDS variants are defective. SBDS directly interacts with the GTPase elongation factor-like 1 (EFL1) on nascent 60S subunits in vivo and together they catalyze eviction of the ribosome antiassociation factor eukaryotic initiation factor 6 (eIF6), a prerequisite for the translational activation of ribosomes. Importantly, lymphoblasts from SDS patients harbor a striking defect in ribosomal subunit joining whose magnitude is inversely proportional to the level of SBDS protein. These findings in Dictyostelium and SDS patient cells provide compelling support for the hypothesis that SDS is a ribosomopathy caused by corruption of an essential cytoplasmic step in 60S subunit maturation.

SBDS Protein Plays a Role in Ribosome Biogenesis.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 185-185
Author(s):  
Karthik A. Ganapathi ◽  
Karyn M. Austin ◽  
Maggie Malsch ◽  
Akiko Shimamura
Keyword(s):  
Ribosome Biogenesis ◽  
Actinomycin D ◽  
Bone Marrow Failure ◽  
Pancreatic Insufficiency ◽  
Protein Translation ◽  
Exocrine Pancreatic Insufficiency ◽  
Nucleolar Localization ◽  
28S Rrna ◽  
Wild Type ◽  
Shwachman Diamond Syndrome

Abstract Shwachman-Diamond syndrome is an autosomal recessive disorder characterized by exocrine pancreatic insufficiency, bone marrow failure, and leukemia predisposition. The majority of patients with Shwachman-Diamond syndrome harbor mutations in the SBDS gene. SBDS is a novel gene of unknown function and is highly conserved throughout evolution. Studies of the yeast orthologue, YLR022c/SDO1, suggest that SBDS may play a role in ribosome biogenesis. In support of this hypothesis, we have found that the SBDS protein shuttles in and out of the nucleolus. Previously we have shown that SBDS nucleolar localization is regulated in a cell cycle-dependant manner. We now find that SBDS nucleolar localization is also lost following exposure to actinomycin D, suggesting that SBDS nucleolar localization is dependent on active ribosomal RNA (rRNA) transcription. In cell survival assays, SBDS−/− patient-derived cells are sensitive to actinomycin D treatment relative to normal control cells. Introduction of the wild-type SBDS cDNA into SBDS−/− cells corrects their actinomycin D sensitivity, confirming that the observed sensitivity is SBDS-dependent. In contrast, SBDS−/− cells do not exhibit increased sensitivity to cyclohexamide, a protein translation inhibitor. Consistent with this result, SBDS protein co-localizes with ribosomal precursor subunits but not with mature polysomes upon sucrose gradient sedimentation. No differences in polysome profiles are observed between SBDS−/− cells and wild type control cells. Gel filtration studies suggest that SBDS associates into a complex with other proteins. SBDS co-immunoprecipitates with other nucleolar proteins involved in rRNA biogenesis. RNA immunoprecipitation studies reveal that SBDS also associates with the 28S rRNA but not the 18S rRNA. These findings support the hypothesis that SBDS plays a role in ribosome biogenesis

scholarly journals Enhanced p53 Levels Are Involved in the Reduced Mineralization Capacity of Osteoblasts Derived from Shwachman–Diamond Syndrome Subjects

2021 ◽  
Vol 22 (24) ◽  
pp. 13331
Author(s):  
Annalisa Frattini ◽  
Simona Bolamperti ◽  
Roberto Valli ◽  
Marco Cipolli ◽  
Rita Maria Pinto ◽  
...  
Keyword(s):  
Gene Expression ◽  
Alkaline Phosphatase ◽  
Ribosome Biogenesis ◽  
Collagen Type ◽  
Bone Marrow Failure ◽  
Pancreatic Insufficiency ◽  
Collagen Type I ◽  
Type I ◽  
Protein Levels ◽  
Shwachman Diamond Syndrome

Shwachman–Diamond syndrome (SDS) is a rare autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, and skeletal abnormalities, caused by loss-of-function mutations in the SBDS gene, a factor involved in ribosome biogenesis. By analyzing osteoblasts from SDS patients (SDS-OBs), we show that SDS-OBs displayed reduced SBDS gene expression and reduced/undetectable SBDS protein compared to osteoblasts from healthy subjects (H-OBs). SDS-OBs cultured in an osteogenic medium displayed a lower mineralization capacity compared to H-OBs. Whole transcriptome analysis showed significant differences in the gene expression of SDS-OBs vs. H-OBs, particularly in the ossification pathway. SDS-OBs expressed lower levels of the main genes responsible for osteoblastogenesis. Of all downregulated genes, Western blot analyses confirmed lower levels of alkaline phosphatase and collagen type I in SDS-OBs than in H-OBs. Interestingly, SDS-OBs showed higher protein levels of p53, an inhibitor of osteogenesis, compared to H-OBs. Silencing of Tp53 was associated with higher collagen type I and alkaline phosphatase protein levels and an increase in SDS-OB mineralization capacity. In conclusion, our results show that the reduced capacity of SDS-OBs to mineralize is mediated, at least in part, by the high levels of p53 and highlight an important role of SBDS in osteoblast functions.

Mouse Model for Shwachman-Diamond Syndrome with the R126T Disease Mutation Leads to Severe Growth and Developmental Deficiencies with Impairment of Hematopoiesis.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1283-1283
Author(s):  
Siyi Zhang ◽  
Jian Zhong ◽  
Olga I. Gan ◽  
John E. Dick ◽  
Johanna M. Rommens
Keyword(s):  
Ribosome Biogenesis ◽  
Bone Marrow Failure ◽  
Pancreatic Insufficiency ◽  
Mutant Mice ◽  
Null Alleles ◽  
Wild Type ◽  
Disease Mutation ◽  
Disease Phenotypes ◽  
Growth Difference ◽  
Shwachman Diamond Syndrome

Abstract Shwachman-Diamond syndrome (SDS) is a bone marrow failure syndrome characterized by exocrine pancreatic insufficiency and skeletal abnormalities, as well as hematological dysfunction. SDS is caused by mutations in SBDS, a highly conserved gene that has been suggested to be involved in RNA metabolism and/or ribosome biogenesis. It is essential, based on our mouse knock-out model studies and the absence of observed patients with the combination of two null alleles. We have generated an allele with the disease mutation, R126T, in the murine ortholog in order to develop new models of SDS. This mutation has been interpreted to be hypomorphic in nature, as it occurs in combination with the common null disease allele in two patients. Interestingly, these patients also have severe hematological disease phenotypes. SbdsR126T/+mice develop normally and show no disease phenotypes, in accordance with the recessive inheritance of SDS. However, the SbdsR126T/R126T and SbdsR126T/- mice did not survive birth, and exhibited marked size reduction. The growth difference became apparent in embryos during the mid-fetal period, at E12.5–14.5; there were also noted disturbances of major organs including the skeleton, brain and lung. Comparable deficiencies were noted overall, but the SbdsR126T/- embryos were consistently more severely affected than were SbdsR126T/R126T embryos. Examination of hematopoietic progenitors from the fetal livers of SbdsR126T/R126T and SbdsR126T/- mutant mice also showed marked reductions in BFU-E, CFU-G, CFU-M, CFU-GM and CFU-GEMM numbers, as revealed by standard colony formation assays, when compared to wild type and heterozygote littermates. In additional studies, primary fibroblast cultures from E16.5 day mutant embryos were found to exhibit slower growth and an extended G1 phase of the cell cycle compared to fibroblasts from wild type embryos. Further, total protein synthesis was measured by incorporation of radio-labeled amino acids and found to be notably reduced in the mutant fibroblasts. The small size, organ deficiencies and early death of the mutant mice together with the cellular deficiencies, which indicate severe autologous growth problems, emphasize the severe consequences of loss of Sbds. These animal disease models provide new avenues for investigation to elucidate basic functions of SBDS and the pathobiology of SDS.

SBDS and eIF6 Modulate Ribosome Subunit Joining in Shwachman Diamond Syndrome,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3438-3438
Author(s):  
Nicholas Burwick ◽  
Scott Coats ◽  
Akiko Shimamura
Keyword(s):  
Stromal Cells ◽  
Ribosome Biogenesis ◽  
Conflicts Of Interest ◽  
Ribosomal Subunit ◽  
Marrow Stromal Cells ◽  
Vitro Assay ◽  
Amino Terminal ◽  
Shwachman Diamond Syndrome ◽  
Subunit Joining

Abstract Abstract 3438 Shwachman Diamond syndrome (SDS) is an autosomal recessive marrow failure syndrome with a predisposition to leukemia. Over 90% of SDS patients harbor biallelic mutations in the SBDS gene. SBDS has been implicated in several cellular functions including ribosome biogenesis and mitotic spindle stabilization. Deletion of SBDS orthologues in yeast results in a severe slow growth phenotype and depressed polysomes. Homozygous deletion of Sbds in murine models results in early embryonic lethality, while conditional deletion of Sbds in mouse liver demonstrates accumulation of 40S and 60S subunits and halfmer formation consistent with impaired ribosome joining. SBDS facilitates the release of eIF6, a factor that prevents ribosome joining. The dramatic phenotypic and polysome changes noted in these experimental models were not observed in cells derived from SDS patients. SDS patient cells have only a mildly reduced growth rate compared to heatlhy controls, and polysome profiles do not demonstrate depressed polysomes or halfmer formation. Since complete abrogation of SBDS expression is lethal and biallelic null mutations in SBDS have not been reported, we examined the role of SBDS and eIF6 in SDS patients and human cell models. We first investigated whether ribosome subunit homeostasis is impaired in SDS patient cells. We find that the 60S:40S ribosomal subunit ratio is consistently reduced in bone marrow stromal cells from SDS patients of different genotypes (n=4). This impairment in 60S:40S ratio is demonstrated in both SDS patient stromal cells and patient lymphoblasts. Stable lentiviral knockdown of SDS in normal marrow stromal cells recapitulates the reduction in 60S:40S ratio. SBDS and eIF6 co-sediment in polysome gradients of human SDS cells. This co-sedimentation is specific for the 60S ribosomal subunit. Since eIF6 has a role as an anti-joining factor, we next developed an in vitro assay to test for ribosome subunit joining in human cells. In this assay, we validate that over-expression of eIF6 results in reduced ribosome joining, and eIF6 knockdown promotes ribosome joining. Moreover, we find that SDS patient stromal cells and patient lymphoblasts both demonstrate impaired ribosome subunit joining, compared with healthy controls. Importantly, the addition of wild type SBDS or depletion of eIF6 improve ribosome joining in SDS patient cells. We demonstrate that the amino terminal sequences of SBDS are necessary but not sufficient for the association of SBDS with the 60S ribosomal subunit. Insertion of a patient-derived N-terminal SBDS point mutation also results in decreased association of SBDS with the 60S ribosomal subunit. These structure-function studies may help to inform genotype:phenotype correlations in SDS. The role of defective ribosome joining in promoting the SDS hematopoietic phenotype is of particular interest. Ongoing studies are interrogating the role of eIF6 modulation on the hematopoietic phenotype in SBDS- depleted cells. Insights garnered from these experiments will help inform the development of novel agents to improve the hematopoetic defect in human SDS. Disclosures: No relevant conflicts of interest to declare.

Linking Defective Ribosome Maturation to Shwachman-Diamond Syndrome

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. SCI-36-SCI-36
Author(s):  
Alan John Warren
Keyword(s):  
Ribosome Biogenesis ◽  
Conflicts Of Interest ◽  
Ribosomal Subunit ◽  
Protein Translation ◽  
Ribosome Assembly ◽  
Genetic Dissection ◽  
Gtp Hydrolysis ◽  
Shwachman Diamond Syndrome ◽  
Novel Therapeutic Strategies ◽  
Syndrome Protein

Abstract Ribosomes are RNA-protein machines that translate the genetic information encoded by the mRNA template in all living cells. Recent high-resolution structures of the ribosome have revolutionized our understanding of protein translation. However, the mechanisms of ribosome assembly and the surveillance mechanisms that monitor this process and couple it to growth are poorly understood. Causative mutations and deletions of genes involved in ribosome biogenesis define an emerging group of disorders known as the ribosomopathies. Recent work from my laboratory strongly supports the hypothesis that Shwachman-Diamond syndrome (SDS) is a ribosomopathy caused by defective maturation of the large ribosomal subunit. Elucidation of the specific function of the SBDS protein that is deficient in SDS is revealing unexpected new insights that extend our understanding of the mechanisms underlying the late cytoplasmic steps of ribosome assembly and the quality control surveillance pathways that monitor 60S maturation. Genetic dissection of this pathway may inform novel therapeutic strategies for SDS. 1. Wong C.C., Traynor D., Basse N., Kay R.R., Warren A.J. Defective ribosome assembly in Shwachman-Diamond syndrome. Plenary Paper, Blood. 2011 Oct 20;118(16):4305-12. 2. Finch A.J., Hilcenko C., Basse N., Drynan L.F., Goyenechea B., Menne T.F., González Fernández Á., Simpson P., D’Santos C.S., Arends M.J., Donadieu J., Bellanné-Chantelot C., Costanzo M., Boone C., McKenzie A.N., Freund S.M., Warren A.J. Uncoupling of GTP hydrolysis from eIF6 release on the ribosome causes Shwachman-Diamond syndrome. Genes and Development (2011) 25: 917-929. 3. Menne T.M., Goyenechea B., Sánchez-Puig N., Wong C.C., Tonkin L.M., Ancliff P., Brost R.L., Costanzo M., Boone C. and Warren A.J. The Shwachman-Bodian-Diamond syndrome protein mediates translational activation of ribosomes in yeast. Nature Genetics (2007) 39: 486-95. Disclosures: No relevant conflicts of interest to declare.

Shwachman-Diamond Syndrome and the Quality Control of Ribosome Assembly

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. SCI-42-SCI-42
Author(s):  
Alan J. Warren
Keyword(s):  
Quality Control ◽  
Ribosomal Proteins ◽  
Active Sites ◽  
Structural Integrity ◽  
Conflicts Of Interest ◽  
Bone Marrow Failure ◽  
Ribosomal Subunit ◽  
Ribosome Assembly ◽  
Final Maturation ◽  
Shwachman Diamond Syndrome

Abstract The synthesis of new ribosomes is a fundamental conserved process in all cells. Ribosomes are pre-assembled in the nucleus and subsequently exported to the cytoplasm where they acquire functionality through a series of final maturation steps that include formation of the catalytic center, recruitment of the last remaining ribosomal proteins and the removal of inhibitory assembly factors. Surprisingly, a number of key factors (SBDS, DNAJC21, RPL10 (uL16)) involved in late cytoplasmic maturation of the large (60S) ribosomal subunit are mutated in both inherited and sporadic forms of leukemia. In particular, biallelic mutations in the SBDS gene cause Shwachman-Diamond syndrome (SDS), a recessive bone marrow failure disorder with significant predisposition to acute myeloid leukemia. By using the latest advances in single-particle cryo-electron microscopy to elucidate the function of the SBDS protein, we have uncovered an elegant mechanism that couples final maturation of the 60S subunit to a quality control assessment of the structural integrity of the active sites of the ribosome. Further molecular dissection of this pathway may inform novel therapeutic strategies for SDS and leukemia more generally. References: 1. Weis F, Giudice E, Churcher M,et al. Mechanism of eIF6 release from the nascent 60S ribosomal subunit. Nat Struct Mol Biol, (2015) Nov;22(11):914-9. 2. Wong CC, Traynor D, Basse N, et al. Defective ribosome assembly in Shwachman-Diamond syndrome. Plenary Paper, Blood. 2011 Oct 20;118(16):4305-12. 3. Finch AJ, Hilcenko C, Basse N, et al. Uncoupling of GTP hydrolysis from eIF6 release on the ribosome causes Shwachman-Diamond syndrome. Genes Dev (2011) 25: 917-929. 4. Menne TM, Goyenechea B, Sánchez-Puig N, et al. The Shwachman-Bodian-Diamond syndrome protein mediates translational activation of ribosomes in yeast. Nature Genetics (2007) 39: 486-95. Disclosures No relevant conflicts of interest to declare.

scholarly journals EFL1 mutations impair eIF6 release to cause Shwachman-Diamond syndrome

Blood ◽  
2019 ◽  
Vol 134 (3) ◽  
pp. 277-290 ◽  
Author(s):  
Shengjiang Tan ◽  
Laëtitia Kermasson ◽  
Angela Hoslin ◽  
Pekka Jaako ◽  
Alexandre Faille ◽  
...  
Keyword(s):  
Hematological Malignancies ◽  
Bone Marrow Failure ◽  
Ribosomal Subunit ◽  
Elongation Factor ◽  
Protein Translation ◽  
Allosteric Regulator ◽  
Shwachman Diamond Syndrome ◽  
Biallelic Mutations ◽  
Key Aspects ◽  
Subunit Joining

Abstract Shwachman-Diamond syndrome (SDS) is a recessive disorder typified by bone marrow failure and predisposition to hematological malignancies. SDS is predominantly caused by deficiency of the allosteric regulator Shwachman-Bodian-Diamond syndrome that cooperates with elongation factor-like GTPase 1 (EFL1) to catalyze release of the ribosome antiassociation factor eIF6 and activate translation. Here, we report biallelic mutations in EFL1 in 3 unrelated individuals with clinical features of SDS. Cellular defects in these individuals include impaired ribosomal subunit joining and attenuated global protein translation as a consequence of defective eIF6 eviction. In mice, Efl1 deficiency recapitulates key aspects of the SDS phenotype. By identifying biallelic EFL1 mutations in SDS, we define this leukemia predisposition disorder as a ribosomopathy that is caused by corruption of a fundamental, conserved mechanism, which licenses entry of the large ribosomal subunit into translation.

scholarly journals Attenuated Protein Synthesis Drives the Hematopoietic Defects in Shwachman-Diamond Syndrome

Blood ◽  
2017 ◽  
Vol 130 (Suppl_1) ◽  
pp. 876-876
Author(s):  
Pekka Jaako ◽  
Chi C Wong ◽  
David Adams ◽  
Alan J. Warren
Keyword(s):  
Bone Marrow ◽  
Protein Synthesis ◽  
Progenitor Cells ◽  
Bone Marrow Failure ◽  
Ribosomal Subunit ◽  
Hematopoietic Progenitor ◽  
Assembly Factor ◽  
Shwachman Diamond Syndrome ◽  
Subunit Joining

Abstract Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by bone marrow failure and a striking propensity to develop poor prognosis myelodysplastic syndrome and acute myeloid leukemia. In 90 % of cases the disease is caused by biallelic mutations in the gene encoding SBDS. We have shown previously that SBDS is a cytoplasmic ribosome assembly factor that catalyzes the release of the eukaryotic initiation factor 6 (eIF6) from the subunit joining interface of 60S ribosomal subunit (Menne et al, 2007; Finch et al, 2011). Deficiency of SBDS therefore results in aberrant retention of eIF6 on the 60S subunits that in turn perturbs ribosomal subunit joining and the formation of translation-competent 80S ribosomes. However, the mechanism linking defective ribosome assembly to marrow failure and leukemia in SDS remain poorly understood. Lack of viable mouse models presents a barrier to progress in understanding SDS disease pathophysiology and to evaluate novel therapies. We hypothesized that induced overexpression of eIF6 would mimic the consequences of SBDS deficiency by reducing the cytoplasmic pool of free 60S subunits and impairing translation. To test this hypothesis we have generated a novel transgenic eIF6 mouse model for SDS using KH2 embryonic stem cells that constitutively express the M2-reverse tetracycline transactivator at the Rosa26 locus with the EIF6 gene targeted downstream of the Col1a1 locus. This strategy permits systemic doxycycline-inducible and graded overexpression of eIF6 through control of the transgene copy number. We have validated that eIF6 overexpression promotes an increase in eIF6-bound cytoplasmic 60S subunits with a concomitant reduction in 80S ribosomes and polysomes in c-kit+ hematopoietic progenitor cells isolated from the transgenic eIF6 mice, thereby recapitulating the ribosomal subunit joining defect observed in patients with SDS. In vitro, the hematopoietic progenitor cells exhibit a strict eIF6 dose-dependent expansion defect. In vivo, mice with graded eIF6 overexpression are viable but develop macrocytic anemia with reticulocytopenia, thrombocytosis and mild leukopenia. Bone marrow transfer experiments demonstrate that the phenotype is autonomous to the hematopoietic system. Longitudinal phenotypic analyses in primary and transplanted animals are ongoing. Flow cytometric analysis of the bone marrow from transgenic eIF6 mice reveals a significant increase in the frequencies of preCFU-E and CFU-E erythroid progenitor cells and erythroblasts, but a significant reduction in the frequency of reticulocytes. Furthermore, we observe a striking accumulation of abnormal orthochromatic erythroblast-like cells that appear to have failed to enucleate, comprising approximately 1.5 % of the total bone marrow cells. Amnis ImageStream analysis, which combines flow cytometry with fluorescent microscopy, reveals a significant decrease in the frequency of erythroblasts that are able to complete the enucleation process. To address the underlying mechanism, we hypothesized that by impairing the formation of translation-competent 80S ribosomes, eIF6 overexpression would reduce the global rate of protein synthesis. Indeed, O-propargyl-puromycin incorporation assays established that the erythroblasts from the transgenic eIF6 mice have an approximately 3-fold reduction in global protein synthesis rate. Furthermore, our preliminary data suggest that the erythroid phenotype is p53-independent. Finally, erythroblasts from the transgenic eIF6 mice show a significant increase in levels of reactive oxygen species, but the functional significance of this finding remains unclear. We conclude that reduced rates of global translation drive defective hematopoiesis in the transgenic eIF6 mice. Importantly, eIF6 overexpression in vivo phenocopies SBDS depletion in human CD34+ cells (Sen et al, 2011). Together with the recent discovery of DNAJC21 (the human homologue of the 60S ribosomal assembly factor JJJ1 in yeast) as an SDS disease gene, our data support the hypothesis that deregulated cytoplasmic 60S subunit maturation and reduced translation are the primary drivers of the hematopoietic defect in SDS. Our viable transgenic eIF6 mouse model provides a unique tool to further dissect the mechanisms that underlie bone marrow failure and malignant transformation in SDS and for the development of novel therapeutics. Disclosures No relevant conflicts of interest to declare.

scholarly journals The human Shwachman-Diamond syndrome protein, SBDS, associates with ribosomal RNA

Blood ◽  
2007 ◽  
Vol 110 (5) ◽  
pp. 1458-1465 ◽  
Author(s):  
Karthik A. Ganapathi ◽  
Karyn M. Austin ◽  
Chung-Sheng Lee ◽  
Anusha Dias ◽  
Maggie M. Malsch ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Ribosomal Rna ◽  
Ribosome Biogenesis ◽  
Actinomycin D ◽  
Bone Marrow Failure ◽  
Ribosomal Subunit ◽  
Autosomal Recessive Disorder ◽  
Multifunctional Protein ◽  
Rrna Transcription ◽  
Shwachman Diamond Syndrome

Abstract Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic dysfunction, and leukemia predisposition. Mutations in the SBDS gene are identified in most patients with SDS. SBDS encodes a highly conserved protein of unknown function. Data from SBDS orthologs suggest that SBDS may play a role in ribosome biogenesis or RNA processing. Human SBDS is enriched in the nucleolus, the major cellular site of ribosome biogenesis. Here we report that SBDS nucleolar localization is dependent on active rRNA transcription. Cells from patients with SDS or Diamond-Blackfan anemia are hypersensitive to low doses of actinomycin D, an inhibitor of rRNA transcription. The addition of wild-type SBDS complements the actinomycin D hypersensitivity of SDS patient cells. SBDS migrates together with the 60S large ribosomal subunit in sucrose gradients and coprecipitates with 28S ribosomal RNA (rRNA). Loss of SBDS is not associated with a discrete block in rRNA maturation or with decreased levels of the 60S ribosomal subunit. SBDS forms a protein complex with nucleophosmin, a multifunctional protein implicated in ribosome biogenesis and leukemogenesis. Our studies support the addition of SDS to the growing list of human bone marrow failure syndromes involving the ribosome.

scholarly journals Pluripotent stem cell model of Shwachman–Diamond syndrome reveals apoptotic predisposition of hemoangiogenic progenitors

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Takayuki Hamabata ◽  
Katsutsugu Umeda ◽  
Kagehiro Kouzuki ◽  
Takayuki Tanaka ◽  
Tomoo Daifu ◽  
...  
Keyword(s):  
Ribosome Biogenesis ◽  
Cell Model ◽  
Bone Marrow Failure ◽  
Pancreatic Insufficiency ◽  
Autosomal Recessive Disorder ◽  
Exocrine Pancreatic Insufficiency ◽  
Stem Cell Model ◽  
Shwachman Diamond Syndrome ◽  
Induced Pluripotent

Abstract Shwachman–Diamond syndrome (SDS), an autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, and skeletal abnormalities, is caused by mutations in the Shwachman–Bodian–Diamond syndrome (SBDS) gene, which plays a role in ribosome biogenesis. Although the causative genes of congenital disorders frequently involve regulation of embryogenesis, the role of the SBDS gene in early hematopoiesis remains unclear, primarily due to the lack of a suitable experimental model for this syndrome. In this study, we established induced pluripotent stem cells (iPSCs) from patients with SDS (SDS-iPSCs) and analyzed their in vitro hematopoietic and endothelial differentiation potentials. SDS-iPSCs generated hematopoietic and endothelial cells less efficiently than iPSCs derived from healthy donors, principally due to the apoptotic predisposition of KDR+CD34+ common hemoangiogenic progenitors. By contrast, forced expression of SBDS gene in SDS-iPSCs or treatment with a caspase inhibitor reversed the deficiency in hematopoietic and endothelial development, and decreased apoptosis of their progenitors, mainly via p53-independent mechanisms. Patient-derived iPSCs exhibited the hematological abnormalities associated with SDS even at the earliest hematopoietic stages. These findings will enable us to dissect the pathogenesis of multiple disorders associated with ribosomal dysfunction.

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