Project description:Background and purposeShwachman-Diamond Syndrome (SDS) is an autosomal recessive disease belonging to the inherited bone marrow failure syndromes and characterized by hypocellular bone marrow, exocrine pancreatic insufficiency, and skeletal abnormalities. SDS is associated with increased risk of developing myelodysplastic syndrome (MDS) and/or acute myeloid leukemia (AML). Although SDS is not primarily considered an inflammatory disorder, some of the associated conditions (e.g., neutropenia, pancreatitis and bone marrow dysfunction) may involve inflammation or immune system dysfunctions. We have already demonstrated that signal transducer and activator of transcription (STAT)-3 and mammalian target of rapamycin (mTOR) were hyperactivated and associated with elevated IL-6 levels in SDS leukocytes. In this study, we analyzed the level of phosphoproteins involved in STAT3 and mTOR pathways in SDS lymphoblastoid cells (LCLs) and the secretomic profile of soluble pro-inflammatory mediators in SDS plasma and LCLs in order to investigate the systemic inflammation in these patients and relative pathways.MethodsTwenty-six SDS patients and seven healthy donors of comparable age were recruited during the programmed follow-up visits for clinical evaluation at the Verona Cystic Fibrosis Center Human. The obtained samples (plasma and/or LCLs) were analyzed for: phosphoproteins, cytokines, chemokines and growth factors levels by Bio-plex technology; microRNAs profiling by next generation sequencing (NGS) and microRNAs expression validation by Real Time-PCR (RT-PCR) and droplet digital PCR (ddPCR) .ResultsWe demonstrated dysregulation of ERK1/2 and AKT phosphoproteins in SDS, as their involvement in the hyperactivation of the STAT3 and mTOR pathways confirmed the interplay of these pathways in SDS pathophysiology. However, both these signaling pathways are strongly influenced by the inflammatory environment. Here, we reported that SDS is characterized by elevated plasma levels of several soluble proinflammatory mediators. In vitro experiments show that these pro-inflammatory genes are closely correlated with STAT3/mTOR pathway activation. In addition, we found that miR-181a-3p is down-regulated in SDS. Since this miRNA acts as a regulator of several pro-inflammatory pathways such as STAT3 and ERK1/2, its down-regulation may be a driver of the constitutive inflammation observed in SDS patients.ConclusionsThe results obtained in this study shed light on the complex pathogenetic mechanism underlying bone marrow failure and leukemogenesis in SDS, suggesting the need for anti-inflammatory therapies for SDS patients.
Project description:Shwachman-Diamond syndrome (SDS) is an inherited bone marrow failure syndrome with leukemia predisposition. An understanding of the hematologic complications of SDS with age could guide clinical management, but data are limited for this rare disease. We conducted a cohort study of 153 subjects from 143 families with confirmed biallelic SBDS mutations enrolled on the North American Shwachman Diamond Registry or Bone Marrow Failure Registry. The SBDS c.258 + 2T>C variant was present in all but 1 patient. To evaluate the association between blood counts and age, 2146 blood counts were analyzed for 119 subjects. Absolute neutrophil counts were positively associated with age (P < .0001). Hemoglobin was also positively associated with age up to 18 years (P < .0001), but the association was negative thereafter (P = .0079). Platelet counts and marrow cellularity were negatively associated with age (P < .0001). Marrow cellularity did not correlate with blood counts. Severe marrow failure necessitating transplant developed in 8 subjects at a median age of 1.7 years (range, 0.4-39.5), with 7 of 8 requiring transplant prior to age 8 years. Twenty-six subjects (17%) developed a myeloid malignancy (16 myelodysplasia and 10 acute myeloid leukemia) at a median age of 12.3 years (range, 0.5-45.0) and 28.4 years (range, 14.4-47.3), respectively. A lymphoid malignancy developed in 1 patient at the age of 16.9 years. Hematologic complications were the major cause of mortality (17/20 deaths; 85%). These data inform surveillance of hematologic complications in SDS.
Project description:Shwachman-Diamond syndrome (SDS) is an autosomal-recessive marrow failure syndrome with a predisposition to leukemia. SDS patients harbor biallelic mutations in the SBDS gene, resulting in low levels of SBDS protein. Data from nonhuman models demonstrate that the SBDS protein facilitates the release of eIF6, a factor that prevents ribosome joining. The complete abrogation of Sbds expression in these models results in severe cellular and lethal physiologic abnormalities that differ from the human disease phenotype. Because human SDS cells are characterized by partial rather than complete loss of SBDS expression, we interrogated SDS patient cells for defects in ribosomal assembly. SDS patient cells exhibit altered ribosomal profiles and impaired association of the 40S and 60S subunits. Introduction of a wild-type SBDS cDNA into SDS patient cells corrected the ribosomal association defect, while patient-derived SBDS point mutants only partially improved subunit association. Knockdown of eIF6 expression improved ribosomal subunit association but did not correct the hematopoietic defect of SBDS-deficient cells. In summary, we demonstrate an SBDS-dependent ribosome maturation defect in SDS patient cells. The role of ribosomal subunit joining in marrow failure warrants further investigation.
Project description:Shwachman-Diamond syndrome (SDS) is an autosomal recessive genetic disorder, consisting of exocrine pancreatic insufficiency, chronic neutropenia, neutrophil chemotaxis defects, metaphyseal dysostosis, short stature, dental caries, and multiple organ involvements. Although SDS is the second most common hereditary abnormality of exocrine pancreas following cystic fibrosis in the Western countries, it has rarely been reported in Asia. We diagnosed a case of SDS in a 42-month-old girl, and genetic analysis including the relatives of the patient confirmed the diagnosis for the first time in Korea. She had short stature, steatorrhea, dental caries, and recurrent prulent otitis media and pneumonias. Laboratory studies revealed cyclic neutropenia, and serum levels of trypsin, amylase, and lipase were decreased. Simple radiography revealed metaphyseal sclerotic changes at the distal femur. A CT scan demonstrated a fatty infiltration and atrophy of the pancreas. On direct sequencing analysis of Shwachman-Bodian-Diamond Syndrome gene exon 2 region, the patient was homozygous for the c.258+2T>C mutation and heterozygous for the c.183_184TA>CT mutation and c.201A>G single nucleotide polymorphism. Treatment with pancreatic enzyme replacement, multivitamin supplementation, and regular to high fat diet improved her weight gain and steatorrhea.
Project description:BACKGROUND: The differential diagnosis of a neonate or fetus presenting with a bell-shaped or long narrow thorax includes a wide range of bony dysplasia syndromes. Where this is accompanied by respiratory distress, asphyxiating thoracic dystrophy (ATD, Jeune syndrome) is an important potential diagnosis. Shwachman-Diamond syndrome (SDS) is widely recognised as a cause of exocrine pancreatic dysfunction, short stature and bone marrow failure. It is not so well appreciated that rib and/or thoracic cage abnormalities occur in 30-50% of patients and that, in severe cases, these abnormalities may lead to thoracic dystrophy and respiratory failure in the newborn. There are, however, at least three previous case reports of children who were initially diagnosed with ATD who were subsequently shown to have SDS. CASE PRESENTATION: This report details the case history of a patient misdiagnosed as having ATD as a neonate following the neonatal asphyxial death of her brother. She subsequently developed progressive pancytopenia but was only diagnosed with SDS at 11 years of age after referral for haematopoietic stem cell transplantation for bone marrow failure accompanied by trilineage dysplasia and clonal cytogenetic abnormalities on bone marrow examination. Subsequent testing revealed the presence of fat globules in stools, reduced faecal chymotrypsin, fat-soluble vitamin deficiency, metaphyseal dysplasia on skeletal survey and heterozygous mutations of the SBDS gene. CONCLUSION: This report highlights the potential for diagnostic confusion between ATD and SDS. It is important to include SDS in the differential diagnosis of newborns with thoracic dystrophy and to seek expert clinical and radiological assessment of such children.
Project description:Mutations that target the ubiquitous process of ribosome assembly paradoxically cause diverse tissue-specific disorders (ribosomopathies) that are often associated with an increased risk of cancer. Ribosomes are the essential macromolecular machines that read the genetic code in all cells in all kingdoms of life. Following pre-assembly in the nucleus, precursors of the large 60S and small 40S ribosomal subunits are exported to the cytoplasm where the final steps in maturation are completed. Here, I review the recent insights into the conserved mechanisms of ribosome assembly that have come from functional characterisation of the genes mutated in human ribosomopathies. In particular, recent advances in cryo-electron microscopy, coupled with genetic, biochemical and prior structural data, have revealed that the SBDS protein that is deficient in the inherited leukaemia predisposition disorder Shwachman-Diamond syndrome couples the final step in cytoplasmic 60S ribosomal subunit maturation to a quality control assessment of the structural and functional integrity of the nascent particle. Thus, study of this fascinating disorder is providing remarkable insights into how the large ribosomal subunit is functionally activated in the cytoplasm to enter the actively translating pool of ribosomes.
Project description:Exocrine pancreatic insufficiency, haematological dysfunction, and skeletal abnormalities are the three clinical characteristics of the rare inherited bone marrow failure syndrome (IBMFS), known as Shwachman-Diamond syndrome (SDS). Cirrhosis at a neonatal age is uncommon and is typically not documented, as in neonatal presentation. Here, we present a case of SDS in which bi-cytopenia with macro-nodular cirrhosis emerged before the age of one month. Utilising genetic testing on the infant and both parents, we were able to confirm the diagnosis. We were expecting a higher-level liver transplant set-up, but the infant passed away in the interim. Genetic studies play a significant part in the diagnosis of difficult cases.
Project description:Background and objectivesShwachman Diamond syndrome (SDS) is an inherited bone marrow failure syndrome (IBMFS) associated with pancreatic insufficiency, neutropenia, and skeletal dysplasia. Biallelic pathogenic variants (PV) in SBDS account for >90% of SDS. We hypothesized that the SDS phenotype varies based on genotype and conducted a genotype-phenotype correlation study to better understand these complexities.MethodsWe reviewed records of all patients with SDS or SDS-like syndromes in the National Cancer Institute's (NCI) IBMFS study. Additional published SDS cohorts were reviewed and compared with the NCI cohort.ResultsPVs in SBDS were present in 32/47 (68.1%) participants. Biallelic inheritance of SBDS c.258 + 2T > C and c.183_184TA > CT was the most common genotype in our study (25/32, 78.1%) and published cohorts. Most patients had the SDS hallmark features of neutropenia (45/45, 100%), pancreatic insufficiency (41/43, 95.3%), and/or bony abnormalities (29/36, 80.6%). Developmental delay was common (20/34, 58.8%). Increased risk of hematologic malignancies at young ages and the rarity of solid malignancies was observed in both the NCI cohort and published studies.ConclusionsSDS is a complex childhood illness with a narrow genotypic spectrum. Patients may first present to primary care, gastroenterology, orthopedic, and/or hematology clinics. Coordinated multidisciplinary care is important for diagnosis and patient management.Clinical trial registrationClinicalTrials.gov Identifier: NCT00027274.ImpactThe clinical and genetic spectrum of Shwachman Diamond Syndrome was comprehensively evaluated, and the findings illustrate the importance of a multidisciplinary approach for these complex patients. Our work reveals: 1. a narrow genotypic spectrum in SDS; 2. a low risk of solid tumors in patients with SDS; 3. patients with SDS have clinical manifestations in multiple organ systems.
Project description:Shwachman-Diamond syndrome is a rare disorder of unknown cause. Reports have indicated the occurrence of affected siblings, but formal segregation analysis has not been performed. In families collected for genetic studies, the mean paternal age and mean difference in parental ages were found to be consistent with the general population. We determined estimates of segregation proportion in a cohort of 84 patients with complete sibship data under the assumption of complete ascertainment, using the Li and Mantel estimator, and of single ascertainment with the Davie modification. A third estimate was also computed with the expectation-maximization (EM) algorithm. All three estimates supported an autosomal recessive mode of inheritance, but complete ascertainment was found to be unlikely. Although there are no overt signs of disease in adult carriers (parents), the use of serum trypsinogen levels to indicate exocrine pancreatic dysfunction was evaluated as a potential measure for heterozygote expression. No consistent differences were found in levels between parents and a normal control population. Although genetic heterogeneity cannot be excluded, our results indicate that simulation and genetic analyses of Shwachman-Diamond syndrome should consider a recessive model of inheritance.
Project description:Shwachman-Diamond syndrome (SDS) is a bone marrow failure (BMF) syndrome associated with an increased risk of myelodysplasia and leukemia. The molecular mechanisms of SDS are not fully understood. We report that primitive hematopoietic cells from SDS patients present with a reduced activity of the small RhoGTPase Cdc42 and concomitantly a reduced frequency of HSCs polar for polarity proteins. The level of apolarity of SDS HSCs correlated with the magnitude of HSC depletion in SDS patients. Importantly, exogenously provided Wnt5a or GDF11 that elevates the activity of Cdc42 restored polarity in SDS HSCs and increased the number of HSCs in SDS patient samples in surrogate ex vivo assays. Single cell level RNA-Seq analyses of SDS HSCs and daughter cells demonstrated that SDS HSC treated with GDF11 are transcriptionally more similar to control than to SDS HSCs. Treatment with GDF11 reverted pathways in SDS HSCs associated with rRNA processing and ribosome function, but also viral infection and immune function, p53-dependent DNA damage, spindle checkpoints, and metabolism, further implying a role of these pathways in HSC failure in SDS. Our data suggest that HSC failure in SDS is driven at least in part by low Cdc42 activity in SDS HSCs. Our data thus identify novel rationale approaches to attenuate HSCs failure in SDS.