Knockdown of the Shwachman-Diamond syndrome gene, SBDS, induces galectin-1 expression and impairs cell growth.

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by exocrine pancreatic insufficiency and bone marrow failure. The depletion of SBDS protein by RNA interference has been shown to cause inhibition of cell proliferation in several cell lines. However, the precise mechanism by which the loss of SBDS leads to inhibition of cell growth remains unknown. To evaluate the impaired growth of SBDS-knockdown cells, we analyzed Epstein-Barr virus-transformed lymphoblast cells (LCLs) derived from two patients with SDS (c. 183_184TA > CT and c. 258 + 2 T > C). After 3 days of culture, the growth of LCL-SDS cell lines was considerably less than that of control donor cells. By annealing control primer-based GeneFishing PCR screening, we found that galectin-1 (Gal-1) mRNA expression was elevated in LCL-SDS cells. Western blot analysis showed that the level of Gal-1 protein expression was also increased in LCL-SDS cells as well as in SBDS-knockdown 32Dcl3 murine myeloid cells. We confirmed that recombinant Gal-1 inhibited the proliferation of both LCL-control and LCL-SDS cells and induced apoptosis (as determined by annexin V-positive staining). These results suggest that the overexpression of Gal-1 contributes to abnormal cell growth in SBDS-deficient cells.

Ataluren improves myelopoiesis and neutrophil chemotaxis by restoring ribosome biogenesis and reducing p53 levels in Shwachman-Diamond syndrome cells.

Shwachman-Diamond syndrome (SDS) is characterized by neutropenia, exocrine pancreatic insufficiency and skeletal abnormalities. SDS bone marrow haematopoietic progenitors show increased apoptosis and impairment in granulocytic differentiation. Loss of Shwachman-Bodian-Diamond syndrome (SBDS) expression results in reduced eukaryotic 80S ribosome maturation. Biallelic mutations in the SBDS gene are found in ~90% of SDS patients, ~55% of whom carry the c.183-184TA>CT nonsense mutation. Several translational readthrough-inducing drugs aimed at suppressing nonsense mutations have been developed. One of these, ataluren, has received approval in Europe for the treatment of Duchenne muscular dystrophy. We previously showed that ataluren can restore full-length SBDS protein synthesis in SDS-derived bone marrow cells. Here, we extend our preclinical study to assess the functional restoration of SBDS capabilities in vitro and ex vivo. Ataluren improved 80S ribosome assembly and total protein synthesis in SDS-derived cells, restored myelopoiesis in myeloid progenitors, improved neutrophil chemotaxis in vitro and reduced neutrophil dysplastic markers ex vivo. Ataluren also restored full-length SBDS synthesis in primary osteoblasts, suggesting that its beneficial role may go beyond the myeloid compartment. Altogether, our results strengthened the rationale for a Phase I/II clinical trial of ataluren in SDS patients who harbour the nonsense mutation.

M phase-specific interaction between SBDS and RNF2 at the mitotic spindles regulates mitotic progression.

Shwachman-Diamond syndrome (SDS) is an autosomal recessive inherited disorder caused by biallelic mutations in the Shwachman-Bodian-Diamond syndrome (SBDS) gene. SBDS protein is involved in ribosome biogenesis; therefore SDS is classified as a ribosomopathy. SBDS is localized at mitotic spindles and stabilizes microtubules. Previously, we showed that SBDS interacts with ring finger protein 2 (RNF2) and is degraded through RNF2-dependent ubiquitination. In this study, we investigated when and where SBDS interacts with RNF2 and the effects of the interaction on cells. We found that SBDS co-localized with RNF2 on centrosomal microtubules in the mitotic phase (M phase), whereas SBDS and RNF2 localized to the nucleolus and nucleoplasm in the interphase, respectively. The microtubule-binding assay revealed that SBDS interacted directly with microtubules and RNF2 interacted with SBDS bound to microtubules. In addition, SBDS was ubiquitinated and degraded by RNF2 during the M phase. Moreover, RNF2 overexpression accelerated mitotic progression. These findings suggest that SBDS delays mitotic progression, and RNF2 releases cells from suppression through the ubiquitination and subsequent degradation of SBDS. The interaction between SBDS and RNF2 at mitotic spindles might be involved in mitotic progression as a novel regulatory cascade.

[Diagnosis and treatment of Shwachman-Diamond syndrome in Chinese children: An evidence-based study].

OBJECTIVE: To explore the characteristics of Shwachman-Diamond syndrome (SDS) in Chinese children in order to provide a reference for early diagnosis. METHODS: With Shwachman-Diamond syndrome, SDS, SBDS gene and inherited bone marrow failure as the keywords, the search period was set from January 2002 to October 2022. Relevant literature was retrieved from the Wanfang Database and China National Knowledge Infrastructure (CNKI) database. In addition, by using Shwachman-diamond syndrome as a keyword, the search period was also retrieved from the Web of Science, PubMed, and MEDLINE databases from January 2002 to October 2022. A child with SDS treated at the Tongji Hospital was also included. A total of 44 cases with complete clinical data were analyzed with reference to the International Standard for SDS Diagnosis. Chi-square test and t test were used for statistical analysis. Evidence-based research was carried out in the form of systematic review. The epidemiology, clinical characteristics and key points of early diagnosis of the Chinese SDS children were summarized and compared with the international data. RESULTS: The main characteristics of SDS in Chinese children were summarized as follows: The ratio of males to females was about 1.3 : 1, the median age of onset was 3 months, and the median age of diagnosis was 14 months. The first symptoms were often exocrine pancreatic insufficiency (31.8%) and granulocytopenia with infection (31.8%). According to the international consensus, the incidence rates of the three major diseases of SDS were hemocytopenia (95.4%), pancreatic disease (72.7%), and bone abnormality (40.9%). The common factors underlying SDS disease were variants of the SBDS gene (c.258+2T>C and c.183_184TA>CT), albeit there was no significant correlation between genotype and phenotype (P > 0.05). Compared with international reports, the clinical manifestations and genotypes of Chinese SDS children are different (P < 0.05). CONCLUSION: The SDS children have an early age of onset and significant individual difference. It is necessary to analyze the case-related data to facilitate early recognition, diagnosis and clinical intervention.

Spectrum of diabetes mellitus in patients with Shwachman-Diamond syndrome: case report and review of the literature.

BACKGROUND: Shwachman-Diamond syndrome (SDS) is a rare congenital disorder caused by mutations in the SBDS gene and characterized by exocrine pancreatic deficiency, hematologic dysfunction, and skeletal growth failure. Although the hematologic features and characteristics of the somatic disorders commonly associated with SDS are well known, emerging data from case reports and patient registries suggest that SDS may also be associated with an increased risk of diabetes mellitus. However, currently available data on SDS-associated diabetes are limited and do not allow conclusions regarding prevalence and incidence rates, clinical course, and outcomes. CASE PRESENTATION: Here we report the case of a 5-year-old girl with SDS who underwent bone marrow transplantation at the age of 3 months and developed autoantibody-positive type 1 diabetes mellitus at the age of 1.8 years. The manifestation and course of diabetes development were mild, complicated by concurrent spontaneous episodes of hypoglycemia even before the onset of antidiabetic treatment. Currently, adequate metabolic control can be achieved by dietary intervention. CONCLUSIONS: Considering that the SBDS protein regulates mitosis and ribosomal biosynthesis and that its suppression may cause immunologic instability and chronic inflammation, this case provides insight into the phenotype of rare Shwachman-Diamond syndrome-associated diabetes mellitus, which may be characterized by significant age-dependent differences in clinical course.

Shwachman-Diamond syndromes: clinical, genetic, and biochemical insights from the rare variants.

Shwachman-Diamond syndrome is a rare inherited bone marrow failure syndrome characterized by neutropenia, exocrine pancreatic insufficiency, and skeletal abnormalities. In 10-30% of cases, transformation to a myeloid neoplasm occurs. Approximately 90% of patients have biallelic pathogenic variants in the SBDS gene located on human chromosome 7q11. Over the past several years, pathogenic variants in three other genes have been identified to cause similar phenotypes; these are DNAJC21, EFL1, and SRP54. Clinical manifestations involve multiple organ systems and those classically associated with the Shwachman-Diamond syndrome (bone, blood, and pancreas). Neurocognitive, dermatologic, and retinal changes may also be found. There are specific gene-phenotype differences. To date, SBDS, DNAJC21, and SRP54 variants have been associated with myeloid neoplasia. Common to SBDS, EFL1, DNAJC21, and SRP54 is their involvement in ribosome biogenesis or early protein synthesis. These four genes constitute a common biochemical pathway conserved from yeast to humans that involve early stages of protein synthesis and demonstrate the importance of this synthetic pathway in myelopoiesis.

Inherited causes of exocrine pancreatic insufficiency in pediatric patients: clinical presentation and laboratory testing.

Pediatric patients with exocrine pancreatic insufficiency (EPI) have symptoms that include abdominal pain, weight loss or poor weight gain, malnutrition, and steatorrhea. This condition can be present at birth or develop during childhood for certain genetic disorders. Cystic fibrosis (CF) is the most prevalent disorder in which patients are screened for EPI; other disorders also are associated with pancreatic dysfunction, such as hereditary pancreatitis, Pearson syndrome, and Shwachman-Diamond syndrome. Understanding the clinical presentation and proposed pathophysiology of the pancreatic dysfunction of these disorders aids in diagnosis and treatment. Testing pancreatic function is challenging. Directly testing aspirates produced from the pancreas after stimulation is considered the gold standard, but the procedures are not standardized or widely available. Instead, indirect tests are often used in diagnosis and monitoring. Although indirect tests are more widely available and easier to perform, they have inherent limitations due to a lack of sensitivity and/or specificity for EPI.

Predisposition to myeloid malignancies in Shwachman-Diamond syndrome: biological insights and clinical advances.

Shwachman-Diamond syndrome (SDS) is an inherited multisystem ribosomopathy characterized by exocrine pancreatic deficiency, bone marrow failure, and predisposition to myeloid malignancies. The pathobiology of SDS results from impaired ribosomal maturation due to the deficiency of SBDS and the inability to evict the antiassociation factor eIF6 from the 60S ribosomal subunit. Clinical outcomes for patients with SDS who develop myeloid malignancies are extremely poor because of high treatment-related toxicities and a high rate of refractory disease/relapse even after allogeneic hematopoietic stem cell transplant (HSCT). Registry data indicate that outcomes are improved for patients with SDS who undergo routine bone marrow surveillance and receive an HSCT before developing an overt malignancy. However, the optimal approach to hematologic surveillance and the timing of HSCT for patients with SDS is not clearly established. Recent studies have elucidated distinct patterns of somatic blood mutations in patients with SDS that either alleviate the ribosome defect via somatic rescue (heterozygous EIF6 inactivation) or disrupt cellular checkpoints, resulting in increased leukemogenic potential (heterozygous TP53 inactivation). Genomic analysis revealed that most myeloid malignancies in patients with SDS have biallelic loss-of-function TP53 mutations. Single-cell DNA sequencing of SDS bone marrow samples can detect premalignant biallelic TP53-mutated clones before clinical diagnosis, suggesting that molecular surveillance may enhance the detection of incipient myeloid malignancies when HSCT may be most effective. Here, we review the clinical, genetic, and biologic features of SDS. In addition, we present evidence supporting the hematologic surveillance for patients with SDS that incorporates clinical, pathologic, and molecular data to risk stratify patients and prioritize transplant evaluation for patients with SDS with high-risk features.

Elevated Levels of Toxic Bile Acids in Serum of Cystic Fibrosis Patients with CFTR Mutations Causing Pancreatic Insufficiency.

Hepatobiliary involvement is a hallmark in cystic fibrosis (CF), as the causative CF Transmembrane Conductance Regulator (CFTR) defect is expressed in the biliary tree. However, bile acid (BA) compositions in regard to pancreatic insufficiency, which is present at an early stage in about 85% of CF patients, have not been satisfactorily understood. We assess the pattern of serum BAs in people with CF (pwCF) without CFTR modulator therapy in regard to pancreatic insufficiency and the CFTR genotype. In 47 pwCF, 10 free and 12 taurine- and glycine-conjugated BAs in serum were prospectively assessed. Findings were related to genotype, pancreatic insufficiency prevalence (PIP)-score, and hepatic involvement indicated by serum liver enzymes, as well as clinical and ultrasound criteria for CF-related liver disease. Serum concentrations of total primary BAs and free cholic acid (CA) were significantly higher in pwCF with higher PIP-scores (p = 0.025, p = 0.009, respectively). Higher total BAs were seen in pwCF with PIP-scores ≥0.88 (p = 0.033) and with pancreatic insufficiency (p = 0.034). Free CA was higher in patients with CF-related liver involvement without cirrhosis, compared to pwCF without liver disease (2.3-fold, p = 0.036). pwCF with severe CFTR genotypes, as assessed by the PIP-score, reveals more toxic BA compositions in serum. Subsequent studies assessing changes in BA homeostasis during new highly effective CFTR-modulating therapies are of high interest.

Association between phenotypic and genotypic characteristics and disease severity in individuals with cystic fibrosis.

OBJECTIVE: To analyze the association between phenotypic and genotypic characteristics and disease severity in individuals with cystic fibrosis treated at a reference center in Minas Gerais, Brazil. METHODS: This is a retrospective study that collected clinical and laboratory data, respiratory and gastrointestinal manifestations, type of treatment, Shwachman-Kulczycki score, and mutations from the patients' medical records. RESULTS: The sample included 50 participants aged one to 33 years, 50% of whom were female. Out of the one hundred alleles of the Cystic Fibrosis Transmembrane Conductance Regulator gene, the most prevalent mutations were DeltaF508 (45%) and S4X (18%). Mutation groups were only associated with pancreatic insufficiency (p=0.013) and not with disease severity (p=0.073). The latter presented an association with colonization by Pseudomonas aeruginosa and Staphylococcus aureus (p=0.007) and with underweight (p=0.036). Death was associated with age at diagnosis (p=0.016), respiratory symptomatology (p=0.013), colonization (p=0.024), underweight (p=0.017), and hospitalization (p=0.003). CONCLUSIONS: We could identify the association of mutations with pancreatic insufficiency; the association of Staphylococcus aureus colonization and underweight with disease severity; and the lack of association between mutations and disease severity. Environmental factors should be investigated more thoroughly since they seem to have an important effect on disease severity.

[Clinical phenotypes and genotypic spectrum of cystic fibrosis with pancreatic insufficiency in children].

Objective: To investigate the clinical phenotypes and genotypic spectrum of exocrine pancreatic insufficiency in children with cystic fibrosis. Methods: This was a retrospective analysis of 12 children with cystic fibrosis who presented to Children's Hospital of Fudan University from December 2017 to December 2021. Clinical features, fecal elastase-1 level, genotype, diagnosis and treatment were systematically reviewed. Results: A total of 12 children, 7 males and 5 females, diagnosis aged 5.4 (2.0, 10.6) years, were recruited. Common clinical features included chronic cough in 12 cases, malnutrition in 7 cases, steatorrhea in 7 cases, bronchiectasis in 5 cases and electrolyte disturbance in 4 cases. Exocrine pancreatic insufficiency were diagnosed in 8 cases,the main clinical manifestations were steatorrhea in 7 cases, of which 5 cases started in infancy; 6 cases were complicated with malnutrition, including mild in 1 case, moderate in 2 cases and severe in 3 cases; 3 cases had abdominal distension; 2 cases had intermittent abdominal pain; 4 cases showed fatty infiltration or atrophy of pancreas and 3 cases showed no obvious abnormality by pancreatic magnetic resonance imaging or B-ultrasound. All 8 children were given pancreatic enzyme replacement therapy, follow-up visit of 2.3 (1.2,3.2) years. Diarrhea significantly improved in 6 cases, and 1 case was added omeprazole due to poor efficacy. A total of 20 variations of CFTR were detected in this study, of which 7 were novel (c.1373G>A,c.1810A>C,c.270delA,c.2475_2478dupCGAA,c.2489_c.2490insA, c.884delT and exon 1 deletion). Conclusions: There is a high proportion of exocrine pancreatic insufficiency in Chinese patients with cystic fibrosis. The main clinical manifestations are steatorrhea and malnutrition. Steatorrhea has often started from infancy. Pancreatic enzyme replacement therapy can significantly improve the symptoms of diarrhea and malnutrition.

Phenotypic Variation in Two Siblings Affected with Shwachman-Diamond Syndrome: The Use of Expert Variant Interpreter (eVai) Suggests Clinical Relevance of a Variant in the KMT2A Gene.

Introduction. Shwachman-Diamond Syndrome (SDS) is an autosomal-recessive disorder characterized by neutropenia, pancreatic exocrine insufficiency, skeletal dysplasia, and an increased risk for leukemic transformation. Biallelic mutations in the SBDS gene have been found in about 90% of patients. The clinical spectrum of SDS in patients is wide, and variability has been noticed between different patients, siblings, and even within the same patient over time. Herein, we present two SDS siblings (UPN42 and UPN43) carrying the same SBDS mutations and showing relevant differences in their phenotypic presentation. Study aim. We attempted to understand whether other germline variants, in addition to SBDS, could explain some of the clinical variability noticed between the siblings. Methods. Whole-exome sequencing (WES) was performed. Human Phenotype Ontology (HPO) terms were defined for each patient, and the WES data were analyzed using the eVai and DIVAs platforms. Results. In UPN43, we found and confirmed, using Sanger sequencing, a novel de novo variant (c.10663G > A, p.Gly3555Ser) in the KMT2A gene that is associated with autosomal-dominant Wiedemann−Steiner Syndrome. The variant is classified as pathogenic according to different in silico prediction tools. Interestingly, it was found to be related to some of the HPO terms that describe UPN43. Conclusions. We postulate that the KMT2A variant found in UPN43 has a concomitant and co-occurring clinical effect, in addition to SBDS mutation. This dual molecular effect, supported by in silico prediction, could help to understand some of the clinical variations found among the siblings. In the future, these new data are likely to be useful for personalized medicine and therapy for selected cases.

Shwachman-Diamond Syndrome With Congenital Myogenic Ptosis: Case Report of a Rare Association?

BACKGROUND: Shwachman-Diamond syndrome (SDS) is a multisystem disorder characterized by exocrine pancreatic insufficiency and bone marrow failure. There is considerable variation in the phenotypes of SDS. We present a case of an infant presenting with SDS and left-sided ptosis. OBSERVATION: We report a case of an infant who presented with 2 episodes of severe sepsis and cytopenia, without overt symptoms of exocrine pancreatic deficiency or skeletal abnormalities. Persistent left-sided ptosis was noted in both presentations. Genetic testing confirmed the diagnosis of SDS. The left-sided ptosis was diagnosed as congenital myogenic ptosis. CONCLUSION: The association of ptosis and other congenital bone marrow failure syndromes is well established, but this is the first description of SDS with ptosis. This association may expand our understanding of SDS phenotypes if similar cases are reported in the future.

Shwachman Diamond syndrome: narrow genotypic spectrum and variable clinical features.

BACKGROUND AND OBJECTIVES: Shwachman 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. METHODS: We 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. RESULTS: PVs 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. CONCLUSIONS: SDS 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 REGISTRATION: ClinicalTrials.gov Identifier: NCT00027274. IMPACT: The 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.

Inherited pancreatic exocrine insufficiency and pancreatitis: When children transition to adult care.

Hereditary pancreatitis (HP) encompasses two distinct disease groups: the first manifests as congenital exocrine pancreatic insufficiency (EPI), and the second includes hereditary forms of pancreatitis. EPI represents the ultimate expression of gland function loss. Cystic fibrosis is by far the most frequent aetiology of early-onset EPI; genetics and a growing understanding of the disease mechanisms have paved the way for innovative and personalized treatment approaches. Efforts are ongoing to further decipher the pathophysiology and explore new therapies for other causes of EPI. HP occurs in patients carrying mutations in genes encoding digestive proteases or proteins playing an important role in proper pancreatic function and homeostasis. Improved sequencing techniques have led to the discovery of several causal and disease promoting genes. Most forms of HP have a paediatric onset but complications usually manifest during adulthood. Surveillance in experienced centres is mandatory to diagnose and address these complications in a timely manner.

Pancreatic Insufficiency in a Child with p.Gly542* and c.2657+5G>A Heterozygote CFTR: A Case Report.

Cystic fibrosis is a monogenic and autosomal recessive disease. It is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator gene responsible for encoding the CFTR protein. Involvement of the gastrointestinal and respiratory systems is the main clinical manifestation. In this case, we report a heterozygous CFTR patient harboring class I (p.Gly542*) and class V (c.2657+5G>A) mutations. The importance of this case report lies in the clinical features because the patient, aged 3 years, presented with early exocrine pancreatic insufficiency, which can be considered atypical, as most individuals with this genotype are pancreatic sufficient or develop pancreatic insufficiency later in life. This report aims at presenting the tests requested that contributed to the patient's diagnosis, as well as at understanding the association between these mutations and their phenotypic presentation. Interpretation of the genotype-phenotype relationship represents a challenge, as genetic analysis alone is not sufficient to clearly predict severity of the disease. This is because the significant phenotypic heterogeneity existing among patients with the same genotype may exert socioeconomic and sociocultural influences, or by the action of CFTR modifiers, such as environmental and modifying genes, which can alter the protein's function and exert an impact on the individual's phenotype.