Homozygous Gene Mutation Research Articles

Prenatal Diagnosis and Management of Generalized Arterial Calcification of Infancy

BACKGROUND: Generalized arterial calcification of infancy is a rare genetic disorder that was first reported in 1899. Since then, slightly more than 200 cases have been documented. This rare autosomal recessive disorder occurs when the homozygous ENPP1 gene mutation is associated with abnormal calcification in the medium and large arteries in the fetus. Overall mortality in individuals with generalized arterial calcification of infancy is high (55%) before the age of 6 months, with 24.4% dying in utero. Due to the high mortality rate, there is a critical need for additional reports and research regarding generalized arterial calcification of infancy. CASE: We submit a case report of a child with generalized arterial calcification of infancy—a unique instance in which the diagnosis was established prenatally and treatment was initiated in utero. Patient care was continued through a multidisciplinary approach coordinated between specialists across India, Australia, and the United States. There was an almost complete resolution of the calcification, with near-normal development and intellectual capacity of the child for age. CONCLUSION: Clear guidelines are needed regarding prenatal use of bisphosphonate therapy, timing, dosage, and duration of treatment for fetuses with ENPP1 gene mutations to minimize disease progression and improve neonatal health at birth. This case further illustrates how involving well-informed parents in decision making can help tailor the appropriate treatment. Our report also describes the possibility of new, ongoing clinical trials that may pave the way for a cure for this child and others.

Clinical, Laboratory, and Molecular Characteristics of Inherited Vitamin K-Dependent Coagulation Factors Deficiency.

Vitamin K-dependent coagulation factors deficiency (VKCFD) is a rare autosomal recessive genetic disease characterized by impaired levels of multiple coagulation factors (II, VII, IX, and X) and natural anticoagulants (proteins C and S). VKCFD is part of familial multiple coagulation factor deficiencies, reporting overall 50 affected families thus far. Disease manifestations are quite heterogeneous, bleeding symptoms may vary, and even, although generally mild, some patients may succumb to fatal outcomes. VKCFD diagnosis may be delayed because the disease phenotype simulates the most frequently acquired deficiencies of vitamin K. First-line coagulation assays, prothrombin time/international normalized ratio (PT/INR) and activated partial thromboplastin time (aPTT), are both prolonged; mixing test typically normalizes the clotting times; and vitamin K-dependent coagulation factors will be variably decreased. Molecularly, VKCFD is associated with mutations in γ-glutamyl-carboxylase (GGCX) or vitamin K epoxide reductase complex subunit 1 (VKORC1) genes. Vitamin K is involved not only in the biosynthesis of coagulation proteins but also in bone metabolism and cell proliferation. Therapeutic options are based on vitamin K supplementation, coagulation factors (prothrombin complex), and fresh frozen plasma, in case of severe bleeding episodes. Two case studies here illustrate the diagnostic challenges of VKCFD: case 1 depicts a woman with a history of bleeding episodes, diagnosed, only in her third decade of life with inherited homozygous GGCX gene mutation. Case 2 shows a man with an acquired vitamin K deficiency caused by Crohn's disease. Better understanding of GGCX and VKORC1 mutations aids in prognosis and treatment planning, with emerging insights suggesting potential limitations in the effectiveness of vitamin K supplementation in certain mutations.

Novel splicing mutations in PATL2 and WEE2 cause oocyte degradation and fertilization failure.

To determine the genetic cause of infertility in two unrelated families of female patients suffering from oocyte degeneration and fertilization failure. Whole exome sequencing and Sanger sequencing were performed to identify the disease-causing genes of infertility in two unrelated female patients. Minigene experiments were conducted to confirm the effect of splice site mutations on mRNA splicing. In two unrelated female infertility patients, a novel compound heterozygous splicing mutation (c.516-1G > T and c.877-1G > A) in PATL2 gene and a novel homozygous splicing mutation (c.1222-1G > A) in WEE2 gene were identified. Minigene splicing assays revealed that the c.516-1G > T mutation in PATL2 resulted in a deletion of 8 bases in mRNA that causes a frameshift (c.516-523delTCCCCCAG, p.P173Q fs*13). The c.877-1G > A mutation led to the skipping of exons 10 and 11 and retention of introns 8-9 in PATL2 mRNA. The c.1222-1G > A mutation resulted in the deletion of exon 9 in WEE2 mRNA, leading to an in-frame deletion of 57 amino acids in the WEE2 protein (p.408-464del). Our study discovered novel splicing mutations in PATL2 and WEE2, further expanding the mutation spectrum of these two genes and providing guidance for genetic counseling and diagnosis of female infertility.

Hereditary Multiple Intestinal Atresia With a Novel TTC7A Pathogenic Variant: Gastrointestinal Manifestations in Two Cases.

Hereditary multiple intestinal atresia (HMIA) with TTC7A mutation is caused by homozygous or compound heterozygous TTC7A gene mutation. It is characterized by multiple small and large intestinal atresias and/or stenoses. TTC7A mutation is described in some patients with inflammatory bowel disease and mild-severe forms of severe combined immunodeficiency without intestinal atresia or stenosis. We present 2 cases of intestinal atresia and documented TTC7A mutation with a novel variant. Both cases had different clinical and pathological manifestations. The first case is a male infant born at 35 weeks of gestation with failure to pass meconium. Intestinal biopsy reveals apoptotic enteropathy with villous atrophy and increased mucosal eosinophils. The second case is referred at birth for antenatally detected umbilical hernia, polyhydramnios and possible upper intestinal obstruction. The resected specimen reveals ileal atresia with partial villous atrophy, decreased number of lamina propria inflammatory cells and absence of plasma cells. In conclusion, these cases reflect an emerging TTC7A pathogenic variant with different histological manifestations and leads to characterization as immune dysregulation disorder. There is a need to differentiate TTC7A mutation associated ones from cases labeled as very early onset IBD and rule out other hereditary immunodeficiencies.

Evaluation of galectin-3 and titin in cats with a sarcomeric gene mutation associated with echocardiography.

Cardiac biomarkers, such as serum galectin-3 (Gal-3) and titin levels, may be related to cats with sarcomeric gene mutations. This study evaluated cardiac biomarkers and echocardiographic parameters in cats with or without myosin-binding protein C3 (MYBPC3) gene mutations. Forty-two healthy cats without cardiac symptoms, including Bengal, Maine Coon, Scottish fold, and Ragdoll cats, were enrolled in this study. Cats were categorized into three groups: Homozygous wild type (n = 17), homozygous MYBPC3 gene mutation (n = 14), and heterozygous MYBPC3 gene mutation (n = 11). All recruited cats underwent echocardiography, and blood samples were collected for DNA extraction. DNA sequencing for MYBPC3 gene mutations at A31P and A74T loci was first examined by Sanger sequencing. The biomarkers of cardiac fibrosis (Gal-3) and myocardial stiffness (titin) were measured by enzyme-linked immunosorbent assay. Gal-3 levels >250 pg/mL were associated with echocardiographic parameters. However, Gal-3 levels were not significantly different between cats with MYBPC3 gene mutations and those in the wild-type group. Titin was associated with the left ventricular (LV) thickness and systolic function (r = 0.405, p = 0.013). Qualitative measurement of titin antibodies showed that the highest percentage of these antibodies was found in homozygous wild-type cats. No correlation was found between titin levels and MYBPC3 gene mutations. Weight was positively associated with interventricular septum (r = 0.312, p = 0.056) and LV wall thickness (LVPW) (r = 0.219, p = 0.187). However, they were not associated with Gal-3 levels. LVPW was correlated with weight in cats with sarcomeric gene mutations. Serum titin may be an underlying factor for cardiac hypertrophy in cats.

Potential Involvements of Cilia-Centrosomal Genes in Primary Congenital Glaucoma.

Primary congenital glaucoma (PCG) occurs in children due to developmental abnormalities in the trabecular meshwork and anterior chamber angle. Previous studies have implicated rare variants in CYP1B1, LTBP2, and TEK and their interactions with MYOC, FOXC1, and PRSS56 in the genetic complexity and clinical heterogeneity of PCG. Given that some of the gene-encoded proteins are localized in the centrosomes (MYOC) and perform ciliary functions (TEK), we explored the involvement of a core centrosomal protein, CEP164, which is responsible for ocular development and regulation of intraocular pressure. Deep sequencing of CEP164 in a PCG cohort devoid of homozygous mutations in candidate genes (n = 298) and controls (n = 1757) revealed CEP164 rare pathogenic variants in 16 cases (5.36%). Co-occurrences of heterozygous alleles of CEP164 with other genes were seen in four cases (1.34%), and a physical interaction was noted for CEP164 and CYP1B1 in HEK293 cells. Cases of co-harboring alleles of the CEP164 and other genes had a poor prognosis compared with those with a single copy of the CEP164 allele. We also screened INPP5E, which synergistically interacts with CEP164, and observed a lower frequency of pathogenic variants (0.67%). Our data suggest the potential involvements of CEP164 and INPP5E and the yet unexplored cilia-centrosomal functions in PCG pathogenesis.

Clinical features associated with maternal uniparental disomy for chromosome 6

BackgroundMaternal uniparental disomy for chromosome 6 (upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat) has been previously reported to cause intrauterine growth restriction (IUGR), but the specific clinical phenotype has not been defined. Based on clinical data from two new cases and patients from the literature, specific phenotypes and mechanisms will be discussed further.Case presentation: In case 1, a maternal isodisomy mixed with a heterodisomy was found on chromosome 6, including a regional absence of heterozygosity between 6q23.3 and 6q27. In case 2, a homozygous SCUBE3 mutation and upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat, involving the 6p21.1-25.1 region were found. Clinical data related to upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat were also reviewed. Of all the 21 reported cases with upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat (including our 2 cases), 18 (85.7%) presented IUGR.ConclusionsThe phenotypes of the two newly identified patients with upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat further suggest that IUGR is associated with upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat and case 2 is the first reported upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat patient with a homozygous SCUBE3 gene mutation. However, the specific phenotypes involved in upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996–2002.)mat and the related mechanisms need to be further studied.

Modification in Gene Expression of CCR5 Co-Receptor and Down Regulation of Virion Molecule with Primary Human T- cell in HIV Infection

About 1 2% of population in western European white people are resistant to hiv-1 infection due to modified gene of ccr5 receptor molecule. Modification of ccr5 receptor gene blocks the virion molecule to enter into the host cell. Mutations gene lead to slow progress rate of infection and low expression of cd4 + T cell. The hypothesis of researcher is that the modified allogeneic transplant with modified M303/M303 gene in ccr5 leads to resistant for HIV and AIDS patient. Deletion of gene in ccr5 receptor develops the ability of resistant with HIV-1. Down regulation of ccr5 receptor with macrophages T cell reduce the immune response and lead to slow progressive rate of infection. Different gene-editing methods are involved in ccr5 gene editing such as TALEN, ZFN, and CRISP/Cas. Mutant gene transplant in ccr5 receptor prevent the further exposure of dangerous retrovirus. As comparison of heterogeneous and homogenous .The heterogeneous analogues has more resistance as compare to homogenous genetic order. Chemokine and inflammatory mediator are the less active in heterogeneous. The homozygous mutation in ccr5 gene (ccr5∆32) base pair deletion induces nonfunctional ccr5 receptor and heterogonous mutation has resistant of HIV 1 and slow progressive effect.

HIF3A gene disruption causes abnormal alveoli structure and early neonatal death.

Transcriptional response to changes in oxygen concentration is mainly controlled by hypoxia-inducible transcription factors (HIFs). Besides regulation of hypoxia-responsible gene expression, HIF-3α has recently been shown to be involved in lung development and in the metabolic process of fat tissue. However, the precise mechanism for such properties of HIF-3α is still largely unknown. To this end, we generated HIF3A gene-disrupted mice by means of genome editing technology to explore the pleiotropic role of HIF-3α in development and physiology. We obtained adult mice carrying homozygous HIF3A gene mutations with comparable body weight and height to wild-type mice. However, the number of litters and ratio of homozygous mutation carriers born from the mating between homozygous mutant mice was lower than expected due to sporadic deaths on postnatal day 1. HIF3A gene-disrupted mice exhibited abnormal configuration of the lung such as a reduced number of alveoli and thickened alveolar walls. Transcriptome analysis showed, as well as genes associated with lung development, an upregulation of stearoyl-Coenzyme A desaturase 1, a pivotal enzyme for fatty acid metabolism. Analysis of fatty acid composition in the lung employing gas chromatography indicated an elevation in palmitoleic acid and a reduction in oleic acid, suggesting an imbalance in distribution of fatty acid, a constituent of lung surfactant. Accordingly, administration of glucocorticoid injections during pregnancy resulted in a restoration of normal alveolar counts and a decrease in neonatal mortality. In conclusion, these observations provide novel insights into a pivotal role of HIF-3α in the preservation of critically important structure and function of alveoli beyond the regulation of hypoxia-mediated gene expression.

Pituitary involvement in familial hemophagocytic lymphohistiocytosis type 5 associated with homozygous mutation in the syntaxin-binding protein-2 gene (STXBP2)

Pituitary involvement in familial hemophagocytic lymphohistiocytosis type 5 associated with homozygous mutation in the syntaxin-binding protein-2 gene (STXBP2)

First case of 5-oxoprolinuria with two homozygous mutations in GSS and OPLAH genes: A case with neonatal presentation and rapid fatal outcome

First case of 5-oxoprolinuria with two homozygous mutations in GSS and OPLAH genes: A case with neonatal presentation and rapid fatal outcome

Long term clinical follow up of four patients with Wolfram syndrome and urodynamic abnormalities.

Wolfram syndrome is characterised by insulin-dependent diabetes (IDDM), diabetes insipidus (DI), optic atrophy, sensorineural deafness and neurocognitive disorders. The DIDMOAD acronym has been recently modified to DIDMOAUD suggesting the rising awareness of the prevalence of urinary tract dysfunction (UD). End stage renal disease is the commonest cause of mortality in Wolfram syndrome. We present a case series with main objective of long term follow up in four children having Wolfram syndrome with evaluation of their urodynamic profile. A prospective follow up of four genetically proven children with Wolfram syndrome presenting to a tertiary care pediatric diabetes clinic in Pune, India was conducted. Their clinical, and urodynamic parameters were reviewed. IDDM, in the first decade, was the initial presentation in all the four children (three male and one female). Three children had persistent polyuria and polydipsia despite having optimum glycemic control; hence were diagnosed to have DI and treated with desmopressin. All four patients entered spontaneous puberty. All patients had homozygous mutation in WFS1 gene; three with exon 8 and one with exon 6 novel mutations. These children with symptoms of lower urinary tract malfunction were further evaluated with urodynamic studies; two of them had hypocontractile detrusor and another had sphincter-detrusor dyssynergia. Patients with hypocontractile bladder were taught clean intermittent catheterization and the use of overnight drain. We report a novel homozygous deletion in exon 6 of WFS-1 gene. The importance of evaluation of lower urinary tract malfunction is highlighted by our case series. The final bladder outcome in our cases was a poorly contractile bladder in three patients.

Late Onset of Severe Demyelinating Peripheral Neuropathy in a 62-Year-Old African American Woman.

Hereditary neuropathies are typically associated with an early onset of symptoms, but same types of neuropathies may also manifest late, after the age 50 years. A 62-year-old African American woman presented with a 6-year history of gait unsteadiness and has been using a walker since the age 57 years after an unwitnessed fall. Gradual worsening of walking difficulties was later followed by decreased dexterity. The family history was negative for neuromuscular disorders, including neuropathy. On examination, the patient had both distal and proximal weakness with distal sensory loss to all modalities and hyporeflexia. Charcot Marie Tooth Examination Score was 12. Previous electrodiagnostic testing at the age 60 years showed severe sensorimotor demyelinating polyneuropathy with bilateral severe carpal tunnel syndrome. Genetic testing showed a homozygous pathogenic mutation in SH3TC2 gene (c.2860C>T; p.Arg954*), associated with CMT4C. CMT4C is the most common recessive demyelinating sensorimotor polyneuropathy and overall comprises 0.4%-1.7% of all patients with Charcot-Marie-Tooth disease. It is more common in French Canadians and Spanish Roma and in recent natural history study; only 1 of 56 patients was African American. This report demonstrates sporadic occurrence of CMT4C in other ethnic groups as well.

Genetic and clinical characterization of Niemann-Pick disease type C with homozygous NPC1 gene mutation: insights from whole exome sequencing and advanced neuroimaging of two familial cases

Background: Niemann-Pick disease Type C (NPC) is a rare genetic lipid storage disorder characterized by heterogeneous clinical presentations primarily affecting the neurological and visceral systems. This study aims to elucidate the clinical manifestations, radiological findings, and genetic characteristics of NPC, emphasizing the implications of familial aggregation and consanguinity. Case Presentation: We present two cases from a single family, detailing the clinical progression, radiological findings, and genetic mutations. Case 1 involves a 39-year-old male exhibiting symptoms such as dysarthria, cerebellar ataxia, and progressive neurological decline over eight years. Case 2, a relative aged five, displays similar early-onset neurological symptoms. Both cases demonstrate significant cerebellar atrophy on MRI and share a familial NPC1 gene mutation, suggesting a hereditary pattern influenced by consanguineous relationships. Whole Exome Sequencing identified a pathogenic homozygous mutation in the NPC1 gene, confirming the diagnosis of NPC. This finding underscores the genetic basis of the disease and highlights the role of familial genetics in its pathogenesis. Conclusion: These cases underscore the critical role of genetic testing, particularly whole exome sequencing, in diagnosing NPC, which can often present with diverse clinical symptoms. The familial clustering observed also draws attention to the genetic counseling needs in populations with high rates of consanguinity, emphasizing the importance of community genetic studies to understand and manage such rare disorders.

Severe Neonatal Presentation of Progressive Familial Intrahepatic Cholestasis Type 4 in an Omani Infant

Progressive familial intrahepatic cholestasis type 4 (PFIC4) is a relatively newly described autosomal recessive disorder caused by biallelic mutations in the gene encoding tight junction protein 2 (TJP2) which is located in chromosome 9q21. PFIC4 is characterised by cholestasis with or without other extrahepatic manifestations. Bleeding tendency due to vitamin k deficiency is a well-known complication of cholestasis. We present a neonate who presented to the Emergency Department at a tertiary care hospital in 2021 with cholestasis and multiple intracranial bleeds. He was found to have severe coagulopathy and his genetic work up revealed a homozygous variant mutation in TJP2 gene causing PFIC4. He had persistent cholestasis that necessitated an internal biliary diversion with some clinical improvement. Keywords: Jaundice; Intracranial haemorrhage; Progressive Familial Intrahepatic Cholestasis type 4; Case Report; Oman.

A Descriptive Analysis of Patients with ABCG8 Mutation and Anemia. a Meta-Analysis and Systematic Review of an Uncommon Cause of Unexplained Anemia

Background Sitosterolemia is a rare inherited condition caused by elevated levels of plant sterols in the plasma. The genetic basis of the condition is characterized by homozygous and compound heterozygous mutations in ABCG5 and ABCG8 genes. The condition is very rare that information about this in literature is limited to case reports, case series and translational observational studies. A scarce occurrence in this already infrequent condition are hematological abnormalities such as hemolytic anemia, stomatocytosis, and macrothrombocytopenia. Basic details of the disease such are frequency of occurrence, demographic details of patients, and degree and type of anemia are not available. We conducted a meta-analysis and systematic review to answer these questions regarding patients who have hemolytic anemia and ABCG8 mutation. The study was also prompted by a clinical experience that our group encountered, of an adult male who had chronic severe hemolysis, at times requiring transfusion support, in whom, extensive investigation failed to reveal a cause for the hemolysis. The patient was ultimately found to have a mutation in the ABCG8 gene. Methods A controlled vocabulary encompassing ABCG8, sitosterolemia, phytosterolemia, anemia and hemolysis was used to perform a systematic search in PubMed, Embase, Scopus and Cochrane, from inception to July 2023. No restrictions on date, language, status, or outcomes were applied. 532 records were identified after duplicates were removed using Mendeley 1.19.8. The titles and abstracts were screened independently by 2 reviewers. We only included studies pertaining to patients with sitosterolemia, ABCG8 mutation and anemia of any cause or severity. Studies associated with ABCG5 mutation alone or lacked anemia were excluded. 13 reports were shortlisted for the final analysis (Observational studies-6, case series-4, case reports-3). Descriptive statistics were utilized to study the patient characteristics. The proportion of patients having both anemia and any ABCG8 mutation among all cases of sitosterolemia was determined using the DerSimonian-Laird random effects model with OpenMeta. Results From the 13 reports that we found in available literature, we identified 19 cases of ABCG8 mutation and anemia. From the random-effects proportions model, the chance of this event occurring among patients with sitosterolemia was 6.8% [0.068, 95% Confidence Interval (CI) 0.016-0.120, p=0.010] (I 2 24.68%) (14/145) (figure 1). Various characteristics of the cohort analyzed, including the different ABCG8 mutations, are summarized in figure 2. The mean age of the patients was 26 years (Age range: 0.1-61 years) and included neonates, pediatric, and adult patients. There were 7 females and 7 males among those whose sex were reported. 9/13 studies documented elevated sterols, while 8/13 clearly stated hemolysis as the cause of anemia. The hemoglobin ranged between 6.1 to 12.6 g/dl with a mean of 10.2 g/dl. Thrombocytopenia and stomatocytosis were frequently reported. Splenomegaly and xanthomas were other common associations. One example demonstrated an improvement in anemia after ezetimibe therapy, while splenectomy and supportive care was utilized in a couple of other reports to treat hemolysis. Conclusions To the best of our knowledge, we provide the first report of the prevalence of anemia, specifically in patients with sitosterolemia caused by a mutation in the ABCG8 gene. At 6.8%, this is an extremely rare occurrence in an already infrequent disease. A high index of suspicion is required to arrive at this diagnosis. The age distribution demonstrates a peculiar aspect of the disease, that it can occur very early in infancy, as well as in adults, likely triggered by environmental factors in an already predisposed patient. Unexplained hemolytic anemia, especially if associated with thrombocytopenia, splenomegaly and xanthomas should prompt testing for sterol levels and genomic sequencing to identify pathogenic variants of ABCG8 or ABCG5. The degree of anemia was mild in our analysis and hence unlikely to lead to significant mortality or morbidity. Heterogeneity between the various reports is a limitation of our analysis. While we specifically focused on ABCG8 and anemia, future research can also include ABCG5 related anemia and attempt to compare the two cohorts.

Targeting Nucleotide Biosynthesis Ameliorates Neutropenia in a Zebrafish Model of Dnajc21-Mutant Shwachman-Diamond Syndrome

Germline mutations in the ribosome maturation factors, SBDS, DNAJC21 and EFL1, lead to Shwachman-Diamond syndrome (SDS), a type of inherited bone marrow failure syndrome characterized by neutropenia, exocrine pancreatic insufficiency and growth restriction. Further, SDS patients have a 36% increased cumulative risk of developing myelodysplastic syndrome (MDS) and/or acute myeloid leukemia (AML) by 30 years of age. Given the rarity of SDS, large numbers of primary human samples are not readily available for mechanistic studies, warranting the use of animal models. Mouse and zebrafish models of SBDS mutations exhibit early lethality. In contrast, no in vivo models of DNAJC21 mutations have been published to date. We generated the first in vivo model of dnajc21 loss using zebrafish ( Danio rerio), given their highly conserved hematopoietic program and ease of genetic manipulation. Introduction of a homozygous deletion mutation in the zebrafish dnajc21 gene using CRISPR-Cas9 genomic editing resulted in stunted body growth and neutropenia, recapitulating hallmark SDS patient phenotypes. Whole-mount in situ hybridization for key hematopoietic lineage markers revealed reduced l-plastin +mature leukocytes and hbbe3 + mature erythrocytes in dnajc21 mutant embryos at 48 hours post-fertilization (hpf). A concomitant accumulation of myb + hematopoietic stem and progenitor cells (HSPCs) both in the dorsal aorta (equivalent to aorta-gonad-mesonephros) and the caudal hematopoietic tissue (fetal liver equivalent) was observed. Treatment of embryos with zebrafish granulocyte colony stimulating factor (gcsf) mRNA resulted in a modest expansion of neutrophils in dnajc21 mutant zebrafish compared to wildtype. Further, we observed reduced cell proliferation marked by phosphohistone-H3 (pH3) as well as low ATP:AMP levels measured by liquid chromatography/mass-spectrometry (LC/MS) in the dnajc21 mutants, suggesting a poor bioenergetic profile. At 4 months of age, flow cytometry and histopathological analysis identified reduced mature myelomonocytes and mild erythroid dysplasia in the whole kidney marrow (human bone marrow equivalent) of mutant fish. The link between TP53 somatic mutations and MDS/AML has been established in SBDS-mutant SDS, but has not been explored for DNAJC21-mutant SDS. We hence crossed our dnajc21 mutant zebrafish with a zebrafish line carrying a gain-of-function mutation (R217H) in the tp53 gene. Compound mutant fish had improved neutrophil counts but importantly, this was accompanied by an expansion of myeloid progenitors and significant erythroid dysplasia. To understand the disease mechanisms underlying the neutropenia and hypoproliferation in SDS, we performed bulk RNA sequencing of whole zebrafish larvae at 48 hpf. Biological processes such as oxidative stress response, drug catabolism and pre-mRNA spliceosome assembly were downregulated; whereas, acyl-CoA and nucleotide metabolism were upregulated in the mutants. In parallel, we performed untargeted metabolomics by LC/MS to determine the metabolic changes induced by dnajc21 loss. Upregulated pathways included urea cycle, amino acid and phenylacetate metabolism. Pyrimidine biosynthesis, including both the de novo and salvage pathways were downregulated in the mutants. Remarkably, exogenous supplementation with uridine or thymidine significantly improved neutrophil counts in the mutants. Our findings suggest that in dnajc21-mutant SDS1) neutropenia is caused by a combination of impaired granulocyte differentiation and cell proliferation; 2) the kidney marrow features myelodysplasia-like changes and 3) nucleotide biosynthesis may be a previously unrecognized therapeutic strategy in SDS.

Patients with Non-Transfusion-Dependent Thalassemia May Evolve to Transfusion-Dependent Thalassemia in Adulthood

Introduction: Non-transfusion-dependent thalassemia (NTDT) describes a prevalent and clinically heterogeneous group of patients in the United States. Adults with significant forms of NTDT display progressive age-related complications due to chronic anemia and ineffective erythropoiesis. While the importance of early diagnosis and close monitoring in pediatric patients with NTDT is well-established, the characteristics and complications of adults with NTDT in the United States is poorly described. Many adult patients with NTDT are managed by community providers who often have limited experience with this condition.This single-center observational study describes the clinical characteristics of patients with NTDT during their initial presentation to an adult thalassemia treatment center and identifies intervenable complications related to NTDT. Methods: We evaluated patients referred to the Penn Comprehensive Adult Thalassemia Program between 2013 and 2023 who carried a diagnosis of NTDT (defined as alpha or beta thalassemia and requiring fewer than 8 units of red cells in the 12 months preceding their initial visit). Data was collected via manual chart review. Clinical complications were defined as symptoms at presentation, history of splenectomy, hepatosplenomegaly, paraspinal masses, pulmonary hypertension, cardiac arrhythmia, endocrine complications (hypothyroidism, hypogonadism, diabetes, decreased bone mineral density), thrombotic events, and iron overload requiring chelation. Laboratory markers of disease severity included hemoglobin (Hgb), markers of hemolysis, nucleated red blood cells, serum ferritin and MRI quantitation of liver and cardiac iron. Results: Of the 94 patients with thalassemia referred to the Penn Comprehensive Adult Thalassemia Program, 34 carried a diagnosis of NTDT. Of these, 13 had α- thalassemia (deletional and non-deletional HbH), 19 had β-thalassemia variants (homozygous or double heterozygous β-globin gene mutations), and 2 had hemoglobin E/β-thalassemia. The median age at referral was 37.5 years (range 20-74); 71% were female. In general, patients with β-thalassemia had a larger number of significant complications than those with α-thalassemia. Overall, 11 patients (32%, all with β-thalassemia) had a history of splenectomy, 21 (62%) had evidence of extramedullary hematopoiesis with hepatosplenomegaly, and 7 (21%) had paraspinal masses. Pulmonary hypertension was seen in 5 of 21 patients with β-thalassemia and hemoglobin E/β-thalassemia (24%) while 4 patients overall (11%) had a history of thrombosis. The most common endocrinopathy was decreased bone mineral density (32%). Mean Hgb was 9.1 g/dL, however, 53% had a Hgb < 9 g/dL. Seven patients had an increase in nucleated red blood cells (range 161-1522 %) as a marker of ineffective erythropoiesis. Serum ferritin exceeded international NTDT guidelines for tissue evaluation (> 800 ng/mL) in 32% of patients; the mean ferritin for all patients was 897 ng/mL (range 45-7601 ng/mL). A liver MRI was obtained in 56% of patients with mean iron content of 25 mg/g dry weight (range 1.5 - 41.2 mg/g dry weight). No patients had evidence of cardiac iron overload. Of the 34 patients referred for NTDT, 14 (41%) met criteria to initiate a chronic transfusion regimen to maintain a pre-transfusion Hgb > 9.5 g/dL per established guidelines. Criteria included fatigue (all patients), extramedullary hematopoiesis (32%), Hgb < 7 g/dL (8%), and pulmonary hypertension (15%). Several patients had more than one indication for chronic transfusion. Conclusions: This is the first report of patients with NTDT in the United States that highlights clinically significant complications that accumulate in adults. Our results demonstrate a previously unknown high prevalence of conditions that warrant close monitoring, screening and intervention. Clinically, 41% of adult NTDT patients referred to our comprehensive adult thalassemia program met criteria to initiate a chronic transfusion program, a number that is significantly higher than previously published rates outside of the USA. These findings indicate a critical need for thalassemia education of adult providers that emphasizes the importance of monitoring for early complications of NTDT, as well as criteria for initiating a chronic transfusion program to mitigate complications and provide meaningful impacts in clinical outcomes.

Two cases of familial hypocalciuric hypercalcaemia (FHH) due to a homozygous CaSR gene mutation (c.-10C>T)

Two cases of familial hypocalciuric hypercalcaemia (FHH) due to a homozygous CaSR gene mutation (c.-10C>T)

"Progressive myoclonic ataxia and developmental/epileptic encephalopathy associated with a novel homozygous mutation in TCN2 gene".

Transcobalamin II (TCN2) defect is a rare metabolic disorder associated with a range of neurological manifestations, including mild developmental delay, severe intellectual disability, ataxia, and, in some cases, seizures. Cobalamin, an essential nutrient, plays a crucial role in central nervous system myelination. We present a family with an index patient who exhibited progressive neurodevelopmental regression starting at 9 months of age, accompanied by myoclonic seizures, ataxia, and tremor. No significant hematological abnormalities were observed. Exome sequencing analysis identified a novel homozygous mutation, c.3G>A - P(Met1I), affecting the acceptor site of intron 4 of the TCN2 gene (chromosome 22: 31003321, NM_000355.4), leading to likely pathogenic variant potentially affecting translation. Following treatment with hydroxocobalamin, the patient demonstrated partial clinical improvement. He has a sibling with overt hematological abnormalities and subtle neurological abnormalities who is homozygous to the same mutation. Both parents are heterozygous for the same mutation. In infants presenting with unexplained non-specific neurological symptoms, irrespective of classical signs of vitamin B12 deficiency, evaluation for TCN2 defect should be considered. Early diagnosis and appropriate management can lead to favorable outcomes.