Autosomal Recessive Inheritance Research Articles

Clinical and genetic analysis of three children with Hyperekplexia

To explore the clinical and genetic characteristics of three children with Hyperekplexia. Three children who were diagnosed with Hyperekplexia at the Third Affiliated Hospital of Zhengzhou University between June 2018 and March 2020 were selected as the study subjects. Clinical data of the three children were collected. All children were subjected to whole exome sequencing. Pathogenicity of candidate variants were verified by Sanger sequencing and bioinformatic analysis. The three children were all males, and had presented exaggerated startle reflexes and generalized stiffness in response to unexpected auditory or tactile stimulation, or had frequent traumatic falls following exaggerated startle. All children had shown positive nose-tapping reflex, though EEG and cranial MRI exams were all negative. Whole exome sequencing revealed that two children had harbored homozygous variants of the GLRB gene, of which the c.1017_c.1018insAG (p.G340Rfs*14) was unreported previously. The third child had harbored compound heterozygous variants of the GLRA1 gene, among which the c.1262T>A (p.IIe421Asn) variant showed an unreported autosomal recessive inheritance. All children had responded well to clonazepam treatment. Patients with Hyperekplexia have typical clinical manifestations. Early clinical identification and genetic analysis can facilitate their diagnosis.

Prevalence of pathogenic genetic variants in patients with gastric cancer ascertained through multi-gene panel testing.

10578 Background: Gastric cancer (GC) is the fourth leading cause of cancer-related deaths worldwide. The role of pathogenic/likely pathogenic variants (PVs) in cancer predisposition genes is not well understood. We aimed to assess the prevalence of PVs in GC patients undergoing germline genetic testing (GGT) via multi-gene panel testing (MGPT) at a large commercial laboratory. Methods: Retrospective review of MGPT (>10 genes) in GC patients at a large commercial laboratory (Invitae Corp.) from March 2015 to July 2023 was performed. GC included diffuse type, intestinal type or unspecified type, as provided by ordering clinicians. Association of patient characteristics with positive GGT results was assessed with logistic regression with a significance threshold of p < 0.05. Results: 3,706 GC patients underwent GGT(Table). Overall, 495 (13.4%) patients were found to carry ≥1 PV, including 29 patients with 2 PVs and 3 patients with 3 PVs. GGT was negative in 1,890 (51.0%) patients, 1,199 (32.4%) had a variant of uncertain significance-only and 121 (3.3%) carried a single PV in a gene associated with autosomal recessive inheritance. PVs were identified in 38 genes; 77.7% (385/495) were in a gene previously associated with GC, primarily the homologous recombination repair genes ( BRCA1, BRCA2, PALB2and ATM, 34.9%), the Hereditary Diffuse Gastric Cancer genes ( CDH1and CTNNA1, 19.6%) and mismatch repair genes ( MLH1, MSH2, MSH6, PMS2and EPCAM, 17.4%). Males were more likely to carry a PV than females (OR 1.4, 95% CI 1.1-1.7) and having a personal history of another cancer increased the odds of carrying a PV (OR 1.3, 95% CI 1.0-1.7). Age, number of genes tested and histology were not significantly associated with PV. Conclusions: In this large study of GGT in GC patients, the prevalence of PVs in cancer associated genes was 13.4%, higher than previous estimates of 3-5%. PVs were predominantly in genes associated with GC. Male sex and history of other cancers were associated with a PV. Limitations include incomplete histologic data, varying panel size, and ascertainment bias as patients may have had additional personal/family history that prompted GGT. These results support consideration of GGT in all GC patients as prevalence of PVs is similar to other cancer types for which guidelines recommend universal genetic testing.[Table: see text]

Distinct neurological phenotypes associated with biallelic loss of NOTCH3 function: evidence for recessive inheritance.

NOTCH3 variants are known to be linked to cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). However, some null NOTCH3 variants with homozygous inheritance cause neurological symptoms distinct from CADASIL. The aim of this study was to expand the clinical spectrum of this distinct condition and provide further evidence of its autosomal recessive inheritance. Whole exome sequencing (WES) was performed on a proband who exhibited livedo racemosa, ataxia, cognitive decline, seizures, and MRI white matter abnormalities without anterior temporal pole lesions. Segregation analysis was conducted with Sanger sequencing. WES of the proband identified a novel homozygous NOTCH3 null variant (c.2984delC). The consanguineous parents were confirmed as heterozygous variant carriers. In addition, three heterozygous NOTCH3 null variants were reported as incidental findings in three unrelated cases analyzed in our center. The findings of this study suggest an autosomal recessive inheritance pattern in this early-onset leukoencephalopathy, in contrast to CADASIL's dominant gain-of-function mechanism; which is a clear example of genotype-phenotype correlation. Comprehensive genetic analysis provides valuable insights into disease mechanisms and facilitates diagnosis and family planning for NOTCH3-associated neurological disorders.

First report of Mycobacterium chimaera infection in a patient with chronic granulomatous disease

Chronic granulomatous disease (CGD) is an inborn error of immunity (IEI). NADPH oxidase is an enzyme complex that produces various reactive oxygen species, such as superoxide anions and hydrogen peroxide. Pathogenic variants in cytochrome B (CYB)-B, CYBA, CYBC1, neutrophil cytosolic factor (NCF)-1, NCF2, and NCF4 genes of the NADPH oxidase enzyme complex are responsible for the clinical phenotype of CGD [1]. CGD has an X-linked or autosomal recessive inheritance pattern [1]. Patients with CGD present with various inflammatory and infectious diseases [1]. They are susceptible to fungal and bacterial infections, including mycobacterial infections [1]. Mycobacterium tuberculosis infections have been observed in Bacillus Calmette–Guérin (BCG)-vaccinated patients with CGD [2]. Mycobacterial infections in CGD are commonly observed in countries with a high prevalence of these microorganisms, such as those receiving the BCG vaccination at birth or those with a high prevalence of tuberculosis [2]. Nontuberculous mycobacterial (NTM) infections are rare in CGD [2]. Here, we described the first M. chimaera infection in a female patient with autosomal recessive CGD caused by a pathogenic variant in CYBA.

Modelling of a RYR2-associated left ventricular non-compaction and sudden cardiac death overlap syndrome in hiPSC-EHTs

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ESC training grant; DZHK Background Genetic cardiomyopathies contribute to a significant proportion of morbidity and mortality among young people. Over the past decades, a wide range of underlying molecular mechanisms has been discovered. The current project arose from the clinical observation of a left ventricular non-compaction and sudden cardiac death overlap syndrome in a large family in northern Italy. Whole exome sequencing performed on family members of different generations revealed a single nucleotide polymorphism in the RYR2 gene (RYR2 c.5654G>A homozygous – RyR2 p.G1885E - exon37:missense) with an autosomal-recessive inheritance pattern. The mutation is localized in the DR3 region of the RyR2 protein, adjacent to the FKBP12.6 binding site, a protein that is known to stabilize RyR2, preventing aberrant activation of the channel. Methods and Results Patient-derived, human induced pluripotent stem cells (hiPSCs), carrying the variant homo- and heterozygously, were generated by reprogramming patient-derived peripheral blood mononuclear cells using a non-integrative Sendai virus protocol. The lines were fully characterized and expressed high levels of pluripotency markers at the RNA and protein level. Patient lines were all able to efficiently differentiate into cardiomyocytes. Subsequently, 3D strip-format, force-generating Engineered Heart Tissues (EHTs) were cast and structurally and functionally characterized. Contraction analysis over 60 days showed differences in force development of the patient-derived lines. In particular, the EHTs carrying the homozygous pathogenic variant showed progressive reduction in both beating rate and force over time, increased spontaneous arrhythmogenicity and reduced inotropic response after exposure to isoprenaline, compared to the heterozygous line and unrelated healthy controls. Starting from day 30 after casting, patient-derived EHTs developed morphological changes with areas of marked cellular overgrowth and reduced troponin expression. Transcriptomic and proteomic analysis at 30 and 60 days after EHTs generation, as well as in 2D cardiomyocytes, complement the phenotyping and provide molecular insights into the underlying pathophysiology. To directly evaluate pathogenicity of the genetic variant identified, we generated isogenic homo- and heterozygously corrected hiPSCs, using CRISPR/ Cas9 technology, starting from the homozygous patient-line. The characterization of these corrected clones is currently ongoing. The genetically corrected 3D tissue models will be critical not only in defining the role of the novel RyR2 variant in the familial phenotype described, but also to unveil mechanistic roles of ryanodine receptor in cardiac disease. Conclusion We describe a novel recessive RYR2 variant associated with a left ventricular non- compaction and sudden cardiac death overlap syndrome. 3D cardiac tissue modelling based on patient-derived hiPSCs uncovered a proarrhythmic and structural phenotype of the mutated lines.

Patients and mice with deficiency in the SNARE protein SYNTAXIN-11 have a secondary B cell defect.

SYNTAXIN-11 (STX11) is a SNARE protein that mediates the fusion of cytotoxic granules with the plasma membrane at the immunological synapses of CD8 T or NK cells. Autosomal recessive inheritance of deleterious STX11 variants impairs cytotoxic granule exocytosis, causing familial hemophagocytic lymphohistiocytosis type 4 (FHL-4). In several FHL-4 patients, we also observed hypogammaglobulinemia, elevated frequencies of naive B cells, and increased double-negative DN2:DN1 B cell ratios, indicating a hitherto unrecognized role of STX11 in humoral immunity. Detailed analysis of Stx11-deficient mice revealed impaired CD4 T cell help for B cells, associated with disrupted germinal center formation, reduced isotype class switching, and low antibody avidity. Mechanistically, Stx11-/- CD4 T cells exhibit impaired membrane fusion leading to reduced CD107a and CD40L surface mobilization and diminished IL-2 and IL-10 secretion. Our findings highlight a critical role of STX11 in SNARE-mediated membrane trafficking and vesicle exocytosis in CD4 T cells, important for successful CD4 T cell-B cell interactions. Deficiency in STX11 impairs CD4 T cell-dependent B cell differentiation and humoral responses.

Homozygous mutation of OCLN gene in Pseudo-TORCH Syndrome Type I : A Case Report

Clinical similarities of TORCH syndrome but serological negative findings for an infectious agent named it Pseudo-TORCH syndrome, which follows autosomal recessive inheritance but it has genetic heterogeneity. Here we reported a case of 11 month old girl of consanguineous parent with psychomotor retardation, microcephaly and intracranial calcifications but she was serologically negative for TORCH infection and positive for homozygous mutation in the gene encoding occluding (OCLN) on chromosome 5. BANGLADESH J CHILD HEALTH 2022; VOL 46 (2) : 95-97

Cystic fibrosis in childhood and adulthood

Cystic fibrosis (CF, or mucoviscidosis) is one of the rare diseases with a fatal course and with the highest prevalence. Formerly known as apurely childhood disease, this multisystemic disease follows an autosomal recessive inheritance pattern and results in amalfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) channel, leading to the production of viscous secretions. The prognosis and outcome of CF are determined by the severity of the involvement of the lungs. Other typically affected organs include the pancreas, liver and intestines. This article reviews the clinical presentation and evolution of CF with afocus on the new era of the highly effective CFTR modulator treatment. An overview of the current state of knowledge on the care for CF patients is presented. The introduction of the CF newborn screening, the increased understanding of the disease and the development of novel treatment options have substantially increased the quality of life and life expectancy of people with CF. As aresult, more than half of CF patients in Germany are now older than 18years of age and the complications of a chronic disease as well as organ damage due to the intensive treatment are gaining in importance. The highly effective CFTR modulator treatment results in a significant improvement in CFTR function, lung function, body mass index and quality of life and is available to approximately 90% of patients in Germany, based on the genotype. Nevertheless, further research including the development of causal treatment, e.g., gene therapy, targeting the underlying defect in the remaining 10% of CF patients, is urgently needed. Even in adult patients, CF with a mild course or aCFTR-related disease should be considered, e.g., in cases of bronchiectasis and/or recurrent abdominal complaints.

Genetic and clinical profile of 15 Chinese families with GDAP1-related Charcot-Marie-Tooth disease and identification of H256R as a frequent mutation.

Mutations in ganglioside-induced differentiation-associated protein 1 (GDAP1) cause axonal or demyelinating Charcot-Marie-Tooth disease (CMT) with autosomal dominant or recessive inheritance. In this study, we aim to report the genotypic and phenotypic features of GDAP1-related CMT in a Chinese cohort. Clinical, neurophysiological, genetic data, and available muscle/brain imaging information of 28 CMT patients with GDAP1 variants were retrospectively collected. We identified 16 GDAP1 pathogenic variants, among which two novel variants c.980dup(p.L328FfsX25) and c.480+4T>G were first reported. Most patients (16/28) presented with AR or AD CMT2K phenotype. Clinical characteristics in our cohort demonstrated that the AR patients presented earlier onset, more severe phenotype compared with the AD patients. Considerable intra-familial phenotypic variability was observed among three AD families. Muscle atrophy and fatty infiltration in the lower extremity were detected by Muscle magnetic resonance imaging (MRI) scans in four patients. MRI showed two AR patients showed more severe muscle involvement of the posterior compartment than those of the anterolateral compartment in the calf. One patient carrying Q38*/H256R variants accompanied with mild periventricular leukoaraiosis. In this study, we conducted an analysis of clinical features of the GDAP1-related CMT patients, expanded the mutation spectrum in GDAP1 by reporting two novel variants, and presented the prevalent occurrence of the H256R mutation in China. The screening of GDAP1 should be particularly emphasized in Chinese patients with CMT2, given the incomplete penetrance and pathogenic inheritance patterns involving dominant and recessive modes.

Two case reports of a novel missense mutation in the PNPLA6 gene in two siblings with chorioretinal dystrophy, hypogonadotropic hypogonadism, and cerebellar ataxia.

Boucher Neuhäuser Syndrome (BNS) is a rare disease with autosomal recessive inheritance defined by the classical triad; early-onset ataxia, hypogonadism and chorioretinal dystrophy. We present two siblings diagnosed with BNS at midlife, identified with homozygous state of a novel PNPLA6 missense mutation. One healthy sibling and the mother were heterozygous carriers of the mutation. The proband presented with the classical triad and the other sibling presented with visual problems at first. The proband was referred to our department by a private Neurologist, in early adulthood, because of hypogonadism, cerebellar ataxia, axonal neuropathy, and chorioretinal dystrophy for further evaluation. The sibling was referred to our department for evaluation, at childhood, due to visual problems. Later, the patient displayed the triad of ataxia, hypogonadotropic hypogonadism, and chorioretinal dystrophy. The unusual medical history of the two siblings led to further examinations and eventually the diagnosis of the first BNS cases in Cyprus. WES-based ataxia in silico gene panel analysis revealed 15 genetic variants and further filtering analysis revealed the PNPLA6 c.3323G > A variant. Segregation analysis in the family with Sanger sequencing confirmed the PNPLA6 homozygous variant c.3323G > A, p.Arg1108Gln in exon 29. This highlights the importance of considering rare inherited causes of visual loss, spinocerebellar ataxia, or/and HH in a neurology clinic and the significant role of genetic sequencing in the diagnostic process.

Understanding Pediatric Hemoglobinopathies: Epidemiology, Genetics, and Management Strategies

Children's hemoglobinopathies, such as thalassemias and sickle cell disease (SCD), present a diverse range of symptoms and complex genetic causes, which provide significant challenges for therapy. This website provides comprehensive information on the genetics, prevalence, and many treatment options available for baby hemoglobinopathies. Research in global epidemiology suggests that individuals suffer from a diverse array of ailments. Therefore, it is crucial to prioritize targeted screening programs and medicines. Understanding the fundamental concepts of basic genetics, such as autosomal recessive inheritance patterns and specific gene mutations, is crucial for developing precise diagnostic tools and personalized treatment strategies. Comprehensive management strategies encompass several approaches such as providing supportive care, utilizing pharmaceutical therapy, and implementing advanced techniques like gene therapy for treating disorders. Due to continuous research that enhances our comprehension of hemoglobinopathies, we should expect improved results and an enhanced standard of living for individuals affected by them. The purpose of this study is to enhance our comprehension of pediatric hemoglobinopathies and our approach to therapy by gathering the perspectives of epidemiology, genetics, and clinical practice.

Syndromic Retinitis Pigmentosa: A 15-Patient Study.

Retinitis pigmentosa is a group of genetically determined retinal dystrophies characterized by primary photoreceptor apoptosis and can occur in isolated or syndromic conditions. This study reviewed the clinical data of 15 patients with syndromic retinitis pigmentosa from a Rare Disease Reference Center in Brazil and the results of their next-generation sequencing tests. Five males and ten females participated, with the mean ages for ocular disease onset, fundoscopic diagnosis, and molecular evaluation being 9, 19, and 29 years, respectively. Bardet-Biedl syndrome (n = 5) and Usher syndrome (n = 3) were the most frequent diagnoses, followed by other rare conditions. Among the patients, fourteen completed molecular studies, with three negative results and eleven revealing findings in known genes, including novel variants in MKKS (c.432_435del, p.Phe144Leufs*14), USH2A (c.(7301+1_7302-1)_(9369+1_9370-1)del), and CEP250 (c.5383dup, p.Glu1795Glyfs*13, and c.5050del, p.Asp1684Thrfs*9). Except for Kearn-Sayre, all presented an autosomal recessive inheritance pattern with 64% homozygosity results. The long gap between symptom onset and diagnosis highlights the diagnostic challenges faced by the patients. This study reaffirms the clinical heterogeneity of syndromic retinitis pigmentosa and underscores the pivotal role of molecular analysis in advancing our understanding of these diseases.

The prevalence and clinical features of MYO7A-related hearing loss including DFNA11, DFNB2 and USH1B

The MYO7A gene is known to be responsible for both syndromic hearing loss (Usher syndrome type1B:USH1B) and non-syndromic hearing loss including autosomal dominant and autosomal recessive inheritance (DFNA11, DFNB2). However, the prevalence and detailed clinical features of MYO7A-associated hearing loss across a large population remain unclear. In this study, we conducted next-generation sequencing analysis for a large cohort of 10,042 Japanese hearing loss patients. As a result, 137 patients were identified with MYO7A-associated hearing loss so that the prevalence among Japanese hearing loss patients was 1.36%. We identified 70 disease-causing candidate variants in this study, with 36 of them being novel variants. All variants identified in autosomal dominant cases were missense or in-frame deletion variants. Among the autosomal recessive cases, all patients had at least one missense variant. On the other hand, in patients with Usher syndrome, almost half of the patients carried biallelic null variants (nonsense, splicing, and frameshift variants). Most of the autosomal dominant cases showed late-onset progressive hearing loss. On the other hand, cases with autosomal recessive inheritance or Usher syndrome showed congenital or early-onset hearing loss. The visual symptoms in the Usher syndrome cases developed between age 5–15, and the condition was diagnosed at about 6–15 years of age.

Genetic aspects of ataxias in a cohort of Turkish patients.

Ataxia is one of the clinical findings of the movement disorder disease group. Although there are many underlying etiological reasons, genetic etiology has an increasing significance thanks to the recently developing technology. The aim of this study is to present the variants detected in WES analysis excluding non-genetic causes, in patients with ataxia. Thirty-six patients who were referred to us with findings of ataxia and diagnosed through WES or other molecular genetic analysis methods were included in our study. At the same time, information such as the onset time of the complaints, consanguinity status between parents, and the presence of relatives with similar symptoms were evaluated. If available, the patient's biochemical and radiological test results were presented. Thirty-six patients were diagnosed through WES or CES. The rate of detected autosomal recessive inheritance disease was 80.5%, while that of autosomal dominant inheritance disease was 19.5%. Abnormal cerebellum was detected on brain MRI images in 26 patients, while polyneuropathy was detected on EMG in eleven of them. While the majority of the patients were compatible with similar cases reported in the literature, five patients had different/additional features (variants in MCM3AP, AGTPBP1, GDAP2, and SH3TC2 genes). The diagnosis of ataxia patients with unknown etiology is made possible thanks to these clues. Consideration of a genetic approach is recommended in patients with ataxia of unknown etiology.

Deciphering the Genomic Complexity of Acromesomelic Dysplasia Type Maroteaux: Insights from a Consanguineous Pakistani Family

Purpose: This study delves into the genetic basis of Acromesomelic Dysplasia (AMD), a rare skeletal disorder, particularly focusing on the Maroteaux type within a consanguineous Pakistani family. The purpose is to explore the genetic landscape beyond known mutations and understand the underlying causes of AMD.
 Methodology: A comprehensive approach was adopted, combining detailed clinical examinations with advanced genomic methodologies. Ethical clearance was obtained, and pedigree design facilitated the identification of affected individuals. Molecular techniques including DNA extraction and linkage analysis were conducted to investigate known AMD-related genes such as NPR2, BMPR1B, GDF5, GALNS, GLB1, and GHR. Whole-genome sequencing was emphasized despite financial constraints to uncover potential novel genetic loci associated with AMD.
 Findings: Despite exhaustive analysis, no mutations in known AMD-related genes were identified within the studied family. Linkage analysis did not correlate with any known genetic loci, suggesting the presence of unidentified genetic elements contributing to AMD. Autosomal recessive inheritance was confirmed through pedigree and molecular scrutiny, highlighting the complexity of AMD genetics.
 Unique Contribution to Theory, Policy and Practice: This research underscores the importance of employing advanced genomic strategies, such as whole-genome sequencing, in decoding rare genetic disorders like AMD. By revealing the limitations of current diagnostic approaches and advocating for collaborative efforts and resource pooling, this study contributes to the advancement of genetic counseling, therapeutic interventions, and precision medicine in rare genetic disorders.

Screening of Spinal Muscular Atrophy Carriers and Prenatal Diagnosis in Pregnant Women in Yancheng, China.

Spinal muscular atrophy (SMA) is a neuromuscular disorder with an autosomal recessive inheritance pattern. Patients with severe symptoms may suffer respiratory failure, leading to death. The homozygous deletion of exon 7 in the SMN1 gene accounts for nearly 95% of all cases. Population carrier screening for SMA and prenatal diagnosis by amniocentesis for high-risk couples can assist in identifying the risk of fetal disease. We provided the SMA carrier screening process to 55,447 pregnant women in Yancheng from October 2020 to December 2022. Among them, 8185 participated in this process, with a participation rate of around 14.76% (95% CI 14.47-15.06%). Quantitative real-time polymerase chain reaction (qPCR) was used to detect deletions of SMN1 exons 7 and 8 (E7, E8) in screened pregnant women. 127 were identified as carriers (111 cases of E7 and E8 heterozygous deletions, 15 cases of E7 heterozygous deletions, and 1 case of E7 heterozygous deletions and E8 homozygous deletions), resulting in a carrying rate of around 1.55% (95% CI 1.30-1.84%). After genetic counseling, 114 spouses of pregnant women who tested positive underwent SMA carrier screening; three of them were screened as SMA carriers. Multiplexed ligation-dependent probe amplification (MLPA) was used for the prenatal diagnosis of the fetuses of high-risk couples. Two of them exhibited two copies of SMN1 exon 7 (normal), and the pregnancy was continued; one exhibited no copies of SMN1 exon 7 and exon 8 (SMA patient), and the pregnancy was terminated. Analyzing SMN1 mutations in Yancheng and provide clinical evidence for SMA genetic counseling and birth defect prevention. Interventional prenatal diagnosis for high-risk families can promote informed reproductive selection and prepare for the fetus's early treatment.

A novel homozygous missense mutation in the RPE65 gene in an Iranian family with retinitis pigmentosa

Hereditary retinal dystrophies such as retinitis pigmentosa (RP) are genetically and phenotypically heterogeneous and result in total blindness. One of the key genes causing RP is RPE65. In 2017, a gene therapy drug, voretigene neparvovec-rzyl, for RP associated with RPE65 mutations, received Food and Drug Administration approval. So, identification of RPE65 gene mutations in affected patients which may be amenable to genetic treatment is critical. Here, we examine three related Iranian patients with RP which have not been previously described in the population. Whole exome sequencing (WES) using next-generation Illumina sequencing was utilized to identify the disease-causing mutation in the proband. Subsequently, Sanger sequencing was performed to confirm the identified mutation in the patients and their family members. Finally, the possible effect of the reported mutation on the target protein was also evaluated using bioinformatics tools. WES identified a novel homozygous missense mutation c.T170C: p.F57S in exon 3 of the RPE65 gene. Sanger sequencing confirmed the mutation found in the patients and their healthy family members. This mutation segregated with the autosomal recessive inheritance pattern of RP disorder. Furthermore, the pathogenic nature of the identified mutation was confirmed by in silico approaches and genotype-phenotype correlation analysis. Our findings revealed a novel missense mutation c.T170C: p.F57S in the RPE65 gene and could expand the pathogenic mutations spectrum of the RPE65 gene. Additionally, such studies can aid to conduct genetic counseling, prenatal diagnosis, clinical management and even genetic treatment more accurately for all affected patients with RPE65 gene mutations.

Novel compound heterozygous variants in LTBP2 associated with relative anterior microphthalmos.

Relative anterior microphthalmos (RAM) is a rare congenital defect associated with severe vision impairment that is primarily caused by genetic alterations. The purpose of this study was to identify the causative genetic variants in two Chinese families with RAM with an autosomal recessive inheritance pattern. DNA samples were obtained from two probands and their family members. Targeted next-generation sequencing (NGS) was used to screen 425 genes associated with inherited eye diseases to identify possible disease-causing variants in the two patients. Sanger sequencing was subsequently used to validate the results in both families. The targeted NGS panel identified potentially causative novel variants of the latent transforming growth factor beta binding protein 2 (LTBP2) gene in the two RAM families: a missense variant (c.2771C > T; p.Ala924Val) and an intronic variant (c.4582 + 9A > G) in Family A and a different missense variant (c.5239C > A; p.Arg1747Ser) and a synonymous variant (c.951G > A; p.Pro317Pro) in Family B. These four novel variants all cosegregated with the disease phenotype. To our knowledge, this is the first study to report novel LTBP2 gene variants related to RAM. Considering the importance of LTBP2 in ocular development, we provide initial insights into the potential pathogenic mechanisms of LTBP2 in RAM.

Expanding the genetic and phenotypic spectrum of TRAPPC9 and MID2-related neurodevelopmental disabilities: report of two novel mutations, 3D-modelling, and molecular docking studies.

Intellectual disabilities (ID) and autism spectrum disorders (ASD) have a variety of etiologies, including environmental and genetic factors. Our study reports a psychiatric clinical investigation and a molecular analysis using whole exome sequencing (WES) of two siblings with ID and ASD from a consanguineous family. Bioinformatic prediction and molecular docking analysis were also carried out. The two patients were diagnosed with profound intellectual disability, brain malformations such as cortical atrophy, acquired microcephaly, and autism level III. The neurological and neuropsychiatric examination revealed that P2 was more severely affected than P1, as he was unable to walk, presented with dysmorphic feature and exhibited self and hetero aggressive behaviors. The molecular investigations revealed a novel TRAPPC9 biallelic nonsense mutation (c.2920 C > T, p.R974X) in the two siblings. The more severely affected patient (P2) presented, along with the TRAPPC9 variant, a new missense mutation c.166 C > T (p.R56C) in the MID2 gene at hemizygous state, while his sister P1 was merely a carrier. The 3D modelling and molecular docking analysis revealed that c.166 C > T variant could affect the ability of MID2 binding to Astrin, leading to dysregulation of microtubule dynamics and causing morphological abnormalities in the brain. As our knowledge, the MID2 mutation (p.R56C) is the first one to be detected in Tunisia and causing phenotypic variability between the siblings. We extend the genetic and clinical spectrum of TRAPPC9 and MID2 mutations and highlights the possible concomitant presence of X-linked as well as autosomal recessive inheritance to causing ID, microcephaly, and autism.

Biallelic variants in Plexin B2 (PLXNB2) cause amelogenesis imperfecta, hearing loss and intellectual disability

BackgroundPlexins are large transmembrane receptors for the semaphorin family of signalling proteins. Semaphorin-plexin signalling controls cellular interactions that are critical during development as well as in adult life stages. Nine...