Defining the Genetic Landscape of Congenital Mirror Movements in 80 Affected Individuals.

BACKGROUND: Congenital mirror movements (CMM) is a rare neurodevelopmental disorder characterized by involuntary movements from one side of the body that mirror voluntary movements on the opposite side. To date, five genes have been associated with CMM, namely DCC, RAD51, NTN1, ARHGEF7, and DNAL4. OBJECTIVE: The aim of this study is to characterize the genetic landscape of CMM in a large group of 80 affected individuals. METHODS: We screened 80 individuals with CMM from 43 families for pathogenic variants in CMM genes. In large CMM families, we tested for presence of pathogenic variants in multiple affected and unaffected individuals. In addition, we evaluated the impact of three missense DCC variants on binding between DCC and Netrin-1 in vitro. RESULTS: Causal pathogenic/likely pathogenic variants were found in 35% of probands overall, and 70% with familial CMM. The most common causal gene was DCC, responsible for 28% of CMM probands and 80% of solved cases. RAD51, NTN1, and ARHGEF7 were rare causes of CMM, responsible for 2% each. Penetrance of CMM in DCC pathogenic variant carriers was 68% and higher in males than females (74% vs. 54%). The three tested missense variants (p.Ile164Thr; p.Asn176Ser; and p.Arg1343His) bind Netrin-1 similarly to wild type DCC. CONCLUSIONS: A genetic etiology can be identified in one third of CMM individuals, with DCC being the most common gene involved. Two thirds of CMM individuals were unsolved, highlighting that CMM is genetically heterogeneous and other CMM genes are yet to be discovered. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

De Novo Pathogenic Variants in N-cadherin Cause a Syndromic Neurodevelopmental Disorder with Corpus Collosum, Axon, Cardiac, Ocular, and Genital Defects.

Cadherins constitute a family of transmembrane proteins that mediate calcium-dependent cell-cell adhesion. The extracellular domain of cadherins consists of extracellular cadherin (EC) domains, separated by calcium binding sites. The EC interacts with other cadherin molecules in cis and in trans to mechanically hold apposing cell surfaces together. CDH2 encodes N-cadherin, whose essential roles in neural development include neuronal migration and axon pathfinding. However, CDH2 has not yet been linked to a Mendelian neurodevelopmental disorder. Here, we report de novo heterozygous pathogenic variants (seven missense, two frameshift) in CDH2 in nine individuals with a syndromic neurodevelopmental disorder characterized by global developmental delay and/or intellectual disability, variable axon pathfinding defects (corpus callosum agenesis or hypoplasia, mirror movements, Duane anomaly), and ocular, cardiac, and genital anomalies. All seven missense variants (c.1057G>A [p.Asp353Asn]; c.1789G>A [p.Asp597Asn]; c.1789G>T [p.Asp597Tyr]; c.1802A>C [p.Asn601Thr]; c.1839C>G [p.Cys613Trp]; c.1880A>G [p.Asp627Gly]; c.2027A>G [p.Tyr676Cys]) result in substitution of highly conserved residues, and six of seven cluster within EC domains 4 and 5. Four of the substitutions affect the calcium-binding site in the EC4-EC5 interdomain. We show that cells expressing these variants in the EC4-EC5 domains have a defect in cell-cell adhesion; this defect includes impaired binding in trans with N-cadherin-WT expressed on apposing cells. The two frameshift variants (c.2563_2564delCT [p.Leu855Valfs∗4]; c.2564_2567dupTGTT [p.Leu856Phefs∗5]) are predicted to lead to a truncated cytoplasmic domain. Our study demonstrates that de novo heterozygous variants in CDH2 impair the adhesive activity of N-cadherin, resulting in a multisystemic developmental disorder, that could be named ACOG syndrome (agenesis of corpus callosum, axon pathfinding, cardiac, ocular, and genital defects).

Diagnostic Yield of Intellectual Disability Gene Panels.

BACKGROUND: Recent technological advances have improved the understanding and identification of the genetic basis of intellectual disability (ID) and global developmental delay (GDD). Next-generation sequencing panels of ID genes are now available for clinical testing; however, their overall yield in clinical practice has not yet been investigated. AIM: We determined the diagnostic yield of ID gene panels in a clinical setting and explored whether any clinical features are associated with an increased diagnostic yield. METHODS: We performed a systematic retrospective chart review of all patients with ID/GDD who underwent an ID gene panel between April 2014 and July 2017 at our institution. Chi-square analysis assessed whether any specific clinical features were significantly associated with a positive diagnostic yield. RESULTS: Forty-eight subjects (18 females, 30 males; median age: 7.5 years) were included. Consanguinity was present in 17%, autism in 38%, seizures in 42%, nonspecific dysmorphic features in 67%, and abnormalities on neurological examination in 56%; furthermore, 29% of the cohort was nonverbal and 4% was nonambulatory. Four different gene panels were used. The diagnostic yield was 21% (10/48) overall, and 38% with the more recent trio-based panel. Eight of 10 patients had de novo pathogenic dominant mutations, one had an inherited pathogenic autosomal dominant mutation, and one had compound heterozygous pathogenic recessive mutations. No clinical feature was significantly associated with an increased diagnostic yield. CONCLUSIONS: Our study suggests that ID gene panels have a high yield and are a valuable diagnostic tool in the evaluation of children with ID/GDD.

Oxidative status and plasma lipid profile in ß-thalassemia patients.

Abstract ß-Thalassemia (ß-thal) is a genetic disorder, representing a major health problem in Algeria. It is associated with altered lipid levels and a state of oxidative stress that can lead to cardiac complications and premature death. We examined the plasma lipid profile and redox status of 46 patients with ß-thal major (ß-TM) and ß-thal intermedia (ß-TI) compared to 36 healthy subjects. Plasma lipids including total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were investigated. Oxidative status was evaluated by measuring malondialdehyde (MDA), reduced glutathione (GSH) and catalase (CAT) activity. The potential relationships between these parameters and the hemoglobin (Hb) blood concentrations, serum ferritin, duration and frequency of transfusion, splenectomy as well as age, were examined. Our data indicated that the study patients were under increased state of oxidative stress associated with hypertriglyceridemia, and hypocholesterolemia. The CAT activity was negatively correlated with Hb concentration and LDL-C/TG ratio and positively with years of transfusion. The elevated TC/HDL-C ratio particularly in ß-TM patients who were younger, correlated positively with ferritinemia and triglyceride levels and suggested an increased coronary risk. This heightened risk state should lead to the inclusion of this index (TC/HDL-C) in clinical management, particularly in splenectomized patients.

Molecular heterogeneity of beta-thalassemia in Algeria: how to face up to a major health problem.

This study concerns the molecular characterization of beta-thalassemia (beta-thal) alleles in 210 chromosomes. In the studied population, mutations were detected in 98% of the beta-thalassemic chromosomes. Twenty-one molecular defects have been found, where the five dominant mutations, IVS-I-110 (G>A), nonsense mutation at codon 39 (C>T), the frameshift codon (FSC) 6 (-A), IVS-I-1 (G>A), and IVS-I-6 (T>C), account for 80% of the independent chromosomes. Among the remaining alleles, 16 different mutations were identified, half of them being described for the first time in Algeria. These include the -101 (C>T) and the -90 (C>T) mutations in the distal and proximal promoter elements, respectively, the FSC 8 (-AA), IVS-I-5 (G>T), IVS-I-128 (T>G), FSC 47 (+A), IVS-II-1 (G>A), and the substitution in the polyadenylation signal (poly A) site AATAAA>AATGAA. Haplotype analyses on rare variants were performed. The possible origin of these mutations either by founder effect or by migrations is discussed, and raises the question of an adequate strategy to be used adapted to socio-economical status.