genomic rearrangements in a 391 French bilateral periventricular nodular heterotopia cohort: prevalence and phenotypic correlations.

Background: loss of function manifests across a broad spectrum of phenotypes, ranging from severe prenatal onset to asymptomatic cases. Bilateral periventricular nodular heterotopia (BPNH) consistently occurs in affected individuals. This retrospective study involving French patients with BPNH evaluates the prevalence of gene dosage anomalies and investigates genotype-phenotype correlations in a large cohort of French patients with BPNH.

From spastic paraplegia to infantile neurodegenerative disorder: Expanding the phenotypic spectrum associated with biallelic SPAST variants.

Purpose: Heterozygous pathogenic variants in SPAST are known to cause Hereditary Spastic Paraplegia 4 (SPG4), the most common form of HSP, characterized by progressive bilateral lower limbs spasticity with frequent sphincter disorders. However, there are very few descriptions in the literature of patients carrying biallelic variants in SPAST.

Methods: Targeted Sanger sequencing, panel sequencing and exome sequencing were used to identify the genetic causes in 9 patients from 6 unrelated families with symptoms of HSP or infantile neurodegenerative disorder.

Intensification of Diurnal Abnormal Movements During Sleep in Huntington's Disease.

Huntington's disease (HD) is a rare neurodegenerative disorder with a distinct phenotype, including involuntary movements, cognitive decline, and behavioral disturbances. Sleep disorder include insomnia, increased sleep onset latency, decrease in total sleep time with frequent nocturnal awakenings and excessive daytime sleepiness. Increased sleep motor activities and abnormal nocturnal agitation have been increasingly recognized as an important component affecting negatively the sleep quality.

CAG repeat mosaicism is gene specific in spinocerebellar ataxias.

Expanded CAG repeats in coding regions of different genes are the most common cause of dominantly inherited spinocerebellar ataxias (SCAs). These repeats are unstable through the germline, and larger repeats lead to earlier onset. We measured somatic expansion in blood samples collected from 30 SCA1, 50 SCA2, 74 SCA3, and 30 SCA7 individuals over a mean interval of 8.

Upstream open reading frame-introducing variants in patients with primary familial brain calcification.

More than 50% of patients with primary familial brain calcification (PFBC), a rare neurological disorder, remain genetically unexplained. While some causative genes are yet to be identified, variants in non-coding regions of known genes may represent a source of missed diagnoses. We hypothesized that 5'-Untranslated Region (UTR) variants introducing an AUG codon may initiate mRNA translation and result in a loss of function in some of the PFBC genes.

Mutation on MT-CO2 gene induces mitochondrial disease associated with neurodegeneration and intracerebral iron accumulation (NBIA).

Mitochondrial diseases are genetic disorders impairing mitochondrial functions. Here we describe a patient with a neurodegenerative condition associated with myopia, bilateral sensorineural hearing loss and motor disorders. Brain MRIs showed major cortico-subcortical and infra-tentorial atrophies, as well as intracerebral iron accumulation and central calcifications, compatible with a NBIA-like phenotype.

Autosomal Dominant MPAN: Mosaicism Expands the Clinical Spectrum to Atypical Late-Onset Phenotypes.

Background: Mitochondrial membrane protein-associated neurodegeneration (MPAN) is caused by mutations in the C19orf12 gene. MPAN typically appears in the first two decades of life and presents with progressive dystonia-parkinsonism, lower motor neuron signs, optic atrophy, and abnormal iron deposits predominantly in the basal ganglia. MPAN, initially considered as a strictly autosomal recessive disease (AR), turned out to be also dominantly inherited (AD).

White matter abnormalities in 15 subjects with SPG76.

Background And Objectives: Hereditary spastic paraplegias (HSPs) are heterogenous genetic disorders characterized by progressive pyramidal tract involvement. SPG76 is a recently identified form of HSP, caused by biallelic calpain-1 (CAPN1) variants. The most frequently described MRI abnormality in SPG76 is mild cerebellar atrophy and non-specific white matter abnormalities were reported in only one case.

Extreme phenotypic heterogeneity in non-expansion spinocerebellar ataxias.

Although the best-known spinocerebellar ataxias (SCAs) are triplet repeat diseases, many SCAs are not caused by repeat expansions. The rarity of individual non-expansion SCAs, however, has made it difficult to discern genotype-phenotype correlations. We therefore screened individuals who had been found to bear variants in a non-expansion SCA-associated gene through genetic testing, and after we eliminated genetic groups that had fewer than 30 subjects, there were 756 subjects bearing single-nucleotide variants or deletions in one of seven genes: CACNA1A (239 subjects), PRKCG (175), AFG3L2 (101), ITPR1 (91), STUB1 (77), SPTBN2 (39), or KCNC3 (34).

Renal involvement is frequent in adults with primary mitochondrial disorders: an observational study.

Background: Mitochondrial functions are controlled by genes of both mitochondrial and nuclear DNA. Pathogenic variants affecting any of these are responsible for primary mitochondrial disorders (MIDs), which can be diagnosed during adulthood. Kidney functions are highly dependent on mitochondrial respiration.

Intermediate repeat expansions of TBP and STUB1: Genetic modifier or pure digenic inheritance in spinocerebellar ataxias?

Purpose: CAG/CAA repeat expansions in TBP are responsible for spinocerebellar ataxia (SCA) type 17 (SCA17). We previously detected cosegregation of STUB1 variants causing SCA48 with intermediate alleles of TBP in 2 families. This cosegregation questions the existence of SCA48 as a monogenic disease.

The burden of Huntington's disease: A prospective longitudinal study of patient/caregiver pairs.

Background: Caregiver burden is widely recognized in Huntington's disease, but little is known about the factors determining its evolution over time in the absence of longitudinal studies. Our objective was to identify typical patterns of caregiver burden level and evolution using both patients' and caregivers' characteristics over a one-year period to identify potential levers for alleviation.

Methods: We conducted a prospective multicenter longitudinal study in caregiver/patient pairs in Huntington's disease (NCT02876445) between March 2011 and May 2015.

Noninvasive prenatal diagnosis of genetic diseases induced by triplet repeat expansion by linked read haplotyping and Bayesian approach.

The field of noninvasive prenatal diagnosis (NIPD) has undergone significant progress over the last decade. Direct haplotyping has been successfully applied for NIPD of few single-gene disorders. However, technical issues remain for triplet-repeat expansions.

KCNQ2 R144 variants cause neurodevelopmental disability with language impairment and autistic features without neonatal seizures through a gain-of-function mechanism.

Background: Prior studies have revealed remarkable phenotypic heterogeneity in KCNQ2-related disorders, correlated with effects on biophysical features of heterologously expressed channels. Here, we assessed phenotypes and functional properties associated with KCNQ2 missense variants R144W, R144Q, and R144G. We also explored in vitro blockade of channels carrying R144Q mutant subunits by amitriptyline.

From Negative to Positive Diagnosis: Structural Variation Could Be the Second Mutation You Are Looking for in a Recessive Autosomal Gene.

Next-generation sequencing (NGS) allows the detection of plentiful mutations increasing the rate of patients getting a positive diagnosis. However, while single-nucleotide variants (SNVs) or small indels can be easily detected, structural variations (SVs) such as copy number variants (CNVs) are often not researched. In Charcot-Marie-Tooth disease (CMT), the most common hereditary peripheral neuropathy, the -duplication was the first variation detected.

Whole-exome sequencing confirms implication of VPS13D as a potential cause of progressive spastic ataxia.

Background: VPS13D is a large ubiquitin-binding protein playing an essential role in mitophagy by regulating mitochondrial fission. Recently, VPS13D biallelic pathogenic variants have been reported in patients displaying variable neurological phenotypes, with an autosomic recessive inheritance. The objectives of the study were to determine the genetic etiology of a patient with early onset sporadic progressive spastic ataxia, and to investigate the pathogenicity of VPS13D variants through functional studies on patient's skin fibroblasts.

Safety and efficacy of riluzole in spinocerebellar ataxia type 2 in France (ATRIL): a multicentre, randomised, double-blind, placebo-controlled trial.

Background: Riluzole has been reported to be beneficial in patients with cerebellar ataxia; however, effectiveness in individual subtypes of disease is unclear due to heterogeneity in participants' causes and stages of disease. Our aim was to test riluzole in a single genetic disease, spinocerebellar ataxia type 2.

Methods: We did a randomised, double-blind, placebo-controlled, multicentre trial (the ATRIL study) at eight national reference centres for rare diseases in France that were part of the Neurogene National Reference Centre for Rare Diseases.

Cardiovascular and connective tissue disorder features in FLNA-related PVNH patients: progress towards a refined delineation of this syndrome.

Background: FLNA Loss-of-Function (LoF) causes periventricular nodular heterotopia type 1 (PVNH1), an acknowledged cause of seizures of various types. Neurological symptoms are inconstant, and cardiovascular (CV) defects or connective tissue disorders (CTD) have regularly been associated. We aimed at refining the description of CV and CTD features in patients with FLNA LoF and depicting the multisystemic nature of this condition.