Gain-of-function variants in CLCN7 cause hypopigmentation and lysosomal storage disease.

Together with its β-subunit OSTM1, ClC-7 performs 2Cl/H exchange across lysosomal membranes. Pathogenic variants in either gene cause lysosome-related pathologies, including osteopetrosis and lysosomal storage. CLCN7 variants can cause recessive or dominant disease.

Fatty acid synthesis suppresses dietary polyunsaturated fatty acid use.

Dietary polyunsaturated fatty acids (PUFA) are increasingly recognized for their health benefits, whereas a high production of endogenous fatty acids - a process called de novo lipogenesis (DNL) - is closely linked to metabolic diseases. Determinants of PUFA incorporation into complex lipids are insufficiently understood and may influence the onset and progression of metabolic diseases. Here we show that fatty acid synthase (FASN), the key enzyme of DNL, critically determines the use of dietary PUFA in mice and humans.

A novel TTC26 variant in a patient with hexadactyly, pituitary stalk interruption, hepatopathy, nephropathy, and bilateral lip-palate cleft: A case report and expansion of the phenotype.

Biallelic pathogenic variants in the TTC26 gene are known to cause BRENS (biliary, renal, neurological, skeletal) syndrome, an ultra-rare autosomal recessive condition with only few patients published to date. BRENS syndrome is characterized by hexadactyly, severe neonatal cholestasis, and involvement of the brain, heart, and kidney, however the full phenotypic and genotypic spectrum is unknown. Here, we report on a previously undescribed homozygous intronic TTC26 variant (c.

Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes.

AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) mediate fast excitatory neurotransmission in the brain. AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal. Increasing numbers of GRIA3 missense variants are reported in patients with neurodevelopmental disorders (NDD), but only a few have been examined functionally.

An autosomal-dominant childhood-onset disorder associated with pathogenic variants in VCP.

Valosin-containing protein (VCP) is an AAA+ ATPase that plays critical roles in multiple ubiquitin-dependent cellular processes. Dominant pathogenic variants in VCP are associated with adult-onset multisystem proteinopathy (MSP), which manifests as myopathy, bone disease, dementia, and/or motor neuron disease. Through GeneMatcher, we identified 13 unrelated individuals who harbor heterozygous VCP variants (12 de novo and 1 inherited) associated with a childhood-onset disorder characterized by developmental delay, intellectual disability, hypotonia, and macrocephaly.

TMCO3, a Putative K :Proton Antiporter at the Golgi Apparatus, Is Important for Longitudinal Growth in Mice and Humans.

Isolated short stature, defined as short stature without any other abnormalities, is a common heterogeneous condition in children. Exome sequencing identified the homozygous nonsense variant c.1832G>A/p.

De novo PHF5A variants are associated with craniofacial abnormalities, developmental delay, and hypospadias.

Purpose: The SF3B splicing complex is composed of SF3B1-6 and PHF5A. We report a developmental disorder caused by de novo variants in PHF5A.

Methods: Clinical, genomic, and functional studies using subject-derived fibroblasts and a heterologous cellular system were performed.

Modulating effects of FGF12 variants on Na1.2 and Na1.6 being associated with developmental and epileptic encephalopathy and Autism spectrum disorder: A case series.

Objective: Fibroblast Growth Factor 12 (FGF12) may represent an important modulator of neuronal network activity and has been associated with developmental and epileptic encephalopathy (DEE). We sought to identify the underlying pathomechanism of FGF12-related disorders.

Methods: Patients with pathogenic variants in FGF12 were identified through published case reports, GeneMatcher and whole exome sequencing of own case collections.

Biallelic variants in ZNF142 lead to a syndromic neurodevelopmental disorder.

Biallelic variants of the gene encoding for the zinc-finger protein 142 (ZNF142) have recently been associated with intellectual disability (ID), speech impairment, seizures, and movement disorders in nine individuals from five families. In this study, we obtained phenotype and genotype information of 26 further individuals from 16 families. Among the 27 different ZNF142 variants identified in the total of 35 individuals only four were missense.

De novo FZR1 loss-of-function variants cause developmental and epileptic encephalopathies.

FZR1, which encodes the Cdh1 subunit of the anaphase-promoting complex, plays an important role in neurodevelopment by regulating the cell cycle and by its multiple post-mitotic functions in neurons. In this study, evaluation of 250 unrelated patients with developmental and epileptic encephalopathies and a connection on GeneMatcher led to the identification of three de novo missense variants in FZR1. Whole-exome sequencing in 39 patient-parent trios and subsequent targeted sequencing in an additional cohort of 211 patients was performed to identify novel genes involved in developmental and epileptic encephalopathy.

Dominant KPNA3 Mutations Cause Infantile-Onset Hereditary Spastic Paraplegia.

Objective: Hereditary spastic paraplegia (HSP) is a highly heterogeneous neurologic disorder characterized by lower-extremity spasticity. Here, we set out to determine the genetic basis of an autosomal dominant, pure, and infantile-onset form of HSP in a cohort of 8 patients with a uniform clinical presentation.

Methods: Trio whole-exome sequencing was used in 5 index patients with infantile-onset pure HSP to determine the genetic cause of disease.

Prevalence and clinical prediction of mitochondrial disorders in a large neuropediatric cohort.

Neurological symptoms are frequent and often a leading feature of childhood-onset mitochondrial disorders (MD) but the exact incidence of MD in unselected neuropediatric patients is unknown. Their early detection is desirable due to a potentially rapid clinical decline and the availability of management options. In 491 children with neurological symptoms, a comprehensive diagnostic work-up including exome sequencing was performed.

Whole-Exome Sequencing in Critically Ill Neonates and Infants: Diagnostic Yield and Predictability of Monogenic Diagnosis.

Introduction: Monogenic diseases play an important role in critically ill neonates and infants treated in the intensive care unit. This study aimed to determine the diagnostic yield of whole-exome sequencing (WES) for monogenic diseases and identify phenotypes more likely associated with a genetic etiology.

Methods: From March 2017 to 2020, a comprehensive diagnostic workup including WES in a single academic center was performed in 61 unrelated, critically ill neonates and infants with an unknown underlying disease within the first year of life.

Unique variants in CLCN3, encoding an endosomal anion/proton exchanger, underlie a spectrum of neurodevelopmental disorders.

The genetic causes of global developmental delay (GDD) and intellectual disability (ID) are diverse and include variants in numerous ion channels and transporters. Loss-of-function variants in all five endosomal/lysosomal members of the CLC family of Cl channels and Cl/H exchangers lead to pathology in mice, humans, or both. We have identified nine variants in CLCN3, the gene encoding CIC-3, in 11 individuals with GDD/ID and neurodevelopmental disorders of varying severity.

More evidence on TRIO missense mutations in the spectrin repeat domain causing severe developmental delay and recognizable facial dysmorphism with macrocephaly.

TRIO is a Dbl family guanine nucleotide exchange factor (GEF) and an important regulator of neuronal development. Most truncating and missense variants affecting the Dbl homology domain of TRIO are associated with a neurodevelopmental disorder with microcephaly (MIM617061). Recently, de novo missense variants affecting the spectrin repeat region of TRIO were associated with a novel phenotype comprising severe developmental delay and macrocephaly (MIM618825).

The natural history of Canavan disease: 23 new cases and comparison with patients from literature.

Background: Canavan disease (CD, MIM # 271900) is a rare and devastating leukodystrophy of early childhood. To identify clinical features that could serve as endpoints for treatment trials, the clinical course of CD was studied retrospectively and prospectively in 23 CD patients. Results were compared with data of CD patients reported in three prior large series.

CDK19-related disorder results from both loss-of-function and gain-of-function de novo missense variants.

Purpose: To expand the recent description of a new neurodevelopmental syndrome related to alterations in CDK19.

Methods: Individuals were identified through international collaboration. Functional studies included autophosphorylation assays for CDK19 Gly28Arg and Tyr32His variants and in vivo zebrafish assays of the CDK19 and CDK19.

De novo loss-of-function variants in X-linked MED12 are associated with Hardikar syndrome in females.

Purpose: Hardikar syndrome (MIM 612726) is a rare multiple congenital anomaly syndrome characterized by facial clefting, pigmentary retinopathy, biliary anomalies, and intestinal malrotation, but with preserved cognition. Only four patients have been reported previously, and none had a molecular diagnosis. Our objective was to identify the genetic basis of Hardikar syndrome (HS) and expand the phenotypic spectrum of this disorder.