Aug 2026· International Journal of Molecular Sciences· Vol 27, pp. 7065· 0 citations· 35 references
Medicine
Abstract
Hypotonia, Ataxia, Developmental Delay, and Tooth Enamel Defect Syndrome (HADDTS; OMIM #617915) is an ultra-rare autosomal dominant disorder caused by predominantly de novo pathogenic variants in CTBP1, encoding a NAD(H)-dependent transcriptional corepressor. We reviewed all HADDTS cases reported from database inception to July 2026, searching PubMed/MEDLINE, Google Scholar, ClinVar, DECIPHER, OMIM, preprint servers, and the HADDTS Foundation, identifying 25 peer-reviewed cases from at least 11 countries; registries indicate at least 50 known individuals. Global developmental delay and language impairment were universal (25/25, 100%), followed by intellectual disability (24/25, 96%), hypotonia (22/25, 88%), ataxia and enamel defects (19/25, 76% each), cerebellar atrophy (18/25, 72%), feeding difficulties (15/25, 60%), myopathy (15/25, 60%), regression (10/25, 40%), oculomotor apraxia (7/25, 28%), scoliosis (6/25, 24%), respiratory chain dysfunction (5/25, 20%), skeletal anomalies (4/25, 16%), and seizures (2/25, 8%). The recurrent p.Arg342Trp (NM_001328.2; p.Arg331Trp, MANE Select NM_001012614.2) accounts for 84%, with severity from mild impairment to profound disability. In all four non-recurrent-variant carriers the canonical tetrad was incomplete; seizures and classifying skeletal anomalies occurred only in that group. Mutant CTBP1 acts dominant-negatively and heterodimerises with the essential paralog CTBP2, explaining the multisystem severity. HADDTS is a neurodevelopmental-mitochondrial overlap disorder; registries, mitochondrial evaluation, and allele-specific therapies are priorities.
PPP1R21-related neurodevelopmental disorder (PPP1R21-NDD) is an ultra-rare autosomal-recessive encephalopathy caused by dysfunction of the Five-subunit Endosomal Rab5 and RNA/ribosome intermediarY (FERRY) complex. To delineate the clinical, neuroimaging, and molecular spectrum of PPP1R21-NDD and outline diagnostic and research priorities. Targeted searches of PubMed, EMBASE, Scopus, Web of Science, and Google Scholar through January 2026 were performed. Eligible reports included molecularly confirmed biallelic PPP1R21 cases and related functional studies. Two researchers independently extracted individual-level data following narrative review quality criteria. Twenty-five individuals from 21 families harbored 17 distinct variants (15 loss-of-function, 2 missense), all homozygous, reflecting high consanguinity. Profound global developmental delay/intellectual disability was universal; hypotonia near-universal (22/25, 88%). Ambulation was delayed and ataxic when achieved; expressive language was minimal or absent. A recognizable coarse facial gestalt was observed with thick eyebrows, broad nasal bridge, thick lips, and low-set ears. Systemic features included feeding dysfunction and respiratory morbidity requiring gastrostomy or tracheostomy in severe cases. Mortality was 17% (4/24). Neuroimaging showed callosal thinning, white-matter volume loss, ventricular enlargement, and vermian hypoplasia. Patient fibroblasts showed delayed transferrin clearance and elevated proteasome activity, suggesting endosomal dysfunction and proteasome hyperactivation. PPP1R21-NDD is a severe recessive encephalopathy with a convergent phenotype and evidence of endo-lysosomal dysfunction. Diagnosis should be pursued with exome or genome sequencing in patients with characteristic clinical and neuroimaging features, particularly in consanguineous families. Research priorities include natural history studies, standardized magnetic resonance imaging (MRI) protocols, neural disease models, and therapeutic strategies targeting endosomal trafficking.
F. Comisi, G. Di Pasquale, A. Comisi et al.· Neurogenetics· 0 citations
A case series of an additional 13 affected individuals with RNF13 variants (2 missense, 11 truncating) supports and broadens previous reports and helps to define a narrow but critical region of the protein that is intolerant to truncating variation, although the gene is not highly constrained.
D. Latner, S. Hiatt, C. Finnila et al.· American Journal of Medical...· 0 citations
Loss-of-function (LoF) variants in the PRPS1 gene, encoding the phosphoribosyl pyrophosphate (PRPP) synthetase 1 enzyme, cause rare neurometabolic disorders historically viewed as discrete entities: nonsyndromic deafness (DFNX1), Charcot–Marie–Tooth disease type X5 (CMTX5), and Arts syndrome. A major clinical challenge is the temporal dissociation between early auditory failure and subsequent neurodegeneration, causing fragmented diagnostics. We systematically quantified this diagnostic latency and reconceptualized the disease spectrum through a molecular lens. A PRISMA-compliant systematic review identified 19 patients with genetically confirmed PRPS1 LoF variants, including our index case (c.362C>G) presenting a 15-year diagnostic delay. Kaplan–Meier analysis revealed sensorineural hearing loss manifested acutely (median 0 years; 95% CI: 0–1). In contrast, neurological deficits demonstrated a prolonged latency (median 3 years; 95% CI: 1–8), followed by ophthalmological signs (median 11.5 years). The median symptomatic delay was 3 years (range up to 19). We posit that this temporal dissociation reflects differential tissue vulnerability to intracellular ATP/GTP and NAD+ depletion caused by the primary enzymatic defect. Ultimately, DFNX1, CMTX5, and Arts syndrome represent a continuous PRPS1-related neurometabolic spectrum. Because targeted metabolic interventions (such as S-adenosylmethionine or nicotinamide riboside) have limited efficacy on advanced structural nerve damage, recognizing this early diagnostic window to initiate biochemical rescue prior to irreversible axonal degeneration is critical.
Bartosz Rodziewicz, M. Kacperski, Kacper Kisiński et al.· Biomolecules· 0 citations
Background: Variants in SOX4 cause intellectual developmental disorder with speech delay and dysmorphic facies (IDDSDF), an autosomal dominant disorder characterized by global developmental delay, mild-to-severe intellectual disability, speech delay, distinctive facial features, digital anomalies, congenital heart defects (unique), and behavioral abnormalities. To date, only a limited number of patients have been described and the phenotypic spectrum of this disorder has yet to be fully delineated. Methods: Clinical data from three patients were collected, including clinical features, growth and developmental profiles, neuropsychological assessments, and urogenital evaluations. Whole-exome sequencing (WES) was performed to screen for candidate variants, and variant pathogenicity was interpreted following the American College of Medical Genetics and Genomics (ACMG) guidelines. Results: All three patients carried previously unreported de novo truncating variants in SOX4: c.583C>T (p.Gln195*), c.1347del (p.Cys450Alafs*5), and c.153G>A (p.Trp51*). Regarding the clinical phenotypes, Patient 3 (P3) was similar to previously reported cases, whereas Patient 1 (P1) and Patient 2 (P2) each exhibited distinctive features on the basis of overlapping with previous reports: P1 presented with severe hypospadias accompanied by cryptorchidism; to our knowledge, no case with this predominant clinical feature has been reported previously. P2 exhibited nystagmus, a novel phenotype not yet reported in the literature. Conclusions: We report three previously unreported de novo truncating variants in SOX4, expand the phenotypic spectrum of SOX4-related disorders to include nystagmus for the first time, and document one patient presenting with severe hypospadias and cryptorchidism. Our findings further expand the mutational and clinical phenotypic spectra of SOX4, underscore the marked clinical heterogeneity of this disorder, and provide new evidence to facilitate clinical recognition and genetic counseling.
H. Miao, Ting Zhang, Kexin Fang et al.· Genes· 0 citations
Rationaleγ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the brain and is implicated in the modulation of central reward processes. Acute or chronic administration of GABAB receptor agonists or positive modulators decreased self-administration of various drugs of abuse. Furthermore, GABAB receptor agonists inhibited cue-induced reinstatement of nicotine- and cocaine-seeking behavior. Because of their fewer adverse side effects compared with GABAB receptor agonists, GABAB receptor positive modulators are potentially improved therapeutic compounds for the treatment of drug dependence compared with agonists.Objectives and methodsWe examined whether the acute effects of the GABAB receptor positive modulator N-[(1R,2R,4S)-bicyclo[2.2.1]hept-2-yl]-2-methyl-5-[4-(trifluoromethyl)phenyl]-4-pyrimidinamine (BHF177) on nicotine self-administration and food-maintained responding under a fixed-ratio 5 schedule of reinforcement were maintained after repeated administration. The effects of acute BHF177 administration on cue-induced nicotine- and food-seeking behavior, a putative animal model of relapse, were also examined.ResultsRepeated administration of BHF177 for 14 days decreased nicotine self-administration, with small tolerance observed during the last 7 days of treatment, whereas BHF177 minimally affected food-maintained responding. Acute BHF177 administration dose-dependently blocked cue-induced reinstatement of nicotine-, but not food-, seeking behavior after a 10-day extinction period.ConclusionsThese results showed that BHF177 selectively blocked nicotine self-administration and prevented cue-induced reinstatement of nicotine seeking, with minimal effects on responding for food and no effect on cue-induced reinstatement of food seeking. Thus, GABAB receptor positive modulators could be useful therapeutics for the treatment of different aspects of nicotine dependence by facilitating smoking cessation by decreasing nicotine intake and preventing relapse to smoking in humans.
S. Vlachou, S. Guéry, Wolfgang Froestl et al.· Psychopharmacology· 770 citations· ⚡47