Intrafamilial Variability in NRXN1-Associated Neurodevelopmental Disorders: Clinical and Genetic Insights from a Family Case Study with Literature Review

Elucidating the Role of SET as a Key Contributor to Neurodevelopmental Disability Within the 9q34.11 Deletion Syndrome Interval.

The 9q34.11 chromosomal region contains multiple neurodevelopmental genes involved in synaptic transmission, axonal structure and neuronal maturation. Pathogenic microdeletions, duplications and single nucleotide variants in numerous genes were previously linked with neurodevelopmental disorders (NDDs). Amongst them, SET has recently been implicated in a rare NDD with speech delay and facial dysmorphism. This study reports a female with a heterozygous de novo deletion impacting SET but not other NDD-associated genes at 9q34.11. The proband was initially diagnosed with atypical Rett syndrome with overlapping clinical features of SET haploinsufficiency. The deletion was confirmed using microarray and long-read sequencing. Subsequent quantitative proteomic evaluation identified a significant decrease of SET protein in patient-derived fibroblasts compared to control lines. This study provides insights into the proband's clinical course over their 28 year diagnostic odyssey, and emphasises the benefits of early speech therapy interventions. The proband had no functional speech, but regained the capacity to meaningfully communicate and articulate a limited vocabulary in adulthood, concordant with other reported non-paediatric cases of SET-NDD. This study expands current knowledge on the genotypic and phenotypic spectra of SET-NDD, and pinpoints a smaller 9q34.11 critical region excluding upstream NDD-associated genes, STXBP1 and SPTAN1, implicating SET as a significant NDD-associated gene.

CMIP as a novel candidate gene for neurodevelopmental and neuropsychiatric disorders

Clinical Phenotypes Associated with NRXN1 Deletions in Five Children with Autism Spectrum Disorder in Oman

Summary NRXN1 (2p16.3) is essential for synaptic function and has been implicated in autism spectrum disorder (ASD) and other neurodevelopmental disorders. However, the phenotypic features associated with NRXN1 copy number variants remains incompletely characterised, which complicates risk assessment in genetic counselling. This case series describes five children, who were evaluated at the Genetics and Developmental Pediatrics Clinic of a tertiary care hospital in Muscat, Oman, from 2011 to 2023, with rare NRXN1 deletions (57–150 kb). All met DSM-5 criteria for ASD and had speech and language delays with cognitive impairment. Consanguinity was reported in three of the families and two had a family history of ASD. Microcephaly was present in four children and one showed facial dysmorphism. Generalised tonic-clonic seizures were present in one child and one child had comorbid attention deficit hyperactivity disorder. These findings illustrate clinical heterogeneity among children with NRXN1 deletions and supports the need for larger studies to better define genotype-phenotype relationships.

THUMPD1-Related Neurodevelopmental Disorder: A Novel Homozygous Loss-of-Function Variant with an Unusual Skeletal Phenotype - A Case Report.

Introduction Genes involved in tRNA modification are critical contributors to a broad range of human neurodevelopmental disorders, reflecting the essential role of RNA modifications in brain development and function. The THUMPD1 gene plays a key role in tRNA modification, and biallelic loss-of-function variants in this gene are known to cause Neurodevelopmental Disorder with Speech Delay and Variable Ocular Anomalies (NEDSOA), an autosomal-recessive condition. Case Presentation We report two sisters harboring a novel homozygous frameshift variant in THUMPD1(NM_017736.5):c.311del;p.(Gly104ValfsTer9), who presented with global developmental delay, severe speech impairment, and ocular anomalies. One affected individual also exhibited severe unilateral skeletal abnormalities on the left hand, including aplasia of the middle and distal phalanges of the fourth finger and the middle phalanx of the fifth finger. To our knowledge, this skeletal feature has not previously been reported in a patient with THUMPD1-related neurodevelopmental disorder. Conclusion Although this skeletal anomaly contributes to the clinical description of the present family, the presence of the finding in only 1 of the 2 affected siblings, both of whom carry the same homozygous variant, limits the strength of the genotype-phenotype association. Therefore, a definitive causal relationship between the THUMPD1 variant and the skeletal phenotype cannot be established, and confirmation in additional individuals will be required.

Biallelic EZH1 Nonsense Novel Variant in Two Siblings with Neurodevelopmental Disorder and Central Precocious Puberty: A Case Report from a Consanguineous Saudi Family

Neurodevelopmental disorders (NDDs) are a group of conditions that impair the development and function of the central nervous system. Recently, variants in the EZH1 gene have been associated with neurodevelopmental disorders. Here, using whole-exome sequencing coupled with confirmatory Sanger sequencing, we identified a homozygous nonsense variant in EZH1 in two affected siblings. Both parents were heterozygous carriers of the variant. The variant is predicted to result in a 44-amino acid C-terminal truncation within the catalytic SET domain, leading to loss of protein function. RT-qPCR analysis revealed significantly reduced EZH1 mRNA expression in patient-derived peripheral blood cells. The index patient (female) also exhibited elevated gamma-glutamyl transferase (GGT) levels and hypoalbuminemia, whereas the affected male presented with central precocious puberty. This study further expands the clinical, genetic, and molecular spectrum of EZH1-associated neurodevelopmental disorders by demonstrating that reduced EZH1 expression is consistent with a loss-of-function disease mechanism.

Variants leading to ELAVL2 haploinsufficiency cause a neurodevelopmental disorder with prominent cognitive, behavioral, and neurological features.

An integrative study combining Mendelian genetics, clinical and association studies, and animal and molecular modeling supports variants in ELAVL2 as a cause of a neurodevelopmental disorder, with haploinsufficiency as the disease mechanism, and identifies crucial roles of ELAVL2 in neuronal function, cognition, and behavior.