A familial case of overgrowth syndrome caused by a 9q22.3 microdeletion in a mother and daughter

An investigation of the etiology and follow-up findings in 35 children with overgrowth syndromes, including biallelic SUZ12 variant

Overgrowth-intellectual disability (OGID) syndromes are clinically and genetically heterogeneous group of disorders. The aim of this study was to examine the molecular etiology and long-term follow-up findings of Turkish OGID cohort. Thirty-five children with OGID were included in the study. Single gene sequencing, clinical exome analysis, chromosomal microarray analysis and whole exome sequencing were performed. Five pathogenic copy number variants were detected in the patients; three of them located on chromosome 5q35.2 (encompassing NSD1), others on 9q22.3 and 22q13.31. In 19 of 35 patients; we identified pathogenic variants in OGID genes associated with epigenetic regulation, NSD1 (n = 15), HIST1H1E (n = 1), SETD1B (n = 1), and SUZ12 (n = 2). The pathogenic variants in PIK3CA (n = 2), ABCC9 (n = 1), GPC4 (n = 2), FIBP (n = 1), and TMEM94 (n = 1) which had a role in other growth pathways were detected in seven patients. The diagnostic yield was 31/35(88%). Twelve pathogenic variants were novel. The common facial feature of the patients was prominent forehead. The patients with Sotos syndrome were observed to have milder intellectual disability than patients with other OGID syndromes. In conclusion, this study showed, for the first time, that biallelic variants of SUZ12 caused Imagawa-Matsumoto syndrome, monoallelic variants in SETDIB resulted in OGID. Besides expanded the phenotypes of very rare OGID syndromes caused by FIBP and TMEM94.

Genomics of human congenital hydrocephalus

Congenital hydrocephalus (CH), characterized by enlarged brain ventricles, is considered a disease of pathological cerebrospinal fluid (CSF) accumulation and, therefore, treated largely by neurosurgical CSF diversion. The persistence of ventriculomegaly and poor neurodevelopmental outcomes in some post-surgical patients highlights our limited knowledge of disease mechanisms. Recent whole-exome sequencing (WES) studies have shown that rare, damaging de novo and inherited mutations with large effect contribute to ~ 25% of sporadic CH. Interestingly, multiple CH genes are key regulators of neural stem cell growth and differentiation and converge in human transcriptional networks and cell types pertinent to fetal neurogliogenesis. These data implicate genetic disruption of early brain development as the primary pathomechanism in a substantial minority of patients with sporadic CH, shedding new light on human brain development and the pathogenesis of hydrocephalus. These data further suggest WES as a clinical tool with potential to re-classify CH according to a molecular nomenclature of increased precision and utility for genetic counseling, outcome prognostication, and treatment stratification.

Microdeletion of 9q22.3: A patient with minimal deletion size associated with a severe phenotype

Basal cell nevus syndrome (also known as Gorlin Syndrome; MIM109400) is an autosomal dominant disorder characterized by recurrent pathological features such as basal cell carcinomas and odontogenic keratocysts as well as skeletal abnormalities. Most affected individuals have point mutations or small insertions or deletions within the PTCH1 gene on human chromosome 9, but there are some cases with more extensive deletion of the region, usually including the neighboring FANCC and/or ERCC6L2 genes. We report a 16‐year‐old patient with a deletion of approximately 400,000 bases which removes only PTCH1 and some non‐coding RNA genes but leaves FANCC and ERCC6L2 intact. In spite of the small amount of DNA for which he is haploid, his phenotype is more extreme than many individuals with longer deletions in the region. This includes early presentation with a large number of basal cell nevi and other skin lesions, multiple jaw keratocysts, and macrosomia. We found that the deletion was in the paternal chromosome, in common with other macrosomia cases. Using public databases, we have examined possible interactions between sequences within and outside the deletion and speculate that a regulatory relationship exists with flanking genes, which is unbalanced by the deletion, resulting in abnormal activation or repression of the target genes and hence the severity of the phenotype.