We report on a case of satellited 15q with subtelomeric deletion in a girl with delayed development and severe growth retardation. The patient also has a triangular face, downturned angles of the mouth, micrognathia, and minor limb malformations including mild talipes equinovarus, genu recurvatum, and increased dorsiflexion of both limbs. Cytogenetic analysis using standard GTG banding showed a female karyotype with a satellited-like structure at the distal long arm of one chromosome 15. Silver staining of the nucleolar organizing region (AgNOR) confirmed the presence of a satellite DNA translocation at the lesion. Analysis using fluorescent in situ hybridization (FISH) detected a subtelomeric deletion of the terminal 15q. Additional molecular analysis using microsatellite markers along the long arm of chromosome 15 defined a maximally deleted region at approximately 4.7 Mb. Haploinsufficiency of the IGF1R gene expression is thought to be the cause of growth delay in all 15q terminal deletion including our patient.
To identify the underlying genetic cause of autism spectrum disorder (ASD), we performed whole-exome sequencing in 10 unrelated Thai patients with ASD. We identified a novel heterozygous missense variant (c.425C>G, p.Pro142Arg) in the Engrailed 2 (EN2) gene in two patients. The G variant has never been reported in public databases and was absent in 100 Thai patients with ASD and 435 Thai controls. A case-control study showed that the G allele of c.425C>G was significantly associated with ASD (Fisher's exact test, P=0.0359). In addition, the new variant was predicted to be possibly damaging to the EN2 protein by the PolyPhen-2 and FATHMM bioinformatic programs. Our findings suggest that the arginine variant of the EN2 protein may play an important role in the pathology of ASD. Therefore, EN2 protein functional studies should be carried out to determine whether the novel variant has an effect on protein expression.
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