Further evidence of <i>RNU4ATAC</i> variants causing Joubert syndrome with skeletal involvement.

Abstract

<i>RNU4ATAC</i> is a non-coding gene involved in the minor spliceosome, and is mutated in a spectrum of syndromic skeletal disorders with recessive inheritance. Recently, biallelic <i>RNU4ATAC</i> pathogenic variants were detected in five patients presenting a complex syndromic phenotype and a brain malformation resembling the 'molar tooth sign' (MTS). This is the hallmark of Joubert syndrome (JS), a neurodevelopmental ciliopathy with multiorgan involvement.We reanalysed exome sequencing (ES) from 53 patients with JS, who lacked coding variants in known JS-associated genes. Four <i>RNU4ATAC</i> variants (n.16G>A, n.51G>A, n.13C>T and n.30G>A) were identified in compound heterozygosity in three probands, accounting for 5.6% of negative cases. All patients displayed the MTS and clinical features overlapping those of JS and <i>RNU4ATAC</i>-related skeletal disorders.These findings expand the phenotypic spectrum of <i>RNU4ATAC</i>-related disorders to include a complex neurological-skeletal ciliopathy phenotype, and highlight the relevance of ES reanalysis to uncover non-coding variants often undetected by conventional diagnostics.