Clinical report and genetic analysis of a child with Aicardi-Goutières syndrome type 3 due to compound heterozygous variants of RNASEH2C gene

Abstract

To explore the clinical characteristics and genetic etiology of a child with Aicardi-Goutières syndrome 3 (AGS3). Trio whole exome sequencing was carried out for the child and his parents, and candidate variants were verified by Sanger sequencing. To further clarify their pathogenicity, the crystal structure of the variants was simulated and analyzed, and the plasmid of variants was expressed in vitro. A literature search was also carried out to summarize the phenotypic and genetic characteristics of AGS3. The child was found to harbor novel compound heterozygous variants of the RNASEH2C gene, namely c.434G>T (p.Arg145Leu) and c.494G>C (p.Ter165Ser), which were inherited from his mother and father, respectively. Analysis of protein crystal structure suggested that the c.434G>T (p.Arg145Leu) variant may affect the stability of local structure, and in vitro experiments showed that this variant can lead to protein degradation. The c.494G>C (p.Ter165Ser) variant has destroyed the stop codon, resulting in prolonged variant. The novel compound heterozygous variants of the RNASEH2C gene probably underlay the AGS3 in this child, which has enriched the phenotypic and mutational spectrum of this disorder.