Identification of variants in ACAN and PAPSS2 leading to spondyloepi(meta)physeal dysplasias in four Chinese families

Spondyloepi(meta)physeal dysplasias (SE[M]D) are a group of inherited skeletal disorders that mainly affect bone and cartilage, and next-generation sequencing has aided the detection of genetic defects of such diseases. In this study, we aimed to identify causative variants in four Chinese families associated with SE(M)D.We recruited four unrelated Chinese families all displaying short stature and growth retardation. Clinical manifestations and X-ray imaging were recorded for all patients. Candidate variants were identified by whole-exome sequencing (WES) and verified by Sanger sequencing. Pathogenicity was assessed by conservation analysis, 3D protein modeling and in silico prediction, and was confirmed according to American College of Medical Genetics and Genomics.Three novel SE(M)D-related variants c.1090dupG, c.7168 T > G, and c.2947G > C in ACAN, and one reported variant c.712C > T in PAPSS2 were identified. Among them, c.1090dupG in ACAN and c.712C > T in PAPSS2 caused truncated protein and the other two variants led to amino acid alterations. Conservation analysis revealed sites of the two missense variants were highly conserved, and bioinformatic findings confirmed their pathogenicity. 3D modeling of mutant protein encoded by c.7168 T > G(p.Trp2390Gly) in ACAN proved the structural alteration in protein level.Our data suggested ACAN is a common pathogenic gene of SE(M)D. This study enriched the genetic background of skeletal dysplasias, and expanded the mutation spectra of ACAN and PAPSS2.