CBX2 gene analysis in patients with 46,XY and 46,XX gonadal disorders of sex development

Abstract

Objective: To investigate a cohort of patients with gonadal disorders of sex development (DSD) for causative CBX2 gene mutations and or gene copy number changes.

Design: Genetic association study.

Setting: University laboratory and tertiary university-based referral center.

Patient(s): 47 patients with different forms of 46,XY or 46,XX gonadal DSD.

Intervention(s): CBX2 gene sequencing and development of a synthetic probe set for multiplex ligation probe amplification (MLPA) to detect CBX2 copy number changes, and reverse-transcriptase polymerase chain reaction (RT-PCR) to evaluate CBX2 expression in two different cell-line types.

Main outcome measure(s): Gene sequence alteration and or partial or complete gene copy number variations, and detection of CBX2 mRNA isoforms.

Result(s): We detected 10 sequence alterations, 9 reported single nucleotide polymorphisms (SNPs), and a previously unreported variant. This was a silent c.1356G>A transition that may represent a normal variant. A rare SNP (c.1411C>G, p.471Pro>Ala) was found in heterozygous form in one patient. No deletions or duplications were detected by MLPA. Expression of both CBX2 mRNA isoforms was documented in gonadal fibroblasts and Epstein Barr virus (EBV)-transformed lymphocytes.

Conclusion(s): No pathogenic CBX2 mutation was detected. Both CBX2 isoforms are expressed in gonadal fibroblasts and EBV-transformed lymphocytes. This study does not support CBX2 gene disruption as a common cause of gonadal DSD.