A novel homozygous COL11A2 deletion causes a C-terminal protein truncation with incomplete mRNA decay in a Turkish patient.

Recessive mutations in COL11A2 (collagen, type XI, alpha 2), are responsible for otospondylomegaepiphyseal dysplasia (OSMED) and non-syndromic hearing loss while dominant mutations are associated with Stickler type III, isolated cleft palate, Robin sequence, non-ophthalmic Stickler syndrome, early onset osteoarthritis and autosomal dominant hearing loss. We describe here the clinical findings of two Turkish cousins with OSMED carrying a novel homozygous truncating mutation in exon 38 of COL11A2 gene, c.2763delT, identified on cDNA and confirmed at gDNA. This mutation is located on triple helix repeat domain of the collagen alpha-2(XI) chain, where the majority of the previously identified mutations are located. Real-time RT-PCR experiment provided that mutated transcript does not decay completely. Although our analysis displays the partial survival of the mutant transcript from blood tissue, not from cartilage, we propose that this mechanism may play an important role on the variable expressivity of the heterozygous COL11A2 gene mutations.