Identification of COL6A2 mutations in progressive myoclonus epilepsy syndrome

Siamak Karkheiran, Catharine E. Krebs, Vladimir Makarov, Yalda Nilipour, Benjamin Hubert, Hossein Darvish, Steven Frucht, Gholam Ali Shahidi, Joseph D. Buxbaum, Coro Paisán-Ruiz

In this study, a consanguineous family with progressive myoclonus epilepsy (PME) was clinically examined and molecularly investigated to determine the molecular events causing disease. Since exclusion of known genes indicated that novel genes causing PME still remained unidentified, homozygosity mapping, exome sequencing, as well as validation and disease-segregation analyses were subsequently carried out for both loci and gene identification. To further assure our results, a muscle biopsy and gene expression analyses were additionally performed. As a result, a homozygous, disease-segregating COL6A2 mutation, p.Asp215Asn, absent in a large number of control individuals, including control individuals of Iranian ancestry, was identified in both affected siblings. COL6A2 was shown to be expressed in the human cerebral cortex and muscle biopsy revealed no specific histochemical pathology. We conclude that the COL6A2 p.Asp215Asn mutation is likely to be responsible for PME in this family; however, additional studies are warranted to further establish the pathogenic role of both COL6A2 and the extracellular proteolysis system in the pathogenesis of PME.