CLCN7 and TCIRG1 mutations in a single family: Evidence for digenic inheritance of osteopetrosis

: Osteopetrosis is a monogenic condition with various inheritance patterns, including autosomal dominant, autosomal recessive and X‑linked. Several disease‑causing genes have been identified and three distinguished types of osteopetrosis have been reported. In the present study, a family with osteopetrosis was investigated. Two novel mutations in chloride voltage‑gated channel 7 (CLCN7) and T cell immune regulator 1 (TCIRG1) were identified by exome sequencing, Sanger sequencing and microsatellite marker analysis. The CLCN7 mutation occurred in amino acid R286, the same position as previously reported. The TCIRG1 mutation occurred on a splicing site of exon 15, thereby leading to a truncated transcript. These two mutations were undetected in 496 ethnic‑matched controls. To the best of our knowledge, this is the first report of human osteopetrosis involving digenic inheritance in a single family, which has important implications for decisions on clinical therapeutic regimen, prognosis evaluation and antenatal diagnosis.