Investigation of tcirg1 and snx10 gene mutations in patients with osteopetrosis

Objective: Autosomal recessive osteopetrosis (ARO) is a rare genetic bone disease characterized by dense and fragile bone, caused by a defect in osteoclasts responsible for bone destruction. In this study, we aimed to investigate the mutations in TCIRG1 and SNX10 that are responsible for 50% and 4% of the cases respectively. Method: 12 cases aged between 0 and 37 months were included in the study. In line with this purpose, coding exons of these two genes were amplified by using PCR after DNA isolation from peripheral blood. All amplicons were sequenced by Sanger sequencing. The obtained results were evaluated according to the NCBI database. Results: As a result, five different mutations of the TCIRG1 gene were found in four of 12 unrelated cases. These include two novel mutations namely g.9486G>T (IVS6+1G>T) splice-site mutation in intron 6 that is described in one of the patients as heterozygous and g.10170_10171delTG mutation (p.V595LfsX) in exon 15 of the gene which is identified in another patient in the homozygous state. A compound heterozygousity of known mutations g.9574_9599del26 (p.Met217fsX) deletion in exon 7 and g.13698G>A (p.Gly458Ser) missense mutation in exon 12 was found in another patient. A known g.11240G>A (IVS18+1G>A) splice-site mutation was also observed as homozygous in another patient. In TCIRG1, g.7786C>T (p.Arg56Trp) missense mutation, which is indicated as likely benign according to ClinVar database, in exon 3 was heterozygous in two of the patients. In SNX10, g.85603C>G (p.Ser177=) variation in exon 7 was detected as heterozygous in a patient. This variation, which is 7 nucleotides far from the splice site is estimated to be "likely pathogenic" by in silico analyses. Of the known polymorphisms, IVS+83T>C, IVS4+11A>G and IVS7-14C>A in TCIRG1 gene; IVS2+36T>A and IVS3-84G>A in SNX10 gene were detected. Conclusion: In conclusion, our study revealed that 4 of the 12 cases (30%) carry at least one mutation of TCIRG1 gene. Further studies with more patients and other genes would help better understanding of genetic etiology of the disease. Key words: osteopetrosis, TCIRG1, SNX10, mutation analysis