Thus, it followed that this patient's pathogenic genetic mutation was inherited from both of his parents, and the mutation was complex heterozygous mutation in the TCIRG1 gene.
During acidification, H+ is transported into secondary lysosomes by vacuolar type H+ adenosine triphosphatase (V-ATPase), and TCIRG1 encodes its a3 subunit.
Approximately 10% of children with IMO in the TCIRG1 gene have extensive and severe neurological damage, including optic atrophy, VEP loss, nystagmus, and blind.
The molecular analysis of genes TCIRG1, CLCN7, OSTM1, that are responsible for approximately 70% of autosomal recessive osteopetrosis cases, was performed by amplification and sequencing of all exons and intron-exon boundaries.
In this study, an affected girl with osteopetrosis was introduced who had no mutation in most common causative genes (TCIRG1, CLCN7 and OSTM1) for the disease, but analysis of SNX10 gene was able to detect a novel homozygous deletion in her.
 Human genes: CLCN7, chloride channel, voltage-sensitive 7; TCIRG1
, T-cell, immune regulator 1, ATPase, H+ transporting, lysosomal V0 subunit A3; CA2, carbonicanhydrase II; TNFSF11, tumor necrosis factor superfamily member 11 (also known as RANKL).
Most ARO cases have been ascribed to mutations in the TCIRG1 gene and only a few cases have been ascribed to mutations in the CLCN7 gene (10).
For ARO, there are at least 7 disease-causing genes located on 7 different chromosomes; TCIRG1 is located on chromosome 11.