Identification and characterisation of candidate genes in inherited renal tubular acidoses

The inherited renal tubular acidoses are a group of disorders affecting acid-base homeostasis. Defects in either acid excretion - distal renal tubular acidosis (dRTA) - or bicarbonate absorption - proximal renal tubular acidosis - can be seen independently, in combination, or in a syndrome with osteopetrosis. This thesis examines two of these disorders - dRTA with osteopetrosis, and primary recessive dRTA. It reports the identification of a novel mutation in the CA2 gene, causing carbonic anhydrase II (CAII) deficiency- until now the only known cause of osteopetrosis with RTA. It also describes a unique family with inheritance of two recessive disorders, creating a phenocopy of CAII deficiency. The defects present in this family affect two different tissue-specific isoforms of subunits of the H+-ATPase. A novel mutation in a3, the osteoclast-specific isoform of the a subunit, is the cause of the osteopetrosis in this kindred, whereas a novel mutation in B1, the kidney-specific B subunit isoform, accounts for the dRTA and deafness. Primary recessive dRTA is caused by mutations in either B1 of a4, the kidney-specific isoform of the a subunit. However, further genetic heterogeneity exists and eight dRTA families, where mutations in a4 and B1 have been excluded as the cause, are studied here. An attempt has been made to elucidate the cause of the dRTA in these kindreds using a candidate gene approach. Additional kidney-specific isoforms of other H+- ATPase subunits are excellent disease candidates. Searches of genome databases led to the identification of novel sequences, mainly of renal origin, related to the C and G subunits. These novel genes, designated ATP6V1C2 and ATP6V1G3 respectively, were cloned and characterised, and their involvement in dRTA evaluated. Following cloning and sequencing of these genes, mRNA tissue expression was examined in human and mouse. Polyclonal antibodies raised against peptides from both proteins were used in an attempt to characterise their tissue expression and localisation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo