Mutations in the gene SLC4A4, encoding Na+-HCO3- cotransporter (NBC-1), have been found in proximal RTA with ocular abnormalities; in the gene SLC4A1, encoding Cl(-)-HCO3- exchanger (AE1), in autosomal dominant distal RTA; in the gene ATP6B1, encoding B1 subunit of H+-ATPase, in autosomal recessive distal RTA with sensorineural deafness; and in the gene CA2, encoding carbonic anhydrase II, in autosomal recessive osteopetrosis.
Mutations in the gene SLC4A4, encoding Na+-HCO3- cotransporter (NBC-1), have been found in proximal RTA with ocular abnormalities; in the gene SLC4A1, encoding Cl(-)-HCO3- exchanger (AE1), in autosomal dominant distal RTA; in the gene ATP6B1, encoding B1 subunit of H+-ATPase, in autosomal recessive distal RTA with sensorineural deafness; and in the gene CA2, encoding carbonic anhydrase II, in autosomal recessive osteopetrosis.
By studying molecular mechanisms of human disease-causing missense mutations within <i>a</i> subunit isoforms, we may identify domains critical for V-ATPase targeting, activity and/or regulation. cDNA-encoded FLAG-tagged human wildtype ATP6V0A2 (<i>a</i>2) and ATP6V0A4 (<i>a</i>4) subunits and their mutants, <i>a</i>2<sup>P405L</sup> (causing cutis laxa), and <i>a</i>4<sup>R449H</sup> and <i>a</i>4<sup>G820R</sup> (causing renal tubular acidosis, dRTA), were transiently expressed in HEK 293 cells.
The hearing loss may thus be paralleled by various renal phenotypes including a subtle decrease of proximal Na(+)-coupled transport (KCNE1/KCNQ1), impaired K(+) secretion (KCNMA1), limited HCO(3)(-) elimination (SLC26A4), NaCl wasting (BSND and CLCNKB), renal tubular acidosis (ATP6V1B1, ATPV0A4, and KCC4), or impaired urinary concentration (CLCNKA).
Distal renal tubular acidosis (RTA) with nerve deafness is caused by mutations in the ATP6V1B1 gene causing defective function of the H+ -ATPase proton pump.
Although a single case report, this is the second report documenting ATP6B1 mutations in recessive distal RTA with sensorineural hearing loss after the original report by Karet et al and confirms the novelty of these mutations.
Mutations in the gene SLC4A4, encoding Na+-HCO3- cotransporter (NBC-1), have been found in proximal RTA with ocular abnormalities; in the gene SLC4A1, encoding Cl(-)-HCO3- exchanger (AE1), in autosomal dominant distal RTA; in the gene ATP6B1, encoding B1 subunit of H+-ATPase, in autosomal recessive distal RTA with sensorineural deafness; and in the gene CA2, encoding carbonic anhydrase II, in autosomal recessive osteopetrosis.
The hearing loss may thus be paralleled by various renal phenotypes including a subtle decrease of proximal Na(+)-coupled transport (KCNE1/KCNQ1), impaired K(+) secretion (KCNMA1), limited HCO(3)(-) elimination (SLC26A4), NaCl wasting (BSND and CLCNKB), renal tubular acidosis (ATP6V1B1, ATPV0A4, and KCC4), or impaired urinary concentration (CLCNKA).
CAII-deficient mice demonstrate polyuria and polydipsia as well as an alkaline urine and bicarbonaturia, consistent with a type III renal tubular acidosis.
The carbonic anhydrase II (CAII) deficiency syndrome is a rare autosomal recessive osteopetrosis with renal tubular acidosis (RTA) and cerebral calcifications (MIM259730).
We present here, the clinical and radiographic details along with, results of mutational analysis of the CA2 gene in an individual clinically diagnosed with renal tubular acidosis, osteopetrosis and mental retardation and his family members to establish genotype-phenotype correlation.
Mutations in the gene SLC4A4, encoding Na+-HCO3- cotransporter (NBC-1), have been found in proximal RTA with ocular abnormalities; in the gene SLC4A1, encoding Cl(-)-HCO3- exchanger (AE1), in autosomal dominant distal RTA; in the gene ATP6B1, encoding B1 subunit of H+-ATPase, in autosomal recessive distal RTA with sensorineural deafness; and in the gene CA2, encoding carbonic anhydrase II, in autosomal recessive osteopetrosis.
Genetic mutation on NR3C2 may contribute to the development of type IV RTA as a complication of UTI in infants without identifiable risk factors, such as urinary tract anomalies.
In addition, anemia without ring sideroblasts was found in three other patients with mitochondrial disorders, including two children with later onset of PS and one child with failure to thrive, microcephaly, developmental delay, hypertrophic cardiomyopathy, and renal tubular acidosis due to the heterozygous mutations c.610A>G (p.Asn204Asp) and c.674C>T (p.Pro225Leu) in the COX10 gene encoding the cytochrome c oxidase assembly factor.
In addition, anemia without ring sideroblasts was found in three other patients with mitochondrial disorders, including two children with later onset of PS and one child with failure to thrive, microcephaly, developmental delay, hypertrophic cardiomyopathy, and renal tubular acidosis due to the heterozygous mutations c.610A>G (p.Asn204Asp) and c.674C>T (p.Pro225Leu) in the COX10 gene encoding the cytochrome c oxidase assembly factor.
By studying molecular mechanisms of human disease-causing missense mutations within <i>a</i> subunit isoforms, we may identify domains critical for V-ATPase targeting, activity and/or regulation. cDNA-encoded FLAG-tagged human wildtype ATP6V0A2 (<i>a</i>2) and ATP6V0A4 (<i>a</i>4) subunits and their mutants, <i>a</i>2<sup>P405L</sup> (causing cutis laxa), and <i>a</i>4<sup>R449H</sup> and <i>a</i>4<sup>G820R</sup> (causing renal tubular acidosis, dRTA), were transiently expressed in HEK 293 cells.