Nephrol Dial Transplant (2004) 19: 371-379
© ERA–EDTA 2004; all rights reserved
Original Article
Characterization of a highly polymorphic marker adjacent to the SLC4A1 gene and of kidney immunostaining in a family with distal renal tubular acidosis
1Molecular Medicine and 2Renal Units, Beth Israel Deaconess Medical Center, 4Division of Clinical Laboratories and Department of Pathology, Brigham and Women's Hospital, Departments of 11Medicine and 5Pathology, Harvard Medical School, Boston, MA, USA, 3Department of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand, 6Institute of Hematology and Blood Transfusion, Charles University School of Medicine, Prague, Czech Republic, 8Department of Laboratory Medicine, Fukuoka University, Fukuoka, Japan, 9Department of Medicine, University of Heidelberg, Heidelberg, 10Hegau-Klinikum, Singen and 7Sinsheim, Germany
Correspondence and offprint requests to: Seth L. Alper, MD, PhD, Molecular and Vascular Medicine and Renal Units, Beth Israel Deaconess Medical Center, RW763 East Campus, 330 Brookline Avenue, Boston, MA 02215, USA. Email: salper{at}bidmc.harvard.edu
Background. Mutations in the human SLC4A1 (AE1/band 3) gene are associated with hereditary spherocytic anaemia and with distal renal tubular acidosis (dRTA). The molecular diagnosis of AE1 mutations has been complicated by the absence of highly polymorphic genetic markers, and the pathogenic mechanisms of some dRTA-associated AE1 mutations remain unclear. Here, we characterized a polymorphic dinucleotide repeat close to the human AE1 gene and performed an immunocytochemical study of kidney tissue from a patient with inherited dRTA with a defined AE1 mutation.
Methods. One CA repeat region was identified in a phage P1-derived artificial chromosome (PAC) clone containing most of the human AE1 gene and the upstream flanking region. We determined its heterozygosity value in multiple populations by PCR analysis. Genotyping of one family with dominant dRTA identified the AE1 R589H mutation, and family member genotypes were compared with the CA repeat length. AE1 and vH+-ATPase polypeptides in kidney tissue from an AE1 R589H patient were examined by immunocytochemistry for the first time.
Results. This CA repeat, previously reported as D17S1183, is 
90 kb upstream of the AE1 gene and displayed considerable length polymorphism, with small racial differences, and a heterozygosity value of 0.56. The allele-specific length of this repeat confirmed co-segregation of the AE1 R589H mutation with the disease phenotype in a family with dominant dRTA. Immunostaining of the kidney cortex from one affected member with superimposed chronic pyelonephritis revealed vH+-ATPase-positive intercalated cells in which AE1 was undetectable, and proximal tubular epithelial cells with apparently enhanced apical vH+-ATPase staining.
Conclusions. The highly polymorphic dinucleotide repeat adjacent to the human AE1 gene may be useful for future studies of disease association and haplotype analysis. Intercalated cells persist in the end-stage kidney of a patient with familial autosomal dominant dRTA associated with the AE1 R589H mutation. The absence of detectable AE1 polypeptide in those intercalated cells supports the genetic prediction that the AE1 R589H mutation indeed causes dominant dRTA.
Keywords: anion exchanger 1; dinucleotide repeat; intercalated cell; proximal tubule; spherocytosis; vacuolar H+-ATPase
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