Characterization of the aldose reductase-encoding gene family in rat

Although the enzyme aldose reductase (AR) is implicated in the development of tissue pathology in diabetes, the exact mechanism of this involvement remains unclear. To better understand the role that expression of the aldose reductase-encoding gene (ALR) may play in diabetic complications, we have begun to analyze the gene and its regulatory regions, and we present here the sequence of four ALR genes in the rat. The putative functional gene is 14.1 kb long, has ten exons which show perfect sequence identity to the rat lens AR RNA sequence, and nine introns with classical splice-site consensus sequences. Potential regulatory elements in the 5'-flanking region of this gene include a TATA box and two CCAAT boxes. Probing rat genomic Southern blots with a fragment from the first intron indicates that there is probably only one copy of this gene in the rat genome. The other three genes are processed pseudogenes which show approx. 90% identity to the rat lens AR RNA sequence, contain no introns, and have poly(A) regions at their 3' ends. Chromosomal localization studies show the presence of ALR genes on chromosomes 3, 4 and 6 in the rat with the putative functional gene mapped on chromosome 4.