Mapping of the HSD17B2 gene encoding type II 17 beta-hydroxysteroid dehydrogenase close to D16S422 on chromosome...

The enzymes of the 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) gene family are responsible for a key step in the formation and degradation of androgens and estrogens: catalyzing the interconversion of 17-ketosteroids and their active 17 beta-hydroxysteroid counterparts. The structure of human type II 17 beta-HSD cDNA was recently reported. This enzyme catalyzes the interconversion of delta 4-androstenedione and testosterone, androstanedione and dihydrotestosterone, and estrone and 17 beta-estradiol, whereas type I 17 beta-HSD catalyzes exclusively the interconversion of estrogens. To locate the HSD17B2 gene, the novel dinucleotide CA repeat sequence found 571 bp downstream from the end of exon 1 was genotyped into eight CEPH reference families by PCR. Two-point linkage analysis was performed between the latter polymorphism and the 2066 microsatellite markers of Généthon. The maximal pairwise lod score (Zmax = 33.3) with a maximal recombination fraction (theta max) of 0.008 was obtained with the marker D16S422 located on 16q24.1-q24.2. To define further the localization of the HSD17B2 gene, we constructed a high-resolution genetic map of the region flanking the polymorphic HSD17B2 gene including eight Généthon markers. The order of the HSD17B2 gene and markers is qter-D16S516-D16S504-D16S507-D16S505-D16S511+ ++-[HSD17B2-D16S422]-D16S520- D16S413-tel.