Zebra finch aromatase gene expression is regulated in the brain through analternate promoter

The learned singing behavior in songbirds is sex-steroid-dependent and sexu ally dimorphic. Estrogen plays a major role in masculinizing the song syste m in these songbirds. The songbird brain synthesizes large amounts of estro gen, which, in the case of zebra finches, have been found to enter the syst emic circulation. Aromatase cytochrome P450 is the key enzyme catalyzing th e conversion of androgens to estrogens. We have cloned a novel alternativel y spliced form of aromatase cDNA expressed predominantly in the zebra finch brain. We have also isolated and characterized the gene coding for zebra f inch aromatase which spans 20 kb in length. The alternate forms of aromatas e mRNA (ARO) differ in their 5'-untranslated regions encoded by either exon la or Ib. The putative promoter sequences controlling the regulation of th e alternate forms of ARO in zebra finches contain consensus binding sites f or various transcription factors. While both the promoters have binding sit es for SRY-like transcription factor, a binding site for SF-1 is present on ly in the promoter Ib active in the ovary. Intriguingly, a 55 bp segment wi thin the promoter la sequence appears to be highly conserved among zebra fi nch, mouse and human aromatase promoters active in the brain. (C) 1999 Else vier Science B.V. All rights reserved.