P450 AROMATASE (ARO) mRNA LACKING EXON5 (-E5) ASSOCIATED WITH ARO DEFICIENCY, IS PRESENT IN NORMAL HUMAN STEROIDOGENIC TISSUES. A NEW MECHANISM OF ARO ACTIVITY REGULATION?

CAROLINA M. PEPE, NORA I. SARACO, MARIA SONIA BAQUEDANO, GABRIELA GUERCIO, ELISA VAIANI, ESPERANZA BERENSZTEIN, MARCO A. RIVAROLA, ALICIA BELGOROSKY

Viña del Mar, Chile.

Congreso; XVIII Reunión de la Sociedad Latinoamericana de Endocrinología Pediátrica; 2006

Sociedad Latinoamericana de Endocrinología Pediátrica (SLEP)

ARO, involved in androgens to estrogens conversion, is encoded by single gene in humans and expressed in a broad array of tissues. Alternative splicing of ARO coding region has been described in several species. However, in humans, it has only been described within the 5’ untranslated region, in association with tissue specific expression of different non-coding E1. A unique ARO protein is generated. A mutation c655G>A described in a heterozygous girl (JCEM 2003) and in a homozygous adult male (JCEM 2004) with ARO deficiency, would be involved in an aberrant splicing. “In vivo” consequence of the mutation on ARO mRNA expression was analyzed by RT-PCR of RNA from girl patient’s lymphocytes. An aberrant spliced -E5 mRNA, not found in control samples, was found. Association between E5 skipping and the mutation was confirmed by splicing assays in Y1 cells transfected with wild type (WT) minigene or a mutant one (Mut). WT expression results in the expected mRNA while Mut in complete E5 exclusion. Expression of full length ARO cDNA in Y1 cells was associated with ARO activity, evidenced by estradiol (E2) production. However, no E2 could be detected with –E5 cDNA, in the same experimental conditions. As E5 could be involved in alternative splicing events, presence of the –E5 mRNA was evaluated by RT-PCR in 3 normal steroidogenic tissues. Finding of –E5 mRNA in placenta (n=3), prepubertal (pp) testis (n=10) and pp adrenal (n=10) as well as the absence of ARO activity associated with the –E5 mRNA, lead us to postulate that alternative splicing of coding region would occur in humans and would be involved in the complex ARO activity regulation.