EXPRESSION AND DISTRIBUTION OF CORTICAL TYPE AROMATASE MESSENGER-RNA VARIANT IN THE ADULT-RAT BRAIN

Our previous study showed that a relatively high level of the aromatas e mRNA existed in the cerebral cortex (CC) of the rat, where the aroma tase activity was reported to be little or absent. To elucidate the id entity of the aromatase mRNA in the CC of the rat, we investigated the 5'-region of the aromatase mRNA in the rat CC. When the sequence of t he 5'-region of the cortical message was analysed by the 5'-rapid ampl ification of cDNA ends (5'-RACE) with the antisense primer for exon II using the RNA extracted from the CC, no clone could be isolated. Howe ver, the upstream sequence from the 5'-end of exon IV of tile aromatas e clones, isolated from the CC by RACE with the antisense primers for exon V, was different from that on the aromatase mRNA encoding the ful l. translated region. The new sequence of the cortical type message, c alled the cortical type aromatase mRNA variant, was located on the int ron upstream of exon IV in the genomic cDNA. Distribution of the brain aromatase message with exons III-V and the cortical type aromatase mR NA variant were analysed by the reverse transcription-polymerase chain reaction (RT-PCR) using total RNAs extracted from the hypothalamus-pr eoptic area (HPOA), amygdala (AMY) and CC. The PCR products with prime rs for exons III-V were generated from the HPOA and AMY, but not from the CC. On the other hand, the PCR products with primers for exon IIIv (cortical type aromatase mRNA variant specific)-V were detected in si gnificant amounts in the CC as well as the HPOA and AMY. These results indicate the existence of the aromatase mRNA variant lacking exons I- III in the adult rat brain. This cortical type mRNA variant seemed to be widely distributed in the tissues. (C) 1997 Elsevier Science Ltd.