Temporal expression of two Cytochrome P450 Aromatase isoforms during development in Oreochromis mossambicus, in association with histological development

摘要

Oreochromis mossambicus is targeted as a sentinel species for assay development to detect disruption of estrogen-dependent pathways in Southern Africa. Aromatase - an enzyme encoded by either of two cytochrome P450 19 (cyp 19) genes in O. mossambicus is the only enzyme able to catalyze the aromatization of androgens to estrogens. As part of background studies relating to evaluating the use of early life stages of O. mossambicus as an endocrine disruptor screen, we investigated the tissue specificity and temporal expression of cyp19 transcripts, cyp19a (ovarian cyp19) and cyp19b (brain cyp19) during development and estrogen exposure. The cyp19a transcript was detected only in the ovaries of adults, and expression during development reflected this result as induction of cyp19 a coincides with histological development of putative ovaries. Using primers that only identify the ovarian transcript, cypl9a transcript levels demonstrated a typical reflection of puberty-after an initial surge in cyp19a,juveniles expressed very low levels, which increased again at the time histologically discernable vitellogenic ovaries were detected. Moreover, we found evidence of putative alternate transcript of cypl9a whose function is currently unknown. cyp19b transcripts were expressed in brain and muscle tissue of both male and female adults, in addition to ovaries in females. During development, cyp19b transcript levels were increased coincidental with cypl9a at 20 days post fertilization but the expression pattern was distinct from that observed for cypl9a. These studies set the foundation for utilizing this native species as a possible indicator of endocrine disruption and accentuates the importance of understanding "normal" basal levels of transcript levels and the nature of amplification of QPCR targets. (C) 2008 Elsevier Inc. All rights reserved.