Use of Javanese Medaka (Oryzias javanicus) cDNA Microarrays in Endocrine Disrupting Chemical Risk Assessment

Abstract

Endocrine disrupting activity of environmental chemicals has been one of the major public concerns since it could cause reduction in reproductive success and affect human and wildlife populations. Up to this date, only biomarkers used to detect chemicals’ potential endocrine disruption (estrogenicity) in experimental fish species are vitellogenin (a female-specific glucolipoprotein yolk precursor) and choriogenin (a precursor of egg envelope protein), and this fact motivated us to look for other useful biomarkers to assess endocrine disrupting effects of the environmental chemicals. Furthermore, several reports have shown that fish exposed to environmentally relevant concentrations (up to 100 ng/l) of 17β-estradiol (E2) for the period prior to sex differentiation and the time of sex differentiation caused disruptions in the process of sexual differentiation (oocyte development in genotypic male, significant change of the sex ratio towards the female sex, etc.), and alteration in the egg production pattern in the subsequent adults. This clearly indicated that early life stages of fish development were sensitive to low concentrations of EDC, and such exposure is now known to lead to distinctive pathological endpoints. Therefore, we were interested in the endocrine disruption studies using both adult and embryo of medaka that were exposed by EDCs. Naturally, development of a bioassay tool was important in order to reduce time, cost, and labor of single biomarker- and pathological observation-dependent test methods, thus, we developed adult Javanese medaka cDNA microarrays which contain 2,500 cDNA probes. In this presentation, experiments using these microarrays and EDC-exposed medaka will be introduced in details, and their analyzed results will be discussed as well.