Cloning and expression of desaturase and elongase genes at various stages of oogenesis in female zebrafish Danio rerio
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Date
2008
Authors
Alexender Chong, Shu Chien
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Abstract
Although unsaturated fatty acids such as eicosapentaenoic acid (EPA, C20:5n-3),
docosahexaenoic acid (DHA, C22:6n-3) and arachidonic acid (ARA, C20:4n-6),
collectively known as the highly unsaturated fatty acids (HUFA), play pivotal
roles in vertebrate reproduction, very little is known about their synthesis in the
ovary. The zebrafish display capability to synthesize all three HUFA via
pathways involving desaturation and elongation of two precursors, the linoleic
acid (LA, C18:2n-6) and linolenic acid (LNA, C18:3n-3). As a prerequisite to gain
full understanding on the importance and regulation of ovarian HUFA synthesis,
we described here the mRNA expression pattern of two enzymes; desaturase
(fadsd6) and elongase (elovl5) in different zebrafish ovarian follicle stages. mRNA
levels of fadsd6 and elovlS in different ovarian follicle stages were determined by
semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR)
assays. For analysis of the ovarian follicular fatty acid composition; gas
chromatography was used. Our results have shown that both genes displayed
significant upregulation in expression during the oocyte maturation stage. Fatty
acid composition analysis of different ovarian follicle stages also showed that
ARA and DHA levels are significantly elevated in maturation stage. Collectively,
our findings strongly suggest the existence of a HUFA synthesis system in
zebrafish ovary, responsible for the supply of HUFAs for maturation and possibly
ovulation processes. The versatility and many advantages of zebrafish as model
system for reproduction will provide a useful platform to further elucidate the
regulatory and mechanism aspects of ovarian HUFA synthesis.