Desaturase Delta-6 mRNA Expressions In Highly Unsaturated Fatty Acids Biosynthesis Pathway During Follicle Maturation In Female Zebrafish (Danio rerio)

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Date
2010-06
Authors
Ishak, Sairatul Dahlianis
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Publisher
Universiti Sains Malaysia
Abstract
Very little is known about the synthesis of unsaturated fatty acids such as eicosapentaenoic acid (EPA, C20:5n-3), docosahexaenoic acid (DHA, C22:6n-3) and arachidonic acid (ARA, C20:4n-6), or collectively known as the highly unsaturated fatty acids (HUF A), in the fish ovary although they play pivotal roles in this vertebrate reproduction. The zebrafish (Dania rerio) display capability to synthesize all three HUF A via pathways involving desaturation and elongation of two precursors, the linoleic acid (LA, C18:2n-6) and linolenic acid (LNA, Cl8:3n-3). In order to gain understanding on the importance and regulation of ovarian HUF A synthesis, this study shows the mRNA expression pattern of desaturase (jadsd6), an essential enzyme involved in HUF A biosynthesis pathway, in five different zebrafish ovarian follicle stages; pre-vitellogenic, early vitellogenic, late vitellogenic, maturation and ovulation stages. The mRNA levels of fadsd6 in different ovarian follicle stages were determined by semi-quantitative RT-PCR assays. Concurrently, the fatty acid profile of each follicle stage was also analysed using gas chromatography. Results of RT-PCR assays have shown that desaturase displayed significant upregulation in expression during the oocyte maturation stage compared to the other follicle stages. At the same time, fatty acid composition analysis of different ovarian follicle stages also showed that ARA level was significantly highest in pre-vitellogenic and matured follicles. DHA level was highest in both late vitellogenic and maturation stage. Collectively, the findings seem to suggest the existence of a HUF A synthesis system, which could be responsible for the synthesis of HUF A to promote oocyte maturation and possibly ovulation processes. The many advantages of zebrafish as model system to understand folliculogenesis will be useful platform to further elucidate the regulatory and mechanism aspects of ovarian HUF A synthesis.
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The synthesis of unsaturated fatty acids , in the fish ovary.
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