Targeted gene expression profiling in European sea bass (Dicentrarchus labrax, L.) follicles from primary growth to late vitellogenesis

Abstract

A real-time PCR-based gene expression survey was performed on isolated European sea bass follicles from primary growth to late vitellogenesis. Expression levels of 18 transcripts with demonstrated relevance during oogenesis, encoding gonadotropin, thyrotropin, estrogen, androgen, and vitellogenin receptors, steroidogenesis-related as well as growth and transcription factors were measured. Primary oocytes showed high mRNA levels of insulin-like growth factors 1 and 2, bone morphogenetic protein 4, estrogen receptor 2b, androgen receptor b, and SRY-box containing gene 17 together with low transcript amounts of gonadotropin receptors. Follicles at the lipid vesicles stage (i.e., the beginning of the secondary growth phase) showed elevated mRNA amounts of follicle stimulating hormone receptor (fshr) and anti-Mullerian hormone. Early-to-mid vitellogenic follicles showed high mRNA levels of fshr and cytochrome P450, family 19, subfamily A, polypeptide 1a while mid-to-late vitellogenic follicles expressed increasing transcript amounts of luteinizing hormone/choriogonadotropin receptor, steroidogenic acute regulatory protein, and estrogen receptors 1 and 2a. The molecular data presented here may serve as a solid base for future studies focused on unraveling the specific mechanisms orchestrating follicular development in teleost fish.

Conserved Anti-Müllerian Hormone: Anti-Müllerian Hormone Type-2 Receptor Specific Interaction and Intracellular Signaling in Teleosts1

“…Evaluation of sea bass amh expression levels in gonads of adult female sea bass throughout a complete reproductive cycle showed an up-regulation of this transcript across all stages of vitellogenesis and also during maturation-ovulation stage. Our results do not agree with a previous report on sea bass ovarian follicles that show up-regulation of amh transcripts only during the beginning of secondary growth and early vitellogenesis going back to basal levels during the rest of the vitellogenesis stage [62]. Indeed, important differences in the design and performance of both experiments can be found.…”

“…The previous study was done on isolated ovarian follicles from females sampled only in December while ours used the entire ovaries, sampled all year round, composed mainly by follicles at a developmental stage that serves the classification of the stage per se but also by a minority of follicles less and more developed. In addition, we used (A)+enriched RNA, instead of total RNA and our qPCR assay is designed to amplify a fragment from the coding region of sea bass amh (the protease cleavage region to be more precise) while in the study by García-López et al [62] primers were designed in the 3' UTR. Moreover, our results are also in line with a recent study performed on Atlantic cod showing high amh levels in follicles from pre-, early-, and late-vitellogenic stages [63].…”

Gonadotropins in European sea bass: Endocrine roles and biotechnological applications

“…Follicles at the beginning of the secondary growth phase showed elevated mRNA amounts of fshr. Early-to-mid vitellogenic follicles showed high levels of fshr, while mid-to-late vitellogenic follicles expressed increasing amounts of lhcgr (García-López et al, 2011). Overall, the analysis of these expression profiles in relation to changes in plasma levels of important reproductive hormones, steroidogenesis-related transcripts and histological data, allows us to conclude that the expression of fshr is connected with the early stages of gonadal development and with the spermiation/matura tion-ovulation periods.…”

Sensitive periods for 17β‐estradiol exposure during immune system development in sea bass head kidney

“…Gene-specific primers for IL-1β, IL-6, TNF-α and TGF-β were as described in Seemann et al (2013). Oligonucleotides for ERs α, β1 and β2 were from García-López et al (2011). (For the precise sequences of forward and reverse primers, the reader is referred to Supplementary Fig.…”