Sensitivities of Japanese eel primary ovary on exogenous androgen – correlated with ovarian neuropeptides and their receptors?

Sensitivities of Japanese eel primary ovary on exogenous androgen – correlated with ovarian neuropeptides and their receptors?

Yung-Sen Huang^a*, Chung-Yen Lin^b

^a Department Life Science, National University of Kaohsiung, Kaohsiung, Taiwan.

^b Institute of Information Science, Academia Sinica, Taipei, Taiwan.

^* yshuang@nuk.edu.tw

In mammals, the ovary and the central nervous system through the autonomic pathways is connected, the evidences highlight the role of the superior ovarian nerve (SON) in the ovarian phenomena in rats. Furthermore, effects on the ovary of neurotransmitters and neuropeptides have been found in this organ. If the development of eel ovary was more like to organogesis, the role of angiogenic growth factors in organogenesis has been reviewed, angiogenesis and neurogenesis are coupled processes, VEGF stimulates neurogenesis, vice versa, the vascular cells are also responsive to neurotrophins. In the eel (Anguilla spp.), the positive effect of androgens on the primary ovarian development is established in the last years, but there are few data to elucidate how is this stimulatory effect to exerting. Indeed, by decreasing ovarian PTEN/PTEN levels or by stimulating follicular FSH receptor expression has been documented in the eel by exogenous androgens. In the Mammal, androgens have been shown to stimulate ovarian granulosa cell proliferation, to increase FSHR, and to decrease AMH, furthermore, to down-regulate TGFβ ligands as well as the receptors has also been reported. Actually, in the eel, the variations on exogenous androgen-induced effect in a population is obvious.

The aims of this study are: (1) to explore what caused the variation on exogenous androgen-induced effect; (2) to understand the correlation between gene background pattern and positive effect of exogenous androgen-induced effects based on expression patterns of ovarian neuropeptide receptors, growth factor receptors, and angiogenic as well as neurogenic factors; (3) to find plausible biological markers to predict the results of eel artificial maturation-induce process.

Pond-cultured Japanese eels with similar body weight (c.a. 650 g, n= 7) were operated to sample ovarian tissues before androgen (MT) implant-treatment (to minimalize the injection-procedure-related stress), then, after 4 weeks, ovarian tissues were collected. Sampled ovarian tissues were stored in the liquid nitrogen. The effect of MT on ovarian development was evaluated based on the increase of egg diameter before and after the treatment in the same individual. The ones with a significant difference on egg diameter were selected, and the paired sampled tissues RNAs were sequenced, transcriptome was made of total RNA-Seq analyzes both coding and multiple forms of noncoding RNA. By the way, the Japanese eel genome has been assembled from the blood of female yellow one. By taking 1,211 scaffolds in length larger than 100Kb, these scaffolds can composite 92% of Japanese eel genome. The transcriptome information of 16,104 annotation genes from three paired ones was implemented into a web database (http://molas.iis.sinica.edu.tw/jpeel).

The results indicated that: (1) The positive effects of MT might be in vain if, in the begin, the egg diameter was small than 0.10 mm. (2) By cluster analysis and based on heatmap method, the ones in the same clade had a similar phenotype, although the pattern of heatmap was not identical, and the certain genes seemed to correlate to the androgen stimulatory effects by Venn diagram method. (3) correlation between the patterns of gene expressions of those growth factors as well as their receptors and the phenotype were not totally coincided with.

Our report based on the exploring data from a transcriptome leads arguments that: (1) the importance of various gene isoforms on a biological process, especially in the Teleost; (2) the importance of basal gene expression levels, of induced gene expression ones, or that of gene expression fold-changes; (3) the importance of the understanding of whole genome on NGS and on gene annotation; (4) the importance of new mathematics or/and statistics, and bio informatics methods on biological studies. (5) the importance of complexity in a small, compact, high efficient cell/tissue.