Abstract
Recently, YY super-male yellow catfish had been created by hormonal-induced sex reversal and sex-linked markers, which provides a promising research model for fish sex differentiation and gonad development, especially for testis development. MicroRNAs (miRNAs) have been revealed to play crucial roles in the gene regulation and gonad development in vertebrates. In this study, three small RNA libraries constructed from gonad tissues of XX female, XY male and YY super-male yellow catfish were sequenced. The sequencing data generated a total of 384 conserved miRNAs and 113 potential novel miRNAs, among which 23, 30 and 14 miRNAs were specifically detected in XX ovary, XY testis, and YY testis, respectively. We observed relative lower expression of several miR-200 family members, including miR-141 and miR-429 in YY testis compared with XY testis. Histological analysis indicated a higher degree of testis maturity in YY super-males compared with XY males, as shown by larger spermatogenic cyst, more spermatids and fewer spermatocytes in the spermatogenic cyst. Moreover, five miR-200 family members were significantly up-regulated in testis when treated by 17α-ethinylestradiol (EE2), high dose of which will impair testis development and cell proliferation. The down-regulation of miR-141 and 429 coincides with the progression of testis development in both yellow catfish and human. At last, the expression pattern of nine arbitrarily selected miRNAs detected by quantitative RT-PCR was consistent with the Solexa sequencing results. Our study provides a comprehensive miRNA transcriptome analysis for gonad of yellow catfish with different sex genotypes, and identifies a number of sex-biased miRNAs, some of that are potentially involved in testis development and spermatogenesis.
Highlights
MicroRNAs, a class of small non-coding RNAs (,18–26 nt), have been known to be involved in mRNA degradation and post-transcriptional repression [1]
A total of 35,873,807 raw reads were obtained from the three small RNA (sRNA) libraries
There are more abundant reads of PIWI-interacting RNAs (piRNAs) homologue in XX ovary compared with XY and YY testis (Figure 1)
Summary
MicroRNAs (miRNAs), a class of small non-coding RNAs (,18–26 nt), have been known to be involved in mRNA degradation and post-transcriptional repression [1]. Most mature miRNA sequences are conserved among fish, amphibians, birds and mammals[2]. MiRNAs have been revealed to play important roles in many biological processes, such as tissue development, cell proliferation and differentiation [3]. A subset of miRNAs, such as miR-430 and miR-196 are expressed and functioning during early embryonic development [4,5]. Fish miR-430 regulates early primordial germ cell development by regulating sdf1a, cxcr, TDRD7, nanos and c1q-like expression [6,7,8,9]. In adults of chicken and cattle, some miRNAs have been identified abundantly expressed in gonadal tissues [10,11]. The regulatory and functional roles of miRNAs in gonad development have not been clear in teleosts yet
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