Gonadal Transcriptome Analysis in Sterile Double Haploid Japanese Flounder

Abstract

Sterility is a serious problem that can affect all bionts. In teleosts, double haploids (DHs) induced by mitogynogenesis are often sterile. This sterility severely restricts the further application of DHs for production of clones, genetic analysis, and breeding. However, sterile DH individuals are good source materials for investigation of the molecular mechanisms of gonad development, especially for studies into the role of genes that are indispensable for fish reproduction. Here, we used the Illumina sequencing platform to analyze the transcriptome of sterile female DH Japanese flounder in order to identify major genes that cause sterility and to provide a molecular basis for an intensive study of gonadal development in teleosts. Through sequencing, assembly, and annotation, we obtained 52,474 contigs and found that 60.7% of these shared homologies with existing sequences. A total of 1225 differentially expressed unigenes were found, including 492 upregulated and 733 downregulated genes. Gene Ontology and KEGG analyses showed that genes showing significant upregulation, such as CYP11A1, CYP11B2, CYP17, CYP21, HSD3β, bcl2l1, and PRLR, principally correlated with sterol metabolic process, steroid biosynthetic process, and the Jak-stat signaling pathway. The significantly downregulated genes were primarily associated with immune response, antigen processing and presentation, cytokine–cytokine receptor interaction, and protein digestion and absorption. Using a co-expression network analysis, we conducted a comprehensive comparison of gene expression in the gonads of fertile and sterile female DH Japanese flounder. Identification of genes showing significantly different expression will provide further insights into DH reproductive dysfunction and oocyte maturation processes in teleosts.

microRNA‐mRNA analysis in pituitary and hypothalamus of sterile Japanese flounder

“…Previously, we also did a comprehensive comparison of gene expression in fertile and sterile ovaries of DH Japanese flounders by transcriptome sequencing and found that the reduced levels of expression of genes involved in steroid biosynthesis might affect the development of the ovary (Zhang et al, ). Herein, we compared the hormone levels in sterile and fertile DH flounders and observed that compared to fertile DH flounders, in sterile DHs, the levels of hormones related to reproductive process were lower.…”

“…Transcriptome analysis of ovary samples from DH Japanese flounders revealed that reduced expression of genes involved in steroid biosynthesis might affect the development of ovaries (Zhang et al, ). As a result, pertinent questions that warrant in‐depth study and discussion have been raised about the differences in the hypothalamus and pituitary between sterile DHs and fertile flounders.…”

Developmental competence of eggs produced by rainbow trout Doubled Haploids (DHs) and generation of the clonal lines

“…Similar situation was observed in tilapia where a few gynogenetic females have been found to produce viable eggs (Müller‐Belecke & Hörstgen‐Schwark, ). In Japanese flounder, most of the DH females were sterile with varying levels of dysgenesis (Zhang et al, ).…”

“…However, clonal lines have been generated in a limited number of fish species due to the low survival of DHs and disturbances during their gonadal development and oogenesis (Hou et al, ; Hou, Fujimoto, Saito, Yamaha, & Arai, ; Kato et al, ; Kobayashi, Ide, Hiasa, Fushiki, & Ueno, ; Komen, Bongers, Richter, Van Muiswinkel, & Huisman, ; Naruse, Ijiri, Shima, & Egami, ; Sarder, Penman, Myers, & McAndrew, ; Yamamoto, ; Young, Wheeler, Fields, & Thorgaard, ; Zhang et al, ). DH females may be sterile or produce poor quality eggs exhibiting decreased ability to be fertilized and impaired competences for the proper development of embryos (Migaud et al, ).…”

Development of innovative methods for induction of European eel (Anguilla anguilla) spermatogenesis

“…; Cacot et al 2003;Viveiros et al 2002), to activation of the complete processes as seen in eels (see section below) and golden rabbitfish (Siganus guttatus; Komatsu et al 2006). Although, in some species Fsh has been shown to induce the full process of spermatogenesis and spermiation (Mazón et al 2014;Zhang et al 2015a;Chu et al 2015), most hormonal treatments have used Lh preparations, which acts on the gonad level or GnRH´s, which have the effect of Lh release from the pituitary (Mylonas et al 2017). A commonly used Lh preparation is pituitary extracts (PEs) from spawning fish (commonly carp or salmon).…”