Transcriptome Display During Testicular Differentiation of Channel Catfish (Ictalurus punctatus) as Revealed by RNA-Seq Analysis

Abstract

Channel catfish (Ictalurus punctatus) has been recognized as a dominant freshwater aquaculture species in the United States. It is also a suitable model for studying the mechanisms of sex determination and differentiation because of its sexual plasticity and exhibition of both genetic and environmental sex determination. The testicular differentiation in male channel catfish normally starts between 90 and 102 days postfertilization (dpf), while the ovarian differentiation starts early from 19 dpf. As such, efforts to better understand the postponed testicular development at the molecular level are needed. Toward that end, we conducted transcriptomic comparison of gene expression of male and female gonads at 90, 100, and 110 dpf using high-throughput RNA-Seq. Transcriptomic profiles of male gonads on 90 and 100 dpf exhibited high similarities except for a small number of significantly up-regulated genes that were involved in development of germ cell-supporting somatic cells, while drastic changes were observed during 100-110 dpf, with a group of highly up-regulated genes that were involved in germ cells development, including nanog and pou5f1 Transcriptomic comparison between testes and ovaries identified male-preferential genes, such as gsdf, cxcl12, as well as other cytokines mediated the development of the gonad into a testis. Co-expression analysis revealed highly correlated genes and potential pathways underlying germ cell differentiation and spermatogonia stem cell development. The candidate genes and pathways identified in this study set the foundation for further studies on sex determination and differentiation in catfish as well as other teleosts.

Characterization of the European Sea Bass (Dicentrarchus labrax) Gonadal Transcriptome During Sexual Development

“…82 83 Transcriptomic studies on gonadal tissues have been conducted in a relatively large 84 number of fish species, both cultured and not. For example, in the channel catfish 85 (Ictalurus punctatus), the genes differentially expressed (DEG) were described during 86 testis development (Zeng et al 2016). In fugu (Takifugu rubripes) and in the spotted 87 knifejaw (Oplegnathus punctatus), a larger number of DEG were found in adult testes 88 when compared to ovaries (Du et al 2017; Wang et al 2017).…”

De novo sequencing and comparative analysis of testicular transcriptome from different reproductive phases in freshwater spotted snakehead Channa punctatus

“…Among seasonally breeding vertebrates, fishes comprise the largest and most economically important group contributing fifteen percent of average animal protein intake per person for more than 4.3 billion people in the world [5]. In spite of that most of the studies in fishes to comprehend genetic basis of spermatogenesis are restricted to identifying testicular genes [6–18] and only a few reports are focused on differential expression of genes along the testicular cycle [19,20]. The various techniques adopted in these studies were cDNA microarray, EST sequencing, subtractive and suppressive hybridization (SSH), and RNA sequencing (RNA-Seq).…”

Transcriptome Sequencing Reveals the Traits of Spermatogenesis and Testicular Development in Large Yellow Croaker (Larimichthys crocea)

“…To further comprehensively explore the molecular mechanisms underlying spermatogenesis and testicular development in L. crocea, large-scale genetic resources must be identified and studied.Recently, RNA-Seq technology has been widely used to explain biological processes in almost all organisms. Over the past three years, RNA-Seq analyses of reproductive tissues have been performed in several commercial teleosts, such as Thalassoma bifasciatum [12], Takifugu rubripes [13], and Ictalurus punctatus [14]. Numerous reproductive-related genes and signaling pathways have been screened, which has deepened our understanding of gonadal development and gametogenesis.…”