The hypothalamic-pituitary-gonadal (HPG) axis is critical in the development and regulation of the reproduction, endocrine, and immune systems, in fish and other vertebrates. To evaluate the effects of sGnRH inhibition, the recombinant gene cAsGnRHpc-antisense, expressing antisense sGnRH RNA driven by a carp beta-actin promoter, was constructed by the researchers from the Research Group of Fish Gene-Engineering at Institute of Hydrobiology, Chinese Academy of Sciences (IHB). Blocking sGnRH expression using antisense sGnRH significantly decreased GtH in the blood of male transgenic carp. Furthermore, some antisense transgenic fish had no gonadal development and were completely sterile. (Aquaculture, 2007, 271：498–506). The generation of sterile transgenic carps by using sGnRH antisense provided a novel method for the biological containment of transgenic carp and could eliminate environmental concerns these fish may raise. Meanwhile, the inhibition of GnRH expression may diminish or severely hamper gonadal development due to it being the key regulator of the axis, and then provide a model for the comprehensive study of the expression patterns of genes with respect to the fish reproductive system. 

Under the supervision of IHB Profs. ZHU Zuoyan and HU Wei, IHB doctoral student XU Jing et al. used suppressive subtractive hybridization (SSH) combined with cDNA microarray analysis to screen for the changes in gene expression of the HPG axis between the female sGnRH-antisense transgenic and control common carp. As a result, nine, 28, and 212 genes were separately identified as being differentially expressed in hypothalamus, pituitary, and ovary. Functional analyses showed that these genes involved in several biological processes, such as biosynthesis, organogenesis, metabolism pathways, immune systems, transport links, and apoptosis. Within these categories, significant genes for neuropeptides, gonadotropins, metabolic, oogenesis and inflammatory factors were identified. This study indicated the progressive scaling-up effect of hypothalamic sGnRH antisense on the pituitary and ovary receptors of female carp and provided comprehensive data with respect to global changes in gene expression throughout the HPG signaling pathway.  

This study, entitled “Defining Global Gene Expression Changes of the Hypothalamic-Pituitary-Gonadal Axis in Female sGnRH Antisense Transgenic Common Carp (Cyprinus carpio)”, was published in PLoS One (2011, 6(6): e21057. doi:10.1371/journal.pone.0021057). It provided comprehensive data with respect to changes in gene expression throughout the HPG signaling pathway, as a result of employing combined SSH and microarrays, contributing towards improving our understanding of the molecular mechanisms and regulative pathways in the reproductive system of teleost fish. 

This work was supported by the Development Plan of the State Key Fundamental Research of China, National Natural Science Foundation and Hubei Provincial Foundation for Distinguished Youth Scholar.