Identification of genes in the hypothalamus-pituitary-gonad axis in the brain of Amur sturgeons (Acipenser schrenckii) by comparative transcriptome analysis in relation to kisspeptin treatment.

Kisspeptin plays an important role in the reproduction and onset of puberty in vertebrates through stimulation of gonadotropin-releasing hormone (GnRH). However, the mechanisms whereby kisspeptin-related genes regulate sexual differentiation in teleosts are poorly understood. We aimed to study the relationship between the hypothalamus-pituitary-gonad (HPG) axis and sexual differentiation in relation to kisspeptin in the sturgeon Acipenser schrenckii. We performed comparative transcriptomic analysis of the brains of sturgeons treated with KISS1-10 during the gonadal sex-differentiation-sensitive period (170-210days post-hatching (dph)) using an Illumina sequencing platform. We also analyzed mRNA expression levels of genes in the HPG axis using real-time quantitative polymerase chain reaction, and measured estradiol-17β (E2) and testosterone (T) levels in the brain and gonads using radioimmunological methods. A total of 75,960 and 74,907 unigenes were produced from Kisspeptin-treated and physiological saline-treated fish, respectively, among which 47,891 genes were matched to the non-redundant nr database. Potential genes and their functions were identified by GO (32,435), KEGG (37,619), and COG analyses (18,502). A total of 3169 unigenes were differentially expressed between transcriptomes in KISS1-10- and saline-injected fish, including 300 up-regulated and 2869 down-regulated unigenes. Gene expression levels of KISS1, G protein-coupled receptor-54, GnRH, androgen receptor, estrogen receptor, and Cyp19a in the brain and gonad were significantly affected by KISS1-10 treatment. KISS1-10 injection also significantly increased brain levels of E2 and T, compared with controls. These results support important roles for KISS1 in the regulation of the HPG axis, and in sex differentiation and reproduction in the Amur sturgeon.