Growth differences and differential expression analysis of pituitary adenylate cyclase activating polypeptide (PACAP) and growth hormone-releasing hormone (GHRH) between the sexes in half-smooth tongue sole Cynoglossus semilaevis.
Pituitary adenylate cyclase activating polypeptide (PACAP) and growth hormone-releasing hormone (GHRH) are regulators of growth hormone secretion. In this article, we examined the difference in growth and mRNA expression of PACAP and GHRH between the sexes in half-smooth tongue sole, an important cultured fish species indicating sexually growth dimorphism in China. Firstly, a significant body weight difference between females and males was first observed at 7 months (P<0.05) and at 18 onths the mean body weight of the females (771.0±44.3 g) was as much as 4.9 times higher than that of males (130.6±6.0 g). As a result, half-smooth tongue sole, Cynoglossus semilaevis, is a good model to investigate the effects of growth-related genes expression on sexual growth dimorphism. Secondly, the cDNAs encoding PRP/PACAP and GHRH were isolated. Two differently processed mRNA transcripts of PRP/PACAP (PRP-encoding and PRP splice variant) were found. PACAP and GHRH mRNA was highly abundant in brain and less abundant in other tissues. However, PACAP mRNA was expressed in most brain regions, and was lower in the cerebellum. GHRH mRNA was predominantly expressed in the hypothalamus and weakly expressed in all areas of the brain examined. Ontogenetic expression analysis indicated that PACAP and GHRH mRNA was detected in the early stages of embryogenesis. Finally, differential expression showed that there was no significant difference of the expression level of PACAP or GHRH between the sexes before 8 months of age. However, between 9 and 12 months of age, the GHRH mRNA expression level in males was significantly higher than in females (P<0.05), which might be associated with GH deficiency in males. In contrast, the male PACAP mRNA expression level was not significantly higher than that in females even at 9 and 12 months of age. The present results provide important clues for understanding the sexual growth dimorphism mechanisms in half-smooth tongue sole.
Ji
Xiang-Shan
XS
College of Animal Science and Technology, Shandong Agricultural University, Taian, China.
Chen
Song-Lin
SL
Jiang
Yun-Liang
YL
Xu
Tian-Jun
TJ
Yang
Jing-Feng
JF
Tian
Yong-Sheng
YS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005260:Female; D013007:Growth Hormone-Releasing Hormone / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment
D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D013007:Growth Hormone-Releasing Hormone