Genome-wide identification, evolution of chromobox family genes and their expression in Nile tilapia.
Chromobox (Cbx) family proteins are transcriptional repressors that involved in epigenetic and developmental processes. In this study, comprehensive analyses of Cbxs were performed using available genome databases from representative animal species. The Cbx family were originated from one Polycomb (Pc) gene like the yeast Pc, which duplicated into two and gave rise to the Pc and the Heterochromatin protein 1 (Hp1) identified in invertebrates from protozoon to lancelet. Rapid expansion of Cbx family members was observed in vertebrates as ~8 (5 Pc and 3 Hp1) were identified in spotted gar, coelacanth and tetrapods. Further expansion of the members to ~14 (9 Pc and 5 Hp1) was observed in teleosts due to the third round genome duplication (3R). Based on transcriptome data from eight adult tilapia tissues, most of the Cbxs were found to be dominantly expressed in the brain, testis, ovary and heart. Analyses of the gonadal transcriptome data from four developmental stages revealed that all Cbxs were expressed in both ovary and testis except Cbx7b, with significant increase of the total and average RPKM from 5 to 90dah (days after hatching). By in situ hybridization, the three most highly and sexual dimorphically expressed Cbx genes in gonads, Cbx1b, Cbx3a and Cbx5, were found to be expressed in phase I and II oocytes of the ovary, and in secondary spermatocytes (Cbx1b and Cbx3a) and spermatids (Cbx5) of the testis. Our results revealed the evolution of Cbx genes and indicated a potential role of Cbxs in epigenetic regulation of gametogenesis.
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, 400715 Chongqing, PR China.
Xing-Yong
XY
Liu
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, 400715 Chongqing, PR China.
Xian-Bo
XB
Zhang
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, 400715 Chongqing, PR China.
Ming-Hui
MH
Li
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, 400715 Chongqing, PR China.
Shu-Qing
SQ
Zheng
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, 400715 Chongqing, PR China.
Zhi-Long
ZL
Liu
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, 400715 Chongqing, PR China.
Yun-Ying
YY
Cheng
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, 400715 Chongqing, PR China. Electronic address: wdeshou@swu.edu.cn.
De-Shou
DS
Wang
D000818:Animals; D023681:Cichlids / Q000235:genetics*; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000235:genetics*; D020869:Gene Expression Profiling; D023281:Genomics; D010802:Phylogeny; D063150:Polycomb Repressive Complex 1 / Q000235:genetics*
D029941:Fish Proteins; D063150:Polycomb Repressive Complex 1
Chromobox family; Evolution; Gonad; Temporal and spatial expression profiles; Tilapia