| As a special local breed,Dongtao chicken(DTC)has a unique trait in bone deposition with a pair of thick legs,which exhibits stable phenotype in inheritance,indicating that this breed provides good genetic materials for studying on bone growth and metabolism and breeding in chicken.However,there is limit reports on the unique phenotype and genetic studies on the Dongtao chicken.Therefore,in this study,we tested several growth traits during the growth periods in Dongtao chicken,including body weight and shank circumference,to estimate the growth characters.Also,transcriptome sequencing was employed to explore the gene transcription profiles during the growth periods.Bioinformatic analysis was applied to identify the major candidate genes related to the thick legs of Dongtao chicken.Our results provide the novel clues to study on the bone metabolism.The main results are as follows:(1)Through testing several growth traits,we obtained the growth curve and some key parameters such as growth inflection point in Dongtao chicken.The results showed that the growth inflection points of male and hens were in 8 weeks and 9weeks,respectively,and the body weight was 1146 g and 864 g.As for shank length,the growth rate was slow down after 10 weeks,but the shank circumference displayed a bit difference between the gender and maintained in more than 1.5 times in Dongtao rooster than Huxu chicken(HXC).(2)Through metatarsus transcriptional sequencing and analyses,a total of 1335 genes were identified as differently expressed genes between the DTC and HXC breeds(Fold change >2,P < 0.01,and FDR < 0.1).Comparing the differences at the age of 10 weeks,there were 245 differentially expressed genes(DEG),including 155 DEGs significantly down-regulated and 90 genes significantly up-regulated in Dongtao chicken.At the age of 14 weeks,there were 1033 DEGs,including 434 DEGs down-regulated and 599 DEGs up-regulated in Dongtao chicken.While at the age of 19 weeks,there were 174 DEGs,including 93 significantly down-regulated 81up-regulated DEGs in Dongtao chicken.Combined with the three time points,a total of 10 genes,including 7 coding genes and 3 non-coding genes,showed significantly different expressions.(3)Through further functional annotation and enrichment analysis,a series of functional genes were identified as candidate genes related to the regulation of bone development,which provided the fundamental results for exploring the abnormal phenotype with thick legs in Dongtao chicken.For example,SOST and wnt2,as key genes in the Wnt signaling pathway,were significantly up-regulated and down-regulated in Dongtao chickens at the age of 19 weeks,respectively,and both impacted the bone density and bone metabolism.PTPRT and AVPR1 A genes were significantly inhibited in all the growing periods in Dongtao chicken,which involved in the longitudinal growth and bone hardness in human and mouse,suggesting that they were negative regulatory genes corresponding to thick bone size of Dongtao chicken.GPER1,as an estrogen receptor gene,was significantly up-regulated in Dongtuo chicken,which was reported that elevating this gene significantly promoted the longitudinal growth and development of bone growth.This point was consistent with the significantly activated expression level and large bone size in Dongtao chicken.Based on KEGG enrichment analysis,17 DEGs were significantly enriched in the calcium-binding protein signaling pathway,including TNNT2,TNNC,MYL2,MYL3,CASQ2,MYH7 B and MYH7,a series of functional genes related to growth and development of bone system.In conclusion,based on phenotypic and genomic studies,a series of functional genes were identified as candidate genes related to thick leg traits in Dongtao chicken.Our finding provides the fundamental data for precise gene mapping on the Dongtao chicken unique phenotype in the future.Also,it provides the novel clue to explore the genetic mechanism on bone growth and breeding in chicken. |
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