Detection Of Insertion/Deletion (InDel) Within The Four Fat-related Genes And Their Genetic Effects In Seven Sheep Breeds In China And Mongolia

As the producers of meat,milk,cashmere and leather,sheep are raised in many types of environments.With the development of economy and the improvement of living standards,consumers increasingly prefer high quality lean meat.Therefore,it is an important goal of the international sheep industry to improve sheep growth rate and meat quality.However,it has not been fully explored and found about the genetic polymorphisms of important genes controlling these traits,and the genetic variation and effects of important genes related to fat development in many sheep breeds.So,the aim of this study was to investigate the genetic variations and mRNA expression levels of four fat related genes(ZNF395,CREB1,WDR92,and ETAA1)in Chinese and Mongolian sheep and uncover their associations with growth traits.These results would provide a theoretical basis for future marker-assisted selection(MAS)in Chinese and Mongolian sheep,and scientific information for the international sheep industry.1.Sheep zinc finger proteins 395(ZNF395): insertion/deletion(InDel)variations and its association with growth development traits,mRNA expression patternZinc finger protein 395(ZNF395),an important candidate gene related to fat deposition selected in the previous high-throughput sequencing of our group,belonged to the Krüppel C2H2-type zinc-finger protein family and was involved in many cellular responses,such as cell proliferation,differentiation,metabolism and immunity,especially in the process of adipogenesis.In order to explore the insertion/deletion(InDel)variations of ZNF395 and its association with sheep growth traits,InDel testing were executed in a total of 1934 samples from five Chinese and two Mongolian sheep breeds were investigated.A novel 23 bpInDel on the intron 3 of ZNF395 were found in this research and three genotypes were detected in the population.Correlation analysis showed that the locus was significantly associated with 14 different growth traits(P < 0.05 or P < 0.01),such as the body length,chest width,chest depth,chest circumference,body length index,chest circumference index and chest width index of Small Tail Han sheep(4 growth traits and 3 body size index);the chest width of Tan sheep ewes(1 growth trait);the body length,chest width and chest depth of Tan sheep rams(3 growth traits);cannon circumference and cannon circumference index of Hu sheep(1 growth traits and 1 body size index);the body height of Tong sheep(1 growth trait).In addition,the mRNA expressions of ZNF395 were test in different sheep breeds with different tail types(Lanzhou Fat-Tail sheep and Small Tail Han sheep).In Small Tail Han sheep,the results showed that ZNF395 gene had the highest expression in the liver tissue,followed by kidney,tail fat,subcutaneous fat and omentum,and the expression levels in muscle and visceral fat were low.Moreover,the expression of ZNF395 gene was significantly different in tail fat of Lanzhou Fat-Tail sheep and Small Tail Han sheep(P < 0.05).The studies showed that the 23 bp insertion/deletion mutation of ZNF395 gene was significantly associated with sheep growth traits,which would provide a basis for MAS breeding in sheep.2.The association of sheep CREB1 gene InDels and growth traitsCyclicAMP-responsive element binding 1(CREB1),an important candidate gene related to fat deposition selected in the previous high-throughput sequencing of our group,affected the deposition of sheep tail fat through binding to the cAMP response element.It has not been reported about the CREB1 gene InDel polymorphism and its association with sheep growth traits,so this experiment analyzed the InDel variation of CREB1 gene in Chinese and Mongolian local sheep breeds.As a result,a 26 bpInDel locus was found and three genotypes were detected in the tested population.But it was at low polymorphism in six tested breeds.Correlation analysis showed that CREB1 gene 26-bpInDel was significantly associated with 6 growth traits and 3 body size index of one breed,such as the chest width and chest width index of Tan sheep ewes;the body length,body height,chest width,chest depth and cannon circumference index of Tan sheep rams(P < 0.05),and the sacrum height of Small Tail Han sheep(P < 0.05).These findings not only extended the genetic variation spectrum of sheep CREB1 gene but also contributed to the application of marker-assisted selection(MAS)in sheep genetic breeding.3.The association between ETAA1 gene InDels and growth traits in sheepEwing tumor-associated antigen 1(ETAA1,also known as ETAA16),was identified as a tumor-specific antigen in the Ewing family of tumors,which participated in cellular response to replication stress.ETAA1 was an important candidate gene about fat deposition,who was screened by the previous high-throughput sequencing of our group.However,its InDel variation had not been reported in sheep.Herein,one insertion mutations were detected in the intron of ETAA1.And it belonged to moderately polymorphism in tested breeds(0.25 ≤ PIC ≤ 0.5).Correlation analysis showed that the 8 bp insertion mutation of ETAA1 was significantly associated with growth traits in different breeds,especially the body length(P = 0.022),body height(P = 0.017),chest width(P = 0.039)of Lanzhou Fat-Tailed sheep ewes;the body height(P = 0.018),body length(P = 0.044),body weight(P = 0.047)and cannon circumference(P = 0.038)of Hu sheep ewes;the head depth(P =0.017)of Tong sheep ewes;the hip High(P = 0.020),head depth(P = 0.019)and tail depth(P = 0.017)of Tong sheep rams;the chest circumference(P = 0.044)and cannon circumference(P = 0.020)of Tan sheep rams;the chest depth(P = 0.005)and chest width index(P = 0.018)of Tan sheep ewes.All these findings would lay the foundation for the further research of ETAA1 gene and its application as a molecular marker for sheep breeding in the future.4.Detection of sheep WDR92 gene InDelWD Repeat Domain 92(WDR92)was an important candidate gene associated with fat deposition screened in high-throughput sequencing,which was involved in apoptosis by activating caspase-3.This study aimed to discover novel InDel mutations in WDR92 gene and their effects on growth traits in sheep.However,there was no polymorphism in WDR92 gene among all tested breeds.These revealed that it is not suitable as a candidate gene for marker-assisted selection(MAS).