Study On RAB27A, The Candidate Gene Of Dilute Coat Color In Goat

On the basis of cattle(NW₀01502197)and dog(NC₀06612)RAB27A sequences from GenBank,part of goat RAB27A gene from intron 1 to exon 6 was amplified.The total length of determined sequence was 11483bp,which had been submitted to GenBank with the accession number EU595665.For the purpose of analyse the degree of differentiation among different species,sheep RAB27A gene fragments was also amplified.The total length of determined sequence of sheep was 4728bp,with the accession number was EU599576.A total of 33 point mutations were found in the determinged goat RAB27A gene sequence,of which 2 were in exons,5 in UTR and 26 in introns.These mutations in exons were named as follows:183C＞T and 9669C＞A.There was only one missense mutation, 9669C＞A(Leu180Met).The 31 mutations in UTR and introns were 147G＞A,9967T＞C,10101G＞A,10459G＞C,10483C＞A,523T＞C,571T＞C,699T＞C,2306G＞A,2426A＞T,2428T＞G,2719C＞T,3338A＞T,3636T＞C,3660G＞A,3817A＞C,3907G＞C,4165A＞G,4440G＞A,4492C＞T,4634A＞T,4708C＞T,5198C＞A,5300C＞T,5686G＞A,6472T＞C,6754T＞C,8127C＞G,8316G＞A,8778T＞Cand 8930C＞T.There are deletions of Adenine,Thymine and a short sequence(TTTTGTAACTATTTT) at the locus of 2772,5109 and 4238-4252 respectively.An insertion of two bases(AG)was detected at the 4440 site,and a 6bp nucleotide(AAAACA)was repleaced by 3bp nucleotide(CAA)from 10325 to 10330.Two alleles of G and A was detected at the locus of 147G＞A.Then 333 individials from 8 breeds(Chende Polled goat,Leizhou goat,Chengdu Ma goat,Nanjiang Brown goat(B),Nanjiang Brown goat(F),Jining Gray goat,Liaoning Cashmere goat and Tangshan Dairy goat)were studied.We found that G is the preponderant allele(90.39%).The mutation rate is different among different varieties.GG genotype frequency is 63.83-97.37%,GG genotype frequency is different among different varieties(2.63-31.91%),and the AA genotype were observed in Leizhou goat,Nanjiang Brown goat(B)and Nanjiang Brown goat(F).Based on the Hardy—Weinberg test for 8 native goat breeds,we found that Leizhou goat and Nanjiang Brown goat(B)were deviation from the Hardy-Weinberg equilibrium,the others showed a good fit to Hardy-Weinberg equilibrium.So,we suggest that these 6 native goat breeds have not been selected by artificial selection at corresponding mutation sites.At the same time,we discovered that Leizhou goat and Nanjiang Brown goat(B) both are black.It could be inferred that the 147G＞A might be related to the black coat color of goat.Two alleles,C and A at 9669C＞A were deteced.Based on population analysis,we confirmed that the 9669C＞A was a rare mutation.Compared with the CDS of goat RAB27A gene,the nucleotide similarity is 99.40%for sheep,98.04%for bovine,92.94%for horse,92.79%for pig,91.44%for dog 90.69% for gorilla,90.39%for human,89.79%for rhesus,86.94%for mice,85.44%for norway rat, 86.49%for short-tailed opossum,81.38%for chicken,and 80.63%for xenopus lesvis. There was lowwer divergency of CDS among different species,and the cluster result of species is basically accord with the traditional taxonomy.