Melanoblasts originating from neural crest cells can migrate through the mesenchyme of the developed embryo and give rise to melanocytes.Unlike the melanocytes that are confined to the integument in other vertebrates,melanocytes in Silky Fowl can reach the ventral regions of the embryos owing to differences in gene expression in the process of melanoblasts migration.In this study,we used microarray profiling to identify differences in gene expression between White Leghorn and Silky Fowl.Differential expression of 2517 microarray probes(P<0.01,Fold Change>2)was observed in Silky Fowl compared to White Leghorn.After filtration by cluster analysis,functional annotation and pathway analysis,eight differentially expressed genes were identified to be closely related to the development of melanocytes.Moreover,differences in expression of immune genes were also detected between Silky Fowl and White Leghorn.The differentially expressed genes associated with melanocyte development were verified by q-PCR,and results were highly consistent with the microarray data.The genes with significantly altered expression involved in melanoblast migration and development suggested that different microenvironments resulted in the abnormal melanoblast migration in Silky Fowl,although there were no big differences in melanoblast development between these two breeds.The candidate genes discovered in this study are beneficial to understand the molecular mechanism of hyperpigmentation in Silky Fowl.
Yulin LIDeping HANJunying LIDawn KOLTESXuemei DENG
Marker-assisted selection(MAS) is an important modern breeding technique,but it has been found that the effect of the markers for quantitative trait loci(QTL) is inconsistent,leading in some cases to MAS failure and raising doubts about its effectiveness.Here the model organism Drosophila melanogaster was employed to study whether an effective marker could be found and applied to MAS.We crossed the stock carrying the y0 marker(a recessive mutation allele of the yellow gene on the X chromosome) with three other stocks carrying corresponding wild-type markers in an F2 design,and found that the y0 marker was in significant association with low body weight(P<0.001).This association was consistent across different backgrounds and the marker effects in female and male were approximately 0.95 σP(phenotypic standard deviation) and 0.68 σP,respectively.We next introgressed a fragment via the y0 marker into a wild stock background over 20 generations of marker-assisted introgression(MAI),and constructed the introgression stock y0(OR)20 in which body weight decreased by 13% and 7%,in female and male,respectively,compared to the wild stock(P<0.0001).This indicated that there must be a single QTL for low body weight that is tightly linked to the y0 marker.We then shortened the introgressed fragment to less than 1.5 cM by a deeper MAI using the y0 marker and the white marker.This narrower fragment also resulted in a similar decrease in body weight to that induced by y0(OR)20,indicating that the QTL for low body weight is located within this less-than-1.5 cM interval.Molecular characteristics of the y0 marker by PCR amplification and Southern blotting revealed that yellow gene was deficient in the y0 stock,leading to disappearance of melanin from the cuticle and probably influencing the developmental process.The above results confirmed the existence of effective QTL markers applicable to MAS breeding schemes,and their potential application in breeding new stocks.
Li XinHai & Deng XueMei College of Animal Science and Technology,China Agricultural University,Beijing 100193,China
Phenylalanine hydroxylase is assumed to be a key enzyme in drosopterin metabolism, but direct in vivo evidence to support this hypothesis is still absent.In the present study, we found a new natural reces-sive purple eye mutant of Drosophila melanogaster, Hnbp, which was a 45-nt insertion mutant in the second exon of Henna.The insertion resulted in a predicted protein with 15 additional amino acids as compared to the wild-type protein.Further analysis of protein structure showed that the predicted mutant protein probably had two more β-sheets, which may cause instability of two α-helices near the catalytic centre of the enzyme in the Biopterin-Hydroxyl binding domain.Hnbp mutant showed eye color defect with decrease of mRNA level, as well as drosopterin content reduction.The drosopterin defect could be fully rescued by expression of wild type Henna in the Hnbp background by GMR-GAL4 UAS-Henna/UAS-Henna:Hnbp/Hnbp transgenic line.All taken together, it can be concluded that the mu-tation in Henna is responsible for drosopterin reduction in mutant Hnbp, which provides key in vivo evidence to support the hypothesis that Henna is involved in drosopterin synthesis.
WANG Qin, ZHAO ChunJiang, BAI LiHua, DENG XueMei & WU ChangXin State Key Laboratory of Agrobiotechnology & Key laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
