Artificial selection is often associated with numerous changes in seemingly unrelated phenotypic traits. The genetic mechanisms of correlated phenotypes probably involve pleiotropy or linkage of genes related to such phenotypes. Dongxiang blue-shelled chicken, an indigenous chicken breed of China, has segregated significantly for the dermal hyperpigmentation phenotype. Two lines of the chicken have been divergently selected with respect to comb color for over 20 generations. The red comb line chicken produces significantly higher number of eggs than the dark comb line chicken. The objective of this study was to explore potential mechanisms involved in the relationship between comb color and egg production among chickens. Based on the genome-wide association study results, we identified a genomic region on chromosome 20 involving EDN3 and BMP7, which is associated with hyperpigmentation of chicken comb. Further analyses by selection signatures in the two divergent lines revealed that several candidate genes, including EDN3, BMP7, BPIFB3, and PCK1, closely located on chromosome 20 are involved in the development of neural crest cell and reproductive system. The two genes EDN3 and BMP7 have known roles in regulating both ovarian function and melanogenesis, indicating the pleiotropic effect on hyperpigmentation and egg production in blue-shelled chickens. Association analysis for egg production confirmed the pleiotropic effect of selected loci identified by selection signatures. The study provides insights into phenotypic evolution due to genetic variation across the genome. The information might be useful in the current breeding efforts to develop improved breeds for egg production.

以白莱航鸡为对照，全面对乌骨鸡体内黑色素细胞的分布特点做更系统的阐释。同时，分析了随日龄增加，不同组织内黑色素的沉积程度差异。首次证实黑色素细胞的大量迁移分布会影响乌骨鸡自身免疫系统的发育，并影响盲肠内唾液酸受体的表达。本研究还进一步阐明了黑色素细胞具有一定的免疫学特性，这也是乌骨鸡自身先天免疫抗病的优势所在。通过成功建立黑色素细胞体外分离培养体系，证实了黑色素细胞也能够产生和表达特定非编码RNA,这可能是黑色素细胞调控其它细胞发育的机制之一。

Hyperpigmentation in Silky Fowl (SF) results in aberrant immune cell development. However, how melanocytes regulate B-cell proliferation in the bursa of Fabricius (BF) is unclear. To resolve this conundrum, we collected BFs from three-week-old SF and White Leghorn (WL) female chickens for RNA sequencing. The BF development was relatively weaker in SF than in WL. The transcriptome analyses identified 4848 differentially expressed genes, 326 long noncoding RNAs (lncRNAs), and 67 microRNAs in the BF of SF. The genes associated with melanogenesis was significantly higher, but that of the genes associated with the cytokine-cytokine receptor interactions and JAK-STAT signalling pathway was significantly lower in SF than in WL. Crucial biological processes, such as the receptor activity, cell communication, and cellular responses to stimuli, were clustered in SF. The predicted target lncRNAs genes were mainly associated with cell proliferation pathways such as JAK-STAT, WNT, MAPK, and Notch signalling pathways. Except for the above pathways, the target microRNA genes were related to the metabolism, melanogenesis, autophagy, and NOD-like and Toll-like receptor signalling pathways. The lncRNAs and microRNAs were predicted to regulate the JAK2, STAT3, and IL-15 genes. Thus, B-cell development in the BF of SF might be regulated and affected by noncoding RNAs.

Avian influenza virus has received increasing attention in recent years because of the potential for recombination with the human virus. Distributions of sialic acid receptors on target cells are determinants of the susceptibilities of different species to influenza virus infection. In this study, the distribution of sialic acid receptors in the respiratory and gastrointestinal tracts of Silky Fowl and White Leghorn chickens were compared. The results showed that sialic acid-alpha-2,3-galactose receptors and sialic acid-alpha 6-galactose receptors were both observed in Silky Fowl and White Leghorn, but fewer positive cells were detected in Silky Fowl with significant difference in the cecum. The lower abundance of sialic acid receptors likely results from the lower abundance of CD3 and F4/80 immune cells in the cecum of Silky Fowl.

The Silky Fowl (SF) is known for its special phenotypes and atypical distribution of melanocytes among internal organs. Although the genes associated with melanocyte migration have been investigated substantially, there is little information on the postnatal distribution of melanocytes in inner organs and the effect of hyperpigmentation on the development of SF. Here, we analyzed melanocyte distribution in 26 tissues or organs on postnatal day 1 and weeks 2, 3, 4, 6, 10, and 23. Except for the liver, pancreas, pituitary gland, and adrenal gland, melanocytes were distributed throughout the body, primarily around blood vessels. Interaction between melanocytes and the tissue cells was observed, and melanin was transported by filopodia delivery through engulfed and internalized membrane-encapsulated melanosomes. SFs less than 10 weeks old have lower indices of spleen, thymus, and bursa of Fabricius than White Leghorns (WLs). The expression levels of interferon-gamma and interlukin-4 genes in the spleen, and serum antibody levels against H5N1 and infectious bursal disease virus were lower in SF than in WL. We also found immune organ developmental difference between Black-boned and non-Black-boned chickens from SFs and WLs hybrid F2 population. However, degeneration of the thymus and bursa of Fabricius occurred later in SF than in WL after sexual maturity. Analysis of apoptotic cells and apoptosis-associated Bax and Bcl-2 proteins indicated that apoptosis is involved in degeneration of the thymus and bursa of Fabricius. Therefore, these results suggest that hyperpigmentation in SF may have a close relationship with immune development in SF, which can provide an important animal model to investigate the roles of melanocyte.

旨在建立乌骨鸡黑色素细胞体外培养和鉴定的方法,为研究黑色素细胞功能提供理想的生物材料。本研究选取乌骨鸡腹膜组织,采用DispaseⅡ和胰酶-EDTA混合消化法,经严格控制不同培养阶段的消化时间,对黑色素细胞进行纯化和传代,获取了乌骨鸡黑色素细胞。通过观察各个培养阶段的细胞形态和细胞生长曲线,表明在专用培养基条件下,细胞增殖良好。根据细胞形态特征、电镜下的亚细胞结构、黑色素合成相关基因的表达分析、DOPA染色和细胞免疫化学染色鉴定,表明所获得的细胞符合黑色素细胞特征。细胞经传代后培养至第10代,仍保持了正常的生物学特性,说明所建立的培养体系可以实现乌骨鸡黑色素细胞体外原代培养。综上表明,本研究成功建立了乌骨鸡黑色素细胞体外分离培养体系。

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,