Sato S, Otake T, Suzuki C, Saburi J, Kobayashi E
National Livestock Breeding Center, Nishigo, Fukushima 961-8511, Japan.
Poult Sci. 2007 Oct;86(10):2126-33. doi: 10.1093/ps/86.10.2126.
An F(2) chicken population of 265 individuals, obtained from an intercross between the Japanese Game (colored plumage) and the White Plymouth Rock (the recessive white) and genotyped for microsatellite markers, was used for determining the locus of the gene responsible for the recessive white plumage phenotype in chickens. Two hundred twenty-five markers were mapped in 28 linkage groups. Linkage analysis revealed that the recessive white gene was mapped to chromosome 1. Detailed analysis using additional markers uncovered a significant linkage between 2 new markers, mapped to the flanking region of the tyrosinase gene, which is associated with skin and plumage color. The sequence of the tyrosinase gene was investigated in recessive white chickens and colored chickens. There were no obvious differences in the tyrosinase gene exons between the recessive white chicken and the colored chicken. However, sequence analysis of tyrosinase intron 4 in the recessive white chicken revealed a presence of an insertion of an avian retroviral sequence. The White Plymouth Rock and the F(2) generation with white plumage were identified as homozygous carriers of the retroviral sequence. Expression of the normal transcript containing exon 5 was substantially decreased in the recessive white chicken compared with the colored chicken. Some abnormal tyrosinase gene transcripts were expressed in the skin of the White Plymouth Rock: reverse transcription PCR products amplified from exon 3 to intron 4 and from retroviral sequence 3' long terminal repeat to exon 5. Based on these results, it was confirmed that an avian retroviral sequence insertion in the tyrosinase gene was the cause of recessive white phenotype in chickens.
一个由265只个体组成的F(2)代鸡群，通过日本斗鸡（彩色羽毛）和白普利茅斯岩鸡（隐性白羽）杂交获得，并对其进行微卫星标记基因分型，用于确定鸡中负责隐性白羽表型的基因座。225个标记被定位到28个连锁群中。连锁分析表明，隐性白羽基因被定位到1号染色体上。使用额外标记的详细分析发现，两个新标记与酪氨酸酶基因侧翼区域存在显著连锁，该基因与皮肤和羽毛颜色相关。对隐性白羽鸡和有色鸡的酪氨酸酶基因序列进行了研究。隐性白羽鸡和有色鸡的酪氨酸酶基因外显子没有明显差异。然而，对隐性白羽鸡酪氨酸酶内含子4的序列分析显示存在一个禽逆转录病毒序列插入。白普利茅斯岩鸡和具有白羽的F(2)代被鉴定为该逆转录病毒序列的纯合携带者。与有色鸡相比，隐性白羽鸡中包含外显子5的正常转录本的表达大幅下降。在白普利茅斯岩鸡的皮肤中表达了一些异常的酪氨酸酶基因转录本：从外显子3到内含子4以及从逆转录病毒序列3'长末端重复序列到外显子5扩增的逆转录PCR产物。基于这些结果，证实了酪氨酸酶基因中的禽逆转录病毒序列插入是鸡隐性白羽表型的原因。
