A novel sex-linked mutant affecting tail formation in Hongshan chicken.

The Hongshan chicken is a Chinese indigenous breed that has two distinctly different tail types. Some chickens have stunted tails as compared to the normal phenotype, and they are termed rumpless. Rumplessness in other chicken breeds was caused by a reduction in the number of coccygeal vertebrae. However, X-ray examination showed that rumpless Hongshan chickens possess the normal number of coccygeal vertebrae. Our analyses of the main tail feathers and tissue sections led us to speculate that their stunted tail appearance may be the result of abnormal feather development. To investigate the genetic mechanism underlying rumplessness in Hongshan chickens, we analyzed the results of various crosses. The results indicated that rumplessness is a Z-linked dominant character. In addition, we chose some normal and rumpless individuals for pool-sequencing. Nucleotide diversity and Fst were calculated, and a selective sweep was detected on the Z chromosome. These analyses allowed us to reduce the search area to 71.8-72 Mb on the Z chromosome (galGal5.0). A pseudogene LOC431648 located in this region appeared a strong candidate involving in Wnt/β-catenin signaling pathway to regulate feather development in chickens.