Linkage of the grey coat colour locus to microsatellites on horse chromosome 25.

The study explores the progressive hair color loss in grey horses due to a specific genetic trait (Grey locus GG allele). The researchers discovered a link between this trait and markers on the horse’s 25th chromosome (ECA25).

Objective of the Study

• The prime goal of this research was to explore the genetic factors causing the progressive loss of hair colour in grey horses.

Study Design and Methodology

• Two paternal Quarter Horse families, which showed the GG allele segregation, were genotyped with 101 different microsatellite markers mapping 31 autosomes and the X chromosome.
• A genome scan was performed to identify possible linkages.
• Further, chromosome specific tests were conducted on seven additional Quarter Horse families.

Major Findings

• The results confirmed the linkage of the Grey locus to microsatellites on horse chromosome 25 (ECA25), specifically linking to the COR018 marker.
• A chromosomal map order was generated to better understand the placements and linkages of the GG allele with the microsatellites.
• The study also connected the GG allele to the TXN and COR018 markers on ECA25 although the information wasn’t sufficient to generate significant LODs to place either marker.

Exclusions and Conclusions

• The equine tyrosinase related protein 1 (TYRP1) and melanocyte protein 17 (Pmel17) genes were ruled out as potential candidates for the grey phenotype in horses.
• This means those two genes are not responsible for the greying in horses, at least not in a significant, primary role.
• This research contributes to a better understanding of the genetics of hair colour in grey horses and could potentially have applications in other species as well.