Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Characterization Of A Paracentric Inversion On ECA3 Associated With The Tobiano Spotting Pattern In Horses

Samantha A. Brooks¹ , Teri Lear¹ , David Adelson² , Barbara Murphy¹ , Ernest Bailey¹

¹  Department of Veterniary Science University of Kentucky Lexington KY 40546-0099

²  Department of Animal Science Texas A&M University College Station, TX 77843-2471

The Tobiano coat color pattern is the product of a single dominant allele (TO) mapped to chromosome ECA3 based on several studies. Tobiano is characterized by large patches of white across the body and limbs. The genetic basis for Tobiano coat color pattern has not yet been identified. Phase conservation of the haplotype TO -ALB-GCS has been previously reported and is used to determine zygosity for TO. Based on this phase conservation it was hypothesized that Tobiano was due to a chromosomal inversion. We have previously reported discovery of this inversion on ECA3 associated with Tobiano by FISH. This inversion spans the region between ECA3q13 and ECA3q21. The breakpoints of this inversion occur between the ADH1C and WDFY3 genes near the centromere and between the KIT and KDR genes at the end nearest the telomere. The homologous region in the human gene map (ADH1C-KIT) spans ~45million bases. Similar white spotting patterns in the mouse associated with genomic rearrangements near KIT have been shown to cause altered KIT gene expression leading to the spotted phenotype. Here we describe further characterization of the inversion breakpoint nearest the KIT gene using FISH, southern blotting and sequencing. We hypothesize that this end of the inversion disrupts a regulatory sequence for KIT gene expression, thus causing the Tobiano pattern.