title: Fine-mapping and mutation analysis of TRPM1: a candidate gene for leopard complex (LP) spotting and congenital stationary night blindness in horses.
abstract: Leopard Complex spotting occurs in several breeds of horses and is caused by an incompletely dominant allele (LP). Homozygosity for LP is also associated with congenital stationary night blindness (CSNB) in Appaloosa horses. Previously, LP was mapped to a 6 cm region on ECA1 containing the candidate gene TRPM1 (Transient Receptor Potential Cation Channel, Subfamily M, Member 1) and decreased expression of this gene, measured by qRT-PCR, was identified as the likely cause of both spotting and ocular phenotypes. This study describes investigations for a mutation causing or associated with the Leopard Complex and CSNB phenotype in horses. Re-sequencing of the gene and associated splice sites within the 105 624 bp genomic region of TRPM1 led to the discovery of 18 SNPs. Most of the SNPs did not have a predictive value for the presence of LP. However, one SNP (ECA1:108,249,293 C>T) found within intron 11 had a strong (P < 0.0005), but not complete, association with LP and CSNB and thus is a good marker but unlikely to be causative. To further localize the association, 70 SNPs spanning over two Mb including the TRPM1 gene were genotyped in 192 horses from three different breeds segregating for LP. A single 173 kb haplotype associated with LP and CSNB (ECA1: 108,197,355- 108,370,150) was identified. Illumina sequencing of 300 kb surrounding this haplotype revealed 57 SNP variants. Based on their localization within expressed sequences or regions of high sequence conservation across mammals, six of these SNPs were considered to be the most likely candidate mutations. While the precise function of TRPM1 remains to be elucidated, this work solidifies its functional role in both pigmentation and night vision. Further, this work has identified several potential regulatory elements of the TRPM1 gene that should be investigated further in this and other species.
authors.affiliation: Department of Biology, University of Tampa, Tampa, FL 33611, USA. rbellone@ut.edu
authors.forename: Rebecca R
authors.initials: RR
authors.lastname: Bellone
authors.forename: George
authors.initials: G
authors.lastname: Forsyth
authors.forename: Tosso
authors.initials: T
authors.lastname: Leeb
authors.forename: Sheila
authors.initials: S
authors.lastname: Archer
authors.forename: Snaevar
authors.initials: S
authors.lastname: Sigurdsson
authors.forename: Freyja
authors.initials: F
authors.lastname: Imsland
authors.forename: Evan
authors.initials: E
authors.lastname: Mauceli
authors.forename: Martina
authors.initials: M
authors.lastname: Engensteiner
authors.forename: Ernest
authors.initials: E
authors.lastname: Bailey
authors.forename: Lynne
authors.initials: L
authors.lastname: Sandmeyer
authors.forename: Bruce
authors.initials: B
authors.lastname: Grahn
authors.forename: Kerstin
authors.initials: K
authors.lastname: Lindblad-Toh
authors.forename: Claire M
authors.initials: CM
authors.lastname: Wade
mesh_terms: D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D004252:DNA Mutational Analysis; D005091:Exons; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000151:congenital / Q000235:genetics* / Q000473:pathology; D006736:Horses; D008969:Molecular Sequence Data; D009755:Night Blindness / Q000151:congenital / Q000235:genetics / Q000662:veterinary*; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D050053:TRPM Cation Channels / Q000235:genetics*
chemical_list: D050053:TRPM Cation Channels