Rr. Terry et al., Linked markers exclude KIT as the gene responsible for appaloosa coat colour spotting patterns in horses, ANIM GENET, 32(2), 2001, pp. 98-101
The appaloosa coat colour pattern of the horse is similar to that caused by
the rump-white (Rw) gene in the mouse. In the mouse Rw colour pattern is t
he result of an inversion involving the proto-oncogene c-kit (KIT). Therefo
re, we investigated KIT as a candidate gene that encodes the appaloosa coat
colour gene (Lp) in horses. KIT plays a critical role in haematopoiesis, g
ametogenesis, and melanogenesis and encodes a transmembrane tyrosine kinase
receptor that belongs to the PDGF/CSF-1/c-KIT receptor subfamily. Half-sib
families segregating for Lp were uninformative for a reported polymorphism
in KIT. However, KIT is located on horse chromosome 3 close to albumin (AL
B), serum carboxylesterase (ES), vitamin D-binding protein (GC) and microsa
tellite markers ASB23, LEX007, LEX57, and UCDEQ437. Indeed, KIT and ASB23 w
ere localized to ECA3q21-22.1 and 3q22.1-22.3, respectively, by fluorescent
in situ hybridization. Family studies were conducted to investigate linkag
e of Lp to these markers using eight half-sib families in which Appaloosa s
tallions were mated to solid coloured mares. Linkage of Lp to the chromosom
e region containing ES, ALE, GC, ASB23, UCDEQ437. LEX57, and LEX007 was inv
estigated by a multipoint linkage analysis using the computer program GENEH
UNTER. LOD scores over the interval under investigation ranged from -4.28 t
o -12.48, with a score of -12.48 at the location for ASB23. Therefore. it w
as concluded that appaloosa (Lp) is not linked to any of the tested markers
on ECA3, and thus Lp is unlikely to be the product of KIT.