Catalase gene is associated with facial eczema disease resistance in sheep

Facial eczema (FE) is a hepatogenous photosensitization disease of ruminant animals, particularly in sheep which vary widely in their susceptibility t o the disease, The liver damage is caused by the mycotoxin, sporidesmin. Th ere is evidence that the toxicity of sporidesmin is due to its ability to g enerate 'active oxygen' species. We evaluated the catalase gene, which enco des an enzyme with antioxidant functions, as a candidate for determining th e susceptibility of sheep to the disease. Two microsatellite markers, OarSH P3 and OarSHP4, which flank the sheep catalase gene, were isolated from a Y east Artificial Chromosome (YAC) clone. These markers mapped the catalase l ocus by linkage to ovine chromosome 15. Eleven informative markers spaced t hroughout chromosome 15, inclusive of the catalase marker OarSHP4, gave no significant linkage with the disease traits when analysed in four outcross resource pedigrees. However, OarSHP3 and OarSHP4 allele frequencies showed significant differences between FE resistant and susceptible selection-line s. Comparison of sequences of catalase cDNAs from sheep of resistant and su sceptible lines showed only two silent mutations. A single nucleotide polym orphisms (KP1) in exon 6 of the catalase gene also showed significant diffe rences in allele frequencies between the selection lines. The lack of evide nce for linkage in outcross pedigrees, but the significant association in t he genetic lines, implies that catalase is involved in determining the susc eptibility of sheep to facial eczema, and that the candidate gene's effect is probably recessive or minor.