Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/1997
Publication Date: N/A
Interpretive Summary: Marek's disease (MD) is an important disease of chickens that costs the poultry industry nearly $1 billion annually. The best understood genetic resistance to MD involves the chicken major histocompatibility (MHC) B-complex. Recently, preliminary observations suggested that another group of genes might also influence MD susceptibility. These genes are termed Rfp-Y, and resemble B-complex genes. The results of cosegregation analysi indicate that the variability of MD incidence was not significantly influenced by the Rfp-Y genes. We conclude that Rfp-Y genes do not play a major role in determining the susceptibility to MD in chickens. The effects of Rfp-Y genes on MD susceptibility, if any, are minuscule compared to the effects of other non-MHC genes recently identified in the chicken genome. Therefore, efforts should be concentrated on studying other genes in chickens shown to have a major effect on the genetic susceptibility to MD.
Technical Abstract: Marek's disease (MD) is a lymphoproliferative disease caused by a member of the herpesvirus family, and the best understood genetic resistance to MD involves the chicken MHC B-complex. Preliminary observations have suggested that MHC-like Rfp-Y genes might also influence MD incidence. This study describes the differentiation and definition of unique Rfp-Y genes in inbred lines 63 and 72, lines that possess identical B-complex genes, but that are resistant or susceptible to MD, respectively. To assess if Rfp-Y genes affect MD susceptibility, 265 63X72 F2 chickens were challenged with the DIM strain of MD virus (MDV) at 1 week of age and evaluated for MD lesions up to 10 weeks of age. Genotyping of the F2 chickens for Rfp-Y haplotypes was done by restriction fragment length polymorphism (RFLP) analysis of genomic DNA using TaqI enzyme and B-FIV probe. ANOVA and interval mapping procedures were used to determine association between the F2 chickens Rfp-Y haplotypes and the phenotypic MD values. The cosegregation analysis of 265 F2 chickens indicated that there was no association between Rfp-Y haplotypes and MD susceptibility. Furthermore, the facts that the Rfp-Y haplotypes fit the 1:2:1 segregation ratio and that the Rfp-Y allele frequencies did not significantly differ from 0.5 in the full population and in selected sub-populations of either 40 MD resistant or 39 MD susceptible chickens, also indicate that the Rfp-Y haplotypes do not significantly influence MD susceptibility. We conclude that Rfp-Y haplotypes do not play a major role in determining the genetic susceptibility to MD in 63X72F2 White Leghorn chickens.