MCAM (CD146) Gene Encodes Chicken Blood Alloantigen System H

Alloantigen H is one of thirteen systems in the chicken. Little is known about this system which has two serological alleles. The objectives of this study were (1) to identify the genetic region encoding the chicken alloantigen H, and (2) to develop DNA detection-based methods to aid H system allele identification.

SNP genotypes from Axiom chicken SNP arrays were established for samples with known H system serological types. Sources of DNA included two elite Hy-Line White Leghorn lines segregating for alloantigen H, non-pedigreed samples from the Northern Illinois University (NIU) DNA bank, plus inbred line samples. Sequence information was also available for the commercial and inbred lines.

GWAS results from the elite Hy-Line lines and NIU DNA bank samples showed a very strong peak in the same 4.20-4.30 Mbp region on chromosome 24. Predicted cell membrane expression and the presence of non-synonymous SNP were criteria to identify candidate genes. Seven genes in this region have membrane-associated products: MCAM (CD146), THY1, MFRP, CLDN25, KCNJ14L, ABCG4, and PDZD3. However, only MCAM had an SNP variation that matched the serological haplotypes. Lines known to be segregating for the H system had concordance rates between serological results and SNP haplotype of 95% for both the elite HYL lines and 99% for the NIU samples, indicating that the MCAM (CD146) gene encodes the chicken H blood system.

The gene product is a cell adhesion molecule affecting multiple activities including angiogenesis, development, cell differentiation, cell migration, signaling transduction, and immune responses. Long, short, and soluble isoforms are found in chickens. The described DNA-based typing methods facilitate future investigations to examine H haplotype frequencies in lines with identified differential responses such as growth or immune responses. Determining H haplotype association with egg production, feed conversion, and other traits with economic importance will aid in determining the significance of this immune-related gene in overall poultry health.