THE HMGI-C GENE IS A LIKELY CANDIDATE FOR THE AUTOSOMAL DWARF LOCUS IN THE CHICKEN

In order to map the autosomal dwarf (adw) locus in the chicken, 11 seg regating families were created. Initially five of these families were used for a linkage experiment in which the genome was scanned with mic rosatellites using a technique called bulked segregant analysis, Subse quently animals from 11 families were typed individually for microsate llites that appeared to be linked. We were able to detect genetic link age of the adw locus to five different microsatellite markers on chrom osome 1, the closest showing a recombination fraction of only 0.03 (LO D score 32.12), In mice the phenotype pygmy shows a striking similarit y to the autosomal dwarf phenotype in chickens, both having a dispropo rtionately large head. The pygmy locus has been mapped on mouse chromo some 10 and found to represent a mutation in the gene coding for high- mobility group protein I-C (HMGI-C), Considering the synteny between r egions of chicken chromosome 1, mouse chromosome 10 and human chromoso me 12, and taking into account both the phenotypic characteristics and the mode of inheritance of the chicken adw and the mouse pygmy loci, the HMGI-C gene is a major candidate gene for the adw locus in the chi cken, Fluorescence in situ hybridization of metaphase chromosomes with the chicken HMGI-C gene as a probe, showed that the chicken HMGI-C ge ne is indeed closely linked to marker LEI146 on chromosome 1.