Fine-mapping the POLL locus in Brahman cattle yields the diagnostic marker CSAFG29

Area of Science:

• Genetics
• Animal Breeding
• Genomic Mapping

Background:

• The POLL locus, responsible for the polled (hornless) phenotype in cattle, is located on bovine chromosome 1 (BTA1).
• Previous efforts to identify causative mutations or a definitive DNA marker for the POLL locus have been unsuccessful.
• Mapping in pure-bred zebu cattle remained incomplete.

Purpose of the Study:

• To refine the mapping of the POLL locus in cattle.
• To identify novel DNA markers associated with the POLL locus.
• To evaluate the potential of identified markers as diagnostic tools for the polled phenotype.

Main Methods:

• Genotyping of Brahman and Hereford cattle using 33 DNA microsatellites, including 16 newly identified markers.
• Fine-mapping the POLL locus to the region of IFNAR2 and SYNJ1 genes.
• Association analysis of microsatellite alleles with the POLL phenotype across various taurine and composite breeds.

Main Results:

• The POLL locus was mapped to a specific region on BTA1 containing the IFNAR2 and SYNJ1 genes.
• A novel microsatellite, CSAFG29, demonstrated a strong association between its 303-bp allele and the POLL allele in Brahman cattle.
• This association was confirmed in other taurine and composite breeds, with an additional allele (305 bp) also showing some association.
• CSAFG29 exhibits sufficient linkage disequilibrium for potential use as a diagnostic marker in Australian Brahman cattle.
• Confirmatory evidence suggests the scur phenotype is associated with heterozygosity for the POLL allele.

Conclusions:

• The study successfully refined the mapping of the POLL locus and identified CSAFG29 as a promising diagnostic marker, particularly for Brahman cattle.
• The findings contribute to a better understanding of the genetic basis of the polled phenotype in cattle.
• Further research may be needed to optimize diagnostic utility in diverse cattle breeds.