Two polymorphic microsatellites in a coding segment of the canine androgen receptor gene

Area of Science:

• Genetics
• Molecular Biology
• Canine Genetics

Background:

• The androgen receptor (AR) gene plays a crucial role in male sexual development and function.
• Polymorphisms in the CAG tandem repeats of the AR gene, encoding glutamine homopolymers, are associated with variations in AR activity.
• Understanding AR gene polymorphism in canines is important for canine genetics research.

Purpose of the Study:

• To characterize the polymorphism of CAG tandem repeats in the canine androgen receptor (AR) gene.
• To determine the allelic diversity and genotype frequencies of AR CAG repeats in a canine population.
• To assess the utility of AR gene CAG repeat polymorphisms as a genetic marker in dogs.

Main Methods:

• Amplification of a 0.6-kb segment of exon 1 of the canine AR gene using polymerase chain reaction (PCR).
• Enzymatic cleavage of the amplified segment between CAG tandem repeats using the restriction enzyme EcoO109I.
• Fractionation of restriction fragments by denaturing polyacrylamide gel electrophoresis (PAGE) to determine the number of CAG repeats.

Main Results:

• Analysis of genomic DNA from 80 unrelated dogs (107 X chromosomes) revealed 10-12 CAGs in the 5' repeats and 10-13 CAGs in the 3' repeats.
• Thirteen distinct AR genotypes were identified, with seven distinct haplotypes contributing to these genotypes.
• Allelic variation was observed, with 41% of females being heterozygous in one or both repeat regions, while males showed single bands consistent with X chromosome markers.

Conclusions:

• The canine AR gene exhibits significant CAG repeat polymorphism, leading to multiple genotypes and haplotypes.
• This polymorphism provides a valuable genetic marker for canine population studies and potentially for research into AR-related traits.
• The characterized AR gene CAG repeat variations contribute to the understanding of genetic diversity in the canine population.