A single base transversion in the flanking region of an equine microsatellite locus affects amplification of one allele.

This study examines how a single gene change can affect the amplification of one allele, impacting an equine microsatellite panel used for verifying horse parentage in a California lab.

Background of the Research

• This research was inspired by an irregularity observed during a parentage verification program carried out at the Veterinary Genetics Laboratory in Davis, California, particularly involving a Quarter Horse mare.
• The anomaly concerned the sample from an equine microsatellite locus known as HMS7, part of a broader microsatellite panel used for the procedure.
• The research highlighted a unique case of apparent non-Mendelian inheritance where the offspring shared no alleles with the mother at the HMS7 locus, which is against regular inheritance patterns.

Main Findings of the Research

• The study discovered that although the mare appeared homozygous for HMS7, a unique allele was identified that was different from those found in the two offspring.
• Upon utilizing polymerase chain reaction (PCR) primers designed to bind outside the known primer-binding sites, an additional shared allele was detected in the three horses – the mare and her two offspring.
• This shared allele could validate the ancestry of the horses and establish the mare as the dam.

The Key Genetic Transformation

• After sequencing the newly detected allele, researchers found a C to A transversion (gene alteration) in one of the primer-binding regions.
• It became clear that this genetic alteration was the reason for the apparent non-Mendelian inheritance at the HMS7 locus.

Additional Cases and General Impact of the Finding

• The occurrence of this non-Mendelian inheritance was not limited to just this one instance. The researchers encountered it in another 26 Quarter Horse parentage cases.
• In all instances, the failure of amplification and resultant ‘null’ allele was caused by the same C to A transversion.
• The study thus highlights the impact a single base transversion can have on amplification of an allele, which can complicate genetic assessments and parentage verification.