Blood protein polymorphisms in the donkey (Equus asinus).

The authors of this study sought to identify the presence of different protein variants (polymorphisms) specific to blood of both feral and domesticated donkeys in Australia by using various laboratory techniques. The results suggest that these proteins are mostly donkey-specific and are likely regulated by dominant gene variants with varying commonality among the donkey population.

Methods Used in the Research

• The proteins polymorphism were identified using several laboratory methods:
  • Polyacrylamide gel electrophoresis and starch gel electrophoresis were used to separate the proteins according to differences in their charge and size.
  • Autoradiography employed radioactive isotopes to visualize the separated proteins on a film.
  • Immunoblotting involved the detection of specific proteins using antibodies designed to bind to them.
  • Activity staining enabled visualization of protein variants after gel electrophoresis.

Main Findings

• The polymorphisms of four proteins namely transferrin (TF), albumin (ALB), 6-phosphogluconate dehydrogenase (PGD) and vitamin D-binding protein or Group-specific component (GC) were identified.
• All four TF and two ALB variants were specific to donkeys while only one of the PGD variants was donkey specific. Two variants of GC were identical electrophoretically to those in horses, Equus caballus.
• In the donkey population, glucose phosphate isomerase and plasminogen proteins were found to be monomorphic, i.e., having only one form. This contrasts with the polymorphic proteins previously identified.
• Based on the findings, the researchers proposed that these protein systems are controlled by co-dominant alleles. In genetics, co-dominant alleles are a pair of genes where both make a distinct contribution to the organism’s traits.
• The most common alleles or gene variants for each system have frequencies of 0.831 (for TF), 0.946 (for ALB), 0.957 (for PGD) and 0.861 (for GC), indicating the proportion of donkeys in the population carrying these common alleles.

Significance of the Study

• This study provides valuable information about the genetic map and blood characteristics unique to donkeys, which could be useful in defining the biological variations of the species.
• The identified blood protein polymorphisms and the understanding of their control by co-dominant alleles can be useful for genetic studies, breeding and management of donkey populations.
• The study provides an understanding of certain underlying physiological processes that are specific to donkeys, which may also be employed in comparative studies with related species such as the horse.