Prevalence of the Glycogen Branching Enzyme Deficiency Mutation in Quarter Horses in Brazil

Abstract

Glycogen branching enzyme deficiency (GBED) is a fatal autosomal inherited disease affecting horses and caused by a nonsense mutation (c.102C>A) in the GBE1 gene. This disease strongly impairs the glycogen metabolism of affected animals resulting in abortion or early death of foals. Although understanding the prevalence of heterozygous for GBED is imperative to estimate the impact of the disease, prevalence studies have yet to be performed in Brazil. The aim of this study was to determine the prevalence of heterozygous of the GBED mutation in a population of Quarter Horses in Brazil. Blood samples were obtained from 742 animals competing in distinct disciplines including cutting, halter, race, reining, and barrel racing. All samples were submitted to DNA purification, amplification, and sequencing of the target fragment. The overall GBED prevalence of carriers was 7.95% (59/742). The prevalence of heterozygotes by discipline was considered higher in cutting (19.75% [32/162]) and reining (10% [16/160]) subgroups followed by barrel racing (5% [8/160]) and halter (3% [3/100]) horses. There were none heterozygous in the racing subgroup. These results demonstrate the GBED causative mutation in the Brazilian Quarter Horse herd and suggest the occurrence of the disease. Therefore, GBED is a disease that should be considered in the differential diagnosis of abortion and stillbirths, especially if suspect foals are products of two heterozygous. Besides testing aborted foals for the GBED mutation, the molecular diagnosis should be recommended to owners and breeders, at least for those breeding the at-most-risk subgroups of horses, to guiding their mating selections and, therefore, prevent the transmission of the mutation.

Prevalence of the E321G MYH1 variant in Brazilian Quarter Horses

“…As observed for MYH1 , the frequencies of alleles involved in other genetic diseases, that is, PSSM1, 4 HYPP, 10 GBED 13 and hereditary equine regional dermal asthenia (HERDA), 14 in Brazilian QHs were also similar to those found in American QHs 3 . The results obtained in this study and in previous studies 4,10,11,15 suggest that the similarity in the allele frequencies of these mutations may be because Brazilian QHs are often closely related to American QHs 14 and reining is a popular discipline in both countries.…”

“…The foals (foals 1 and 2) and their healthy sires/dams (horses 3‐6) were genotyped for MYHM following the protocols detailed below. In addition, these horses were also genotyped for PSSM1, MH, HYPP and GBED following previously described protocols 4,10,11 . After the death of foal 1, histopathological analysis of semimembranosus, semitendinosus and cardiac muscles was performed with formalin‐fixed paraffin‐embedded tissue stained with haematoxylin and eosin, periodic acid Schiff (PAS) and amylase‐PAS.…”

“…For validation, the genotypes were determined in 10 DNA samples from MYH1 heterozygotes and 20 wild‐type horses at the Veterinary Genetics Laboratory at the University of California‐Davis/USA (VGL‐UCDavis). The genotypes of PSSM1, HYPP, GBED and MH had previously been analysed 4,10,11 and were collated for this subset of horses.…”

Prevalence of the Mutations Responsible for Glanzmann Thrombasthenia in Horses in Brazil

“…Other studies on prevalence of different diseases with hereditary patterns that affect horses, but no related to hemostasis alterations, have been performed in Brazil: Hereditary equine regional dermal asthenia [17], Hyperkalemic periodic paralysis [18], Type 1 polysaccharide storage myopathy mutation [18], Malignant hyperthermia [19], Glycogen branching enzyme deficiency [20], and Warmblood fragile foal syndrome [21]. Many of these studies demonstrated similar results as found in other countries, such as the USA [16,22].…”