A Single Nucleotide Polymorphism (BIEC2‐808543) on Eca3 Is Associated with Recurrent Laryngeal Neuropathy Independent of Height in Thoroughbred Horses

Abstract

IntroductionRecurrent laryngeal neuropathy (RLN) is considered height‐linked in Thoroughbreds. A SNP (BIEC2‐808543) proximal to the LCORL/NCAPG gene significantly influences height variation in horses. It has been suggested that the C‐allele of this SNP is associated with RLN risk. Our objective was to investigate the association between the BIEC2‐808543 C‐allele, RLN and height in a cohort of Thoroughbreds.MethodsResting and exercising upper respiratory tract endoscopic videos, laryngeal ultrasonograms, wither height, age and sex were recorded in 79 Thoroughbreds (age 34 ± 11 months). The Havemeyer grading scale was used to characterise RLN cases (Grade B or C at exercise) and controls (Grade 1.1 or 2.1 at rest, Grade A at exercise, normal laryngeal ultrasound). All horses were genotyped for the BIEC2‐808543 SNP using a custom TaqMan SNP Genotyping assay. Logistic regression was performed measuring additive effects of allele dosage with sex, age and height as covariates (P≤0.05). Horses were subcategorised into tall (T,≥162 cm) and short (S,<162 cm) groups for C‐allele frequency determination, with data presented as mean ± SD.ResultsThere were 16 RLN cases (height 164.5 ± 4 cm) and 32 controls (height 156.2 ± 4 cm). With sex and age as covariates, a significant association between the C‐allele and RLN cases was observed (P = 0.01). With height included as a covariate, a strong trend of association between the C‐allele and RLN remained (P = 0.06). C‐allele frequency was 41.7% for the T‐RLN group (n = 12, height 166.2 ± 3 cm), 12.5% for the S‐RLN group (n = 4, height 159.5 ± 2 cm), 13% for the T‐Control group (n = 16, height 165.1 ± 2 cm) and 14% for the S‐Control group (n = 16, height 156.2 ± 4 cm).ConclusionsThe association between the BIEC‐808543 C‐allele and RLN appears to be independent of height.Ethical Animal ResearchInstitutional Animal Research Ethics Committee approval was obtained. Explicit owner informed consent for participation in this study is not stated. Sources of funding: Science Foundation Ireland under Grant Number 11/PI/1166. Competing interests: Dr Hill is a co‐founder and Chairman of Equinome Ltd.