A Candidate Gene Study of Recurrent Laryngeal Neuropathy in Belgian Draft Horses

Recurrent Laryngeal Neuropathy (RLN) causes inspiratory air obstruction, during maximal exercise, thus leading to poor performance in athletic horses. Several studies have investigated the genetic risk factors associated with RLN, no clear factors have been identified.

Our aim was to investigate the genetic risk factors associated with RLN in Draft-breed horses using a candidate gene (CG) approach.

Four Draft breed horse RLN cases (Percheron n=1, Belgian Draft horses n= 1 and Clydesdales n=2) and 4 Draft breed horse controls (Percheron n=1, Belgian Draft horses n=1 and Clydesdales n=2) were selected for whole genome next generation sequencing, from cases that exhibited a Havemeyer grade IV/IV left laryngeal paralysis phenotype, during resting endoscopy. Reads were sequenced using Illumina HiSeq, 100 bp paired-end and 6x coverage per horse (150-180 million reads/horse). Each sample was sequenced in more than one lane. An initial list of CGs was complied from genes associated with similar human peripheral neuropathies; Charcot Marie Tooth Types 1, 2 and 4 and Hereditary Motor Neuropathy. Additional CGs were identified using the CG prioritization tool Phenolyzer.

A total of 106 CGs have been identified; with 80 CGs within the initial list, and 25 added after Phenolyzer consultation. The CGs equine equivalents have been identified, their annotations checked and each gene is currently being checked for potential causative mutations.