Lavender foal syndrome in Arabian horses is caused by a single‐base deletion in the MYO5A gene

Abstract

Summary Lavender Foal Syndrome (LFS) is a rare autosomal recessive lethal disorder affecting Arabian foals which is also characterized by a dilute coat colour and severe neurological signs. Dilute mouse and rat mutants, and Griscelli syndrome type 1 in humans, which are characterized by similar clinical signs, are caused by mutations in the MYO5A gene. MYO5A was, therefore, identified as a possible candidate gene for LFS. Sequencing of the coding region identified a single‐base deletion in a conserved region of the tail domain. The deletion produces a truncated protein product through the insertion of a premature stop codon (p.Arg1487AlafsX13). The deletion was confirmed as the causative mutation by genotyping affected, carrier and normal individuals.

Investigation of Known Genetic Mutations of Arabian Horses in Egyptian Arabian Foals with Juvenile Idiopathic Epilepsy

“…A coat color predilection such as that reported in foals with LFS has not been noted in foals with JIE . In contrast, foals with LFS are born with profound neurologic dysfunction resulting in euthanasia within a few days of life . The most commonly reported abnormalities include lateral recumbency with inability to rise or assume sternal recumbency, opisthotonus, intermittent paddling, and extensor rigidity .…”

“…The mutation affects myosin Va which is part of a complex of proteins involved in the trafficking of melanosomes to keratinocytes, and transportation of secretory granules, glutamate receptors, and mRNA in neurons . Mutation of the MYO5A gene explains the observed dilute color and various neurologic deficits in diseased foals . Phenotypically, JIE and LFS are different.…”

“…Most foals have a strong suckle reflex, and the remainder of the neurologic examination is normal . Coat colors in foals with LFS include dilute pale chestnut and lavender . A sex predisposition has not been noted for either disorder …”

“…Genetic disorders have been reported in various pure‐bred horses . Disorders caused by known genetic mutations that are present in Arabian horses include lavender foal syndrome (LFS), cerebellar abiotrophy (CA), severe combined immunodeficiency (SCID), and occipitoatlantoaxial malformation (OAAM1) . Lavender foal syndrome is a lethal disorder of Egyptian Arabian foals characterized by foals born with a dilute coat color and profound neurologic dysfunction .…”

“…Lavender foal syndrome is a lethal disorder of Egyptian Arabian foals characterized by foals born with a dilute coat color and profound neurologic dysfunction . It is an autosomal recessive inherited disorder caused by a frameshift mutation in exon 30 of the myosin Va gene ( MYO5A ) that results in premature termination of transcription . Myosin Va protein is essential for the normal function of melanocytes and neurons .…”