Loading...
Gene or Region: MYO5A
Reference Variant: C
Mutant Variant: -
Affected Breeds: Arabian
Research Confidence: High confidence - Findings reproduced multiple studies
Explanation of Results: lfs/lfs = homozygous for Lavender Foal Syndrome, lethal lfs/n = heterozygous for Lavender Foal Syndrome, carrier n/n = no variant detected
Lavender Foal Syndrome (LFS), also known as coat color dilution lethal, is a neurological dysfunction in newborn foals. Symptoms are apparent at birth and include seizures, severe hyper-extension of limbs, neck and back, stiff paddling leg movements, involuntary eye movement and inability to stand or sit upright. The coat usually has a dilute color that ranges in shade from silver to a pale lavender/pink. As there is no treatment, affected foals are humanely euthanized. LFS is an autosomal recessive condition, thus a horse must inherit two copies of the allele (LFS/LFS) to show any signs. Horses with only one copy of the allele (LFS/n) are known as carriers due to their ability to produce affected foals.
MYO5A functions as part of a trafficking complex that serves to move important molecules in pigment cells and neurons. Mutations in humans result in Griscelli syndrome, which is characterized by dilute hair and neurological dysfunction. The LFS mutation is a single base deletion that results in a premature stop codon, and thus a truncated protein.
Brooks SA et al., “Whole-genome SNP association in the horse: identification of a deletion in myosin Va responsible for Lavender Foal Syndrome.” (2010) PLoS Genet. 6: e1000909. PMID: 20419149
Gabreski NA et al., “Investigation of allele frequencies for Lavender foal syndrome in the horse.” (2012) Anim Genet. 43: 650. PMID: 22497275
Tarr CJ et al., “The carrier prevalence of severe combined immunodeficiency, lavender foal syndrome and cerebellar abiotrophy in Arabian horses in South Africa.” (2014) Equine Vet J. 46: 512-4. PMID: 24033554
Lordosis (L1, L2, L3, L4), also known as "Swayback", is a curvature or dip in the spine that is often seen in older horses. However, in the American Saddlebred, this condition also affects younger horses. These animals do not appear to experience pain from their condition and are still able to be used under saddle.
Malignant hyperthermia (MH) is a muscle disorder in which anesthesia, stress, or extreme exercise trigger a hyperthermic state. Symptoms include high temperature, increased heart rate, high blood pressure, sweating, acidosis, and muscle rigidity. If symptoms are not immediately resolved, death is likely to occur.
Myosin-Heavy Chain Myopathy (MY; previously "IMM") is a genetic muscle disease found most commonly in stock-type horses that can result in two different presentations, Immune-Mediated Myositis (IMM) and Nonexertional Rhabdomyolysis “tying up,” which are both characterized by muscle damage or loss. Both presentations are associated with the same genetic variant. Horses with MYHM may exhibit one or both presentations at different times in their lives, although some horses carrying the variant might not display any symptoms at all.
Myotonia (MYT) is a rare disorder involving a slowed relaxation of muscles after contraction. The most well-known example of myotonia is “fainting goats,” a breed that is characterized by sudden rigidy and/or falling over when startled. In the single documented horse, this resulted in a protruding third eyelid when excited, as well as problems with muscle stiffness.
