Test Detail

Equine colour: Leopard complex

Color & coat · Horse

Test for the leopard complex (leopard complex spotting, LP), a set of white-spotting patterns characteristic of breeds such as the Appaloosa, Knabstrupper or Pony of the Americas. It analyses the retroviral insertion in TRPM1 associated with the pattern and with the risk of congenital stationary night blindness (CSNB) in homozygotes. It is complementary to, not a substitute for, clinical and ophthalmological examination.
Inheritance patternIncomplete autosomal dominant for the spotting and autosomal recessive for congenital night blindness (TRPM1). The pattern is modulated by PATN1.
Gene / MutationTRPM1: 1378 bp retroviral insertion in intron 1 (EquCab3.0 g.109211964_109211965insN[1378]); a single LP locus associated with both the spotting and CSNB. PATN1 modifier: variant in RFWD3 associated with a greater extent of white. No other main causal variant has been described.
PenetranceThe spotting has high penetrance but variable expression (dose-dependent on LP and PATN1). CSNB is recessive and manifests in LP/LP homozygotes; LP/N heterozygotes are not affected.
Sample type0,5-1 ml sangre-EDTA o 20-30 pelos de la crin o la cola
Codeasrk
Turnaround time15 days
Price52,60 €
Breedstodas las razas

Incidence

Applicable breeds: Appaloosa, Knabstrupper, Pony of the Americas, Miniature Horse, Shetland Pony and other spotted breeds. Frequencies: limited data.

Clinical signs

• LP/N and LP/LP: white spots over the croup and loins, with blanket, snowflake or leopard pattern.\n• LP/LP homozygosity: greater extent of white and congenital stationary night blindness (CSNB), with difficulty seeing in low light.\n• The pattern varies greatly between individuals and depends on modifier alleles such as PATN1.

History

The LP locus was assigned to chromosome 1 and in 2013 Bellone and colleagues identified a 1378 bp retroviral insertion in intron 1 of TRPM1, fully associated with the pattern and with CSNB. The extent of the spotting is modulated by the PATN1 gene (variant in RFWD3, Holl 2016).

Breeder management

• Avoid LP/LP × LP/LP: all offspring will be LP/LP and affected by CSNB.\n• Before mating, assess the LP genotype and that of PATN1 to estimate the extent of white.\n• In LP carriers, assess vision in low light and, if appropriate, perform an ophthalmological examination.\n• Selection solely for the extent of white increases the risk of CSNB.

Specialist notes

Differential diagnosis with other white patterns (tobiano, splashed white, sabino). CSNB is confirmed by electroretinography; do not confuse it with uveitis. In LP/LP homozygotes a higher risk of insidious uveitis has been described.

References

1. Bellone 2013, Evidence for a retroviral insertion in TRPM1 as the cause of CSNB and leopard complex spotting (PMID 24167615); OMIA:002139-9796.
2. Holl 2016, Variant in the RFWD3 gene associated with PATN1, a modifier of leopard complex spotting (PMID 26568529); OMIA:002139-9796.
Price: 52,60 € · Turnaround time: 15 days

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