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Horse Genetics / Horse Color Genetics / Pattern 1

Pattern 1 (PATN1)

Gene or Region: RFWD3

Reference Variant: T (N)

Mutant Variant: G (patn1)

Affected Breeds: Several

Research Confidence: High - Strong association in studied population

Explanation of Results: PATN1/PATN1 = homozygous for Pattern 1, trait expressed PATN1/n = heterozygous for Pattern 1, trait expressed n/n = no variant present

General Description

Pattern-1 (PATN1) is strongly association with a variant of the RFWD3 gene that modifies the expression of leopard complex spotting. Horses that inherit PATN1 are generally born with a large amount (>60%) of LP-associated white spotting, whereas those without tend to have lower amounts (<40%). However, PATN1 has no apparent effect on any other white markings or spotting, and thus effectively “hides” in lp/lp horses. PATN1 is an example of a dominant trait, with both homozygous (PATN1/PATN1) and heterozygous (PATN1/patn1) displaying the same effect on patterning. Other minor variants further modify the extent of white patterning present at birth. The adult color is not a good indicator of PATN1 genotype as some low pattern horses “roan out” to large amounts of white patterning.

Genotype and Phenotype

  • Double leopard with pattern-1 (LP/LP PATN1/n): Fewspot, Near Fewspot with CSNB

  • Single leopard with pattern-1 (LP/lp PATN1/n): Leopard, Near Leopard

  • Non-leopard with pattern-1 (lp/lp PATN1/n): No leopard Complex Spotting

  • Double leopard without pattern-1 (LP/LP patn1/patn1): Snowcap, Varnish with CSNB

  • Single leopard without pattern-1 (LP/lp patn1/patn1): Spotted blanket, Varnish

  • Non-leopard without pattern-1 (lp/lp patn1/patn1): No Leopard Complex Spotting

  • Spotting patterns generally follow after the color of the pigmented regions, for example “dun leopard” or “black silver snowcap.”

Gene Information

RFWD3 is a ubiquitin ligase that functions in the DNA damage response and DNA replication control. There are no known mutations in other species. The PATN1 associated variant is located within the 3' untranslated region and thus may regulate the expression of RFWD3.

References

Bellone RR et al., “Evidence for a retroviral insertion in TRPM1 as the cause of congenital stationary night blindness and leopard complex spotting in the horse.” (2013) PLoS One. 8 :e78280. PMID: 24167615

Holl H et al., “Variant in the RFWD3 Gene Associated with PATN1, a Modifier of Leopard Complex Spotting.” (2015) Anim Genet. 47: 91-101.

Druml T et al., "Phenotypic and genetic analysis of the leopard complex spotting in Noriker horses." (2017) J Hered. doi: 10.1093/jhered/esx039.

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