Sabino and Sabino 1

What it looks like

Sabino-like markings often include a broad white facial marking, white reaching high up the legs, white on the belly, and irregular borders mixed with white hairs. The amount of white ranges from subtle markings to an almost white coat. These descriptions help record what a horse looks like, but several genetic causes can produce similar appearances.

Sources for this explanation [1]

What happens biologically

Sabino 1, abbreviated SB1, is a specific DNA variant in KIT, a gene that helps pigment cells develop. To use a gene, a cell first makes a working copy of its instructions called messenger RNA. SB1 changes how that message is assembled, so part of the usual instructions can be skipped. Identifying this mechanism does not mean that every irregular white border or scattered white hair is caused by SB1.

Sources for this explanation [2]

Inheritance and DNA testing

A horse inherits one KIT copy from each parent. On an SB1 test, N means that the SB1 variant was not detected on the corresponding copy. The results are N/N, no SB1 copy; SB1/N, one SB1 copy; and SB1/SB1, two SB1 copies. The effect shows incomplete dominance: one copy usually gives sabino markings, while two commonly give a predominantly white coat.

A one-copy horse passes SB1 to about half its foals; a two-copy horse passes it to all. For example, a tested SB1/N × N/N mating gives a 50% chance of an SB1/N foal and a 50% chance of N/N at each conception. A negative SB1 test rules out this variant, not a similar appearance caused by something else.

Sources for this explanation [1] · [3]

Confusions, limits and health

Dominant-white KIT variants and splashed-white variants can resemble sabino, and combinations make the appearance harder to interpret. Keep the visible description separate from the laboratory result. A mostly white SB1/SB1 horse should not be described as a lethal-white foal merely because it is white: the EDNRB disorder has a different cause. When health matters for a breeding decision, test the relevant variants rather than relying on appearance.

Sources for this explanation [3] · [4]

Where the explanations come from

Laboratory resources explain which variants are tested and how to read their results. Research papers describe the evidence, discoveries and remaining uncertainties. Each article links its explanations to the relevant sources. Published titles stay in their original language so you can find the exact work.

1. 1 · Laboratory explanation

   UC Davis VGL — Sabino 1

2. 2 · Research paper

   Brooks & Bailey (2005) — Exon skipping in the KIT gene causes a Sabino spotting pattern in horses

3. 3 · Research paper

   Druml et al. (2018) — Novel insights into Sabino1 and splashed white coat color patterns in horses

4. 4 · Research paper

   Haase et al. (2007) — Allelic heterogeneity at the equine KIT locus in dominant white horses