Genetic testing of stationary night blindness (CSNB) in white spotted horses

Genetic testing as a tool for diagnosis of congenital stationary night blindness (CSNB) in white spotted breeds in Poland
J Equine Vet Sci. 2025 Feb 26:105405. doi: 10.1016/j.jevs.2025.105405. Online ahead of print.
Authors
M Stefaniuk-Szmukier 1 , A Bieniek 2 , K Ropka-Molik 2 , R R Bellone 3
Affiliations

1 Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland. Electronic address: monika.stefaniuk@iz.edu.pl.
2 Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland.
3 Veterinary Genetics Laboratory, Department of Population Health and Reproduction, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA; Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA.

PMID: 40021102
DOI: 10.1016/j.jevs.2025.105405

Abstract

Congenital stationary night blindness (CSNB) has been connected to the leopard complex spotting phenotype (LP) in various horse breeds. CSNB associated with LP is thought to be caused by a 1378bp insertion in TRPM1, with homozygotes being nightblind and having few to no spots of pigment in their white patterned area. This study aimed to assess the prevalence of CSNB alleles in tarant-colored horses in Poland through a three-primer system for an allele-specific Polymerase Chain Reaction (PCR). The TRPM1 gene insertion was genotyped in 221 horses belonging to Małopolska, Felin and Shetland Ponies. The chi-square (χ²) test indicates, that χ2 <5.991 suggesting that the population is in Hardy-Weinberg equilibrium. Of the horses carrying the LP allele, 7% of Małopolska horses, 4,8% of Felin ponies and 6.25 % of the Shetland ponies were homozygous for the TRMP1 insertion, indicating low-light vision issues, crucial for horses working in dim conditions. This study highlights the utility of genetic testing for accurate phenotype evaluation, and clinical and breeding management.

Keywords: Felin ponies; Leopard complex phenotype; Leopard spotting pattern; Malopolska horses.

Copyright © 2025. Published by Elsevier Inc.