The Genetics of Variant Red and Changeling Coat Colour Phenotypes in Holstein Cattle
Date
2008
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
Although most Holstein cattle are either black with white spots or red with white spots,
two new coat colour traits called Variant Red (VR) and changeling, have recently been
recognized by Holstein Canada. Variant red cattle look the same as red and white Holsteins but
VR appears to be inherited as a dominant trait. Changeling cattle are born red and turn black by
adulthood. Candidate genes for changeling included melanocortin 1 receptor (MC1R), agouti
signalling protein (ASIP), attractin (ATRN), and melatonin receptor 1A (MTNR1A). Candidate
genes for variant red included these same genes and β-defensin300 (putative K locus).
Polymerase chain reaction restriction fragment length polymorphisms (PCR-RFLP) and
sequencing were used to genotype single nucleotide polymorphisms (SNPs), which were recently
discovered in our lab, for use in determining co-segregation in appropriate families. Cosegregation
analysis excluded MC1R, ASIP, ATRN, or MTNR1A for changeling and VR,
assuming single gene inheritance. Microsatellites and SNPs were used to map VR to a region on
BTA27 surrounding and including β-defensin300 (LOD = 3.255). Cattle β-defensin300 was
characterized from genomic DNA and mRNA from skin and appears to be homologous to canine
β-defensin103 which is involved in black/red coat colour differentiation in many dog breeds.
Although no mutations were found in the coding sequence, several were found in the 5’, putative
promoter region. No polymorphisms consistently and exclusively occurred in VR and not in
changeling and/or black and white Holstein cattle. Common relatives occurred in the pedigrees
of several variant red and changeling cattle. A hypothesis was developed which suggests that a
common mutation is required for the occurrence of either phenotype. A dominant mutation in a
second gene would be required for VR, potentially a promoter mutation in β-defensin300. Two
recessive alleles at a yet unidentified second gene, potentially a promoter mutation in ASIP,
would be required for the changeling phenotype to occur.
Description
Keywords
colour, cattle, genetics
Citation
Degree
Master of Science (M.Sc.)
Department
Animal and Poultry Science
Program
Animal and Poultry Science