OMIA 001544-9913 : Hypotrichosis with coat-colour dilution (rat-tail syndrome) in Bos taurus

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Dominant

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2016

Species-specific name: rat-tail syndrome

Species-specific symbol: RTS

Species-specific description: Knaust et al. (2016) reported: "evidence that the RTS phenotype results from an epistatic interaction between three independent loci: dilution (that corresponds to the PMEL gene at 55 Mb on BTA5), extension (that corresponds to the MC1R gene on BTA18) and the RTS locus that is located in the interval between 14 and 22 Mb on BTA5. The prerequisites for expression of the RTS phenotype are a eumelanic background due to the presence of the dominant ED allele at MC1R (extension locus) and a heterozygous genotype at the PMEL gene variant c.64G>A (dilution locus). The positions of the RTS and dilution loci on BTA5 are clearly distinct."

Mapping: Knaust et al. (2016) mapped RTS to a region of chromosome BTA5 "between 14 and 22 Mb ".

Molecular basis: Jolly et al. (2008) summarised the results in an unpublished thesis by Hecht (2006) as: "In a genetic study of an experimental Simmental crossbred herd, the coat-colour dilution/hypotrichosis phenotype segregated with a three-base (CTT) deletion at nucleotide 54 in exon 1 of the PMel17 gene (Hecht 2006). Although the study was not conclusive, this is the presumptive mutation for the disorder. A second single nucleotide polymorphism, a C→A transition in exon 11 in the second nucleotide of codon 612 of the same PMel17 gene, segregated with most, but not all, animals with the same phenotype."

Reporting their investigation of the same disorder in Hereford-cross cattle, Jolly et al. (2008) identified the same two mutations: "a three-base deletion (CTT) at nucleotide 54" in exon 1 and "a single missence [sic] mutation in one copy of this exon, resulting in a C→A substitution in codon 612" in exon 11.

However, as reported by Knaust et al. (2016), in two papers published in 2007 (both listed below), Kühn and Weikard "showed that neither mutations in the coding and regulatory regions of the PMEL gene, nor splicing variants of this gene are associated with RTS". Knaust et al. (2016) went on to report that RTS in a German Holstein x Charolais population is due to the interaction of three loci: "In this population, the RTS is exclusively expressed in animals with a eumelanic background that is due to the dominant ED allele at the melanocortin 1 receptor gene located on Bos taurus autosome (BTA) 18. In addition, only the individuals that are heterozygous at the dilution locus on BTA5 that corresponds to the premelanosome protein or silver gene variant c.64G>A were classified as displaying a RTS phenotype. Linkage and whole-genome association analyses using different models and different pedigrees allowed us to map a third locus (hereafter referred to as the RTS locus) that is essential for the expression of the RTS phenotype to the chromosomal region between 14 and 22 Mb on BTA5. Our findings clearly demonstrate that the RTS and dilution loci are distinct loci on BTA5".

Knaust et al. (2020) "concluded that at least in cattle PMEL potentially has additional, yet unexplored functions, which might contribute to effects of PMEL mutations on pheomelanin coat color dilution and charcoal coat color in RTS animals".

Hauser et al. (2020) reported 33 Swiss cattle with rat-tail f pigmentation-associated hypotrichosis were all heterozygous for dominant black (E^D) and recessive red (e) variants at the MC1R locus and were also heterozygous at the PMEL locus for a dilution variant. These authors noted that "The introgression of Holstein cattle into the Original Simmental. breed, which has been practised for decades, explains the occasional occurrence of this phenomenon in Swiss cattle breeding."

Associated genes:

Symbol Description Species Chr Location OMIA gene details page Other Links
MC1R melanocortin 1 receptor (alpha melanocyte stimulating hormone receptor) Bos taurus 18 NC_037345.1 (14705093..14706843) MC1R Homologene, Ensembl, NCBI gene
PMEL premelanosome protein Bos taurus 5 NC_037332.1 (57344579..57353378) PMEL Homologene, Ensembl, NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Breed(s) Variant Phenotype Gene Allele Type of Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Year Published PubMed ID(s) Acknowledgements
Rat-tail syndrome MC1R E^D missense UMD3.1 18 g.14757910T>C c.296T>C p.L99P rs109688013 2016 27037038
Rat-tail syndrome PMEL deletion, small (<=20) UMD3.1 5 g.57669913_57669915delTTC c.50_52delTTC p.Leu19del rs385468954 2016 27037038


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.
2020 Hauser, M., Wolf-Hofstetter, S., Acklin-Menzi, F., Studer, E., Rediger, D., Seefried, F.R., Drögemüller, C. :
Graue, kraus- und kurzhaarige Schweizer Holstein Rinder weisen genetische ­Spuren der Rasse Simmental auf [Grey, curly and short-haired Swiss Holstein cattle show genetic traces of the Simmental breed] Schweizer Archiv fur Tierheilkunde 162:551-559, 2020. DOI: 10.17236/sat00272.
Knaust, J., Weikard, R., Albrecht, E., Brunner, R.M., Günther, J., Kühn, C. :
Indication of Premelanosome Protein (PMEL) Expression Outside of Pigmented Bovine Skin Suggests Functions Beyond Eumelanogenesis. Genes (Basel) 11:, 2020. Pubmed reference: 32668786. DOI: 10.3390/genes11070788.
2016 Knaust, J., Hadlich, F., Weikard, R., Kuehn, C. :
Epistatic interactions between at least three loci determine the "rat-tail" phenotype in cattle. Genet Sel Evol 48:26, 2016. Pubmed reference: 27037038. DOI: 10.1186/s12711-016-0199-8.
2008 Jolly, RD., Wills, JL., Kenny, JE., Cahill, JI., Howe, L. :
Coat-colour dilution and hypotrichosis in Hereford crossbred calves. N Z Vet J 56:74-7, 2008. Pubmed reference: 18408794. DOI: 10.1080/00480169.2008.36812.
2007 Kuehn, C., Weikard, R. :
Multiple splice variants within the bovine silver homologue (SILV) gene affecting coat color in cattle indicate a function additional to fibril formation in melanophores. BMC Genomics 8:335, 2007. Pubmed reference: 17892572. DOI: 10.1186/1471-2164-8-335.
Kühn, C.h., Weikard, R. :
An investigation into the genetic background of coat colour dilution in a Charolais x German Holstein F2 resource population. Anim Genet 38:109-13, 2007. Pubmed reference: 17302792. DOI: 10.1111/j.1365-2052.2007.01569.x.
2006 Hecht, B.C. :
Sequence analysis of PMel17 as a candidate gene for causing rat-tail syndrome in cattle MSc thesis, Brigham Young University, Provo UT, USA :, 2006.
1999 Schalles, R.R., Cundiff, L.V. :
Inheritance of the "rat-tail" syndrome and its effect on calf performance Journal of Animal Science 77:1144-1147, 1999. Pubmed reference: 10340580.
1989 Ayers, JR., Leipold, HW., Schalles, R., Cole, D. :
Pathological studies of cross-related congenital hypotrichosis in cattle. Zentralbl Veterinarmed A 36:447-52, 1989. Pubmed reference: 2508373.

Edit History

  • Created by Frank Nicholas on 30 Mar 2011
  • Changed by Frank Nicholas on 09 Dec 2011
  • Changed by Frank Nicholas on 18 Jun 2013
  • Changed by Frank Nicholas on 13 Apr 2016
  • Changed by Frank Nicholas on 02 Mar 2020
  • Changed by Frank Nicholas on 23 Oct 2020