title: The 1.78-kb insertion in the 3'-untranslated region of RXFP2 does not segregate with horn status in sheep breeds with variable horn status.
abstract: The mode of inheritance of horn status in sheep is far more complex than a superficial analysis might suggest. Observations, which were mostly based on crossbreeding experiments, indicated that the allele that results in horns is dominant in males and recessive in females, and some authors even speculated about the involvement of more than two alleles. However, all recent genome-wide association analyses point towards a very strong effect of a single autosomal locus on ovine chromosome 10, which was narrowed down to a putatively causal insertion polymorphism in the 3'-untranslated region of the relaxin/insulin-like family peptide receptor 2 gene (RXFP2). The main objective of this study was to test this insertion polymorphism as the causal mutation in diverse sheep breeds, including breeds with a variable and/or sex-dependent horn status.
  
  
  
  After re-sequencing a region of about 246 kb that covered the RFXP2 gene and its flanking regions for 24 sheep from six completely horned and six completely polled breeds, we identified the same insertion polymorphism that was previously published as segregating with horn status in these breeds. Multiplex PCR genotyping of 489 sheep from 34 breeds and some crosses between sheep breeds showed a nearly perfect segregation of the insertion polymorphism with horn status in sheep breeds of Central and Western European origin. In these breeds and their crossings, heterozygous males were horned and heterozygous females were polled. However, this segregation pattern was not, or at least not completely, reproducible in breeds with sex-dependent and/or variable horn status, especially in sheep that originated from even more southern European regions and from Africa. In such breeds, we observed almost all possible combinations of genotype, sex and horn status phenotype.
  
  
  
  The 1.78-kb insertion polymorphism in the 3'-untranslated region of RXFP2 and SNPs in the 3'-UTR, exon 14 and intron 11 of this gene that we analyzed in this study cannot be considered as the only cause of polledness in sheep and are not useful as a universal marker to define the genetic horn status in sheep.
authors.affiliation: Department of Animal Breeding and Genetics, Justus Liebig University of Gießen, Ludwigstrasse 21a, 35390, Giessen, Germany.
authors.forename: Gesine
authors.initials: G
authors.lastname: Lühken
authors.affiliation: Laboratory for Functional Genome Analysis (LAFUGA), Gene Center Munich, LMU Munich, Feodor-Lynen-Strasse 25, 81377, Munich, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Krebs
authors.affiliation: Chair of Animal Genetics and Husbandry, LMU Munich, Veterinaerstrasse 13, 80539, Munich, Germany.
authors.forename: Sophie
authors.initials: S
authors.lastname: Rothammer
authors.affiliation: Department of Animal Breeding and Genetics, Justus Liebig University of Gießen, Ludwigstrasse 21a, 35390, Giessen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Küpper
authors.affiliation: Department of Animal Science and Technology, Faculty of Agriculture, University of Zagreb, Svetošimunska cesta 25, 10000, Zagreb, Croatia.
authors.forename: Boro
authors.initials: B
authors.lastname: Mioč
authors.affiliation: Tierzuchtforschung e.V. München, Senator-Gerauer-Strasse 23, 85586, Poing, Germany.
authors.forename: Ingolf
authors.initials: I
authors.lastname: Russ
authors.affiliation: Chair of Animal Genetics and Husbandry, LMU Munich, Veterinaerstrasse 13, 80539, Munich, Germany. ivica.medjugorac@gen.vetmed.uni-muenchen.de.
authors.forename: Ivica
authors.identifier: 0000-0002-6891-3039
authors.initials: I
authors.lastname: Medugorac
mesh_terms: D020413:3' Untranslated Regions; D000483:Alleles; D000818:Animals; D002874:Chromosome Mapping / Q000379:methods; D005260:Female; D056726:Genetic Association Studies; D055106:Genome-Wide Association Study; D006733:Horns / Q000254:growth & development; D008297:Male; D016254:Mutagenesis, Insertional; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*; D000068618:Selective Breeding / Q000235:genetics; D012737:Sex Factors; D034561:Sheep, Domestic / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; D043562:Receptors, G-Protein-Coupled