A polymorphism within the equine CRISP3 gene is associated with stallion fertility in Hanoverian warmblood horses

Fertility of stallions is of high economic importance, especially for large breeding organisations and studs. Breeding schemes with respect to fertility traits and selection of stallions at an early stage may be improved by including molecular genetic markers associated with traits. The genes coding for equine cysteine-rich secretory proteins (CRISPs) are promising candidate genes because previous studies have shown that CRISPs play a role in the fertilising ability of male animals. We have previously characterised the three equine CRISP genes and identified a non-synonymous polymorphism in the CRISP1 gene. In this study, we report one non-synonymous polymorphism in the CRISP2 gene and four non-synonymous polymorphisms in the CRISP3 gene. All six CRISP polymorphisms were genotyped in 107 Hanoverian breeding stallions. Insemination records of stallions were used to analyse the association between CRISP polymorphisms and fertility traits. Three statistical models were used to evaluate the influence of single mutations, genotypes and haplotypes of the polymorphisms. The CRISP3 AJ459965:c.+622G>A SNP leading to the amino acid substitution E208K was significantly associated with the fertility of stallions. Stallions heterozygous for the CRISP3 c.+622G>A SNP had lower fertility than homozygous stallions (P = 0.0234). The pregnancy rate per cycle in these stallions was estimated to be approximately 7% lower than in stallions homozygous at this position.     

The complete map of the Ig heavy chain constant gene region reveals evidence for seven IgG isotypes and for IgD in the horse

This report contains the first map of the complete Ig H chain constant (IGHC) gene region of the horse (Equus caballus), represented by 34 overlapping clones from a new bacterial artificial chromosome library. The different bacterial artificial chromosome inserts containing IGHC genes were identified and arranged by hybridization using overgo probes specific for individual equine IGHC genes. The analysis of these IGHC clones identified two previously undetected IGHC genes of the horse. The newly found IGHG7 gene, which has a high homology to the equine IGHG4 gene, is located between the IGHG3 and IGHG4 genes. The high degree of conservation shared between the nucleotide sequences of the IGHG7 and IGHG4 genes is unusual for the IGHG genes of the horse and suggests that these two genes duplicated most recently during evolution of the equine IGHG genes. Second, we present the genomic nucleotide sequence of the equine IGHD gene, which is located downstream of the IGHM gene. Both the IGHG7 and IGHD genes were found to be expressed at the mRNA level. The order of the 11 IGHC genes in the IGH-locus of the horse was determined to be 5'-M-D-G1-G2-G3-G7-G4-G6-G5-E-A-3', confirming previous studies using lambda phage clones, with the exception that the IGHG5 gene was found to be the most downstream-located IGHG gene. Fluorescence in situ hybridization was used to localize the IGHC region to Equus caballus (ECA) 24qter, the horse chromosome corresponding to human chromosome 14, where the human IGH locus is found.