Nucleotide polymorphisms in the canine Noggin gene and their distribution among dog (Canis lupus familiaris) breeds.

Noggin (NOG) is an important regulator for the signaling of bone morphogenetic proteins. In this study, we sequenced the complete coding sequence of the canine NOG gene and characterized the nucleotide polymorphisms. The sequence length varied from 717 to 729 bp, depending on the number of a 6-bp tandem repeat unit (GGCGCG), an insertion that has not been observed in other mammalian NOG genes investigated to date. It results in extensions of (Gly-Ala)3-5 in the putative NOG protein. To survey the distribution of these tandem repeat polymorphisms, we analyzed 126 individuals in seven dog breeds. We identified only three alleles: (GGCGCG)3, (GGCGCG)4, and (GGCGCG)5. Although the allele frequencies were remarkably different among the breeds, the three alleles were present in all seven of the breeds and did not show any deviation from Hardy-Weinberg equilibrium.