Mexican hairless dog were sacred by the Aztecs and there are statues of them dating back 3700, hairless dogs were also described in Ancient Egypt. Scientists using nowadays hairless dogs have discovered the mutated gene responsible for this strange appearance. Hairless dogs not only have a hair coat sparse or absent but also missing or abnormally shaped teeth. The inheritance of this phenotype is a monogenic semi-dominant trait meaning that heterozygous dogs are hairless but homozygous mutant die during embryogenesis.
By genotyping only 20 hairless and 19 coated Chinese Crested dogs with the 50K canine Affymetrix v2 array, the mutation was mapped to the canine chromosome 17 in a region of 1.7 Mb. Fine mapping with a larger set of Chinese dogs along with Mexican and Peruvian hairless dogs reduced the associated region to a 102 Kb interval containing two genes including one truncated pseudogene. The other gene was similar to the FOX transcription factor family, important regulators of development, and showed the highest similarity with FOXI3 gene. In mice this gene is expressed in the epithelium of the hair and whisker placodes and developing teeth. Sequencing analysis of the FOXI3 gene in all hairless dogs revealed a 7-bp duplication in the exon 1 that produces a frameshift and a premature Stop codon. So the most likely explanation for this phenotype is a haplo-insufficiency of the FOXI3 protein whereas a complete lack of the protein will cause embryonic lethality. This study in dog genetics is giving new insight into general developmental biology.
Reference: “a mutation in hairless dogs implicates FOXI3 in ectodermal development” Drögemüller C, Karlsson EK, Hytönen MK, Perloski M, Dolf G, Sainio K, Lohi H, Lindblad-Toh K, Leeb T. Science. 2008 Sep 12;321 (5895) 1462.
PMID: 18787161 [PubMed – Indexed forMEDLINE]