ORIGIN OF THE NORTH-AMERICAN HOUSE MOUSE

The house mouse, Mus domesticus, was introduced to the American continent in the post-Columbian era. We have used mouse chromosome 17 DNA probes to trace the origin of the wild house mice on the East Coast of the United States. Of the four probes used, one in particular proved to be informative in this regard. The D17Tu20 probe defines a polymorphism at at a locus telomeric of the H-2 complex. TaqI restriction enzyme digests of genomic DNA blotted and hybridized with the D17Tu20 probe revealed the existence of restriction fragments shared by mice from the Atlantic coast of England, France, and the United States but absent in all other tested populations sampled from different parts of the world. This unique polymorphic pattern apparently arose by the loss of two restriction sites in the population on the coast of Brittany. The mutations then presumable spread to England, and from there to the United States. Since the mutations are also present in mice from Florida, English (rather than Spanish) mouse populations may have been either the sole or the main source of immigrants to the eastern United States. This conclusion is also supported by data obtained with the other probes. Presence of the D17Tu20 mutations in some of the laboratory strains indicates that American wild mice contributed to the gene pool of the inbred strains. We postulate that the colonization of North America by English wild mice began in the second half of the seventeenth century.