The rat shorn mutation (shn) maps between D7Got143 and D7Rat94.

The recessive shorn (shn) mutation in the rat generates an almost complete absence of normal hair. Previous analysis of 85 backcross rats typed for shn-generated hypotrichosis located this marker between the telomere and D7Mgh1 on distal rat Chromosome 7. Here, we present a microsatellite polymorphism analysis of a 184-member backcross panel-including 99 new rats-that places shn within a 2.7cM interval between markers D7Got143 and D7Rat94. In addition, this analysis has allowed meiotic ordering of 18 microsatellite markers-including 10 D7Got markers previously positioned only by radiation reduced hybrid analysis-across the 16.8cM region between D7Mit16 (Cyp2d4) and D7Rat94. Our inability to meiotically separate shn from 8 microsatellite markers (mapped by others over some 2-4cM or more than 40cR of genetic distance) suggests that the shn mutation may result from a chromosomal rearrangement that suppresses recombination throughout this interval.

The Charles River "hairless" rat mutation maps to chromosome 1: allelic with fuzzy and a likely orthologue of mouse frizzy.

Recent evidence has indicated that the recessive mutation affecting hypotrichosis in the Charles River (CR) "hairless" rat does not involve the hairless gene (hr) on rat chromosome 15. To determine if this mutation might be allelic (or orthologous) with any other previously mapped hypotrichosis-generating mutation in mammals, we have produced a panel of backcross rats segregating for the CR hairless rat mutation as well as numerous other markers from throughout the rat genome. Analysis of this panel has located the CR hairless rat's hypotrichosis-generating mutation on chromosome 1, near Myl2, where only the fuzzy mutation in rat (fz) and the frizzy mutation in mouse (fr) have been previously localized. Intercrossing fz/fz and CR hairless rats produced hybrid offspring with abnormal hair, showing that these two rat mutations are allelic. We suggest that the CR hairless rat mutation and fuzzy be renamed frizzy-Charles River (fr(CR)) and frizzy-Harlan (fr(H)), respectively, to reflect their likely orthology with the mouse fr mutation.