Evidence for X linkage of the mouse tear protein system-3 (Mtp-3) with mosaic expression in heterozygous females.

Electrophoretic variations exhibited by some tear proteins have been observed using 20 strains of mice. Fifteen to twenty protein components were detected in tears, and one of the proteins, designated Mtp-3 (mouse tear protein system-3), is found only in the NZB strain. NZB animals were crossed to BALB/c animals with no Mtp-3 and the results showed that Mtp-3 was controlled by a pair of alleles on the X chromosome. Mosaic expression was detected in females heterozygous for the Mtp-3 alleles when tear samples were examined separately from the right or left eye. This report supports Lyon's hypothesis and shows that mouse tears are useful for genetic research.