THE RAT MICROPHTHALMIA-ASSOCIATED TRANSCRIPTION FACTOR GENE (MITF) MAPS AT 4Q34-Q41 AND IS MUTATED IN THE MIB RATS

The rat gene encoding the microphthalmia-associated transcription fact or (Mitf) was assigned to rat Chromosome (Chr) 4q34-q41, as well as th e Gata2 and Mem1 genes. Rat Chr 4 is homologous to mouse Chr 6 and hum an Chr 3, which carry the Mitf (MITF) gene in these species (MMU 6, 40 .0 cM, and HSA 3p14.1-p12.3). mib/mib rats, which are characterized by depigmentation, microphtalmy, osteopetrosis, and neurological disorde rs were shown to bear a deletion covering several kilobases of genomic DNA in the Mitf gene and to lack Mitf mRNA. The Mitf mutation in the mib/mib rats is thus very likely to be a Mid null mutation, causing a phenotype similar to the one observed in the mi(VGA-9) mice, but inclu ding osteopetrosis as an additional feature.