A novel ENU-induced mutation, peewee, causes dwarfism in the mouse

We identified a novel fertile autosomal recessive mutation called peewee that results in dwarfing, in a region-specific ENU-induced mutagenesis. These mice at litter size were smaller those of other strains. Histological analysis revealed that the major organs appear normal, but abnormalities in cellular proliferation were observed in bone, liver, and testis. Haplotype analysis localized the peewee gene to a 3.3-Mb region between D5Mit83 and D5Mit356.3. There are 18 genes in this linkage area. We also performed in silico mapping using the PosMed(SM) program, which searches for connections among keywords and genes in an interval, but no similar phenotype descriptions were found for these genes. In the peewee mutant compared to the normal C57BL/6 J mouse, only Slc10a4 expression was lower. Our preliminary mutation analysis examining the nucleotide sequence of three exons, two introns, and an untranslated region of Slc10a4 did not find any sequence difference between the peewee mouse and the C57BL/6 J mouse. Detailed analysis of peewee mice might provide novel molecular insights into the complex mechanisms regulating body growth.