The phenogenetics of hair mutants in the house mouse: Opossum and Ragged

Abstract

1. The development and morphology of the semi-dominant mutations Ragged and Opossum are compared. The results of the present study support evidence of previous linkage studies which suggest that Ragged (Ra) and Opossum (Raop) are alleles.2. Examination of embryos from 18-day-old first parity matings of + + × Raop + reveals that there is no deficiency of Raop + embryos. However, in Ra + × Raop + and Raop + × Raop + matings some Raop + embryos die in utero in addition to the pre-natal death of the RaRaop and RaopRaop embryos.3. In all matings of Ragged and Opossum, there is a high frequency of oedematous Raop + embryos. In + + × Raop + matings, the frequency of oedema increases with increased age of the embryos.4. Although the pattern of hair follicle formation is the same in both the mutant and normal embryos, follicles begin initiation later in the mutant embryos. The delay in follicle initiation is increased in the following order: Ra +, Raop + (non-oedemic), RaRa and Raop + (oedemic).5. Heterozygous Opossum and Ra + mice have a full complement of pelage follicle primordia, but some follicles fail to differentiate. The differentiating follicles pass through the same developmental stages and require the same time for development as follicles in + + mice.6. Heterozygous Ragged and Raop + mice have a full complement of tylotrichs, whereas the concentration of awls is variable. In Ra + mice there is a reduction in zigzags, and Raop + mice usually lack zigzags. No auchenes are observed in the mutant mice.7. Hair growth is asynchronous in Ra + and Raop + mice, with the exception of the first pelage coat. The quiescent phase of the hair growth cycle is short or even missing.8. The degree of Ra and Raop gene activity is in the following order of increased severity: Ra +, Raop + (semi-lethal), RaRa (semi-lethal), RaRaop (lethal) and RaopRaop (lethal).