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[The expression of the mutant gene mi in mouse aggregation chimeras]
Abstract:
Using aggregation of 8-cell embryos belonging to two mouse strains, we produced 17 chimeras, mi/mi<==>+/+ (3 organisms), mi/+<==>+/+ (9 organisms), and +/+<==>+/+ (5 organisms), that achieved the age of 30 days. Chimerism was identified by mosaic pigmentation of coat and retinal pigment epithelium (RPE). All mi/mi<==>+/+ chimeras suffered from microphthalmia. Disturbances of eye development in these mice were similar to those in mi/mi animals. In all three chimeras, pigmentation of RPE and choroid was represented with alternating pigmented and depigmented patches. Mosaic RPE pattern probably resulted from the effects of para-orbital mesenchyme cells of different genotypes, +/+ or mi/mi. These findings confirm our earlier data that mutant alleles of the mi locus affect ectomesenchyme (neural crest) cells playing an important role in normal RPE development. Coat pigmentation in mi/mi<==>+/+ chimeras had the same spotted pattern as in mi/+ heterozygous mice. Hence, the gene mi functions in melanoblasts, but dermal and epidermal mi/mi cells do not suppress migration, proliferation, and differentiation of +/+ melanoblasts. The mi/mi dermal cells do not interfere with the expression of the gene A. Despite the high proportion of mi/mi cells (58 to 80%), bone resorption and eruption of teeth in mi/mi<==>+/+ chimeras proceeded as in normal animals.
Insights
Mouse chimeras reveal the microphthalmia (mi) gene
Area of Science:
- Developmental biology
- Genetics
- Ophthalmology
Context:
- Mouse models are crucial for understanding genetic mutations affecting development.
- The microphthalmia (mi) gene's role in eye development and pigmentation is under investigation.
- Chimeras allow for the study of gene interactions in mosaic organisms.
Purpose:
- To investigate the function of the microphthalmia (mi) gene in mouse development using chimeric models.
- To determine the cellular basis of microphthalmia and coat pigmentation defects.
- To confirm the role of ectomesenchyme (neural crest) cells in retinal pigment epithelium (RPE) development.
Summary:
- Chimeric mice were generated by aggregating 8-cell embryos from different mouse strains.
- Microphthalmia and mosaic retinal pigment epithelium (RPE) patterns were observed in mi/mi<==>+/+ chimeras.
- The mi gene affects ectomesenchyme and melanoblasts, influencing eye and coat development without impairing bone or tooth development.
Impact:
- Confirms that mutant mi alleles impact ectomesenchyme cells critical for RPE development.
- Demonstrates that the mi gene functions in melanoblasts but does not impede normal melanoblast behavior from wild-type cells.
- Highlights that dermal mi/mi cells do not interfere with tooth and bone development, suggesting tissue-specific roles for the mi gene.