Spatially restricted hypopigmentation associated with an Ednrbs-modifying locus on mouse chromosome 10

Area of Science:

• Genetics
• Developmental Biology
• Mammalian Genetics

Background:

• White spotting (hypopigmentation) in mice exhibits variable expressivity.
• Modifier loci significantly impact the phenotypic patterns of hypopigmentation.
• The endothelin receptor B (Ednrb) gene is crucial for melanocyte development.

Purpose of the Study:

• To identify and characterize genetic modifier loci affecting white spotting patterns in Ednrb(s) mice.
• To investigate the role of specific alleles on chromosome 10 in hypopigmentation.
• To explore the interaction between endothelin and mast cell growth factor signaling pathways in melanocyte development.

Main Methods:

• Intrasubspecific crosses of Ednrb(s) mice (Mayer and C3HeB/FeJ strains).
• Intercross analyses to identify and map modifier loci.
• Molecular linkage analysis using microsatellite markers.
• Complementation crosses with known mutant alleles (Mgf(Sl), Kit(WJ-2)).
• Sequence and genomic analyses of candidate genes.

Main Results:

• A novel modifier locus, k10, was identified on mouse chromosome 10.
• The k10(Mayer) allele is a recessive modifier of dorsal hypopigmentation.
• The k10(C3H) allele is semidominant, affecting white forelock phenotype, similar to Waardenburg syndrome.
• The k10 critical interval cosegregates with mast cell growth factor (Mgf).
• Genomic differences in Mgf between C3HeB/FeJ and C57BL/6J suggest altered Mgf expression contributes to k10(C3H) phenotype.
• Synergistic interaction between Endothelin and MGF signaling pathways was confirmed.

Conclusions:

• Genetic modifiers on chromosome 10, specifically the k10 locus, play a significant role in regulating white spotting patterns.
• The k10(C3H) allele's association with a white forelock phenotype suggests a link to mast cell growth factor (Mgf) expression.
• The Endothelin and MGF signaling pathways interact synergistically to control neural crest-derived melanocyte development in vivo.