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Coordinate extinction of melanocyte-specific gene expression in hybrid cells
1Department of Genetics, University of Illinois College of Medicine, Chicago 60607, USA.
Abstract:
Whole cell hybrids and microcell hybrids between mouse fibroblasts and pigmented Syrian hamster melanoma cells were analyzed for coordinate regulation of melanocyte-specific gene products. Extinction of pigmentation was observed in whole-cell hybrids and in a microcell hybrid containing a single mouse chromosome (mouse chromosome 1). Analysis of melanocyte-specific transcripts using reverse transcription, combined with the polymerase chain reaction (RT-PCR), demonstrated that tyrosinase, TRP-1, TRP-2, and microphthalmia transcripts were all absent in unpigmented whole-cell hybrids and in the monochromosomal unpigmented microcell hybrid. A pigmented subclone of this microcell hybrid, however, re-expressed the tyrosinase, TRP-1, TRP-2, and microphthalmia genes. These data suggest that all of these genes are coordinately extinguished by a single fibroblast locus. Since the only fibroblast chromosome detected in the unpigmented microcell hybrid was mouse chromosome 1, these results also suggest that the extinguisher locus affecting the expression of the tyrosinase, TRP-1, TRP-2, and microphthalmia genes in hybrid cells is located on that mouse chromosome (or on a fragment of another chromosome present in the unpigmented monochromosomal microcell hybrid but undetected in our analyses). In contrast to the results with the melanocyte-specific genes mentioned above, transcripts for the melanocortin 1 receptor gene (MC1R) were present in the monochromosomal unpigmented microcell hybrid (although absent in the whole-cell hybrids). This suggests that regulation of MC1R gene expression is distinct from regulation of the other melanocyte-specific genes.
Insights
A single mouse chromosome (chromosome 1) can extinguish pigmentation and melanocyte-specific genes in hybrid cells. However, the melanocortin 1 receptor gene (MC1R) shows distinct regulation, suggesting a complex genetic control of melanocyte function.
Area of Science:
- Cell Biology
- Genetics
- Molecular Biology
Background:
- Melanocyte-specific gene products are crucial for pigmentation.
- Understanding the genetic regulation of these genes is key to understanding pigmentation disorders.
Purpose of the Study:
- To investigate the coordinate regulation of melanocyte-specific genes in hybrid cells.
- To identify potential genetic loci responsible for the extinction of pigmentation and melanocyte gene expression.
Main Methods:
- Creation of whole-cell and microcell hybrids between mouse fibroblasts and Syrian hamster melanoma cells.
- Analysis of pigmentation in hybrid cells.
- Reverse transcription-polymerase chain reaction (RT-PCR) to quantify melanocyte-specific transcripts (tyrosinase, TRP-1, TRP-2, microphthalmia, MC1R).
Main Results:
- Whole-cell and microcell hybrids showed extinction of pigmentation.
- Key melanocyte genes (tyrosinase, TRP-1, TRP-2, microphthalmia) were absent in unpigmented hybrids, including one with mouse chromosome 1.
- A pigmented subclone re-expressed these genes, indicating coordinate regulation.
- Melanocortin 1 receptor (MC1R) transcripts were present in an unpigmented hybrid, unlike other melanocyte genes.
Conclusions:
- A single locus on mouse chromosome 1 likely extinguishes tyrosinase, TRP-1, TRP-2, and microphthalmia genes coordinately.
- MC1R gene expression is regulated differently from these other melanocyte-specific genes.
- These findings provide insights into the genetic control of melanocyte differentiation and pigmentation.