ABSTRACT
The paired box gene 3 (Pax3) is expressed during pigment cell development. We tested whether the targeted allele Pax3(GFP) can be used as a reporter gene for pigment cells in the mouse. We found that enhanced green fluorescent protein (GFP) can be seen readily in every melanoblast and melanocyte in the epidermis and hair follicles of Pax3(GFP/+) heterozygotes. The GFP was detected at all differentiation stages, including melanocyte stem cells. In the dermis, Schwann cells and nestin-positive cells of the piloneural collars resembling the nestin-positive hair follicle multipotent stem cells exhibited a weaker GFP signal. Pigment cells could be purified by fluorescent activated cell sorting and grown in vitro without feeder cells, giving pure cultures of melanocytes. The Schwann cells and nestin-positive cells of the piloneural collars were FACS-isolated based on their weak expression of GFP. Thus Pax3(GFP) can discriminate distinct populations of cells in the skin.
Subject(s)
Cell Lineage , Genes, Reporter/genetics , Green Fluorescent Proteins/metabolism , Melanocytes/cytology , Melanocytes/metabolism , Paired Box Transcription Factors/metabolism , Skin/metabolism , Alleles , Animals , Dendrites/metabolism , Dermis/cytology , Dermis/metabolism , Embryo, Mammalian/metabolism , Flow Cytometry , Hair Follicle/cytology , Hair Follicle/metabolism , Intermediate Filament Proteins/metabolism , Mice , Mice, Inbred C57BL , Nerve Tissue Proteins/metabolism , Nestin , Neural Crest/cytology , Neural Crest/metabolism , PAX3 Transcription Factor , Pigmentation , Schwann Cells/cytology , Schwann Cells/metabolism , Skin/cytology , Suspensions , beta-Galactosidase/metabolismABSTRACT
The Notch/RBP-J pathway is involved in a variety of developmental processes and in tissue homeostasis. In the melanocyte lineage, it has been shown that Notch signaling acts through Hes1 to maintain the melanocyte stem cell population in the hair follicle. This study was designed to determine whether Notch signaling is implicated in other steps of melanocyte-lineage postnatal development. For this purpose, we developed mice in which the RBP-J gene was conditionally ablated in the melanocyte lineage and used the Dct-lacZ reporter transgene to track melanocytes and their precursors in individual hair follicles. We determine that Notch/RBP-J-deficient melanoblasts are in reduced number within the hair follicle and gather within its lower permanent part. Moreover, our results show that Notch signaling is necessary to prevent differentiation of melanocyte stem cells and of melanoblasts before they reach the hair bulb. Finally, our data show that Notch signaling is involved in proper location of melanoblasts in the outer root sheath and of melanocytes in the hair matrix. These findings reveal previously unrecognized roles for Notch signaling in the melanocyte lineage.
Subject(s)
Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/metabolism , Cell Differentiation/physiology , Hair Follicle/metabolism , Melanocytes/metabolism , Receptors, Notch/metabolism , Signal Transduction/physiology , Stem Cells/metabolism , Animals , Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/genetics , Cell Communication/physiology , Cell Lineage/physiology , Cell Movement/physiology , Hair Follicle/cytology , Immunoglobulin J Recombination Signal Sequence-Binding Protein , Intramolecular Oxidoreductases/genetics , Intramolecular Oxidoreductases/metabolism , Lac Operon/genetics , Melanocytes/cytology , Mice , Mice, Knockout , Receptors, Notch/genetics , Stem Cells/cytology , Transgenes/geneticsABSTRACT
Melanocyte stem cells have been recently localized in mice, in the outer root sheath of the lower permanent portion of the hair follicle. Specific depletion of melanocyte stem cell population is responsible for natural hair greying in aging mice and humans. Melanocyte stem cells also seem to drive the growth of malignant melanomas. A few mutations, either spontaneous or genetically engineered, accelerate the natural process of hair greying with age. These mutations allowed the identification of genes and signalling pathways controlling emergence, maintenance and/or differentiation of melanocyte stem cells. This review summarizes recent studies on the melanocyte stem cells and defines a few major unanswered questions in the field.
