title: A conserved transcriptional enhancer that specifies Tyrp1 expression to melanocytes.
abstract: Pigment cells of mammals originate from two different lineages: melanocytes arise from the neural crest, whereas cells of the retinal pigment epithelium (RPE) originate from the optic cup of the developing forebrain. Previous studies have suggested that pigmentation genes are controlled by different regulatory networks in melanocytes and RPE. The promoter of the tyrosinase-related family gene Tyrp1 has been shown to drive detectable transgene expression only to the RPE, even though the gene is also expressed in melanocytes as evident from Tyrp1-mutant mice. This indicates that the regulatory elements responsible for Tyrp1 gene expression in the RPE are not sufficient for expression in melanocytes. We thus searched for a putative melanocyte-specific regulatory sequence and demonstrate that a bacterial artificial chromosome (BAC) containing the Tyrp1 gene and surrounding sequences is able to target transgenic expression to melanocytes and to rescue the Tyrp1b (brown) phenotype. This BAC contains several highly conserved non-coding sequences that might represent novel regulatory elements. We further focused on a sequence located at -15 kb, which we identified as a melanocyte-specific enhancer as shown by cell culture and transgenic mice experiments. In addition, we show that the transcription factor Sox10 can activate this conserved enhancer. The presence of a distal Tyrp1 regulatory element, which specifies melanocyte-specific expression, supports the idea that separate regulatory sequences can mediate differential gene expression in melanocytes and RPE.
authors.affiliation: ISREC (Swiss Institute for Experimental Cancer Research), National Center of Competence in Research (NCCR) Molecular Oncology, Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland.
authors.forename: Fabien
authors.initials: F
authors.lastname: Murisier
authors.forename: Sabrina
authors.initials: S
authors.lastname: Guichard
authors.forename: Friedrich
authors.initials: F
authors.lastname: Beermann
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D022202:Chromosomes, Artificial, Bacterial; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics; D004742:Enhancer Elements, Genetic; D006609:High Mobility Group Proteins / Q000235:genetics; D006801:Humans; D008544:Melanocytes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism; D055757:SOXE Transcription Factors; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D008562:Membrane Glycoproteins; C527923:SOX10 protein, human; D055757:SOXE Transcription Factors; C527924:Sox10 protein, mouse; D014157:Transcription Factors; D010088:Oxidoreductases; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse