title: TFAP2 paralogs regulate melanocyte differentiation in parallel with MITF.
abstract: Mutations in the gene encoding transcription factor TFAP2A result in pigmentation anomalies in model organisms and premature hair graying in humans. However, the pleiotropic functions of TFAP2A and its redundantly-acting paralogs have made the precise contribution of TFAP2-type activity to melanocyte differentiation unclear. Defining this contribution may help to explain why TFAP2A expression is reduced in advanced-stage melanoma compared to benign nevi. To identify genes with TFAP2A-dependent expression in melanocytes, we profile zebrafish tissue and mouse melanocytes deficient in Tfap2a, and find that expression of a small subset of genes underlying pigmentation phenotypes is TFAP2A-dependent, including Dct, Mc1r, Mlph, and Pmel. We then conduct TFAP2A ChIP-seq in mouse and human melanocytes and find that a much larger subset of pigmentation genes is associated with active regulatory elements bound by TFAP2A. These elements are also frequently bound by MITF, which is considered the "master regulator" of melanocyte development. For example, the promoter of TRPM1 is bound by both TFAP2A and MITF, and we show that the activity of a minimal TRPM1 promoter is lost upon deletion of the TFAP2A binding sites. However, the expression of Trpm1 is not TFAP2A-dependent, implying that additional TFAP2 paralogs function redundantly to drive melanocyte differentiation, which is consistent with previous results from zebrafish. Paralogs Tfap2a and Tfap2b are both expressed in mouse melanocytes, and we show that mouse embryos with Wnt1-Cre-mediated deletion of Tfap2a and Tfap2b in the neural crest almost completely lack melanocytes but retain neural crest-derived sensory ganglia. These results suggest that TFAP2 paralogs, like MITF, are also necessary for induction of the melanocyte lineage. Finally, we observe a genetic interaction between tfap2a and mitfa in zebrafish, but find that artificially elevating expression of tfap2a does not increase levels of melanin in mitfa hypomorphic or loss-of-function mutants. Collectively, these results show that TFAP2 paralogs, operating alongside lineage-specific transcription factors such as MITF, directly regulate effectors of terminal differentiation in melanocytes. In addition, they suggest that TFAP2A activity, like MITF activity, has the potential to modulate the phenotype of melanoma cells.
authors.affiliation: Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Hannah E
authors.identifier: 0000-0003-3846-6132
authors.initials: HE
authors.lastname: Seberg
authors.affiliation: SDM-Craniofacial Biology, University of Colorado - Anschutz Medical Campus, Aurora, Colorado, United States of America.
authors.forename: Eric
authors.identifier: 0000-0001-5958-5742
authors.initials: E
authors.lastname: Van Otterloo
authors.affiliation: Genetic Disease Research Branch, National Human Genome Research Institute, NIH, Bethesda, Maryland, United States of America.
authors.forename: Stacie K
authors.initials: SK
authors.lastname: Loftus
authors.affiliation: Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Greg
authors.identifier: 0000-0002-9808-5430
authors.initials: G
authors.lastname: Bonde
authors.affiliation: Bioinformatics Division, Iowa Institute of Human Genetics, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Ramakrishna
authors.initials: R
authors.lastname: Sompallae
authors.affiliation: Bioinformatics and Scientific Programming Core, Computational and Statistical Genomics Branch, National Human Genome Research Institute, NIH, Bethesda, Maryland, United States of America.
authors.forename: Derek E
authors.initials: DE
authors.lastname: Gildea
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Santana
authors.affiliation: Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, United States of America.|Department of Biology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: J Robert
authors.initials: JR
authors.lastname: Manak
authors.affiliation: Genetic Disease Research Branch, National Human Genome Research Institute, NIH, Bethesda, Maryland, United States of America.
authors.forename: William J
authors.initials: WJ
authors.lastname: Pavan
authors.affiliation: SDM-Craniofacial Biology, University of Colorado - Anschutz Medical Campus, Aurora, Colorado, United States of America.
authors.forename: Trevor
authors.initials: T
authors.lastname: Williams
authors.affiliation: Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, United States of America.|Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Cornell
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics*; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D020869:Gene Expression Profiling / Q000379:methods; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008544:Melanocytes / Q000378:metabolism*; D018345:Mice, Knockout; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics* / Q000378:metabolism; D018613:Microscopy, Confocal; D009154:Mutation; D010858:Pigmentation / Q000235:genetics; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D050656:Transcription Factor AP-2 / Q000235:genetics* / Q000378:metabolism; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D051739:Microphthalmia-Associated Transcription Factor; D050656:Transcription Factor AP-2; D029961:Zebrafish Proteins