Microarray analysis sheds light on the dedifferentiating role of agouti signal protein in murine melanocytes via the Mc1r

Abstract

The melanocortin-1 receptor (MC1R) is a key regulator of pigmentation in mammals and is tightly linked to an increased risk of skin cancers, including melanoma, in humans. Physiologically activated by ␣-melanocyte stimulating hormone (␣MSH), MC1R function can be antagonized by a secreted factor, agouti signal protein (ASP), which is responsible for the lighter phenotypes in mammals (including humans), and is also associated with increased risk of skin cancer. It is therefore of great interest to characterize the molecular effects elicited by those MC1R ligands. In this study, we determined the gene expression profiles of murine melan-a melanocytes treated with ASP or ␣MSH over a 4-day time course using genome-wide oligonucleotide microarrays. As expected, there were significant reductions in expression of numerous melanogenic proteins elicited by ASP, which correlates with its inhibition of pigmentation. ASP also unexpectedly modulated the expression of genes involved in various other cellular pathways, including glutathione synthesis and redox metabolism. Many genes up-regulated by ASP are involved in morphogenesis (especially in nervous system development), cell adhesion, and extracellular matrix-receptor interactions. Concomitantly, ASP enhanced the migratory potential and the invasiveness of melanocytic cells in vitro. These results demonstrate the role of ASP in the dedifferentiation of melanocytes, identify pigment-related genes targeted by ASP and by ␣MSH, and provide insights into the pleiotropic molecular effects of MC1R signaling that may function during development and may affect skin cancer risk.pigmentation ͉ skin cancer A major determinant of the pigment phenotype of the skin is the melanocortin-1 receptor (MC1R), a G protein coupled receptor (GPCR) that regulates many functional aspects of melanocytes, including their dendricity, melanogenesis, and proliferation (1, 2). MC1R function can be activated by ␣-melanocyte-stimulating hormone (␣MSH), a POMC-derived peptide whose production in the skin (3) is increased by exposure to UV radiation (UV) via a p53-dependent mechanism (4). This interaction triggers increased melanin production (5, 6) and stimulates the repair of DNA photoproducts caused by UV (7-9), a phenomenon also induced by forskolin (10). It is therefore not surprising that MC1R polymorphisms are associated with a lighter pigment phenotype, including red hair/fair skin (11), with poor tanning responses (12) and an increased risk for melanoma and other skin cancers (13,14).MC1R signaling can be inhibited by the product of the agouti locus, agouti signal protein (ASP in mice, ASIP in humans), which acts as an inverse agonist of the murine Mc1r (15,16). In mice, ASP is expressed in skin and testis and during embryogenesis. The spatiotemporal expression of ASP in skin is responsible for the agouti hair phenotype (a pheomelanic band against a dark eumelanic background) and for the pale coloration on the neck, breast, and ventral surface (17). A high degree of polymorphism in the promoter of t...

Mapping Loci Associated With Tail Color and Sex Determination in the Short-Lived Fish Nothobranchius furzeri

“…Shriver et al 2003;Hoekstra 2006;Sulem et al 2008;Le Pape et al 2009), the Kit receptor and its ligand (Kitl) (Geissler et al 1988;Miller et al 2007;Sulem et al 2007), CBD103 (Candille et al 2007 Shriver et al 2003;Sulem et al 2007). Of all these genes, only mc1r and slc24a5 were located on the medaka chromosome syntenic to N. furzeri LG V. Conversely, the annotated genes on medaka chromosome 3 do not include any other genes known to be associated with color determination, although this does not rule out their existence.…”

Melanocortin 1 Receptor Regulates Melanoma Cell Migration by Controlling Syndecan-2 Expression

“…For example, melanoma cell migration is reduced by ␣-MSH (7,8), and this inhibition appears to be associated with development of an anti-inflammatory response (9). Conversely, Agouti signal protein (ASP), another MC1R ligand, promotes melanoma cell migration (10).…”

Digital gene expression for non-model organisms

“…Others, such as Iigp1 and Gm12250, are involved in resistance to pathogens/viruses (Supplemental Table S2; Zerrahn et al 2002;Uthaiah et al 2003;Bernstein-Hanley et al 2006;Miyairi et al 2007). Notably, most of these genes are expressed at low levels in skin-the eight anti-viral genes are expressed 17.9 times lower (3.4 vs. 60.9 TPM) than the other 64 genes that were down-regulated in mutant skin-which probably explains why they were missed by previous studies that used microarrays (April and Barsh 2006;Le Pape et al 2009). …”

“…Studies of additional cheetah samples will a Expression levels are given as tags per million reads of an EDGE library prepared from RNA of a black spot or yellow background area of cheetah skin. The genes shown here were chosen based on their roles in pigment cell biology; six are well-established melanocyte transcriptional targets downstream from MC1R signaling (Kobayashi et al 1995;Lamoreux et al 1995;Chintala et al 2005;April and Barsh 2006;Le Pape et al 2009); four encode secreted factors that act upstream, either as ligands or to modify ligands of the MC1R Enshell-Seijffers et al 2008;Kaelin et al 2008); and one, MITF, encodes a transcription factor required for melanocyte development (Steingrímsson et al 2006). The expected direction, increase (+) or decrease (À), for expression level change of each gene is given according to when pigment production switches from yellow pheomelanin to black eumelanin.…”