Project description:Feather coloration is one of the most extraordinary examples of phenotypic diversity. This diversity results both from the variation in hue as well as from the presence/absence of pigment in distinct feather regions. The mechanisms that drive presence/absence of pigmentation in feathers are not yet fully understood. Here we characterize the gene expression profiles associated with differential melanin pigmentation in Dark-eyed junco (Junco hyemalis) tails, a social feather ornament used in courtship and male-male competition. Junco tail feathers contain both white apigmented regions as well as dark melanin-pigmented regions. We compared the transcriptome-wide gene expression in developing white and dark regions of tail feathers to understand the regulatory pathways that may regulate the development of this feather ornament. We show that both white and dark feathers express melanocyte markers, indicating that white feathers contain cells capable of producing pigment. However, only dark cells express genes associated with melanin synthesis. We identify differences in expression of genes that may regulate melanocyte activation in dark feathers. Future studies should experimentally test the role of these genes in driving differences in feather pigmentation.
Project description:During the long history of chicken domestication, eyelid color, like skin color and shank color, has been one of the unique physical traits of Chinese indigenous chickens that influence consumer behavior. In China, the Lindian chicken, which has colored feathers, is renowned for the appetizing flavor of its meat and eggs, and its eyelid colors varies from deep to light shades, including black, gray, red, and light yellow. To identify the genes controlling eyelid pigmentation, the expression profiles of black and light-yellow eyelids of Lindian chickens were analyzed with transcriptome sequencing. We detected 13,466 genes expressed in the eyelids, among which 14 were differentially expressed. A KEGG pathway analysis showed that tyrosine metabolism and melanogenesis genes were significantly enriched among these DEGs (corrected P < 0.05). Therefore, we infer that melanin metabolism is one of main factors affecting Lindian chicken eyelid pigmentation. In summary, we have identified the melanin genes responsible for eyelid pigmentation of the Lindian chicken, and also provide a valuable resource for the future study of the physical traits of chickens.
Project description:In order to reveal the candidate genes related to yellow plumage in Chinese chicken, a hybrid population of Huiyang Bearded chicken and White Leghorn chicken, and transcriptome data were generated from the yellow and white feather follicle of F3 population in two periods (7 and 11weeks) respectively, using RNA-seq. 127 common different expressed genes were obtained(DEGs) between two periods, these DEGs were mainly enriched in the Gene Ontology classes ‘developmental pigmentation’, ‘melanin biosynthetic process’, ‘melanosome organization’, ‘melanosome membrane’ and ‘melanosome’all related to the pigmentation process. And involved genes were considered as pigment genes that play important roles in melanogenesis. The results reveal key functional genes and possible molecular mechanisms for the elucidation of yellow plumage formation in Chinese indigenous chickens.
Project description:Purpose: MicroRNAs (miRNAs) play important roles in many biological processes by regulating gene expression at the post-transcriptional level. However, the mechanism by which specific miRNAs may regulate plumage pigmentation has remained largely elusive. In this study, we sequenced miRNAs using Solexa sequencing and then performed a detailed analysis of their expression profiles between the black and white feather bulbs of ducks. This study provides the foundation for subsequent studies on the prospective practical role for such miRNAs in post-transcriptional gene regulation linked to plumage pigmentation.
Project description:Plumage color plays a prominent role in reproductive isolation and thus understanding the genetic basis of pigmentation patterns can provide critical insight into speciation. Subspecies of the dark-eyed junco (Junco hyemalis) show marked differences in melanic plumage coloration known to have evolved rapidly since the Last Glacial Maximum just 18,000 years ago. To understand this rapid radiation we studied the pigment composition and the genetic basis of coloration in two divergent subspecies, the slate-colored and Oregon juncos. We used HPLC and light microscopy to investigate pigment deposition patterns in feathers from four body areas. RNA-seq data generated under common garden experimental conditions were then used to compare the relative roles of differential gene expression in growing feathers and sequence divergence in loci expressed during feather development. Junco feathers were found to differ in eumelanin and pheomelanin content and distribution, producing a range of black, gray and brown colors. Transcriptomic data revealed marked regulatory differences among subspecies and among body-parts within subspecies in known melanin-pathway genes (including PMEL, TYR, TYRP1, OCA2, MLANA), but also in several novel or poorly known loci (EDAR, VPS33B, HPS1). Within subspecies, lighter feathers expressed less melanin synthesis genes, more ASIP, and showed differential expression of Wnt signaling genes. Feathers from different body regions also showed differential expression of Hox genes. The two subspecies differed in expression of ASIP and three other genes (MFSD12, KCNJ13, HAND2) previously associated with color development. Sequence variation in the expressed genes was not related to color differences between junco subspecies. Our findings suggest that differential expression of a few genes can account for marked differences in plumage color and pattern, a mechanism that can account for the rapid diversification of juncos. Several novel candidate pigmentation genes found in juncos may contribute to the expression of melanic coloration in other vertebrates.
Project description:Lineage-specific differentiation programs are activated by epigenetic changes in chromatin structure. Melanin-producing melanocytes maintain a gene expression program ensuring appropriate enzymatic conversion of metabolites into the pigment, melanin, and its transfer to surrounding cells. During neuroectodermal development, SMARCA4, the catalytic subunit of SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complexes, is essential for lineage specification. SMARCA4 is also required for development of multipotent neural crest precursors into melanoblasts, which differentiate into pigment-producing melanocytes. In addition to the catalytic domain, SMARCA4 and several SWI/SNF subunits contain bromodomains which are amenable to pharmacological inhibition. We investigated the effects of pharmacological inhibitors of SWI/SNF bromodomains on melanocyte differentiation. Strikingly, treatment of murine melanoblasts and human neonatal epidermal melanocytes with selected bromodomain inhibitors abrogated melanin synthesis and visible pigmentation. Using functional genomics, iBRD9, a small molecule selective for the bromodomain of BRD9, repressed pigmentation-specific gene expression. Depletion of BRD9 confirmed a requirement for expression of pigmentation genes in the differentiation program from melanoblasts into pigmented melanocytes and in melanoma cells. Chromatin immunoprecipitation assays showed that iBRD9 disrupts the occupancy of bromodomain containing 9 (BRD9) and the catalytic subunit SMARCA4. These data indicate that BRD9 promotes melanocyte differentiation and pigmentation whereas pharmacological inhibition of BRD9 is repressive.
Project description:Skin color is highly variable in Africans, yet little is known about the underlying molecular mechanism. Here we applied massively parallel reporter assays to screen 1,157 candidate variants influencing skin pigmentation in Africans and identified 165 single-nucleotide polymorphisms showing differential regulatory activities between alleles. We combine Hi-C, genome editing and melanin assays to identify regulatory elements for MFSD12, HMG20B, OCA2, MITF, LEF1, TRPS1, BLOC1S6 and CYB561A3 that impact melanin levels in vitro and modulate human skin color. We found that independent mutations in an OCA2 enhancer contribute to the evolution of human skin color diversity and detect signals of local adaptation at enhancers of MITF, LEF1 and TRPS1, which may contribute to the light skin color of Khoesan-speaking populations from Southern Africa. Additionally, we identified CYB561A3 as a novel pigmentation regulator that impacts genes involved in oxidative phosphorylation and melanogenesis. These results provide insights into the mechanisms underlying human skin color diversity and adaptive evolution.
Project description:MITF, a gene that is mutated in familial melanoma and Waardenburg syndrome, encodes multiple isoforms expressed from alternative promoters that share common coding exons but have unique amino termini. It is not completely understood how these isoforms influence pigmentation in different tissues and how expression of these independent isoforms of MITF are regulated. Here, we show that melanocytes express two isoforms of MITF, MITF-A and MITF-M. Expression of MITF-A is partially regulated by a newly identified retinoid enhancer element located upstream of the MITF-A promoter. Mitf-A knockout mice have only subtle changes in melanin accumulation in the hair and reduced Tyr expression in the eye. In contrast, Mitf-M null mice have enlarged kidneys, lack neural crest derived melanocytes in the skin, choroid, and iris stroma; yet maintain pigmentation within the retinal pigment epithelium and iris pigment epithelium of the eye. Taken together, these studies identify a critical role for MITF-M in melanocytes, a minor role for MITF-A in regulating pigmentation in the hair and Tyr expression in the eye, and a novel role for MITF-M in size control of the kidney.
Project description:Skin color is highly variable in Africans, yet little is known about the underlying molecular mechanism. We identified 1,157 candidate variants influencing skin pigmentation in indigenous Africans by genome-wide association studies and scans of natural selection based on differentiation in allele frequencies between lightly pigmented southern African Khoesan populations and other darkly pigmented African populations. We applied massively parallel reporter and chromosome conformation capture assays to identify novel regulatory variants and their target genes related to skin pigmentation in melanocytic cells. We identified 165 SNPs showing strong differential regulatory activities between alleles. Combining CRISPR-mediated genome editing, transcriptome profiling and melanin assays, we identified causal regulatory variants impacting pigmentation near MFSD12/HMG20B, MITF, OCA2, and DDB1/CYB561A3/TMEM138. We identified CYB561A3 as a novel gene regulating pigmentation by impacting genes involved in oxidative phosphorylation and melanogenesis. Our results broaden our understanding of the genetic basis of human skin color diversity and human adaptation. To identify candidate enhancers and regulatory regions in skin pigmentation, we performed CUT&RUN and ATAC assays in two melanocytic cell lines (MNT-1 and WM88). We used the darkly pigmented MNT-1 cell line because it is widely used for studying skin pigmentation and it has a transcription pattern similar to normal melanocytes. We used the WM88 cell line because the cells are lightly pigmented and may have a different trans-environment (e.g., different levels of transcription factors and open chromatin regions) compared with MNT-1 cells. To identify regulatory regions in MNT-1 cells, we conducted CUT&RUN assays using antibodies against H3K4me3, H3K27ac, MITF and SOX10. We further performed ATAC-seq in both MNT-1 and WM88 cells to identify open chromatin regions.
Project description:We investigated the gene expression changes associated with skin pigmentation variation between Virginia opossum populations inhabiting tropical and temperate environments. We found that gene expression variation in genes with melanocytic and immune functions is associated with the degree of skin pigmentation variation. Further, we found evidence suggesting that the Wnt/ß-catenin signaling pathway might be regulating the depigmentation observed in temperate populations. We present several alternative hypotheses that may explain Gloger’s rule pattern of skin pigmentation variation in the Virginia opossum.