Production of the Soluble Form of KIT, s-KIT, Abolishes Stem Cell Factor-Induced Melanogenesis in Human Melanocytes

Therapeutic modulation of KIT ligand in melanocytic disorders with implications for mast cell diseases

KIT ligand and its associated receptor KIT serve as a master regulatory system for both melanocytes and mast cells controlling survival, migration, proliferation and activation. Blockade of this pathway results in cell depletion, while overactivation leads to mastocytosis or melanoma. Expression defects are associated with pigmentary and mast cell disorders. KIT ligand regulation is complex but efficient targeting of this system would be of significant benefit to those suffering from melanocytic or mast cell disorders. Herein, we review the known associations of this pathway with cutaneous diseases and the regulators of this system both in skin and in the more well-studied germ cell system. Exogenous agents modulating this pathway will also be presented. Ultimately, we will review potential therapeutic opportunities to help our patients with melanocytic and mast cell disease processes potentially including vitiligo, hair greying, melasma, urticaria, mastocytosis and melanoma.

Altered Notch signalling in Dowling-Degos disease: a transcriptomic insight into disease pathogenesis

Dowling-Degos disease (DDD) is a rare autosomal-dominant hyperpigmentation disorder caused by mutations in KRT5, POFUT1, POGLUT1 and PSENEN. Our results suggest that dysfunctional Notch signalling in melanocytes plays a key role in DDD pathogenesis, and that altered biogenesis and intracellular trafficking of melanosomes, receptor tyrosine kinase signalling and oestrogen signalling receptor-mediated signalling may represent downstream molecular mechanisms through which decreased Notch signalling leads to hyperpigmentation in DDD. Furthermore, a common downstream pathomechanism for both POGLUT1 and PSENEN mutation carriers can be assumed.

Initial study of the detection of ADAM 10 in the urine of type-2 diabetic patients

Diabetes mellitus (DM) is a disease of civilization. If left untreated, it can cause serious complications and significantly shortens the life time. DM is one of the leading causes of end-stage renal disease (uremia) worldwide. Early diagnosis is a prerequisite for successful treatment, preferably before the first symptoms appear. In this paper, we describe the optimization and synthesis of the internally quenched fluorescent substrate disintegrin and metalloproteinase 10 (ADAM10). Using combinatorial chemistry methods with iterative deconvolution, the substrate specificity of the enzyme in non-primed and primed positions was determined. We used the ABZ-Lys-Ile-Ile-Asn-Leu-Lys-Arg-Tyr(3-NO2)-NH2 peptide to study ADAM10 activity in urine samples collected from patients diagnosed with type 2 diabetes, compared to urine samples from healthy volunteers. The proteolytically active enzyme was present in diabetes samples, while in the case of healthy people we did not observe any activity. In conclusion, our study provides a possible basis for further research into the potential role of ADAM10 in the diagnosis of type 2 diabetes.

The journey from melanocytes to melanoma

Over the past decade, melanoma has led the field in new cancer treatments, with impressive gains in on-treatment survival but more modest improvements in overall survival. Melanoma presents heterogeneity and transcriptional plasticity that recapitulates distinct melanocyte developmental states and phenotypes, allowing it to adapt to and eventually escape even the most advanced treatments. Despite remarkable advances in our understanding of melanoma biology and genetics, the melanoma cell of origin is still fiercely debated because both melanocyte stem cells and mature melanocytes can be transformed. Animal models and high-throughput single-cell sequencing approaches have opened new opportunities to address this question. Here, we discuss the melanocytic journey from the neural crest, where they emerge as melanoblasts, to the fully mature pigmented melanocytes resident in several tissues. We describe a new understanding of melanocyte biology and the different melanocyte subpopulations and microenvironments they inhabit, and how this provides unique insights into melanoma initiation and progression. We highlight recent findings on melanoma heterogeneity and transcriptional plasticity and their implications for exciting new research areas and treatment opportunities. The lessons from melanocyte biology reveal how cells that are present to protect us from the damaging effects of ultraviolet radiation reach back to their origins to become a potentially deadly cancer.

Acceleration of melanocyte senescence by the proinflammatory cytokines IFNγ and TNFα impairs the repigmentation response of vitiligo patients to narrowband ultraviolet B (NBUVB) phototherapy

Vitiligo is a chronic autoimmune disease characterized by the T helper 1 (Th1) cytokine-driven immune destruction of melanocytes (MCs). Although narrowband ultraviolet B (NBUVB) phototherapy has been proven to be an effective therapeutic option, the repigmentation response to that phototherapy varies greatly in different vitiligo patients. Here, we demonstrate that there is an increase of NBUVB-induced cellular senescence in vitiligo MCs exposed to Th1 cytokine interferon γ (IFNγ) and/or tumor necrosis factor α (TNFα) in lesional vitiligo skin from poor responders who had undergone NBUVB phototherapy. Supplementation with exogenous recombinant human stem cell factor (rhSCF) in the culture medium as well as the lentiviral vector-mediated overexpression of cKIT could prevent the MCs from the IFNγ/TNFα-accelerated cellular senescence. Mechanistic studies indicated that the reduced ratio of membrane-bound KIT (mKIT) to the soluble form of KIT (sKIT) is directly related to the cellular senescence of vitiligo MCs following exposure to IFNγ and TNFα. Furthermore, the matrix metalloprotease 9 (MMP9) inhibitor GM6001 attenuates the production of sKIT via the suppression of cKIT ectodomain shedding. Altogether, our study indicates that the presence of Th1 cytokines IFNγ and/or TNFα in the epidermal milieu might impair the repigmentation response of vitiligo patients to NBUVB phototherapy.

Transcriptomic analysis of mRNA expression in giant congenital melanocytic nevi

BACKGROUND AND OBJECTIVE

GCMN is a sporadic disease with an incidence ranging from 1/20,000 to 1/500000. So far, several studies have found that GCMN is related to somatic mutations, but most of them have focused on known pathogenic genes, and transcriptome sequencing based on large datasets is relatively uncommon. At present, the use of next-generation sequencing technologies and bioinformatics platforms makes genomic information study more comprehensive and efficient. In this study, the transcriptome differences between GCMN lesions and surrounding normal skin tissues were investigated using high-throughput transcriptome sequencing, and hub genes and pathways related to pathogenesis were identified, providing a theoretical foundation for further research into the pathogenesis of GCMN.

METHODS

Pathological skin tissue and surrounding normal skin tissue from GCMN patients, namely the pathological group (PG) and the control group (CG), were obtained. 1. All specimens were stained with HE to ensure that the samples met the experimental requirements. 2. Ten pairs of specimens were selected for high-throughput transcriptome sequencing, and the differentially expressed genes (DEGs) between the PG and the CG were obtained. The DEGs were analyzed by clusterProfiler R software for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The function of the subnetwork was analyzed and the hub genes were identified by the STRING database and Cytoscape software. 3. The expression differences of hub genes PTGS2, EGF, and SOX10 in pathological skin tissues and normal skin tissues were verified by qRT-PCR and immunofluorescence staining.

RESULTS

1. HE staining revealed a lot of melanocytes in the dermis and subcutaneous tissues. They were found around the hair follicles, sweat glands, sebaceous glands, and blood vessel walls, or in a specific pattern. 2. The screening threshold was set at p<0.01 and |log2fc|<1, and a total of 1163 DEGs were discovered between the PG and CG, with 519 genes up-regulated and 644 genes down-regulated in the pathological tissues. According to the GO functional analysis, 29 biological processes, 18 cell compositions, and 17 molecular functions were significantly enriched, with the majority of them being related to keratinocytes and the extracellular matrix. There were 779 nodes and 2359 interactions in the protein interaction network. Using the MCODE plug-in, the network was divided into 25 functional clusters. According to ClueGO results, Cluster5 was involved in melanin biosynthesis and melanocyte proliferation. Using 11 operation methods in the Cytohubba plug-in, PTGS2, EGF, and SOX10 in Cluster5 were chosen as hub genes. 3. qRT-PCR and immunofluorescent staining revealed that compared to normal skin tissue, the expression of SOX10 was significantly up-regulated, and the expression of PTGS2 and EGF was significantly down-regulated in pathological skin tissue(P<0.001).

CONCLUSIONS

In GCMN, keratinocytes and extracellular matrix may directly and indirectly affect melanocyte activity. PTGS2, EGF, and SOX10 are important genes and significantly differentially expressed in pathological and normal skin tissues. These findings may serve as a springboard for future research.

Steroidogenic factor-1 lineage origin of skin lesions in Carney complex syndrome

Carney complex (CNC) is a rare familial multi-neoplastic syndrome predisposing to endocrine and non-endocrine tumors due to inactivating mutations of PRKAR1A leading to perturbations of the cAMP protein kinase A (PKA) signaling pathway. Skin lesions are the most common manifestation of CNC, including lentigines, blue nevi and cutaneous myxomas, in unusual locations such as oral and genital mucosa. Unlike endocrine disorders, the pathogenesis of skin lesions remains unexplained. Here, we show that embryonic invalidation of the Prkar1a gene in Steroidogenic Factor-1-expressing cells, leads to the development of familial skin pigmentation alterations reminiscent of those in patients. Immunohistological and molecular analyses coupled with genetic monitoring of recombinant cell lineages in mouse skin, suggest that familial lentiginosis and myxomas occurs in skin areas specifically enriched in dermal melanocytes. In lentigines and blue nevi-prone areas from mutant mice and patients, Prkar1a/PRKAR1A invalidation occurs in a subset of dermal fibroblasts capable of inducing, under the influence of PKA signaling, the production of pro-melanogenic EDN3 and HGF signals. Our model strongly suggests that the origin of the typical CNC cutaneous lesions is the result of non-cell-autonomous pro-melanogenic activity of a dermal fibroblast population sharing a community of origin with SF-1 lineage.

The association of stem cell factor and soluble c-Kit (s-cKit) receptor serum concentrations with the severity and risk prediction of autism spectrum disorders

S tem cell factor (SCF) and its receptor (c-kit) signaling play important role in normal brain physiology including neurogenesis, synapse formation and spatial learning function of the hippocampal region of the brain. Autism spectrum disorder (ASD) is believed to result from abnormal development of neuronal networks and synaptic function. The aim of this study was to evaluate the SCF and its soluble receptor (s-ckit) serum concentrations in ASD. We also studied the serum SCF and s-ckit concentration with the severity of ASD (Levels 1-3; Mild, Moderate and severe, respectively). Ninety five patients with ASD (Mild; n=33, Moderate; n=32 and severe; n=30) and 82 normal controls age matched were included in this study. The serum concentration of SCF and s-ckit were measured by enzyme-linked immunosorbent assay (ELISA). The SCF serum concentration in control subjects was 3.45±1.06 ng/ml and in ASD was 3.41±0.92 ng/ml (P=0.88). The serum levels of s-ckit in control and ASD groups were 56.82±13.22 ng/ml and 67.11±12.00, respectively (P=001). We have also studied serum SCF and s-ckit concentrations with the severity of ASD. The serum concentration of SCF in mild, moderate and severe ASD groups was 3.45±0.93, 3.4±0.87 and 3.43±0.98 ng/ml, respectively (P>0.05) and for s-ckit was 48.77±9.28, 61.66±12.18 and 93.11±14.81ng/ml, respectively (P<0.05). The result of this study suggests that serum s-cKit concentrations may provide a reliable and practical indicator of ASD and positively correlated with disease severity. It is also concluded that s-cKit might be involved in the pathophysiology of ASD.

Melanosome transport and regulation in development and disease

Melanosomes are specialized membrane-bound organelles that synthesize and organize melanin, ultimately providing color to the skin, hair, and eyes. Disorders in melanogenesis and melanosome transport are linked to pigmentary diseases, such as Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, and Griscelli syndrome. Clinical cases of these pigmentary diseases shed light on the molecular mechanisms that control melanosome-related pathways. However, only an improved understanding of melanogenesis and melanosome transport will further the development of diagnostic and therapeutic approaches. Herein, we review the current literature surrounding melanosomes with particular emphasis on melanosome membrane transport and cytoskeleton-mediated melanosome transport. We also provide perspectives on melanosome regulatory mechanisms which include hormonal action, inflammation, autophagy, and organelle interactions.

Guanine Deaminase in Human Epidermal Keratinocytes Contributes to Skin Pigmentation

Epidermal keratinocytes are considered as the most important neighboring cells that modify melanogenesis. Our previous study used microarray to show that guanine deaminase (GDA) gene expression is highly increased in melasma lesions. Hence, we investigated the role of GDA in skin pigmentation. We examined GDA expression in post-inflammatory hyperpigmentation (PIH) lesions, diagnosed as Riehl’s melanosis. We further investigated the possible role of keratinocyte-derived GDA in melanogenesis by quantitative PCR, immunofluorescence staining, small interfering RNA-based GDA knockdown, and adenovirus-mediated GDA overexpression. We found higher GDA positivity in the hyperpigmentary lesional epidermis than in the perilesional epidermis. Both UVB irradiation and stem cell factor (SCF) plus endothelin-1 (ET-1) were used, which are well-known melanogenic stimuli upregulating GDA expression in both keratinocyte culture alone and keratinocyte and melanocyte coculture. GDA knockdown downregulated melanin content, while GDA overexpression promoted melanogenesis in the coculture. When melanocytes were treated with UVB-exposed keratinocyte-conditioned media, the melanin content was increased. Also, GDA knockdown lowered SCF and ET-1 expression levels in keratinocytes. GDA in epidermal keratinocytes may promote melanogenesis by upregulating SCF and ET-1, suggesting its role in skin hyperpigmentary disorders.

Darwinian Positive Selection on the Pleiotropic Effects of KITLG Explain Skin Pigmentation and Winter Temperature Adaptation in Eurasians

Human skin color diversity is considered an adaptation to environmental conditions such as UV radiation. Investigations into the genetic bases of such adaptation have identified a group of pigmentation genes contributing to skin color diversity in African and non-African populations. Here, we present a population analysis of the pigmentation gene KITLG with previously reported signal of Darwinian positive selection in both European and East Asian populations. We demonstrated that there had been recurrent selective events in the upstream and the downstream regions of KITLG in Eurasian populations. More importantly, besides the expected selection on the KITLG variants favoring light skin in coping with the weak UV radiation at high latitude, we observed a KITLG variant showing adaptation to winter temperature. In particular, compared with UV radiation, winter temperature showed a much stronger correlation with the prevalence of the presumably adaptive KITLG allele in Asian populations. This observation was further supported by the in vitro functional test at low temperature. Consequently, the pleiotropic effects of KITLG, that is, pigmentation and thermogenesis were both targeted by natural selection that acted on different KITLG sequence variants, contributing to the adaptation of Eurasians to both UV radiation and winter temperature at high latitude areas.

Stem Cell Factor-Inducible MITF-M Expression in Therapeutics for Acquired Skin Hyperpigmentation

Rationale: Microphthalmia-associated transcription factor M (MITF-M) plays important roles in the pigment production, differentiation and survival of melanocytes. Stem cell factor (SCF) and its receptor KIT stimulate MITF-M activity via phosphorylation at the post-translation level. However, the phosphorylation shortens half-life of MITF-M protein over the course of minutes. Here, we investigated novel hypotheses of (i) whether SCF/KIT can regulate MITF-M activity through gene expression as the alternative process, and (ii) whether chemical inhibition of KIT activity can mitigate the acquired pigmentation in skin by targeting the expression of MITF-M. Methods: We employed melanocyte cultures in vitro and pigmented skin samples in vivo, and applied immunoblotting, RT-PCR, siRNA-based gene knockdown and confocal microscopy. Results: The protein and mRNA levels of MITF-M in epidermal melanocytes and the promoter activity of MITF-M in B16-F0 melanoma cells demonstrated that SCF/KIT could trigger the expression of MITF-M de novo, following the phosphorylation-dependent proteolysis of pre-existing MITF-M protein. SCF/KIT regulated the transcription abilities of cAMP-responsive element-binding protein (CREB), CREB-regulated co-activator 1 (CRTC1) and SRY-related HMG-box 10 (SOX10) but not β-catenin at the MITF-M promoter. Meanwhile, chemical inhibition of KIT activity abolished SCF-induced melanin production in epidermal melanocyte cultures, as well as protected the skin from UV-B-induced hyperpigmentation in HRM2 mice or brownish guinea pigs, in which it down-regulated the expression of MITF-M de novo at the promoter level. Conclusion: We propose the targeting of SCF/KIT-inducible MITF-M expression as a strategy in the therapeutics for acquired pigmentary disorders.

Morphological Characterization and Gene Expression Patterns for Melanin Pigmentation in Rex Rabbit

Animal melanin has an important role in the formation of animal fur and skin, which is determined by its quantities, character, and distribution. To identify the effect of melanin on the formation of multi-colored Rex rabbits (Black, Chinchilla, Beaver, Protein cyan, Protein yellow, White), the structure of hair follicles and melanin content in multi-colored Rex rabbit skins were observed by Hematoxylin and Eosin (H&E) staining and melanin staining, respectively. The melanin granules were primarily found in the epidermis and hair follicle roots. The melanin content of skin was measured by extracting melanin from skin tissue. The results demonstrated that the melanin content was the highest in the skin of black Rex rabbit. Additionally, we measured the mRNA and protein expression levels of melanin-related key genes (MITF and TYR) in the skin of different hair color by quantitative real-time PCR and Wes assay, respectively. The results revealed that the mRNA expression levels in the skin of black Rex rabbit was highly expressed when as compared with other Rex rabbit skin (P < 0.01), and they were the lowest in the skin of white Rex rabbit. Finally, correlation analysis was conducted between melanin content and the expression levels of mRNA and protein. The results indicated a significant correlation between melanin content and the mRNA expression of MITF (P < 0.05), but it was not correlated with the mRNA expression of TYR (P > 0.05). In summary, melanin deposition has important economic value, and the coat color of fur-bearing animals is partly determined by the melanin-related genes.

The Genetics of Human Skin and Hair Pigmentation

Human skin and hair color are visible traits that can vary dramatically within and across ethnic populations. The genetic makeup of these traits-including polymorphisms in the enzymes and signaling proteins involved in melanogenesis, and the vital role of ion transport mechanisms operating during the maturation and distribution of the melanosome-has provided new insights into the regulation of pigmentation. A large number of novel loci involved in the process have been recently discovered through four large-scale genome-wide association studies in Europeans, two large genetic studies of skin color in Africans, one study in Latin Americans, and functional testing in animal models. The responsible polymorphisms within these pigmentation genes appear at different population frequencies, can be used as ancestry-informative markers, and provide insight into the evolutionary selective forces that have acted to create this human diversity.

Williams Syndrome, Human Self-Domestication, and Language Evolution

Language evolution resulted from changes in our biology, behavior, and culture. One source of these changes might be human self-domestication. Williams syndrome (WS) is a clinical condition with a clearly defined genetic basis which results in a distinctive behavioral and cognitive profile, including enhanced sociability. In this paper we show evidence that the WS phenotype can be satisfactorily construed as a hyper-domesticated human phenotype, plausibly resulting from the effect of the WS hemideletion on selected candidates for domestication and neural crest (NC) function. Specifically, we show that genes involved in animal domestication and NC development and function are significantly dysregulated in the blood of subjects with WS. We also discuss the consequences of this link between domestication and WS for our current understanding of language evolution.

KIT as a therapeutic target for non-oncological diseases

KIT is a receptor tyrosine kinase that after binding to its ligand stem cell factor activates signaling cascades linked to biological processes such as proliferation, differentiation, migration and cell survival. Based on studies performed on SCF and/or KIT mutant animals that presented anemia, sterility, and/or pigmentation disorders, KIT signaling was mainly considered to be involved in the regulation of hematopoiesis, gametogenesis, and melanogenesis. More recently, novel animal models and ameliorated cellular and molecular techniques have led to the discovery of a widen repertoire of tissue compartments and functions that are being modulated by KIT. This is the case for the lung, heart, nervous system, gastrointestinal tract, pancreas, kidney, liver, and bone. For this reason, the tyrosine kinase inhibitors that were originally developed for the treatment of hemato-oncological diseases are being currently investigated for the treatment of non-oncological disorders such as asthma, rheumatoid arthritis, and alzheimer's disease, among others. The beneficial effects of some of these tyrosine kinase inhibitors have been proven to depend on KIT inhibition. This review will focus on KIT expression and regulation in healthy and pathologic conditions other than cancer. Moreover, advances in the development of anti-KIT therapies, including tyrosine kinase inhibitors, and their application will be discussed.

Paracrine regulation of melanogenesis

Melanocytes are generally characterized by the basic ability of melanin synthesis and transfer to adjacent keratinocytes. This constitutes an individual skin phenotype and provides epidermal protection from various stimuli, such as ultraviolet irradiation, through a complex process called melanogenesis, which can be regulated by autocrine or paracrine factors. Recent evidence has revealed the paracrine effects of keratinocytes on melanogenesis by secreting cytokines, including α-melanocyte stimulating hormone and endothelin-1. In addition to keratinocytes, there are other types of cells in the skin, such as fibroblasts and immune cells, which are also actively involved in the regulation of melanocyte behaviour through the production of paracrine factors. In addition, extracellular matrix proteins, which are secreted mainly by skin-resident cells, not only play direct roles in regulating melanocyte morphology and functions but also provide structural support between the epidermis and dermis to control the distribution of various secreted cytokines from keratinocytes and/or fibroblasts, which are potentially involved in the regulation of melanogenesis. Moreover, understanding the origin of melanocytes (neural crest cells) and the presence of nerve endings in the epidermis can reveal the intimate contact between melanocytes and cutaneous specific nervous system proteins. Melanocytes are associated with all these networks with corresponding receptors expressed on the cell surface. In this review, we provide an overview of recent advances in determining the intimate relationships between melanocytes and their surrounding elements, which provide insights into the complex nature of the regulation of melanogenesis.

Repigmentation patterns induced by NB-UVB and their relationship with melanocytic migration and proliferation in vitiligo

BACKGROUND/PURPOSE

Vitiligo is the most commonly acquired depigmentation disorder of the skin and is characterized by the destruction of melanocytes. Ultraviolet phototherapy with narrow band (UVB-NB) induces proliferation, differentiation, maturation, and migration of melanocytes. The clinical repigmentation is featured by follicular, marginal, and diffuse patterns. The aim of this study was to observe the process involved in the melanocyte migration and proliferation among these patterns and the unresponsive lesions following UVB-NB phototherapy. The focal adhesion kinase (FAK) and c-KIT were used as markers of melanocyte migration and differentiation, respectively.

METHODS

A total of 17 vitiligo patients under UVB-NB therapy were selected. The patients expressed the three repigmentation patterns as well as unresponsive lesions at the conclusion of a 30-session cycle. Skin biopsies were evaluated by immunohistochemistry and qRT-PCR.

RESULTS

We found an increased expression of c-KIT in the follicular pattern compared to the diffuse pattern that was expressed predominantly of FAK. Marginal pattern expressed both proteins. The unresponsive achromic lesions showed poor expressions of both markers.

CONCLUSION

Proliferation was prominent in the follicular pattern, but migration was prominent in the diffuse pattern. For the marginal pattern, both dynamics were present. The absence of these markers in vitiligo lesions suggests a lack of response to UVB-NB.

Language Impairments in ASD Resulting from a Failed Domestication of the Human Brain

Autism spectrum disorders (ASD) are pervasive neurodevelopmental disorders entailing social and cognitive deficits, including marked problems with language. Numerous genes have been associated with ASD, but it is unclear how language deficits arise from gene mutation or dysregulation. It is also unclear why ASD shows such high prevalence within human populations. Interestingly, the emergence of a modern faculty of language has been hypothesized to be linked to changes in the human brain/skull, but also to the process of self-domestication of the human species. It is our intention to show that people with ASD exhibit less marked domesticated traits at the morphological, physiological, and behavioral levels. We also discuss many ASD candidates represented among the genes known to be involved in the “domestication syndrome” (the constellation of traits exhibited by domesticated mammals, which seemingly results from the hypofunction of the neural crest) and among the set of genes involved in language function closely connected to them. Moreover, many of these genes show altered expression profiles in the brain of autists. In addition, some candidates for domestication and language-readiness show the same expression profile in people with ASD and chimps in different brain areas involved in language processing. Similarities regarding the brain oscillatory behavior of these areas can be expected too. We conclude that ASD may represent an abnormal ontogenetic itinerary for the human faculty of language resulting in part from changes in genes important for the “domestication syndrome” and, ultimately, from the normal functioning of the neural crest.

Expression of Epidermal c-Kit+ of Vitiligo Lesions Is Related to Responses to Excimer Laser

Background

The survival and growth of melanocytes are controlled by the binding of stem cell factor to its cell surface receptor c-kit+ (CD117). We have observed that c-kit+ melanocytes existed in some lesions of vitiligo, while Melan A+ cells were absent.

Objective

To verify possible relation between c-kit+ expression and treatment response in non-segmental vitiligo lesions

Methods

Skin biopsies were done from the center of the 47 lesions from the 47 patients with non-segmental vitiligo. Expression of c-kit+ and Melan A, and amounts of melanin in the epidermis were assessed in each lesion, and treatment responses to excimer laser were evaluated.

Results

Thirty-five of the 47 lesions (74.5%) had c-kit+ phenotypes. There was significant difference of c-kit staining value between good responders in 3 months of excimer laser treatment (average of 24 sessions) and the others.

Conclusion

c-Kit expression in vitiliginous epidermis may be related to better treatment responses to excimer laser.

Unlocking Doors without Keys: Activation of Src by Truncated C-terminal Intracellular Receptor Tyrosine Kinases Lacking Tyrosine Kinase Activity

One of the best examples of the renaissance of Src as an open door to cancer has been the demonstration that just five min of Src activation is sufficient for transformation and also for induction and maintenance of cancer stem cells [1]. Many tyrosine kinase receptors, through the binding of their ligands, become the keys that unlock the structure of Src and activate its oncogenic transduction pathways. Furthermore, intracellular isoforms of these receptors, devoid of any tyrosine kinase activity, still retain the ability to unlock Src. This has been shown with a truncated isoform of KIT (tr-KIT) and a truncated isoform of VEGFR-1 (i₂₁-VEGFR-1), which are intracellular and require no ligand binding, but are nonetheless able to activate Src and induce cell migration and invasion of cancer cells. Expression of the i₂₁-VEGFR-1 is upregulated by the Notch signaling pathway and repressed by miR-200c and retinoic acid in breast cancer cells. Both Notch inhibitors and retinoic acid have been proposed as potential therapies for invasive breast cancer.

Glyceollins, a novel class of soybean phytoalexins, inhibit SCF-induced melanogenesis through attenuation of SCF/c-kit downstream signaling pathways

The anti-melanogenesis effect of glyceollins was examined by melanin synthesis, tyrosinase activity assay in zebrafish embryos and in B16F10 melanoma cells. When developing zebrafish embryos were treated with glyceollins, pigmentation of the embryos, melanin synthesis and tyrosinase activity were all decreased compared with control zebrafish embryos. In situ expression of a pigment cell-specific gene, Sox10, was dramatically decreased by glyceollin treatment in the neural tubes of the trunk region of the embryos. Stem cell factor (SCF)/c-kit signaling pathways as well as expression of microphthalmia-associated transcription factor (MITF) were determined by western blot analysis. Glyceollins inhibited melanin synthesis, as well as the expression and activity of tyrosinase induced by SCF, in a dose-dependent manner in B16F10 melanoma cells. Pretreatment of B16F10 cells with glyceollins dose-dependently inhibited SCF-induced c-kit and Akt phosphorylation. Glyceollins significantly impaired the expression and activity of MITF. An additional inhibitory function of glyceollins was to effectively downregulate intracellular cyclic AMP levels stimulated by SCF in B16F10 cells. Glyceollins have a depigmentation/whitening activity in vitro and in vivo, and that this effect may be due to the inhibition of SCF-induced c-kit and tyrosinase activity through the blockade of downstream signaling pathway.

Identification and characterization of microRNAs in white and brown alpaca skin

AB BACKGROUND: MicroRNAs (miRNAs) are small, non-coding 21-25 nt RNA molecules that play an important role in regulating gene expression. Little is known about the expression profiles and functions of miRNAs in skin and their role in pigmentation. Alpacas have more than 22 natural coat colors, more than any other fiber producing species. To better understand the role of miRNAs in control of coat color we performed a comprehensive analysis of miRNA expression profiles in skin of white versus brown alpacas.

RESULTS

Two small RNA libraries from white alpaca (WA) and brown alpaca (BA) skin were sequenced with the aid of Illumina sequencing technology. 272 and 267 conserved miRNAs were obtained from the WA and BA skin libraries, respectively. Of these conserved miRNAs, 35 and 13 were more abundant in WA and BA skin, respectively. The targets of these miRNAs were predicted and grouped based on Gene Ontology and KEGG pathway analysis. Many predicted target genes for these miRNAs are involved in the melanogenesis pathway controlling pigmentation. In addition to the conserved miRNAs, we also obtained 22 potentially novel miRNAs from the WA and BA skin libraries.

CONCLUSION

This study represents the first comprehensive survey of miRNAs expressed in skin of animals of different coat colors by deep sequencing analysis. We discovered a collection of miRNAs that are differentially expressed in WA and BA skin. The results suggest important potential functions of miRNAs in coat color regulation.

Human skin model containing melanocytes: essential role of keratinocyte growth factor for constitutive pigmentation-functional response to α-melanocyte stimulating hormone and forskolin

To study human skin pigmentation in a physiological in vitro model, we developed a pigmented reconstructed skin reproducing the three-dimensional architecture of the melanocyte environment and the interactions of melanocyte with its cellular partners, keratinocytes, and fibroblasts. Co-seeding melanocytes and keratinocytes onto a fibroblast-populated collagen matrix led to a correct integration of melanocytes within the epidermal basal layer, but melanocytes remained amelanotic even after supplementation with promelanogenic factors. Interestingly, normalization of keratinocyte differentiation using keratinocyte growth factor instead of epidermal growth factor finally allowed an active pigmentary system to develop, as shown by the expression of key melanogenic markers, the production, and transfer of melanosome-containing melanin into keratinocytes. Various degrees of constitutive pigmentation were reproduced using melanocytes from different skin phenotypes. Furthermore, induction of pigmentation was achieved by treatment with known propigmenting molecules, αMSH and forskolin, thus demonstrating the functionality of the pigmentary system. This pigmented full-thickness skin model therefore represents a highly relevant tool to study the role of cell-cell, cell-matrix, and mesenchymal-epithelial interactions in the control of skin pigmentation.

C-KIT signaling depends on microphthalmia-associated transcription factor for effects on cell proliferation

The development of melanocytes is regulated by the tyrosine kinase receptor c-KIT and the basic-helix-loop-helix-leucine zipper transcription factor Mitf. These essential melanocyte survival regulators are also well known oncogenic factors in malignant melanoma. Despite their importance, not much is known about the regulatory mechanisms and signaling pathways involved. In this study, we therefore sought to identify the signaling pathways and mechanisms involved in c-KIT mediated regulation of Mitf. We report that c-KIT stimulation leads to the activation of Mitf specifically through the c-KIT phosphorylation sites Y721 (PI3 kinase binding site), Y568 and Y570 (Src binding site). Our study not only confirms the involvement of Ras-Erk signaling pathway in the activation of Mitf, but also establishes that Src kinase binding to Y568 and Y570 of c-KIT is required. Using specific inhibitors we observe and verify that c-KIT induced activation of Mitf is dependent on PI3-, Akt-, Src-, p38- or Mek kinases. Moreover, the proliferative effect of c-KIT is dependent on Mitf in HEK293T cells. In contrast, c-KIT Y568F and Y721F mutants are less effective in driving cell proliferation, compared to wild type c-KIT. Our results reveal novel mechanisms by which c-KIT signaling regulates Mitf, with implications for understanding both melanocyte development and melanoma.

The Roles of ADAMs Family Proteinases in Skin Diseases

A disintegrin and metalloproteinases (ADAMs) are members of a new gene family of transmembrane and secreted proteins, which belong to the zinc proteinase superfamily. These molecules are involved in various biological events such as cell adhesion, cell fusion, cell migration, membrane protein shedding, and proteolysis. Growing evidence now attests to the potential involvement of ADAMs proteinases in diverse processes such as skin wound healing, inflammation, pigmentation, tumor development, cell proliferation, and metastasis. This paper focuses on the roles of ADAMs proteinases in a wide variety of skin diseases.

Signaling from the human melanocortin 1 receptor to ERK1 and ERK2 mitogen-activated protein kinases involves transactivation of cKIT

Melanocortin 1 receptor (MC1R), a Gs protein-coupled receptor expressed in melanocytes, is a major determinant of skin pigmentation, phototype and cancer risk. Upon stimulation by αMSH, MC1R triggers the cAMP and ERK1/ERK2 MAPK pathways. In mouse melanocytes, ERK activation by αMSH binding to Mc1r depends on cAMP, and melanocytes are considered a paradigm for cAMP-dependent ERK activation. However, human MC1R variants associated with red hair, fair skin [red hair color (RHC) phenotype], and increased skin cancer risk display reduced cAMP signaling but activate ERKs as efficiently as wild type in heterologous cells, suggesting independent signaling to ERKs and cAMP in human melanocytes. We show that MC1R signaling activated the ERK pathway in normal human melanocytes and melanoma cells expressing physiological levels of endogenous RHC variants. ERK activation was comparable for wild-type and mutant MC1R and was independent on cAMP because it was neither triggered by stimulation of cAMP synthesis with forskolin nor blocked by the adenylyl cyclase inhibitor 2',5'-dideoxyadenosine. Stimulation of MC1R with αMSH did not lead to protein kinase C activation and ERK activation was unaffected by protein kinase C inhibitors. Conversely, pharmacological interference, small interfering RNA studies, expression profiles, and functional reconstitution experiments showed that αMSH-induced ERK activation resulted from Src tyrosine kinase-mediated transactivation of the stem cell factor receptor, a receptor tyrosine kinase essential for proliferation, differentiation, and survival of melanocyte precursors, thus demonstrating a functional link between the stem cell factor receptor and MC1R. Moreover, this transactivation phenomenon is unique because it is unaffected by natural mutations impairing canonical MC1R signaling through the cAMP pathway.

Role of BMP-4 and Its Signaling Pathways in Cultured Human Melanocytes

Bone Morphogenetic Protein (BMP-4) was shown to down-regulate melanogenesis, in part, by decreasing the level of tyrosinase [Yaar et al. (2006) JBC:281]. Results presented here show that BMP-4 down-regulated the protein levels of TRP-1, PKC-β, and MCI-R. When paired cultures of human melanocytes were treated with vehicle or BMP-4 (25 ng/ml), MAPK/ERK were phosphorylated within one hour of BMP-4 treatment. Then the activated MAPK/ERK caused an acute phosphorylation of MITF, followed by proteosome-mediated degradation of MITF, the key transcription factor for melanogenic proteins [Wu et al. (2000) Gene & Development:14]. However, prolonged exposure of melanocytes to BMP-4 (up to 48 hours) caused a decrease in the level of MITF-M transcript. In addition, BMP-4 decreased the intracellular level of cAMP, the key regulator of MITF expression. These results demonstrate that BMP-4 activates MAPK/ERK signaling pathway to transiently activate MITF; however, chronic treatment of BMP-4 to melanocytes causes a down-regulation of the expression of MITF, possibly in a cAMP-dependent pathway.

MicroRNA-221 and -222 pathway controls melanoma progression

MicroRNAs (miRNAs) represent a new family of small noncoding RNAs that negatively regulate gene expression. Recent studies demonstrated miRNA involvement in all the main biological processes, including tumor development as a consequence of an aberrant deregulated expression. Growing evidence is showing the capability of miRNA expression profiles to unequivocally distinguish between normal and neoplastic tissues, leading to the identification of new diagnostic and/or prognostic molecular markers. In addition, miRNAs might eventually represent new targets to aim at as innovative therapeutic approaches, particularly relevant in those types of cancer, such as melanoma, which are still lacking effective traditional therapies. In particular, the inhibition of miRNA-221 and -222, which are abnormally expressed in melanoma and favor the induction of the malignant phenotype by downregulating c-KIT receptor and p27Kip, might in the future represent an efficient treatment for translation into the clinical setting.

Depigmentation of skin and hair color in the somatic cell cloned pig

Previously, we have successfully produced nine cloned piglets using Duroc donor cells. Among these clones, one showed distinct depigmentation of the skin and hair color during puberty. In this study, we selected a clone with depigmentation to investigate the etiology of the anomaly in somatic cell nuclear transfer. We hypothesized that genes related to Waardenburg syndrome (Mitf, Pax-3, Sox-10, Slug, and Kit) are closely associated with the depigmentation of pig, which was derived from somatic cell nuclear transfer (scNT). Total RNA was extracted from the ear tissue of affected and unaffected scNT-derived pigs, and the transcripts encoding Mitf, Pax-3, Sox-10, and Slug, together with the Kit gene, were amplified by reverse transcription-polymerase chain reaction, sequenced, and analyzed. The cDNA sequences from the scNT pig that showed progressive depigmentation did not reveal a mutation in these genes. Although we did not find any mutations in these genes, expression of the genes implicated in Waardenburg syndrome was severely down-regulated in the affected scNT pig when compared with unaffected scNT pigs. This down-regulation of gene expression may result in a previously undescribed phenotype that shows melanocyte instability, leading to progressive loss of pigmentation.

KIT variants in bovine ovarian cells and corpus luteum

We report the presence of KIT variants in granulosa and thecal cells of the follicle and endothelial and steroidogenic cells of the corpus luteum. Transcripts of both full-length splice variants, KIT and KITA, were ubiquitously detected in all cell types, in contrast to transcripts for truncated KIT. RT-PCR with exon-intron-specific primers suggested that KIT transcripts retained intron sequences. We used domain-specific KIT antibodies to identify truncated KIT proteins in cell conditioned media and lysates. These proteins represented soluble KIT and a so far disregarded intracellular KIT fragment, and were ubiquitously present. In contrast, glycosylated variants of full-length KIT were predominantly detected in thecal and endothelial cells. All KIT variants were encountered again in COS-7 cells transfected with a vector containing KITA. Phorbol 12-myristate-13-acetate treatment induced levels of truncated KITs, and this effect was repressed by the metalloproteinase inhibitor TAPI-1. Our findings show that ectodomain cleavage of full-length KIT generates an intracellular KIT. Our experiments suggest that replenishing full-length KIT differs among various ovarian cell types.

Association study between keratinocyte-derived growth factor gene polymorphisms and susceptibility to vitiligo vulgaris in a Taiwanese population: potential involvement of stem cell factor

BACKGROUND

Vitiligo vulgaris is a depigmentary disorder resulting from the disappearance of functional melanocytes. Currently, the pathogenesis of this disorder remains obscure.

OBJECTIVES

Genetic analysis of patients with vitilgo may provide important clues for elucidating the complex pathomechanisms involved in the disease process. Because dysfunctional keratinocytes have recently been implicated in the pathogenesis of vitiligo vulgaris, we conducted a case-control association study to investigate this phenomenon.

PATIENTS AND METHODS

Fifty-one patients with vitiligo vulgaris and 118 healthy controls from Taiwan were recruited to investigate the association between relevant keratinocyte-related genes and the occurrence of vitiligo vulgaris. This study genotyped 11 single-nucleotide polymorphisms (SNPs) in five genes including stem cell factor (SCF, also known as KITLG), basic fibroblast growth factor (bFGF, also known as NuDT6), endothelin-1 (EDN1), hepatocyte growth factor (HGF) and stem cell growth factor (SCGF, also known as CLEC11A).

RESULTS

Our results revealed that the A allele for SNP rs11104947 in the SCF gene and the T allele for SNP rs13866 in the SCGF gene were, respectively, associated with a 1.95- and a 2.14-fold risk of developing vitiligo vulgaris. A higher risk was also detected among subjects who carried the SCF rs995029/rs11104947 C/A haplotype (odds ratio = 2.45). Furthermore, the at-risk alleles for SCF rs11104947 (A allele) and for SCGF SNP rs13866 (T allele) were found to display a 7.92-fold increased gene-gene combined risk. No significant relationship between polymorphic frequency for genes bFGF, EDN1 as well as HGF and occurrence of vitiligo vulgaris was observed.

CONCLUSIONS

These novel genetic findings provide new insights in relation to the mechanisms that might be involved in the development of vitiligo vulgaris.