Melanoblast Differentiation Research Articles

Efficient generation of cloned cats with altered coat colour by editing of the KIT gene

Coat colour largely determines the market demand for several cat breeds. The KIT proto-oncogene (KIT) gene is a key gene controlling melanoblast differentiation and melanogenesis. KIT mutations usually cause varied changes in coat colour in mammalian species. In this study, we used a pair of single-guide RNAs (sgRNAs) to delete exon 17 of KIT in somatic cells isolated from two different Chinese Li Hua feline foetuses. Edited cells were used as donor nuclei for somatic cell nuclear transfer (SCNT) to generate cloned embryos presenting an average cleavage rate exceeding 85%, and an average blastocyst formation rate exceeding 9.5%. 131 cloned embryos were transplanted into four surrogates, and all surrogates carried their pregnancies to term, and delivered 4.58% (6/131) alive cloned kittens, with 1.53% (2/131) being KIT-edited heterozygotes (KITD17/+). The KITD17/+ cats presented an obvious darkness reduction in the mackerel tabby coat. Immunohistochemical analysis (IHC) of skin tissues indicated impaired proliferation and differentiation of melanoblasts caused by the lack of exon17 in feline KIT. To our knowledge, this is the first report on coat colour modification of cats through gene editing. The findings could facilitate further understanding of the regulatory role of KIT on feline coat colour and provide a basis for the breeding of cats with commercially desired coat colour.

Requirement of Zebrafish Adcy3a and Adcy5 in Melanosome Dispersion and Melanocyte Stripe Formation.

cAMP-PKA signaling plays a pivotal role in melanin synthesis and melanosome transport by responding to the binding of the α-melanocyte-stimulating hormone (α-MSH) to melanocortin-1 receptor (MC1R). Adenylate cyclases (ADCYs) are the enzymes responsible for the synthesis of cAMP from ATP, which comprises nine transmembrane isoforms (ADCYs 1-9) and one soluble adenylate cyclase (ADCY 10) in mammals. However, little is known about which and how ADCY isoforms regulate melanocyte generation, melanin biosynthesis, and melanosome transport in vivo. In this study, we have generated a series of single and double mutants of Adcy isoforms in zebrafish. Among them, adcy3a-/- and adcy5-/- double mutants cause defects in melanosome dispersion but do not impair melanoblast differentiation and melanocyte regeneration during the embryonic or larval stages. Activation of PKA, the main effector of cAMP signaling, significantly ameliorates the defects in melanosome dispersion in adcy3a-/- and adcy5-/- double mutants. Mechanistically, Adcy3a and Adcy5 regulate melanosome dispersion by activating kinesin-1 while inhibiting cytoplasmic dynein-1. In adult zebrafish, Adcy3a and Adcy5 participate in the regulation of the expression of microphthalmia transcription factor (Mitfa) and melanin synthesis enzymes Tyr, Dct, and Trp1b. The deletion of Adcy3a and Adcy5 inhibits melanin production and reduces pigmented melanocyte numbers, causing a defect in establishing adult melanocyte stripes. Hence, our studies demonstrate that Adcy3a and Adcy5 play essential but redundant functions in mediating α-MSH-MC1R/cAMP-PKA signaling for regulating melanin synthesis and melanosome dispersion.

Role of pigment stem cells in hair follicles in the treatment of vitiligo with a 308‐nm excimer laser: An immunohistochemical study of human cases

An immunohistochemical study of human vitiligo case was performed. The excimer laser irradiation may induce the differentiation of melanoblasts and melanocytes from bulge stem cell.

Isolation of a Melanoblast Stimulator from Dimocarpus longan, Its Structural Modification, and Structure-Activity Relationships for Vitiligo.

A novel melanoblast stimulator (1) was isolated from Dimocarpus longan. Its analogs were also synthesized to support a new furan-based melanoblast stimulator scaffold for treating vitiligo. Isolated 5-(hydroxymethyl)furfural (HMF, 1) is a well-known compound in the food industry. Surprisingly, the melanogenic activity of HMF (1) was discovered here for the first time. Both HMF and its synthetic analog (16) promote the differentiation and migration of melanoblasts in vitro. Typically, stimulator (1) upregulated MMP2 expression, which promoted the migration of melanoblasts in vitro.

Vitiligo: 30years to put together the puzzle pieces and to give rise to a new era of therapeutic options.

Vitiligo: 30years to put together the puzzle pieces and to give rise to a new era of therapeutic options.

Giant congenital melanocytic nevi (garment variety): a case report

Giant congenital melanocytic nevi (GCMN) are large brown-to-black skin lesions caused due to genetic mutations which lead to defective proliferation, differentiation and migration of melanoblasts which are precursor cells of melanocytes. There is a mutation in the NRAS gene causing abnormal proliferation of embryonic melanoblasts. Congenital melanocytic nevus is primarily a clinical diagnosis. The malignant melanoma and neurocutaneous melanosis are the two major complications associated with GCMN. The risk of transformation of GCMN to malignant melanoma varies between 0 and 3.8%. About 1% of live births presents with a CMN. The incidence of GCMN is estimated at less than 1: 20,000 newborns. The variety ‘garment-like’ of GCMN is even scarcer, 1: 5,00,000. GCMN has got major psychosocial impact on the patient and his family due to its unsightly appearance. Treatment includes surgical and non-surgical procedures, psychological intervention and clinical follow-up, with special attention to changes in color, texture on the surface of the lesion. We presented a case of 1-day-old female neonate born with GCMN in our hospital.

NF1-Dependent Transcriptome Regulation in the Melanocyte Lineage and in Melanoma.

The precise role played by the tumor suppressor gene NF1 in melanocyte biology and during the transformation into melanoma is not completely understood. In particular, understanding the interaction during melanocyte development between NF1 and key signaling pathways, which are known to be reactivated in advanced melanoma, is still under investigation. Here, we used RNAseq datasets from either situation to better understand the transcriptomic regulation mediated by an NF1 partial loss of function. We found that NF1 mutations had a differential impact on pluripotency and on melanoblast differentiation. In addition, major signaling pathways such as VEGF, senescence/secretome, endothelin, and cAMP/PKA are likely to be upregulated upon NF1 loss of function in both melanoblasts and metastatic melanoma. In sum, these data bring new light on the transcriptome regulation of the NF1-mutated melanoma subgroup and will help improve the possibilities for specific treatment.

Learning from Embryogenesis-A Comparative Expression Analysis in Melanoblast Differentiation and Tumorigenesis Reveals miRNAs Driving Melanoma Development.

Malignant melanoma is one of the most dangerous tumor types due to its high metastasis rates and a steadily increasing incidence. During tumorigenesis, the molecular processes of embryonic development, exemplified by epithelial–mesenchymal transition (EMT), are often reactivated. For melanoma development, the exact molecular differences between melanoblasts, melanocytes, and melanoma cells are not completely understood. In this study, we aimed to identify microRNAs (miRNAs) that promote melanoma tumorigenesis and progression, based on an in vitro model of normal human epidermal melanocyte (NHEM) de-differentiation into melanoblast-like cells (MBrCs). Using miRNA-sequencing and differential expression analysis, we demonstrated in this study that a majority of miRNAs have an almost equal expression level in NHEMs and MBrCs but are significantly differentially regulated in primary tumor- and metastasis-derived melanoma cell lines. Further, a target gene analysis of strongly regulated but functionally unknown miRNAs yielded the implication of those miRNAs in many important cellular pathways driving malignancy. We hypothesize that many of the miRNAs discovered in our study are key drivers of melanoma development as they account for the tumorigenic potential that differentiates melanoma cells from proliferating or migrating embryonic cells.

Bromodomain and extra-terminal domain (BET) proteins regulate melanocyte differentiation

BackgroundPharmacologic inhibition of bromodomain and extra-terminal (BET) proteins is currently being explored as a new therapeutic approach in cancer. Some studies have also implicated BET proteins as regulators of cell identity and differentiation through their interactions with lineage-specific factors. However, the role of BET proteins has not yet been investigated in melanocyte differentiation. Melanocyte inducing transcription factor (MITF) is the master regulator of melanocyte differentiation, essential for pigmentation and melanocyte survival. In this study, we tested the hypothesis that BET proteins regulate melanocyte differentiation through interactions with MITF.ResultsHere we show that chemical inhibition of BET proteins prevents differentiation of unpigmented melanoblasts into pigmented melanocytes and results in de-pigmentation of differentiated melanocytes. BET inhibition also slowed cell growth, without causing cell death, increasing the number of cells in G1. Transcriptional profiling revealed that BET inhibition resulted in decreased expression of pigment-specific genes, including many MITF targets. The expression of pigment-specific genes was also down-regulated in melanoma cells, but to a lesser extent. We found that RNAi depletion of the BET family members, bromodomain-containing protein 4 (BRD4) and bromodomain-containing protein 2 (BRD2) inhibited expression of two melanin synthesis enzymes, TYR and TYRP1. Both BRD4 and BRD2 were detected on melanocyte promoters surrounding MITF-binding sites, were associated with open chromatin structure, and promoted MITF binding to these sites. Furthermore, BRD4 and BRD2 physically interacted with MITF.ConclusionThese findings indicate a requirement for BET proteins in the regulation of pigmentation and melanocyte differentiation. We identified changes in pigmentation specific gene expression that occur upon BET inhibition in melanoblasts, melanocytes, and melanoma cells.

The efficacy, safety, and stability of tacrolimus 0.03% ointment in treatment of nonsegmental vitiligo

Background Topical immunoarm adulators have been successfully used as a monotherapy or in combination with other therapeutic modalities in vitiligo treatment. Topical tacrolimus has been reported to promote melanoblast differentiation and groth. Additionally, it promotes a favorable environement that enhances the proliferation of melanocytes/ melanoblasts through an interaction with keratinocytes, and thereby repopulating vitigiginous skin lesions. Aim To detect the effect of tacrolimus ointements in treatment of nonsegmental vitiligo. Method A total of 35 patients with vitiligo were enrolled in Tacrolimus this randomized placebo-controlled study. Two vitiliginous patches were chosen in each patient. The firstt lesion (A) was treated by tacrolimus 0.03% ointment, and the second lesion (B) was treated by panthenol cream as a placebo. Treatment course was 3 months, and follow-up was done for three extra months. Vitiliginous patches were assessed at baseline and monthly for 6 months. Results Moderate to excellent response was observed in 25.7% of lesions A compared with 0% of lesions B (P = 0.002). Disease duration has a negative effect on therapeutic response. No adverse effects were noted to tacrolimus ointment except for mild erythema in 6% of the patients. Coclusion Given its immunomodulatory properties and lack of cutaneous adverse effects, tacrolimus is a potential therapeutic alternative for vitiligo, with an improved benefit-risk ratio.

A novel KIT deletion variant in a German Riding Pony with white-spotting coat colour phenotype.

White spotting phenotypes in horses may be caused by developmental alterations impairing melanoblast differentiation, survival, migration and/or proliferation. Candidate genes for white-spotting phenotypes in horses include EDNRB, KIT, MITF, PAX3 and TRPM1. We investigated a German Riding Pony with a sabino-like phenotype involving extensive white spots on the body together with large white markings on the head and almost completely white legs. We obtained whole genome sequence data from this horse. The analysis revealed a heterozygous 1273-bp deletion spanning parts of intron 2 and exon 3 of the equine KIT gene (Chr3: 79 579 925-79 581 197). We confirmed the breakpoints of the deletion by PCR and Sanger sequencing. Knowledge of the functional impact of similar KIT variants in horses and other species suggests that this deletion represents a plausible candidate causative variant for the white-spotting phenotype. We propose the designation W28 for the mutant allele.

Melanophore multinucleation pathways in zebrafish.

In zebrafish, apart from mononuclear melanophores, bi- and trinuclear melanophores are frequently observed; however, the manner in which multinucleation of these cells occurs during fish development remains unknown. Here, we analyzed the processes underlying multinucleation of zebrafish melanophores. Transgenic zebrafish in which melanophore nuclei were labeled with a histone H2B-red fluorescent reporter protein were used to evaluate the distribution of mono-, bi-, and trinuclear melanophores in both the trunk and fin. Half of the melanophores examined were binuclear and approximately 1% were trinuclear. We compared cell size, cell motility, and survival rate between mono- and binuclear melanophores grown in a culture dish, and we found that cell size and survival rate were significantly larger in binuclear melanophores. We then analyzed the behavior of melanoblasts and melanophores from transgenic zebrafish using in vivo and in vitro live-cell imaging. We detected division and differentiation of melanoblasts, as well as melanoblast nuclear division without subsequent cellular division. In addition, we observed cellular and nuclear division in melanophores, although these events were very infrequent in vitro. On the basis of our findings, we present a scheme for melanophore multinucleation in zebrafish.

Restoration of skin pigmentation after deep partial or full-thickness burn injury.

Significant skin pigmentation changes occur when patients suffer deep burn injuries. These pigmentation disorders may cause not only cosmetic and psychological issues, but more importantly it increases the risk of skin cancer or photoaging. Severe burns significantly effect on the process of repigmentation as the pigmentation is tightly regulated by cell proliferation and differentiation of melanocytes and melanocyte stem cells which are housing in the epidermis and hair follicles of the skin. In the present review, we discuss the possible mechanisms to replenish the melanocytes from the healthy epidermis and hair follicles surrounding burn wounds. The molecular mechanisms of skin repigmentation following healing of burn injuries includes the differentiation of melanoblasts into melanocytes, the distribution and responses of melanocytes and melanocyte stem cells after burn injury, and the regulation of melanin production. We also reviewed advanced therapeutic strategies to treat pigmentation disorders, such as convectional surgery, laser, UV treatment and emerging concepts in skin tissue-engineering.

Regional Fluctuation in the Functional Consequence of LINE-1 Insertion in the Mitf Gene: The Black Spotting Phenotype Arisen from the Mitfmi-bw Mouse Lacking Melanocytes.

Microphthalmia-associated transcription factor (Mitf) is a key regulator for differentiation of melanoblasts, precursors to melanocytes. The mouse homozygous for the black-eyed white (Mitfmi-bw) allele is characterized by the white-coat color and deafness with black eyes due to the lack of melanocytes. The Mitfmi-bw allele carries LINE-1, a retrotransposable element, which results in the Mitf deficiency. Here, we have established the black spotting mouse that was spontaneously arisen from the homozygous Mitfmi-bw mouse lacking melanocytes. The black spotting mouse shows multiple black patches on the white coat, with age-related graying. Importantly, each black patch also contains hair follicles lacking melanocytes, whereas the white-coat area completely lacks melanocytes. RT-PCR analyses of the pigmented patches confirmed that the LINE-1 insertion is retained in the Mitf gene of the black spotting mouse, thereby excluding the possibility of the somatic reversion of the Mitfmi-bw allele. The immunohistochemical analysis revealed that the staining intensity for beta-catenin was noticeably lower in hair follicles lacking melanocytes of the homozygous Mitfmi-bw mouse and the black spotting mouse, compared to the control mouse. In contrast, the staining intensity for beta-catenin and cyclin D1 was higher in keratinocytes of the black spotting mouse, compared to keratinocytes of the control mouse and the Mitfmi-bw mouse. Moreover, the keratinocyte layer appears thicker in the Mitfmi-bw mouse, with the overexpression of Ki-67, a marker for cell proliferation. We also show that the presumptive black spots are formed by embryonic day 15.5. Thus, the black spotting mouse provides the unique model to explore the molecular basis for the survival and death of developing melanoblasts and melanocyte stem cells in the epidermis. These results indicate that follicular melanocytes are responsible for maintaining the epidermal homeostasis; namely, the present study has provided evidence for the link between melanocyte development and the epidermal microenvironment.

Multipotency of melanoblasts isolated from murine skin depends on the Notch signal.

Melanoblasts (MBs), derived from neural crest cells, only differentiate into melanocytes (Ms) in vivo. We previously showed that MBs isolated from mouse skin were multipotent, generating neurons (Ns) and glial cells (Gs) together with Ms. Using Sox10-IRES-Venus mice and mouse embryonic stem cells, we investigated how MBs expressed their multipotency. MBs generated colonies containing Ns, Gs, and Ms in the presence of ST2 stromal cells, but they generated only M colonies when incubated with keratinocytes or ST2 culture supernatant, thus showing that MBs required contact with ST2 stromal cells for expression of their multipotency. Notch signaling was shown to be one of the important cues for the maintenance and differentiation of MBs through cell-cell contact. When Notch signaling was inhibited, MBs mainly generated colonies that contained just one type of cells, Ns, Gs, or Ms; the number of colonies containing two or three types of cells markedly decreased even on ST2 stromal cells, showing restriction of their differentiation potency. Whereas when Notch signaling was activated, the number of colonies containing two or three types of cells increased, indicating that their multipotency had been maintained. Our results demonstrate that Notch signaling played novel roles in MB multipotency.

Melanocyte Regeneration in Vitiligo Requires WNT beneath their Wings

Melanocytes in patients with vitiligo possess intrinsic abnormalities that contribute to its pathogenesis. In this issue, Regazzetti, et al. report that CXCL10 expression reflects subtle inflammation in normal-appearing skin but not in stable depigmented lesions, supporting the hypothesis that melanocytes themselves initiate autoimmune inflammation prior to clinically evident disease. In addition, they find that oxidative stress in melanocytes impairs WNT signaling and that targeting this pathway induces melanoblast differentiation. Thus, activating the WNT pathway may serve as an adjunctive strategy to support repigmentation in patients with vitiligo.

Regulation of viability, differentiation and death of human melanoma cells carrying neural stem cell biomarkers: a possibility for neural trans-differentiation.

During embryonic development, melanoblasts, the precursors of melanocytes, emerge from a subpopulation of the neural crest stem cells and migrate to colonize skin. Melanomas arise during melanoblast differentiation into melanocytes and from young proliferating melanocytes through somatic mutagenesis and epigenetic regulations. In the present study, we used several human melanoma cell lines from the sequential phases of melanoma development (radial growth phase, vertical growth phase and metastatic phase) to compare: (i) the frequency and efficiency of the induction of cell death via apoptosis and necroptosis; (ii) the presence of neural and cancer stem cell biomarkers as well as death receptors, DR5 and FAS, in both adherent and spheroid cultures of melanoma cells; (iii) anti-apoptotic effects of the endogenous production of cytokines and (iv) the ability of melanoma cells to perform neural trans-differentiation. We demonstrated that programed necrosis or necroptosis, could be induced in two metastatic melanoma lines, FEMX and OM431, while the mitochondrial pathway of apoptosis was prevalent in a vast majority of melanoma lines. All melanoma lines used in the current study expressed substantial levels of pluripotency markers, SOX2 and NANOG. There was a trend for increasing expression of Nestin, an early neuroprogenitor marker, during melanoma progression. Most of the melanoma lines, including WM35, FEMX and A375, can grow as a spheroid culture in serum-free media with supplements. It was possible to induce neural trans-differentiation of 1205Lu and OM431 melanoma cells in serum-free media supplemented with insulin. This was confirmed by the expression of neuronal markers, doublecortin and β3-Tubulin, by significant growth of neurites and by the negative regulation of this process by a dominant-negative Rac1N17. These results suggest a relative plasticity of differentiated melanoma cells and a possibility for their neural trans-differentiation without the necessity for preliminary dedifferentiation.

Piebaldismo-Moebius y exposición prenatal a misoprostol: reporte de un caso

Piebaldism is a rare congenital disease with prevalence of 1/100.000, characterized by patchy depigmentation of the skin and the presence of a white forelock. Its course is static and otherwise patients are healthy. It is inherited in an autosomal dominant pattern and is caused by mutations in the gene c-kit, a proto-oncogene involved in the migration, proliferation, differentiation and survival of melanoblasts. On the other hand, Moebius syndrome is a congenital palsy of the VII cranial nerve, which may be associated with involvement of other cranial nerves, or even of other systems. In the United States its frequency has been calculated from 0.002% to 0.0002% of total births. We report the case of a newborn girl with piebaldism and Moebius syndrome associated with prenatal exposure to misoprostol. A search was made about these anomalies and the association between prenatal exposure to misoprostol and congenital anomalies. Piebaldism is a rare genetic disorder. On the other hand, the cause of Moebius syndrome is heterogeneous and not well defined, and it has been associated with prenatal exposure to misoprostol. Our patient had simultaneously two diseases: one purely genetic and the other potentially teratogenic.

Piebaldism Associated with Neurofibromatosis Type I: A Case Report

Piebaldism is a rare disorder present at birth and inherited as an autosomal dominant trait. It results from a mutation in the c-kit proto-oncogene and is associated with a defect in the migration and differentiation of melanoblasts from the neural crest. We report a 15-year-old girl with both piebaldism and neurofibromatosis type 1 (NF1). She presented with a congenital depigmented patch of the forehead, as well as acquired white forelock, depigmentation of the medial eyebrows, and depigmented patches of the legs. In addition, some cafe au lait macules were observed at birth on the trunk and neck. To our knowledge, the association of piebaldism and NF1 has been described previously in at least 6 case reports. Awareness of this rare association is relevant to ensure early diagnosis and adequate follow-up for NF1.

Exposure to oxidative by-products during metamorphosis affects pigmentation patterns in flounder, Paralichthys olivaceus

Hatcheries often employ disinfection by electrolysis for water; however, this produces free oxidants that pose practical problems in the production of flounder, Paralichthys olivaceus. Rearing juvenile flounder in electrolyzed seawater (EL-SW) causes pseudo-albinism. To elucidate the mechanism of the onset of EL-SW-induced pseudo-albinism, we compared thyroid hormone (TH) metabolism, melanoblasts, and skin differentiation in flounder reared in normal seawater (normal SW) and EL-SW and determined the critical period for the onset of pseudo-albinism. The number of thyroxin (T4)-positive thyroid follicles increased toward the metamorphic climax. The expression of deiodinase 1 (dio1), which converts plasma T4 to triiodothyronine (T3), in the liver peaked synchronously with the increase in T4-positive thyroid follicles. EL-SW exposure had no effect on TH metabolism. Instead, EL-SW inhibited differentiation of adult-type melanoblasts in the skin of the ocular side together with a loss of structural asymmetry in the bilateral skins. Although EL-SW does not affect TH metabolism, our data indicate that it does inhibit the signaling system that controls differentiation of the blind and ocular lateral halves during the establishment of metamorphic asymmetry. The early-metamorphic stage, E- and F-stages, was demonstrated to be the critical period for the onset of pseudo-albinism in EL-SW-reared larvae. These results suggest that long-term exposure to free oxidants, even at low levels, acts as a chronic stressor on flatfish metamorphosis.