Melanoblast Migration Research Articles

Giant congenital melanocytic nevus in an 8-year-old female: a case report

Giant congenital melanocytic nevus are melanocytic lesions secondary to abnormal melanoblast migration during the embryogenesis. The incidence reported is in 1 case for every 20 000 newborns and it is present since birth. The importance of its detection relies on the associated complications, such as melanoma development or neurocutaneous melanosis, as well as the psychological and social impact they generate; patients will require a long-term multidisciplinary attention. There is no elective treatment, management is still controversial, it must be individualized according to the characteristics of the nevus and the age of the patient. We present the case of an 8-year-old patient where the diagnosis of giant congenital melanocytic nevus is determined for the first time.

Choroidal Nevi in Children: Size, Growth, and Topographic Distribution

PurposeTo explore size, growth, and topographic distribution of choroidal nevi in children to gain insights into choroidal nevogenesis. DesignRetrospective consecutive case series using pediatric clinic - and population - study data, comparing to adult data. MethodsClinical data from Cole Eye Institute (CEI) database (December 2005-January 2023) was derived from a retrospective consecutive case series of 20 children (< 20 years) with choroidal nevi. For population data, 48 children from previously reported pooled data of the participants of Sydney Pediatric Eye Disease Study, Sydney Myopia Study, Sydney Childhood Eye Study, and Sydney Adolescent Vascular and Eye Disease Study were included. Fundus photographs were reviewed and the locations of 18 choroidal nevi seen at CEI with widefield imaging were mapped on a radial scatter plot. For comparison, 100 consecutive adults with choroidal nevi were identified from CEI database. Main outcomes were size, growth, and topographic distribution of choroidal nevi. ResultsThe median largest basal diameter was 1.6 mm (range 0.4-4.2) in children. Most choroidal nevi (75%) remained stable, and 16% demonstrated growth at follow-up. The mean growth rate was calculated as 0.12 mm/year (range 0.10-0.15). Malignant transformation was not noted during childhood. All secondary changes (drusen, orange pigment, and subretinal fluid) associated with choroidal nevi in children were less common than those in adults (p<0.05). Choroidal nevi in children were located significantly more posterior than in adults. The median distance to fovea was 2.1 mm (range 0.5-8.5) in children and 5.1 mm (range 0.4-16) in adults (p<0.0001). ConclusionsThe onset and growth of choroidal nevi in children suggest active choroidal nevogenesis in childhood. A posterior topographic distribution may support the developmental framework for migration and maturation of choroidal melanoblasts.

5'UTR Variant in KIT Associated With White Spotting in Horses.

Mutations in KIT, a gene that influences melanoblast migration and pigmentation, often result in mammalian white spotting. As of February 2023, over 30 KIT variants associated with white spotting were documented in Equus caballus (horse). Here we report an association of increased white spotting on the skin and coat with a variant in the 5'UTR of KIT (rs1149701677: g.79,618,649A>C). Horses possessing at least one alternate allele demonstrate phenotypic characteristics similar to other KIT mutations: clear borders around unpigmented regions on the body, face, and limbs. Using a quantitative measure of depigmentation, we observed an average white score of 10.70 among individuals with rs1149701677, while the average score of the control, homozygous reference sample was 2.23 (P=1.892e-11, n=109, t-test). The rs1149701677 site has a cross-species conservation score of 3.4, one of the highest scores across the KIT 5'UTR, implying regulatory importance for this site. Ensembl also predicted a "moderately impactful" functional effect for the rs1149701677 variant. We propose that this single nucleotide variant likely alters the regulation of KIT, which in turn may disrupt melanoblast migration causing an increase in white spotting on the coat. Alternatively, the rs1149701677 variant may be in linkage with another nearby variant with an as-yet-undiscovered functional impact. We propose to term this new allele "Holiday White" or W35 based on conventional nomenclature.

Analysis of Integrin-Dependent Melanoblast Migration During Development.

The neural crest is a transient embryonic structure that gives rise to a number of important cell types and tissues, including most of the peripheral and enteric nervous systems, pigment-producing skin cells known as melanocytes, and many craniofacial structures. Melanoblasts, the precursors of melanocytes, are derived from the so-called trunk neural crest cells. These cells delaminate and migrate along a dorsolateral pathway to colonize their final destination in the skin, and consequently, defects in melanoblast migration result in pigmentation defects. Studying melanocyte migration is a topic of great interest due to the involvement of melanocytes in highly metastatic skin cancer. A role for integrin-mediated adhesion is well established in neural crest migration, and our recent work has provided direct evidence for a key role for integrin-based adhesion in melanocyte migration. Imaging of melanoblast migration in the context of intact skin has proven to be a particularly powerful tool to study integrin-based adhesion during melanoblast migration. Here, we describe the use of skin explants combined with genetically encoded markers for melanocytes and high-resolution live imaging as a powerful and informative approach to analyze melanoblast migration in an ex vivo context.

Molecular Dynamics Simulation of KIT Mutation in a Patient wıth Piebaldism, Congenital Cataract and Aphakic Glaucoma

Background: Piebaldism (OMIM #172800) is a rare autosomal dominant genodermatosis characterized by congenital poliosis and stable patches of leucoderma. Piebaldism is caused by mutations in the KIT and SNAI2 genes. The most common mutations are detected in the KIT gene. Case presentation: A 5-year-old boy, who was followed-up for aphakic glaucoma after congenital cataract surgery, was consulted to the medical genetics and dermatology departments due to premature graying of the hair, white forelock in the frontal region of the scalp, whitening in the inner part of the eyebrows and eyelashes and patchy leukoderma with hyperpigmented islands inside on the extremities and trunk. DNA sequencing revealed a heterozygous missense c.1861G&amp;gt;A mutation in the KIT gene. Mutation was evaluated using in silico 3D-structure analysis and bioinformatics tools Conclusion: KIT gene has a critical role in melanoblast migration, proliferation, differentiation and survival and molecular dynamics simulation and modeling proved that this variant inhibits the migration of melanoblasts and melanocytes by reducing the enzymatic activity of the KIT protein.

Assessment of tissue expression of matrix metalloproteinase-9 level in patients with vitiligo and its relation to disease pattern, activity, and severity

Background Vitiligo is a common acquired depigmentary disorder characterized by milky-white cutaneous macules devoid of identifiable functional melanocytes of unknown origin. Several hypotheses have been advanced to explain the link between matrix metalloproteinase-9 (MMP-9) and vitiligo. Aim We aimed to compare the tissue expression of MMP-9 in vitiligo lesions with that of healthy controls. Patients and methods A case–control study was performed to evaluate MMP-9 levels by punch biopsies using an immunohistochemistry technique in lesional and nonlesional tissues of the same patient with vitiligo and in comparison with healthy controls. The study included 20 patients (10 patients with vitiligo and 10 healthy controls). Patients included were 18 years of age and older of both sexes, any duration, and any subtype. Results MMP-9 expression was found to be lower in the lesional skin of patients with vitiligo at the basal cell layer, follicular epithelium, and stromal cell layer when compared with nonlesional skin of the same patient with vitiligo and matched control individuals. Conclusion Tissue MMP-9 imbalance has a role in the etiopathogenesis of vitiligo. The low MMP-9 tissue expression may not facilitate the migration of melanoblasts. Tissue MMP-9 is a significant predictor of severity of vitiligo.

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.

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.

Genome-wide association analysis reveals that EDNRB2 causes a dose-dependent loss of pigmentation in ducks

BackgroundBirds have various plumage color patterns, and spot is a common phenotype. Herein, we conducted genome-wide association studies (GWAS) in a population of 225 ducks with different sized black spots to reveal the genetic basis of this phenomenon.Results First, we quantified the black spot phenotype within the duck population. The results showed that the uncolored area of the body surface first appeared on the ventral side. With increasing duck age, the area of the black spots was highly conserved across the whole body surface. The GWAS results identified a 198 kb (Chr4: 10,149,651 bp to 10,348,068 bp) genetic region that was significantly associated with the black spot phenotype. The conditional GWAS and linkage disequilibrium (LD) analysis further narrowed the ultimate candidate region to 167 kb (Chr4: 10,180,939 bp to 10,348,068 bp). A key gene regulating melanoblast migration and differentiation, EDNRB2 (Endothelin B receptor-like), was found in the candidate region and having significant mRNA expression level changes in embryonic duck skin tissue with different spot sizes. The significant SNPs (single nucleotide polymorphisms) associated with the EDNRB2 gene were annotated, and two mutations (Chr4: 10,180,939 T > C and Chr4: 10,190,671 A > T) were found to result in the loss of binding sites for two trans-factors, XBP1 and cMYB. The phenotypic effect of these two mutations suggested that they can regulate the size of black spots in a dose-dependent manner, and Chr4: 10,180,939 T > C was the major allele locus.ConclusionsOur results revealed that EDNRB2 was the gene responsible for the variation in duck body surface spot size. Chr4: 10,180,939 T > C was the major allele that explained 49.5 % (dorsal side) and 32.9 % (ventral side) of the variation in duck body surface spot size, while 32.1 % (dorsal side) and 19.1 % (ventral side) of the variation could be explained by Chr4: 10,190,671 A > T. The trans-factor prediction also suggested that XBP1 and cMYB have the potential to interact with EDNRB2, providing new insights into the mechanism of action of these genes.

Thalamic Melanosis in Goats

Background: Melanosis is a blackened pigmentation resulting from the accumulation of melanocytes in tissues that are not normally pigmented. This change in the color of the organs occurs due to the agglomeration of melanocytes originating from abnormal migration during embryogenesis and does not cause dysfunction to the affected organ. Although melanosis frequently occurs in several species and affects several organs such as the brain and spinal cord leptomeninges, involvement in the thalamus region is unusual. The objective of this work was to report two cases of thalamic melanosis in goats, determining the pathological and histochemical aspects that assist in the diagnosis of this condition.Cases: Two cases of thalamic melanosis in goats were diagnosed. In both cases, the animals had no nervous history disease and clinical signs. The cause of death in cases 1 and 2 was established based on anatomopathological findings and clinical signs being diagnosed with mycoplasmosis and asphyxia, respectively. After fixing and making cross-sections of the brain, a focal lengthy blackened area was observed on the thalamus surface in both cases. Microscopically, lesions in the brain were similar in both cases and exclusively affected the thalamus. These cells had abundant cytoplasm, well delimited with brownish granular pigment. The nuclei were difficult to visualize and in some cells, it was rounded, well-defined, morphologically compatible with melanocytes. Melanocytes were mainly distributed around neurons and often distended the perivascular space of multiple blood vessels. In Fontana Masson staining, the granules in the cytoplasm of these cells stained strongly black. The Prussian Blue, Periodic Acid- Schiff's, Von Kossa, and Giemsa stains were negative, and the pigment remained brown. In the unstained slides, assembled after the deparaffinization and clarification process, it was observed the permanence of cells with blackish-brown pigment in the cytoplasm. In immunohistochemistry, strong immunostaining of pigmented cells with the Anti-MelanA antibodies was observed in both cases.Discussion: The diagnosis of thalamic melanosis in goats was carried out based on the characteristic pathological findings, in which melanin pigments were demonstrated and identified through HE, Fontana-Masson staining, and unstained slides and confirmed by the IHC. The use of complementary histochemical techniques was fundamental for the classification of the pigment as melanin, demonstrating to be an accessible and reliable tool for the diagnosis of pathological processes that lead to the accumulation of pigments and or material in the tissues. The occurrence of melanin in the thalamus may be associated with a failure in the migration of melanoblasts, which would go to the optical pathways or to the thalamus. This erratic migration of melanoblasts can be explained by the fact that the forebrain is the embryogenic origin of the optic and diencephalon pathways. Macroscopically, thalamic melanosis must be differentiated mainly from neoplastic processes such as melanoma and hemangiosarcoma, pigmented fungus infections, Phalaris angusta poisoning, listeriosis, neurocutaneous melanosis, and neuromelanin. It was concluded that thalamic melanosis is an uncommon alteration in goats and although it has been diagnosed as an incidental necropsy finding, should be included in the differential diagnosis of diseases that affect the central nervous system, especially those that have a color change associated with the deposition of pigments in the tissues. Keywords: melanin, necropsy findings, pigment, thalamus.Descritores: melanina, achados de necropsia, pigmento, tálamo.Título: Melanose talâmica em caprinos.

The additive efficacy of therapeutic low-intensity pulsed ultrasound in the treatment of vitiligo: A randomized, left-right comparison clinical trial.

Repigmentation of vitiligo relies on the proliferation and migration of melanoblasts from hair follicles to the epidermis to replenish epidermal melanin. Our previous study has demonstrated low-intensity pulsed ultrasound (LIPUS) can stimulate melanoblast migration in vitro. We sought to evaluate the potential additive efficacy and safety of LIPUS for repigmentation of vitiligo. Twenty-seven adult patients with stable generalized vitiligo on the face or trunk were recruited in this randomized, open, left-right comparison study. In each patient, two symmetric lesional sites were randomly selected; one was assigned as the target lesion, which was treated with add-on LIPUS twice weekly for 24 weeks, and the other as the control lesion, which was administrated with sham sonification. The primary outcome was the difference of repigmentation degree between the target and control lesions at week 24, based on the 7-point physician global assessment score. At the end of study, 23 patients with vitiligo on the face (n = 10) or trunk (n = 13) completed the 24-week treatment course. Enhanced repigmentation for vitiligo receiving LIPUS as compared to sham sonification was observed in 38.5% (5/13) of the patients with truncal vitiligo, but none of those with facial vitiligo. Truncal vitiligo (P = .046) and higher intensity of LIPUS administered (P = .01) were statistically significantly associated with the effectiveness of additive LIPUS treatment. The LIPUS treatment was well-tolerated without remarkable adverse effects. This pilot study showed that LIPUS could provide therapeutic benefits and could be considered as a treatment adjunct for truncal vitiligo.

Differentiated Daughter Cells Regulate Stem Cell Proliferation and Fate through Intra-tissue Tension.

Basal stem cells fuel development, homeostasis, and regeneration of the epidermis. The proliferation and fate decisions of these cells are highly regulated by their microenvironment, including the basement membrane and underlying mesenchymal cells. Basal progenitors give rise to differentiated progeny that generate the epidermal barrier. Here, we present data that differentiated progeny also regulate the proliferation, differentiation, and migration of basal progenitor cells. Using two distinct mouse lines, we found that increasing contractility of differentiated cells resulted in non-cell-autonomous hyperproliferation of stem cells and prevented their commitment to a hair follicle lineage. This increased contractility also impaired movement of basal progenitors during hair placode morphogenesis and diminished migration of melanoblasts. These data suggest that intra-tissue tension regulates stem cell proliferation, fate decisions, and migration and that differentiated epidermal keratinocytes are a component of the stem cell niche that regulates development and homeostasis of the skin.

NF1-RAC1 axis regulates migration of the melanocytic lineage

Metastases's spreading is the main cause of mortality for advanced stage cancer patients, including melanoma. The formation of metastases is favored by enhanced migratory and invasive capacities of tumor cells. Tumor suppressor gene NF1 is a negative regulator of RAS and its deregulation plays an important role in several aspects of melanoma transformation and progression. However, very little is described about the role of NF1 in cellular migration and invasion. In this study, our results show on the one hand, that the loss of NF1 expression delays migration of human melanoblasts via a RAC1-dependent mechanism. On the other hand, our data indicate that NF1 loss in melanoma cells is enhancing migration, intravasation and metastases formation in vivo. Moreover, not only this phenotype is associated with an upregulation of PREX1 but also patient-derived melanoma samples with low NF1 expression present increased levels of PREX1. In sum, our study brings new elements on the mechanism controlling cellular migration in the context of NF1 loss. These data are of prime interest to improve treatment strategies against all NF1-mutated tumors, including this subtype of melanoma.

Precise coordination of cell-ECM adhesion is essential for efficient melanoblast migration during development.

Melanoblasts disperse throughout the skin and populate hair follicles through long-range cell migration. During migration, cells undergo cycles of coordinated attachment and detachment from the extracellular matrix (ECM). Embryonic migration processes that require cell-ECM attachment are dependent on the integrin family of adhesion receptors. Precise regulation of integrin-mediated adhesion is important for many developmental migration events. However, the mechanisms that regulate integrin-mediated adhesion in vivo in melanoblasts are not well understood. Here, we show that autoinhibitory regulation of the integrin-associated adapter protein talin coordinates cell-ECM adhesion during melanoblast migration in vivo Specifically, an autoinhibition-defective talin mutant strengthens and stabilizes integrin-based adhesions in melanocytes, which impinges on their ability to migrate. Mice with defective talin autoinhibition exhibit delays in melanoblast migration and pigmentation defects. Our results show that coordinated integrin-mediated cell-ECM attachment is essential for melanoblast migration and that talin autoinhibition is an important mechanism for fine-tuning cell-ECM adhesion during cell migration in development.

Functional Analysis of KIT Gene Structural Mutations Causing the Porcine Dominant White Phenotype Using Genome Edited Mouse Models.

The dominant white phenotype in pigs is thought to be mainly due to a structural mutation in the KIT gene, a splice mutation (G > A) at the first base in intron 17 which leads to the deletion of exon 17 in the mature KIT mRNA. However, this hypothesis has not yet been validated by functional studies. Here, we created two mouse models, KIT D17/+ to mimic the splice mutation, and KIT Dup/+ to partially mimic the duplication mutation of KIT gene in dominant white pigs using CRISPR/Cas9 technology. We found that the splice mutation homozygote is lethal and the heterozygous mice have a piebald coat. Slightly increased expression of KIT in KIT Dup/+mice did not confer the patched phenotype and had no obvious impact on coat color. Interestingly, the combination of these two mutations reduced the phosphorylation of PI3K and MAPK pathway associated proteins, which may be related to the impaired migration of melanoblasts observed during embryonic development that eventually leads to the dominant white phenotype.

A 14-bp insertion in endothelin receptor B-like (EDNRB2) is associated with white plumage in Chinese geese

BackgroundGang goose is a native species with gray plumage in Sichuan, China. As a result of overhunting, the number of gray Gang geese has decreased dramatically. To keep the species from extinction, conservation work for Gang geese was undertaken. In the process of pure breeding of gray Gang geese, approximately 2% of the offspring of each generation were white. This study aims to explain the genetic mechanism of this phenomenon and provide reliable molecular markers for goose-related plumage color breeding.ResultsWe used the method of pooled whole genome sequencing and Fst (fixation statistics) to identify the differentiation degree of alleles between gray Gang geese and white Gang geese from their offspring. In this way, EDNRB2, a key gene that affects the migration of melanoblasts, was identified. Then, the transcriptome was sequenced for the two geese plumage color populations, and the DEGs (differentially expressed genes) were analyzed. The results indicated that EDNRB2, as a possible candidate gene, had a significantly differential mRNA expression. In addition, a 14-bp insertion (NW_013185915.1: g. 750,748–750,735 insertion. CACAGGTGAGCTCT) in exon 3 of EDNRB2 was analyzed and found to have a significant association between gray geese and Chinese white breeds (P = 0.00), while this mutation was not found in European geese. Meanwhile, the insertion was homozygous in all the white geese we detected and heterozygous in gray geese, indicating that this mutation is recessive. Furthermore, this 14-bp insertion leads to a frameshift mutation in the EDNRB2 coding region and nonsense-mediated mRNA decay.ConclusionOur study strongly suggests that the 14-bp insertion in exon 3 of the EDNRB2 gene is associated with the white plumage phenotype in Chinese geese. This study is the first to investigate the relationship between EDNRB2 and white plumage in geese.

The Arp2/3 complex is crucial for colonisation of the mouse skin by melanoblasts.

ABSTRACTThe Arp2/3 complex is essential for the assembly of branched filamentous actin, but its role in physiology and development is surprisingly little understood. Melanoblasts deriving from the neural crest migrate along the developing embryo and traverse the dermis to reach the epidermis, colonising the skin and eventually homing within the hair follicles. We have previously established that Rac1 and Cdc42 direct melanoblast migration in vivo. We hypothesised that the Arp2/3 complex might be the main downstream effector of these small GTPases. Arp3 depletion in the melanocyte lineage results in severe pigmentation defects in dorsal and ventral regions of the mouse skin. Arp3 null melanoblasts demonstrate proliferation and migration defects and fail to elongate as their wild-type counterparts. Conditional deletion of Arp3 in primary melanocytes causes improper proliferation, spreading, migration and adhesion to extracellular matrix. Collectively, our results suggest that the Arp2/3 complex is absolutely indispensable in the melanocyte lineage in mouse development, and indicate a significant role in developmental processes that require tight regulation of actin-mediated motility.

Giant congenital melanocytic nevi.

Giant congenital melanocytic nevi (GCMN) are melanocytic lesions secondary to the abnormal migration of melanoblasts during the embryogenesis, affecting approximately one in 20,000 live births. They are usually present since birth and are distinguished by changing their morphological characteristics within time, and increasing their size parallel to the growth of the child, reaching a diameter ≥ 20 cm in adulthood. The importance of the GCMN lies in the complications associated to them; mainly the development of melanoma or neurocutaneous melanosis, in addition to the psychological or social impact that generates in most of the cases. Therefore, individuals with GCMN will require a multidisciplinary long-term follow-up. Currently, the management of children with GCMN is still controversial since there is no treatment of choice. Consequently, the treatment must be individualized according to the characteristics of the nevus and the specific needs of each patient.

Modeling and analysis of melanoblast motion.

Melanoblast migration is important for embryogenesis and is a key feature of melanoma metastasis. Many studies have characterized melanoblast movement, focusing on statistical properties and have highlighted basic mechanisms of melanoblast motility. We took a slightly different and complementary approach: we previously developed a mathematical model of melanoblast motion that enables the testing of biological assumptions about the displacement of melanoblasts and we created tests to analyze the geometric features of cell trajectories and the specific issue of trajectory interactions. Within this model, we performed simulations and compared the results with experimental data using geometric tests. In this paper, we developed the associated mathematical model and the main focus is to study the crossings between trajectories with new theoretical results about the variation of number of intersection points with respect to the crossing times. Using these results it is possible to study the random nature of displacements and the interactions between trajectories. This analysis has raised new questions, leading to the generation of strong arguments in favor of a trail left behind each moving melanoblast.

From neural crest cells to melanocytes: cellular plasticity during development and beyond.

Here, we review melanocyte development and how the embryonic melanoblast, although specified to become a melanocyte, is prone to cellular plasticity and is not fully committed to the melanocyte lineage. Even fully differentiated and pigment-producing melanocytes do not always have a stable phenotype. The gradual lineage restriction of neural crest cells toward the melanocyte lineage is determined by both cell-intrinsic and extracellular signals in which differentiation and pathfinding ability reciprocally influence each other. These signals are leveraged by subtle differences in timing and axial positioning. The most extensively studied migration route is the dorsolateral path between the dermomyotome and the prospective epidermis, restricted to melanoblasts. In addition, the embryonic origin of the skin dermis through which neural crest derivatives migrate may also affect the segregation between melanogenic and neurogenic cells in embryos. It is widely accepted that, irrespective of the model organism studied, the immediate precursor of both melanoblast and neurogenic populations is a glial-melanogenic bipotent progenitor. Upon exposure to different conditions, melanoblasts may differentiate into other neural crest-derived lineages such as neuronal cells and vice versa. Key factors that regulate melanoblast migration and patterning will regulate melanocyte homeostasis during different stages of hair cycling in postnatal hair follicles.