Alopecia areata is thought to be a T-cell mediated and cytokine mediated autoimmune disease that results in non-scarring hair loss. Poliosis has been described as a localized depigmentation of hair caused by a deficiency of melanin in hair follicles. A 57-year-old man with a history of alopecia areata developed white hair regrowth in areas of previous hair loss. We retrospectively reviewed the medical literature using PubMed, searching: (1) alopecia areata and (2) poliosis. Poliosis may be associated with autoimmune diseases including alopecia areata, as described in our case. However, it is also reported in patients who have cutaneous lesions, genetic syndromes, infections, medication use, and trauma. Hair regrowth following alopecia areata may be associated with poliosis. We hypothesize that the incidence of poliosis in areas of previous alopecia areata-related hair loss may be greater than reflected in the published literature.

Owing to advances in single cell and omics level profiling methodologies, nuances of cell identity and characterization of novel sub populations has become an active research area for many tissues and organs. However, utilization of these techniques for similar discoveries in the neural crest field have been limited due to technical challenges associated with collecting a transient and highly migratory cell type. Recent advances in human pluripotent stem cell models of neural crest differentiation, allowing for spatial and temporal patterning of neural crest identity, offer an attractive alternative due to their reproducibility, scalability, and availability. Utilization of these systems for omics level experiments with subsequent validation in in vivo models offers a novel approach for advancing the understanding of neural crest identity and fate competency.

This dissertation begins with a history and overview of the works describing neural crest development, identity, and potency, eventually focusing on the melanocyte lineage and how neural crest heterogeneity presents in melanoma. Applications for stem cell-based models to advance these areas of research are also discussed. Stemming from these points, I utilize a stem cell-based model of temporal neural crest patterning to characterize the heterogeneity among temporally distinct neural crest populations and focus in on how temporal patterning affects the melanocyte lineage and melanoma.

To characterize heterogeneity, I employ single cell RNA sequencing with comprehensive downstream expression and lineage analysis to reveal temporally and transcriptionally distinct trajectories of melanocyte specification. I develop a new protocol to differentiate melanocytes from human pluripotent stem cell-derived Schwann cell precursors to perform the first functional and transcriptional comparison of melanocytes derived from temporally distinct progenitor populations. Finally, I leverage data from the cancer genome atlas and an in vivo CRISPR interference screen to reveal that melanoma cases with transcriptional signatures similar to Schwann cell precursor-derived melanocytes display higher rates of metastasis.

Altogether, this work identifies a temporal switch in melanocyte sub population competency in human neural crest cells and systematically characterizes this developmental origin of heterogeneity in melanocyte populations and melanoma. Moreover, it highlights the utility of stem cell-based models of neural crest patterning for novel discovery and lays a framework for future complementary analysis focusing on additional aspects of neural crest spatiotemporal identity or other neural crest lineages.