Faculty Bibliography

Skin, hair, and eye (oculocutaneous) color is due to melanin, a pigment produced by melanocytes. This review considers processes required for pigmentation and the complex genetic network that regulates them. The first requisite is migration of neural crest-derived melanoblasts, which populate various embryonic sites, then differentiate into melanocytes or seed stem cell niches. Differentiation is marked by expression of genes essential for melanogenesis, which takes place in melanosomes and involves conversion of tyrosine into melanin. Melanosome biogenesis requires premelanosome maturation through coordinated delivery of melanogenic enzymes such as tyrosinase (TYR), structural proteins, and transporters that establish an intraluminal environment conducive to melanogenesis. Sorting of proteins through endolysosomal pathways and delivery to melanosomes is facilitated by trafficking protein complexes. Finally, melanin is transferred to keratinocytes to protect against ultraviolet light. Numerous pigment-related disorders result from disruption of these pathways, including Waardenburg syndrome caused by melanoblast migration disruption, oculocutaneous albinism presenting with absent/reduced melanogenesis, and melanoma resulting from dysregulation of proliferation/survival. Genetic variants also determine normal color variation, which is pronounced across populations that, historically, lived in different geographical regions. This variation, shaped by genetic factors, environmental influences, and evolutionary pressures, underpins the wide range of pigmentation phenotypes seen today.

After birth, tissues grow until they reach adult size, with each organ exhibiting unique cellular dynamics, growth patterns, and stem or non-stem cell sources. Using multiscale experimental and computational approaches, we found that aortic enlargement follows distinct growth principles, scaling with the vertebral column. Expansion proceeds via two temporally coordinated, spatially stochastic waves of proliferation aligned with blood flow, each with unique cell-cycle kinetics, with the first wave featuring cycles as short as 6 h. Single-cell RNA sequencing revealed increased fatty acid metabolism accompanying cell enlargement. Mathematical modeling and experiments showed that endothelial cell extrusion is essential for maintaining homeostatic aortic size as it adjusts for proliferation excess. Using a genetic model of achondroplasia, we mechanistically demonstrated that the aorta preserves proper scaling by increasing cell extrusion while keeping proliferation rates intact. These findings provide a blueprint of the principles orchestrating aortic growth, which relies entirely on the proliferation of resident differentiated cells. A record of this paper's transparent peer review process is included in the supplemental information.

Chemotherapy-induced alopecia and radiation-induced alopecia, the thinning or loss of hair due to cytotoxic chemotherapy and radiation therapy, respectively, are distressing adverse effects of cancer treatment. Chemotherapy, targeted therapies, and radiation therapy used in pediatric oncology often lead to alopecia by damaging hair follicles, with varying degrees of severity depending on the specific treatment type, mechanism of action, and damage-response pathway involved. Pediatric chemotherapy-induced alopecia, radiation-induced alopecia, and permanent alopecia, defined as hair regrowth that remains incomplete 6 months or more after treatment, have significant negative impacts on mental health, self-esteem, and social interactions, highlighting the need for further research into supportive care strategies. There are currently no standard interventions for chemotherapy-induced alopecia or radiation-induced alopecia in children, with most recommendations limited to gentle hair care and camouflaging techniques during treatment. Scalp cooling has demonstrated safety and efficacy in reducing chemotherapy-induced alopecia in adults and is currently under investigation in children and adolescents. Topical and low-dose oral minoxidil have been studied in children for other hair loss disorders and may improve hair regrowth after chemotherapy or radiation. Increased awareness and continued research into management strategies for pediatric chemotherapy-induced alopecia and radiation-induced alopecia are necessary to help mitigate its significant negative impact on quality of life.

Animals need daily intakes of three macronutrients: sugar, protein, and fat. Under fasted conditions, however, animals prioritize sugar as a primary source of energy. They must detect ingested sugar-specifically D-glucose-and quickly report its presence to the brain. Hypothalamic neurons that can respond to the caloric content in the gut regardless of the identity of macronutrient have been identified, but until now, the existence of neurons that can encode the specific macronutrients remained unknown. We found that a subset of corticotropin-releasing factor (CRF)-expressing neurons in the hypothalamic paraventricular nucleus (CRF^PVN) respond specifically to D-glucose in the gut, separately from other macronutrients or sugars. CRF^PVN neuronal activity is essential for fasted mice to develop a preference for D-glucose. These responses of CRF^PVN neurons to intestinal D-glucose require a specific spinal gut-brain pathway including the dorsal lateral parabrachial nuclei. These findings reveal the neural circuit that encodes the identity of D-glucose.

OBJECTIVE:This study examined racial and ethnic differences in percent total weight loss (%TWL) and glycemic improvement following sleeve gastrectomy (SG) and explored the role of socioeconomic and psychosocial factors in postsurgical outcomes. METHODS:This longitudinal study included patients who underwent SG between 2017 and 2020, with follow-up visits over 24 months. RESULTS:Non-Hispanic Black (NHB) participants had lower %TWL at 3, 12, and 24 months compared with Hispanic (H) and non-Hispanic White (NHW) participants. Fat mass index was initially lower in NHB, with smaller reductions over time and significant group differences persisting at 24 months. NHB participants had higher baseline fat-free mass index values; by 24 months, fat-free mass index values were lower in H participants. Hemoglobin A1c decreased across all groups but remained consistently higher in NHB and H compared with NHW at 24 months. NHB participants reported higher perceived discrimination, sleep disturbance, and perceived stress than H and NHW participants at all time points. Employment status predicted %TWL at 12 months. There was a significant interaction between race and ethnicity and employment status observed at 12 and 24 months, suggesting that employment-related disparities could impact surgical outcomes. CONCLUSIONS:NHB participants experienced less favorable outcomes following SG, emphasizing the need for tailored interventions addressing socioeconomic and psychosocial disparities.

Allergic contact dermatitis (ACD) is a delayed-type IV hypersensitivity response driven by innate and adaptive immune cells. While specific immune regulations of these cell types are amply elucidated, their regulations by extracellular matrix (ECM) components and T cell mediated adaptive immunity in ACD remains unclear. Lumican and biglycan are ECM proteoglycans abundant in the dermis and lymph node, known to regulate innate immune myeloid cells, but have not been investigated in lymphoid cell regulations in ACD. By immunohistology we localized lumican and biglycan in skin biopsies of psoriatic patients. Using wild type (WT), lumican and biglycan knockout mice, we investigated CD4⁺T cell infiltration, activation and proliferation in the skin and draining lymph node (dLN) of CHS-challenged mice by immunohistochemistry and flow cytometry. We used the OT-II adoptive transfer model to test antigen specific CD4⁺T cell activation. We assessed interactions of the proteoglycans with LFA-1 on T cells by confocal microscopy. Compared to WTs, the knockouts showed severe ear inflammation, with increased CD4⁺T cells infiltration in the dermis. CHS-challenged knockout mice dLN showed increased T-bet, STAT1 and -STAT4 signaling, indicating enhanced Th1 commitment and proliferation. We found that WT lymph node fibroblastic reticular cells (FRCs) secrete lumican, biglycan and decorin, a related proteoglycan, while none are expressed by naive or activated T cells. Lumican and biglycan interact with LFA-1 on T cell surfaces, and in vitro all three proteoglycans suppress CD4⁺T cell activation. Secreted by dLN FRCs, lumican, biglycan, and possibly decorin interact with LFA-1 on CD4⁺T cells to restrict its activation and reduce dermatitis severity.

AIM/OBJECTIVE:To investigate how psychosocial stress contributes to accelerated thrombosis, focusing on platelet activation and hyperreactivity. The specific objective was to identify novel platelet regulators involved in stress-mediated thrombosis, with a particular emphasis on the tetraspanin CD37. METHODS AND RESULTS/RESULTS:To explore how stress contributes to platelet hyperreactivity, platelets were isolated from (1) mice that experienced chronic variable stress and stress-free controls (n=8/group) and (2) human subjects with self-reported high and no stress levels (n=18/group), followed by RNA-sequencing. By comparing mutually expressed transcripts, a subset of genes differentially expressed following psychosocial stress was identified in both human and mouse platelets. In both mice and humans, platelet CD37 positively associates with platelet aggregation responses that underlie thrombosis, with Cd37-/- platelets exhibiting impaired integrin αIIbβ3 signaling, characterized by reduced platelet fibrinogen spreading and decreased agonist-induced αIIbβ3 activation. Consistent with a role for CD37 in regulating platelet activation responses, chimeric mice that received Cd37-/- bone marrow experienced a significantly increased time to vessel occlusion in the carotid artery FeCl3 model compared to mice reconstituted with wild-type bone marrow. CD37 deficiency did not alter hemostasis, as platelet count, coagulation metrics, prothrombin time, and partial thromboplastin time did not differ in Cd37-/- mice relative to wild-type mice. Consistent with this, bleeding time did not differ between wild-type and Cd37-/- mice following tail tip transection. CONCLUSIONS:This study provides new insights into the platelet-associated mechanisms underlying stress-mediated thrombosis. Identifying CD37 as a novel regulator of platelet activation responses offers potential therapeutic targets for reducing the thrombotic risk associated with psychosocial stress. The findings also contribute to understanding how psychosocial stress accelerates thrombotic events and underscore the importance of platelet activation in this process.

Targeted therapies and immunotherapy have improved treatment outcomes for many melanoma patients. However, patients whose melanomas harbor driver mutations in the neurofibromin 1 (NF1) tumor suppressor gene often lack effective targeted treatment options when their tumors do not respond to immunotherapy. In this study, we utilized patient-derived short-term cultures (STCs) and multiomics approaches to identify molecular features that could inform the development of therapies for patients with NF1 mutant melanoma. Differential gene expression analysis revealed that the epidermal growth factor receptor (EGFR) is highly expressed and active in NF1 mutant melanoma cells, where it hyper-activates ERK and AKT, leading to increased tumor cell proliferation, survival, and growth. In contrast, genetic or pharmacological inhibition of EGFR hindered cell proliferation and survival and suppressed tumor growth in patient-derived NF1 mutant melanoma models but not in NF1 wild-type models. These results reveal a connection between NF1 loss and increased EGFR expression that is critical for the survival and growth of NF1 mutant melanoma cells in patient-derived culture and xenograft models, irrespective of their BRAF and NRAS mutation status.

The intestinal secretory lineage is thought to comprise four distinct cell types derived from one Atoh1⁺ progenitor, but the mechanisms that distinguish Paneth and goblet cells are unclear. Bhattacharya et al.¹ argue that these cells are instead phenotypic manifestations of a common terminal Atoh1⁺ cell, actively shaped by niche-derived signals.