Mechanisms underlying the formation and function of the sweat gland dermal niche - PROJECT SUMMARY Humans rely on sweating to remove excess heat from the body, making the eccrine sweat gland an indispensable component of the human thermoregulatory system and an organ essential for human survival. During development, epidermal progenitors within the eccrine placode differentiate into multiple specialized cell types that are ultimately partitioned into specialized, functional compartments. A lack of understanding of how the progressive differentiation of the eccrine anlage occurs has stalled efforts to regenerate these critical skin appendages for the repair of traumatic skin injuries, leaving affected patients with potentially life-threatening deficits in thermoregulation. We have recently identified a novel eccrine dermal population, the Engrailed 1- dependent eccrine niche (EDEN), that is required for eccrine gland formation in mice, and gives rise to a distinct dermal lineage that is persistently associated with each developing human and mouse eccrine gland. A first-of- its kind dermal niche to be described for eccrine glands, understanding how EDEN arises and is maintained, and what factors EDEN produces to instruct eccrine development are entirely unknown. Accordingly, the goals of this proposal are to define the cellular mediators required for EDEN induction, differentiation, and maintenance (Aim 1) and to identify EDEN-produced effectors required for eccrine differentiation (Aim 2). Our research strategy employs: a) functional experiments in mice using existing alleles to carry out targeted genetic perturbations of EDEN and the associated eccrine epidermal anlage and also b) candidate-based and systematic discovery of EDEN molecular effectors required for eccrine differentiation using genetically-targeted, single cell transcriptomics followed by high-throughput seqFISH+ based validation in both human and mouse eccrine- forming skin, and functional testing in vivo using genetic disruption in mice. Our findings will define the regulators, functional properties, and effectors of the eccrine niche to reveal the extrinsic drivers of eccrine developmental progression. Made possible by the unique biological and technical expertise of our team, this first-of-its kind, instructive recipe for eccrine formation will seed translational efforts to regenerate these essential appendages and identify novel genetic targets for alleviating eccrine disorders.
