Project description:Bioactive sphingolipids serve as an essential building block of membranes, forming a selective barrier ensuring subcellular compartmentalization and facilitating cell type-specific intercellular communication through regulation of the plasma membrane receptor repertoire. How the cell type-specific lipid compositions are achieved and what is their functional significance in tissue morphogenesis and maintenance has remained unclear. Here, we identify a stem-cell specific role for ceramide synthase 4 (CerS4) in orchestrating fate decisions in the skin epidermis. Deletion of CerS4 in the epidermis prevents the effective establishment of the adult hair follicle bulge stem cell (HFSCs) niche due to altered differentiation trajectories of HFSC precursors towards upper hair follicle and inner bulge fates. Mechanistically, the HFSC differentiation defects arise from a stem cell intrinsic imbalance of key ceramides and sphingolipids, and associated hyperactivity of canonical Wnt signaling. The lack of HFSCs leads to disruption of hair follicle architecture and hair follicle barrier function, ultimately triggering a Th2-dominated immune infiltration closely resembling human atopic dermatitis. This work uncovers a fundamental role for a cell state-specific sphingolipid profile in epidermal stem cell homeostasis and the role of an intact stem cell niche in maintaining an intact skin barrier.
Project description:Pathological retinal angiogenesis with irregular and fragile vessels (also termed as neovascularization, a response to hypoxia and dysmetabolism) is a leading cause of vision loss in all age groups driven in part by unmet metabolic demand from retinal neurons. Sustaining neural retinal metabolism with an adequate nutrient supply may prevent vision-threatening neovascularization. Low circulating serine levels are associated with neovascularization in macular telangiectasia and altered serine/glycine metabolism is suggested in retinopathy of prematurity. Here we assessed the role of serine metabolism in suppressing hypoxia-driven retinal neovascularization in mice. Systemic serine supplementation decreased, and dietary serine/glycine deficiency worsened retinal neovascularization. Fatty acid oxidation was essential in mediating serine protective effects and serine also increased the levels of phosphatidylcholine, the most abundant phospholipids in the retina. Exogenous serine increased abundance of proteins involved in oxidative phosphorylation in total retinas, as well as increased expression of mitochondrial respiration-related genes and decreased expression of pro-angiogenic genes in rod photoreceptor cluster. Pharmaceutical inhibition of mitochondrial energy production largely attenuated serine suppression of retinal neovascularization. Our data suggested that increasing serine is a potential therapeutic approach for neovascular eye diseases by enhancing retinal mitochondrial function and lipid metabolism to suppress driving factors for uncontrolled angiogenesis.