Loss of cholesterol in Junctional Epidermolysis Bullosa skin identifies a key role for Laminin-332 in actomyosin mediated cholesterol transport

Individuals with Junctional Epidermolysis Bullosa (JEB), a rare genetic skin disease characterised by loss of function mutations in the Laminin332 (Lam332), do not survive beyond their first birthday. Here we report that loss of Lam332 leads to absence of cholesterol lipid from the epidermis in vitro and in vivo . Using 3D skin equivalents, a JEB mouse model and JEB patient samples we confirmed changes in epidermal lipid synthesis, which was further explored using lipidomics. Cholesterol biosynthesis genes were increased with loss of Laminin-332 in vitro, however a decrease in immunofluorescence lipid staining was observed. Cholesterol transport in Laminin-332 knockdown keratinocytes was revealed to be disrupted, which in keratinocytes is dependent on the actomyosin network. In conclusion these findings suggest a role for the basement membrane protein Laminin-332 in lipid metabolism in the skin, and a broader role for epidermal homeostasis and barrier formation. Restoration of cholesterol transport in epidermal keratinocytes of JEB patients offers the potential to improve their skin barrier.