D-Serine controls epidermal vesicle release via NMDA receptor, allowing tissue migration during the metamorphosis of the chordate Ciona

D-Serine, a free amino acid synthesized by serine racemase, is a coagonist of N-methyl-D-aspartate-type glutamate receptor (NMDAR). D-Serine in the mammalian central nervous system modulates glutamatergic transmission. Functions of D-serine in mammalian peripheral tissues such as skin have also been described. However, D-serine's functions in nonmammals are unclear. Here, we characterized D-serine-dependent vesicle release from the epidermis during metamorphosis of the tunicate Ciona. D-Serine leads to the formation of a pocket that facilitates the arrival of migrating tissue during tail regression. NMDAR is the receptor of D-serine in the formation of the epidermal pocket. The epidermal pocket is formed by the release of epidermal vesicles' content mediated by D-serine/NMDAR. This mechanism is similar to observations of keratinocyte vesicle exocytosis in mammalian skin. Our findings provide a better understanding of the maintenance of epidermal homeostasis in animals and contribute to further evolutionary perspectives of D-amino acid function among metazoans.

Automated summary

D-Serine is involved in the modulation of glutamatergic transmission in mammalian central nervous system, while its functions in nonmammals are unclear. This study found that D-Serine is responsible for the release of epidermal vesicles during the metamorphosis of the tunicate Ciona. The formation of an epidermal pocket facilitated the migration of tissue during tail regression, and this mechanism is similar to keratinocyte vesicle exocytosis in mammalian skin.