Glycogen metabolism in Sertoli cells sustains germ cell survival through lactate shuttling

Sertoli cells accumulate glycogen within a specific developmental window, peaking at embryonic day (E) 12.5 and rapidly depleting by E13.5. Using immunofluorescence and single-nuclei RNA-seq, we identified the regulatory mechanisms underlying this transient glycogen storage. Glycogen accumulation correlates with elevated PPP1R3C expression, while its degradation coincides with increased glycogen phosphorylase (PYGB) levels. Functional assays revealed that glycogen metabolism is not required for Sertoli cell differentiation but is essential for germ cell survival. Pharmacological inhibition of glycogen breakdown resulted in germ cell loss, which could not be rescued by exogenous lactate or glucose, highlighting a critical metabolic dependency. Glycogen-derived lactate is transported via the MCT4/MCT1 shuttle from Sertoli cells to germ cells, supporting their survival. These findings establish glycogen metabolism as a key determinant of germ cell viability, emphasizing a metabolic coupling between Sertoli and germ cells during testis development with implications for reproductive health.