Regulator of endoplasmic reticulum secretion that acts as a key determinant of brain size (PubMed:33122427). Required for secretion of extracellular matrix proteins (PubMed:33122427). Required for correct brain development by depositing sufficient extracellular matrix proteins for tissue integrity and the proliferation of neural progenitors (PubMed:33122427). Acts as a regulator of the unfolded protein response (UPR) (By similarity). Highest levels in heart, skeletal muscle, and kidney. The disease is caused by variants affecting the gene represented in this entry. Belongs to the YOS1 family.