Neurogenic protein essential for the development and maintenance of epithelial structure. Required in the germline for establishing the follicular epithelium and for determining the dorsal-ventral polarity. Collaborates with Notch on the apical surface of follicle cells to mediate germline-follicle cell adhesion. Brn has a role in chorion formation. ganglioside GM2 (d18:1(4E)) + UDP-alpha-D-galactose = ganglioside GM1 (d18:1(4E)) + H(+) + UDP Belongs to the glycosyltransferase 31 family.