Induces apoptosis of alpha and beta cells in a dose- and time-dependent manner. Present in insulin secretory granules and likely cosecreted with insulin. Expressed at high levels in the pancreas and, to a lesser extent, in small intestine and prostate. Also detected in stomach, testis and fetal liver. In the pancreas, localized in the islets of Langerhans; in the testis, found primarily in the round spermatids; in the CNS, found in the Purkinje cell layer of the cerebellum and in nerve cell bodies of numerous brainstem nuclei. By glucose. O-glycosylated. It is unclear whether the N-terminus residue of the mature protein is Glu-30 or Ser-46. Belongs to the FAM3 family.