Mesencephalic astrocyte-derived neurotrophic factor, also known as MANF, is a 20 kDa member of the ARMET family of proteins. MANF was initially identified as a protein containing an arginine-rich region that was highly mutated in a variety of tumors. Expression of MANF has also been shown to be induced during ER stress, suggesting that it may play a role in protein quality control during ER stress.