By database searching, they determined that this protein is a member of a family of related proteins with 2 other members in mammals: FAM20B and FAM20C. All FAM20 proteins contain putative conserved signal sequences as well as a conserved C-terminal domain. Fam20a-GFP fusion proteins displayed perinuclear and cytoplasmic staining consistent with localization in the endoplasmic reticulum. Transfection experiments in COS-1 cells demonstrated that Fam20a is a secreted glycoprotein, and immunofluorescence studies showed that an intact signal sequence is required for secretion. Examination of the expression pattern of FAM20A from a panel of cDNAs derived from various human tissues revealed high levels in lung and liver and intermediate levels in thymus and ovary.