GPI-anchored cell membrane protein involved in Nodal signaling. Cell-associated TDGF1 acts as a Nodal coreceptor in cis. Shedding of TDGF1 by TMEM8A modulates Nodal signaling by allowing soluble TDGF1 to act as a Nodal coreceptor on other cells (PubMed:27881714). Could play a role in the determination of the epiblastic cells that subsequently give rise to the mesoderm (PubMed:11909953). Interacts with the activin type-1 receptor ACVR1B. Released from the cell membrane by GPI cleavage. Preferentially expressed in gastric and colorectal carcinomas than in their normal counterparts. Expressed in breast and lung. The GPI-anchor is attached to the protein in the endoplasmic reticulum and serves to target the protein to the cell surface. There, it is processed by GPI processing phospholipase A2 (TMEM8A), removing an acyl-chain at the sn-2 position of GPI and releasing TDGF1 as a lysophosphatidylinositol-bearing form, which is further cleaved by phospholipase D (GPLD1) into a soluble form. Belongs to the EGF-CFC (Cripto-1/FRL1/Cryptic) family.