Necessary for the biogenesis and transport of multi-pass membrane proteins into the endoplasmic reticulum membrane (By similarity). Antagonizes Nodal signaling and subsequent organization of axial structures during mesodermal patterning. Ectopic expression results in cyclopia, due to a defect in mesendoderm patterning (PubMed:15257293). Component of the ribosome-associated endoplasmic reticulum translocon complex. Strongly and ubiquitously expressed at early stage of somatogenesis. Later, expression is prominent in the developing retina, optic tectum and somites. Belongs to the nicastrin family.