Olfactomedin-1/Noelin-1: ProductsOlfactomedin-1, also known as Noelin-1 (neuronal olfactomedin-related endoplasmic reticulum-localized-1), or pancortin, is a 75 kDa secreted extracellular matrix glycoprotein expressed in the brain. Alternate promoter usage and splicing creates four forms of Noelin (Noelin 1-4) that are combinations of a common central region with alternate N- and C-termini. Olfactomedin-1/Noelin-1 is the longest of the four isoforms, encoding a 16 amino acid (aa) signal sequence and a 469 aa mature protein with a coiled-coil region for multimerization and an olfactomedin-like domain. The shortest isoforms, Noelin-3 and -4, are truncated within the coiled-coil region and lack the olfactomedin-like domain. In the species tested, these isoforms appear to oppose actions of the longer isoforms. All isoforms are capable of forming homo- or heterodimers through cysteines in their common central region. The C-terminus of Olfactomedin-1 (mouse aa 482-485) contains a putative endoplasmic reticulum retention sequence that has not been included in the R&D Systems protein. Mouse Olfactomedin-1 (aa 17-481) shares 99%, 99%, 97%, 96% and 93% aa identity with corresponding regions of rat, human, opossum, chicken and Xenopus Olfactomedin-1, respectively. In vivo expression patterns differ somewhat between species. In chick early development, Olfactomedin-1 shows highest concentration in areas that produce neural crest cells and is produced by migrating neural crest cells. Overproduction of Olfactomedin-1 prolongs neural crest cell formation. Olfactomedin-1 is also expressed in mouse neural crest, but not frog. All three species express Olfactomedin-1 later in differentiating neural tissues in the spinal cord, brain and cranial ganglia.