Polygenic expression of somatostatin in lamprey

Previous studies have led to the identification of three biosynthetically related molecular forms of somatostatin (somatostatin-14, -34 and -37) from the pancreas of the sea lamprey (Petromyzon marinus). We have now isolated from the brain of the same species a second form of somatostatin-14 that is identical to mammalian somatostatin-14 and differs from lamprey pancreatic somatostatin-14 by the substitution Ser¹² to Thr. Larger forms of somatostatin were not identified in lamprey brain in this study. These data suggest that the two molecular forms of lamprey somatostatin-14 are the products of different genes that are expressed in a tissue-specific manner.