Immunogen sequence: REVLDGRQVVD MRTNPGDPRE AQEQQNDGKG RGNKAAKRDL PPAKTHLIQE DILPYCRPTF PTSNNPRDPS SSSSMSSRGS GSRQREQANV GRRNIAEMQV LG Highest antigen sequence identity to the following orthologs - mouse 92%, rat 89%. Specialized cells at the midline, whi