Engrailed is expressed in larval development and in the radial nervous system of Patiriella sea stars

Abstract

We documented expression of the pan-metazoan neurogenic gene engrailed in larval and juvenile Patiriella sea stars to determine if this gene patterns bilateral and radial echinoderm nervous systems. Engrailed homologues, containing conserved En protein domains, were cloned from the radial nerve cord. During development, engrailed was expressed in ectodermal (nervous system) and mesodermal (coeloms) derivatives. In larvae, engrailed was expressed in cells lining the larval and future adult coeloms. Engrailed was not expressed in the larval nervous system. As adult-specific developmental programs were switched on during metamorphosis, engrailed was expressed in the central nervous system and peripheral nervous system (PNS), paralleling the pattern of neuropeptide immunolocalisation. Engrailed was first seen in the developing nerve ring and appeared to be up-regulated as the nervous system developed. Expression of engrailed in the nerve plexus of the tube feet, the lobes of the hydrocoel along the adult arm axis, is similar to the reiterated pattern of expression seen in other animals. Engrailed expression in developing nervous tissue reflects its conserved role in neurogenesis, but its broad expression in the adult nervous system of Patiriella differs from the localised expression seen in other bilaterians. The role of engrailed in patterning repeated PNS structures indicates that it may be important in patterning the fivefold organisation of the ambulacrae, a defining feature of the Echinodermata.

Echinodermata

“…Several studies document expression of signaling and homeobox genes in the coeloms (e.g., eng , wnt , hox4 ), indicating a role for these genes in early development of the juvenile (Peterson et al 2000a ;Ferkowicz and Raff 2001 ;Byrne et al 2005 ;Cisternas and Byrne 2009 ). Hox genes are expressed in a spatial and collinear sequence in the coeloms of sea urchin and crinoid larvae (Table 1.2 ; see Peterson et al 2000a ;Hara et al 2006 ).…”

“…The developing fi ve-rayed central nervous system has a distinct pentameral expression of many neural genes (Sly et al 2002 ;Morris et al 2004 ;Byrne et al 2005 ;Morris and Byrne 2005 ). Some of these genes (e.g., otx ) are also expressed in development of the peripheral nervous system of the tube feet, indicating a potential role in patterning a so-called "metameric-type" series of outgrowths from the radial canals (Table 1.2 ; see Byrne et al 2005 ;Morris and Byrne 2005 ).…”

Expression of Hox4 during development of the pentamerous juvenile sea star, Parvulastra exigua

“…Wholemount in situ hybridisation (WMISH) reactions were performed on the same stages used for RT-PCR. The protocol for WMISH followed that of Byrne et al (2005) with the following modifications. NBT/BCIP (Roche) was used to detect alkaline phosphatase activity.…”

Gonad-stimulating substance-like molecule from the radial nerve of the sea cucumber

“…Elphick et al, 1995;Byrne et al, 2005), sea cucumbers (e.g. Garcia-Arraras et al, 1991;Diaz-Miranda et al, 1995;Inoue et al, 2002;Byrne et al, 2006: Diaz-Balzac et al, 2007Bishop and Burke, 2007), and brittle stars (de Bremaeker et al, 1997;Hirokawa et al, 2008), mainly by introducing immunochemistry using antibodies raised against various neurotransmitters or anti-synaptotagmin monoclonal antibody, and molecular biology.…”