BMP2/4 and BMP5-8 in jellyfish development and transdifferentiation

Abstract

Bone morphogenetic proteins (BMPs) have key roles in gastrulation, mesoderm induction and axial patterning. The multitude of bilaterian BMPs employed in these morphogenetic processes contrasts starkly with the scarcity of BMPs in Cnidaria, the most basal eumetazoan phylum. In coral, sea anemone and hydra species, BMPs have been found to be associated with larval and polyp axial patterning. In the hydrozoan jellyfish Podocoryne (Hydractinia) carnea the BMP2/4 and BMP5-8 genes are expressed unilaterally in the larva, corroborating a possible role in larval axial development. With the focal area of BMP expression in the anterior region, however, the jellyfish larva may have a developmental reversal of spatial polarity compared to the anthozoan larva. In medusa development, BMP genes are expressed in divergent expression territories within the presumptive radial canals and in various parts of the endoderm, indicative of an involvement in mesoderm patterning and gastrovascular system formation reminiscent of bilaterian BMP functions. In addition, the BMP2/4 and BMP5-8 genes may play roles in wound response and dedifferentiation or S-phase re-entry, respectively, as the former is expressed in striated muscle cells immediately after excision from the bell and the latter in the initial phase of muscle cell transdifferentiation.

Adoption of conserved developmental genes in development and origin of the medusa body plan

“…Six3/6 has previously been investigated in adult medusae of Podocoryne carnea and Cladonema radiatum , where it showed a fairly similar expression in the tentacle bulbs [44]. Supporting our findings in Clytia , the expression of a twist and a bmp 5/8 homolog was previously reported in P. carnea during medusa formation with very similar expression domains in the developing medusa bell [45, 46].

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On the Independent Origins of Complex Brains and Neurons

“…In cnidarians, neurons also arise in the endoderm [Westfall and Elliott, 2002]; and in echinoderms different nerve nets apparently have coelomic/mesodermal and endodermal origin [see above and Harrison and Chia, 1997]. It is interesting that in cnidarians expression of Hox genes was detected in the endoderm [Finnerty et al, 2004; see also a discussion related to trans-differentiation, mesodermal and muscle specific genes and markers in cnidaria; Seipel et al, 2004;Galle et al, 2005;Schmid, 2005, 2006;Reber-Muller et al, 2006], whereas the expression of 'anterior' Hox genes has been found in the mesoderm of the juvenile rudiment of the sea urchin [Arenas-Mena et al, 1998.…”

Finding partners: How BMPs select their targets

“…1). Ligands and downstream components of the signaling cascade have been found both in Cnidaria (metazoans that include Hydra, the anemone Nematostella, jellyfish, and corals), and also in the sponges, the most ancient metazoan clade (Suga et al, 1999;Hayward et al, 2002;Finnerty et al, 2004;Reinhardt et al, 2004;Rentzsch et al, 2006Rentzsch et al, , 2007Reber-Mü ller et al, 2006;Nichols et al, 2006;Adamska et al, 2007;Zoccola et al, 2009). Thus far, no TGF␤ superfamily signaling components have been reported in taxa "basal to" the sponges, including the single-celled choanoflagellates, fungi, or protozoa (Nichols et al, 2006;King et al, 2008).…”