Cnidarians,
the phylum that contains corals, jellies, and anemones, was once thought to be
simple, humble in their bodily systems and genetic structuring. Some might
claim that these metazoans are even primitive compared to their sister phyla,
the Bilateria species. This is no longer the case. In fact, studies have
confirmed the presence of proteins, genes, and transcription factors in a
species of Cnidaria called Nematostella
vectensis that will change the way that scientists study the evolution of
the nervous system and eventual brain. It is important for scientists to
understand the development of the nervous system on an evolutionary scale so
that knowledge can be applied to other species, including humans. The implicit knowledge

            It is true that Cnidarians have a simple nervous system;
however, their nervous system is an important connection between the evolution
of Porifera, Placozoa, and Ctenophora to the more complex nervous systems of
Bilateria. An important link has been found in a starlet sea anemone called Nematostella vectensis, a member of the
Anthozoans. It is also being used because of its complex genome that includes
major signaling pathways and transcription factors. This original study went
over the structure of the nervous system, its establishment, and the developmental
genetics of the neurons within the Cnidarian evolutionary context (Busengal et
al. 2017).

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            Nematostella is
a diploblast, meaning it has an endoderm and ectoderm but lacks a mesoderm. The
nervous system is composed of only sensory cells, ganglion cells, and Cnidocytes
but neuronal markers have been found that suggest neuronal differentiation.
Some of the gene markers that have been found are NvFoxQ2d, which is a transcription factor expressed in dividing
ectodermal cells, and SoxB(2), an
unprecedented transcription factor found for the use of the neurogenic
developmental process (Busengal et al. 2017., Royo et al. 2011).  These two genetic markers have been found to
be the pinnacle of an advanced regulatory system, specifically the nervous
system. Using a transgenic reporter line, these scientists found that NvFoxQ2d
cells were dividing to create sensory cells. A transgenic reporter line uses
the placement of a reporter gene to sequence a gene of interest. In this study,
researchers used the mOrange fluorescent protein marker to sequence the
surrounding genomic area. By sequencing the genomic data, they were able to
find a novel sensory cell in the ectoderm of the Nematostella.

Originally
thought to be simple, the nervous system of Nematostella
turns out to be quite complex. The finding of these gene markers from the
reporter lines also led to the discovery of specific signaling pathways in Cnidarians,
some that were only thought to be found in vertebrate metazoans. Wnt, or
wingless-type, is a conserved signaling pathway that regulates cell-to-cell interactions
in embryogenesis. BMP, or bone morphogenetic protein, is a signaling pathway
that regulates growth factors. These two pathways have been found in Bilateria
and the discovery of these pathways in Cnidarians suggests an ancestral role in
regional patterning and neurogenesis, though the pattern is quite different in Nematostella. Unfortunately, this
pathway is not understood. Through genetic analysis, the conclusion of the study
makes the claim that the “common ancestor of Bilateria and Cnidaria was an
animal with a well-established nervous system”.