Second batch of oral reports (For Dec. 26-29, 2021)

BIO 133 LEC2 (TF 10 - 11:30 AM) - Neurulation

BIO 133 LEC2 (TF 10 - 11:30 AM) - Neurulation

by Christine Jem Dogta -
Number of replies: 5

Good day! We are Christine Jem Dogta & Kiara Maye Sta. Rita from BIO 133 LEC2 and this is our presentation on Neurulation regarding Norio Miyamoto & Hiroshi Wada's 2013 study, "Hemichordate Neurulation and the Origin of the Neural Tube"

https://www.youtube.com/watch?v=bJSXGhcXe-w 

Thank you! Also, here's the link to the journal article: https://doi.org/10.1038/ncomms3713

In reply to Christine Jem Dogta

Re: BIO 133 LEC2 (TF 10 - 11:30 AM) - Neurulation

by Lydia LEONARDO -
Thank you for this report that pointed out striking homologies between vertebrates and hemichordates. My questions are:
1. Please elaborate on the hedgehog molecules that you mentioned in your report particularly their importance in the development of the homologous structures in the hemichordates and chordates.
2. What is the conclusion of the study in terms of the homology between notochord and stomochord? Was there a categorical conclusion made?
Thank you.
In reply to Lydia LEONARDO

Re: BIO 133 LEC2 (TF 10 - 11:30 AM) - Neurulation

by Kiara Maye Sta Rita -

Good day, Ma'am! Here are our answers:

1. The Hedgehog (Hh) gene was first identified in Drosophila melanogaster as the one responsible in the establishment of their body plan (i.e., segment polarity). It was also eventually found to be expressed along the midline of chordates (Sato et al., 2009). In chordates, the Hh proteins from the notochord are responsible in signaling the neural plate for floor plate induction and neural tube patterning. In hemichordates, Miyamoto & Wada (2013) found that the stomochord and the dorsal endoderm of the buccal tube release Hh molecules to which the collar cord and the mesoderm have the potential to respond for patterning.

2. The study did not draw any conclusion regarding the homology between the notochord and the stomochord. It was only mentioned that they have a similar genetic regulatory machinery for hydrostatic skeleton and the patterning of the nervous system. However, their findings suggest that the stomochord, together with the endoderm, is responsible in patterning the collar cord—much like how the notochord directs the formation of the neural tube.

Thank you!

 

References:

Miyamoto, N. & Wada, H. (2013). Hemichordate neurulation and the origin of the neural tube. Nature Communications, 4(2713). https://doi.org/10.1038/ncomms3713

Sato, A., White-Cooper, H., Doggett, K., & Holland, P. W. H. (2009). Degenerate evolution of the hedgehog gene in a hemichordate lineage. Proc Natl Acad Sci USA, 106(18), 7491–7494. https://doi.org/10.1073/pnas.0810430106

In reply to Christine Jem Dogta

Re: BIO 133 LEC2 (TF 10 - 11:30 AM) - Neurulation

by Juan Carlos Urbano -
Hello Christine and Kiara!

I would like to commend your group for providing a very comprehensive report on neurulation. I am JC from Group 9 and our group (Idorot, Ngo, Urbano) would like to ask two questions:

1. You have mentioned that the homology between stomochord and notochord has been challenged mainly from two aspects: (a) difference in gene expression and (b) dorsoventral inversion hypothesis. What do these challenges imply?
2. If future researchers want to expand on this research, what aspect of hemichordate developmental biology would you recommend they focus on in order to gain a better understanding of the dramatic events in the chordate body plan’s evolution?

Thank you and happy holidays!
In reply to Juan Carlos Urbano

Re: BIO 133 LEC2 (TF 10 - 11:30 AM) - Neurulation

by Christine Jem Dogta -
Hi Juan Carlos!

To answer your first question, brachyury, a T-box gene, is required for notochord differentiation and studies show that in hemichordates, stomochords had no brachyury gene expression which implies that there is no homology between the notochord and the stomochord, or between the notochord and any hemichordate structure. In dorsoventral axis inversion hypothesis, the homologous structure should occupy the ventral side of the hemichordate endomesoderm since the notochord originates from the dorsal section of the archenteron. The stomochord, on the other hand, emerges from the buccal tube's dorsal wall as an anterior projection. The dorsoventral inversion theory is further contradicted by homology between the hemichordate dorsal collar cord and the chordate CNS.

I think if future researchers want to expand on this research, they can also delve into their life history as some studies suggest that chordate subphyla such as urochordates and hemichordates can have a solitary sexual mode or a colonial life history that permits asexual budding as well as sexual reproduction. These alterations in life history have had a significant impact on body plans, and past morphological assessments may have been perplexed. Future researchers can review recent molecular and developmental comparisons of hemichordate and urochordate embryos and suggest additional research that might provide light on the chordate body plan's evolution.

I hope we answered your questions. Thank you!

References:
Miyamoto, N. & Wada, H. (2013). Hemichordate neurulation and the origin of the neural tube. Nature Communications, 4(2713). https://doi.org/10.1038/ncomms3713

Cameron, C. B., Garey, J. R., & Swalla, B. J. (2000). Evolution of the chordate body plan: New insights from phylogenetic analyses of deuterostome phyla. Proceedings of the National Academy of Sciences, 97(9), 4469–4474. https://doi.org/10.1073/pnas.97.9.4469
In reply to Christine Jem Dogta

Re: BIO 133 LEC2 (TF 10 - 11:30 AM) - Neurulation

by Erica Vera Villegas -
Hi!
I'm Erica Vera Villegas, and I'm a member of Group 11 (Ranoso, Riva, Villegas). Our group would like to congratulate you on a very thorough yet easy-to-understand report on Hemichordate neurulation and the origin of the neural tube.

Here are our questions:
1.) You mentioned that prominent vacuoles and a collagenous sheath are necessary for the notochord to operate as a hydrostatic axial skeleton; could you explain why?
2.) You also highlighted the two challenges encountered in the research; what do these challenges imply? How will these challenges influence/affect future research about hemichordate neurulation?