Biology 133 lecture AY 2021- 2022

Good day, Ma'am Leonardo! Thank you for your interest in our presentation. Here are the group's answers in response to your questions:

1. Obviously, there are a lot of ethical considerations in this kind of study. Can non-human primates serve as better models instead of mice since the former is more closely related to humans?

Nonhuman primates (NHPs) can serve as better models than rodents. This is due to the fact that the former is more closely related to humans in terms of phylogeny (Bales et al., 2014). Data gathered from NHP research will have greater validity and provide unique insights on human development because many features, such as anatomy, physiology, and genetics, are shared by humans and NHPs. This would allow researchers to be able to answer questions that would not have been possible if lower-order organisms had been used.

Reference:

Phillips, K. A., Bales, K. L., Capitanio, J. P., Conley, A., Czoty, P. W., 't Hart, B. A., Hopkins, W. D., Hu, S. L., Miller, L. A., Nader, M. A., Nathanielsz, P. W., Rogers, J., Shively, C. A., & Voytko, M. L. (2014). Why primate models matter. American journal of primatology, 76(9), 801–827. https://doi.org/10.1002/ajp.22281

2. Please elaborate on the 14-day rule. Does this mean that only 14-day old human embryos can be studied?

The 14-day rule refers to the limit imposed on the growth of the human embryo in vitro. It means that no human embryo must be grown past 14 days as it was the approximate time at which the primitive streak appears. There were several key arguments noted by the Warnock Committee in support of the 14-day limit on human embryo culture: (1) Day 14 is the last stage of development where twinning can occur, which therefore represents individuation,  (2) at this point, the founding cells of the nervous system have not been specified prior to this stage, (3) substantial embryo loss from the time of fertilization up until this point, and (4) that the embryo has no potential for further development until implantation is complete. As such, once the embryos reach the 14th day of development, they are to be destroyed (Pera, 2017).

Reference:

Pera, M. F. (2017). Human embryo research and the 14-day rule. Development, 144(11), 1923–1925. https://doi.org/10.1242/dev.151191

3. Could you please elaborate on the differences in morphogenetic strategies involved in human and mouse development?

Mentioned in the presented article are a number of differences between human and mouse development:

Reference:

Ghimire, S., Mantziou, V., Moris, N., & Martinez Arias, A. (2021). Human gastrulation: The embryo and its models. Developmental Biology, 474, 100–108. https://doi.org/10.1016/j.ydbio.2021.01.006

Good day, Elian, Patrick, & Jeliza (Group 1)! Thank you for your interest in our presentation. Here is the group's answer in response to your question:

In your presentation, the 14-day rule was mentioned in the introduction but later figures containing 14 to 20 days post-fertilization were used by Ghimre et al 2021. Could you elaborate on the importance in mentioning the 14 day rule?

The 14-day rule is a time limit imposed on the in vitro growth of a human embryo, a procedure used in embryology research. The rule was mentioned because it has limited the studies of human development during and after gastrulation to the study of existing collections of embryos and fetuses. Because of the ethical implications of growing such embryos, experiments were restricted to day 14 of development, which is the precursor to the process of gastrulation. Even if these ethical implications are not considered, technical challenges must be overcome in order to obtain healthy embryos in vitro at this stage. PSCs are proposed as solutions to these challenges, and the figures that include 14-20 dpf events to compare the similarity of the events in human and mouse embryology are shown as part of the discussion on what is being modeled by the proposed PSCs.