Day 0–28 of Human Embryonic Development: Importance of Studying Cell and Tissue Interactions in Head and Heart Development

Abstract

All vertebrates start their development from a zygote and the processes from this cell to a complex organism are often complicated and include many gene regulatory networks, cell migrations, cell differentiations, communication between cells and between tissues, etc. Earliest mis‐regulations in those processes lead almost always to the demise of the developing embryo – often before the women even realizes she is pregnant. This is because the most exciting and complex processes related to body plan formation happen during the first 8 weeks of embryonic development. Even more fascinating is that at the end of the first months (28 days after fertilization) the head and heart region are clearly distinguishable: the heart is beating, u‐shaped and atria and ventricles are aligned, the pharyngeal arches are present, as are eye and ear anlagen (placodes), in the brain several regions are distinct, including forebrain, midbrain, and hindbrain. There are many remarkable research groups all over the world studying one or the other system (brain, cardiovascular, craniofacial), but only few groups study the interactions between all tissues (ectoderm, mesoderm, endoderm – neural crest as special tissue derived from ectoderm). However, understanding precisely those interactions during earliest and later development will help us to understand human syndromes with the same underlying genetic defect but that present with a huge variety of phenotypes.For example, the DiGeorge Syndrome is caused by a deletion of a region at 22q11.2 that contains 30–40 genes. Due to its involvement of several system it is also called CATCH22 – Cardiac anomalies, Abnormal facies, Thymic hypoplasia, Cleft palate, Hypocalcemia. Each of those abnormalities could be caused by the involvement of cranial neural crest cells during embryonic development, even the heart anomalies as cardiac neural crest cells are part of the posterior population of cranial neural crest cells. Also, in the region of the 22q11.2 is the Tbx1 gene that was shown to be essential during earliest cardiopharyngeal mesoderm development and differentiation. The cardiopharyngeal field is a progenitor field that gives rise to the first heart field and the pharyngeal mesoderm. The latter will differentiate into the second heart field derived cardiac musculature and the branchiomeric (head) muscles. Yet, neither our knowledge of neural crest cell involvement nor our understanding of cardiopharyngeal mesoderm development, fully explains the variety of symptoms seen in DiGeorge Syndrome patients.Therefore, a detailed summary of what is currently known about the first 28 days of head and heart development and the tissue interactions will help us to understand complex syndromes. Furthermore, it will be possible to identify regions that need more research focus. Last, but not least, a better understanding of our own developmental processes also provides insights into evolutionary processes and studying animal developmental processes further contributes to a deepened knowledge of the evolutionary development of our own body. Here, I will present a summary of the first 28 days of head and heart embryonic development in humans and highlight regions of research that next generation scientists might be interested in.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.