Gene Regulatory Network and Tissue Interactions Important for Head and Heart Development and Evolution

Abstract

The evolution of both the head and heart are fascinating subjects to explore. Usually, researcher focus on either heart or head and study their development, anatomy, and/or evolution across vertebrates or at smaller taxonomic scales (genera or species). However, the development and evolution of head and heart are tightly linked. The most recent example is the description of the cardiopharyngeal field, which is an area that contains the anterior lateral mesoderm of the first heart field and the adjacent pharyngeal mesoderm that differentiates into branchiomeric muscles and the second heart field derived heart muscle tissue. Simplified, the cardiopharyngeal mesoderm gives rise to head, neck, and heart musculature. Another example are neural crest cells, which are essential for proper connective tissue development of most – if not all branchiomeric muscles. They also give rise to skeletal structures onto which those muscles attach. Furthermore, neural crest cells influence the heart development, as the separation of the outflow tract into pulmonary trunk and aortic arch. Interestingly, the cardiac neural crest is the caudal part of the cranial neural crest. Similarly, endoderm and its proper communication with surrounding mesenchyme plays an important role in head and heart development. All tissues listed here influence each other and complex gene regulatory networks across all layers ensure the differentiation of the head and heart structures.Most of the knowledge we have today regarding those interactions and gene regulatory networks in and between those tissues are from studies of a few model organisms (Ciona, zebrafish, Xenopus, chick, mouse). Recently more species are included in large scale comparative studies. However, rarely is more than one system analyzed per research group. Research that focusses on the interaction between tissues are still rare – mostly because of their complexity and resources needed. But considering our own species, Homo sapiens, we can observe many congenital defects that simultaneously affect craniofacial and cardiac structures. The same is true for many mutant lines for the model species named above. Taking already available specimens and studying the effects across the tissues of the head, neck, and heart structures will help us understanding common patterns. Those can then be traced through the gene regulatory networks and even reveal new links or new candidate genes participating in those networks.One example is Tbx1, which is a marker for pharyngeal mesoderm that includes the second heart field and branchiomeric mesoderm. A microdeletion in the gene is known to lead to DiGeorge syndrome with specific craniofacial and cardiac anomalies. However, Tbx1 is expressed in all embryonic tissues and patients will show a variety of anomalies not only associated with the cardiopharyngeal mesoderm, as development of brain, thyroid and parathyroid glands, kidneys, etc. are also impacted.Support or Funding InformationJMZ is supported by a Howard University College of Medicine pilot study award (BFPSAP: U100217).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.