MOL BIO COLLOQUIUM
February 24, 2023
Investigating the role of actin in establishing vertebrate heart asymmetry
Asymmetric organ development results from of a cascade of early signaling events that produces asymmetry along the mediolateral body axis, termed left-right (LR) patterning. Errors in LR patterning result in congenital heart defects, which affect 1% of all live births and are the most common structural birth defect in the United States. LR patterning induces left-sided Nodal signaling, which influences the development of the vertebrate heart, producing its asymmetric positioning, structure, and function. A crucial step of heart development is jogging: the formation of the heart tube via the asymmetric migration of a loose epithelial sheet of cardiomyocytes from the cardiac cone. Prior to jogging, left-sided Nodal signaling activates downstream effector genes, producing a faster migration rate in left-sided cardiomyocytes. While a few effector genes have been identified, many remain unknown, making it difficult to determine exactly how Nodal signaling produces this asymmetry in migration rates. I have utilized single-cell RNA sequencing to characterize cardiomyocyte expression profiles just prior to jogging and have identified novel candidate effector genes downstream of Nodal signaling that may be necessary for asymmetric migration during jogging. I have determined that several actin genes are upregulated in the developing heart in response to Nodal signaling, and that this asymmetric expression is Nodal-dependent. This asymmetry in actin persists to the protein level, as F-actin is stronger on the left side of the heart compared to the right side. Further probing the role F-actin in the asymmetric migration of cardiomyocytes during jogging will advance our understanding of vertebrate heart development and give insight into how congenital heart defects arise.
Mechanism and Therapeutic Implications of Host Telomerase Modulation by Human Cytomegalovirus
Human Cytomegalovirus (HCMV) remains highly prevalent and can cause severe disease in immunocompromised hosts. Congenital infection is a leading cause of congenital neurologic defects. There is no method to eradicate latent infection from the human host, and the need for more effective therapies remains. Host telomerase has been implicated in the infection and oncogenesis of several herpesviruses. We and others have demonstrated that host telomerase is upregulated in human fibroblast cell lines following infection with laboratory and clinical strains of HCMV. Our goal is to examine the relationship between HCMV and telomerase to identify the biological mechanism and potential clinical significance. We found increased telomerase activity following HCMV infection of both laboratory and clinical strains, and sharp reduction of respective viral titers following treatment with two telomerase inhibitors of different mechanisms of action as well as siRNA knockdown of hTERT, which suggests a biologically significant relationship between HCMV and host telomerase. Further examination may provide insights to HCMV biology, expand knowledge of herpesvirus interactions with telomerase and telomeres, and provide a greater understanding of mechanisms of telomere homeostasis.