Thomas Juan – Blood flow mechanosensation during cardiovascular development

My laboratory aims to understand how blood flow forces shape the development and function of the cardiovascular system. We generate genetic tools to control cardiac contractions and modulate the function of mechanosensor proteins in cardiovascular subpopulations.
Hemodynamic forces generated by the blood flow are an essential regulator of cardiovascular development and function. Vascular morphogenesis, cardiac differentiation, and organogenesis as such, are steered through the forces from blood flow. Understanding how these forces shape the cardiovascular system is critical to the development of treatments for cardiovascular disease, the leading cause of death worldwide, claiming 18 million lives every year globally.
Blood flow mechanosensation in endothelial cells
Multiple types of cardiovascular cell respond to blood flow, such as the vascular smooth muscle cells that wrap around the blood vessels, the pericytes that are associated with small blood vessels, and the cardiomyocytes that allow cardiac contractions. We focus on endothelial cells, the inner lining of the vasculature, which are in direct contact with blood flow, and are the first line of response to hemodynamic forces. Despite the identification of several endothelial mechanosensitive proteins, which transduce mechanical signals into cellular responses, the precise mechanotransduction mechanisms responsible for these responses remain largely unknown.

Confocal imaging of wild-type (A) and pkd1a mutant (B) hearts. The rightmost image in each pair shows a magnification of the atrioventricular valve region (Juan et al. 2023)
Zebrafish and cardiovascular development
The zebrafish can survive severe cardiac injury and zebrafish larvae can grow without a functional cardiovascular system during the first week of development. Although the zebrafish heart is only two-chambered, zebrafish genetic models recapitulate all cardiovascular diseases. The transparency of the zebrafish during development facilitates the use of optical methods, such as light sheet, confocal, and spinning disc microscopy, enabling high-resolution fast imaging of cardiovascular cell dynamics and cellular trajectories in vivo. These features make zebrafish the best model to study the effects of mechanical forces on cardiovascular development and to dissect the underlying genetic pathways.

Brightfield imaging of a zebrafish embryo; coloring highlights blood flow motion and heart contractions (Juan et al. 2024).
Genetic tools to interrogate cardiovascular gene function
Genetic dissection of cardiovascular phenotypes typically involves mutants that recapitulate human disease. Recently, CRISPR-mediated genome editing has enabled the high-throughput generation of floxed alleles to interrogate gene function conditionally. However, this approach is limited by compensation responses and the stability of target proteins and mRNA. To address these issues, we generate conditional knockdown genetic tools that can bypass these mechanisms. Combined with high-resolution live imaging techniques, these tools allow blood flow control and the systemic identification of mechanosensors.

Confocal imaging of a wild-type zebrafish heart (left) and a heart that has been depleted of the Tnnt2a protein (right).
Group members
Publications
Control of cardiac contractions using Cre-lox and degron strategies in zebrafish.
Part of Proceedings of the National Academy of Sciences of the United States of America, 2024
egr3 is a mechanosensitive transcription factor gene required for cardiac valve morphogenesis.
Part of Science Advances, 2024
Part of Development, 2024
- DOI for flt1 inactivation promotes zebrafish cardiac regeneration by enhancing endothelial activity and limiting the fibrotic response
- Download full text (pdf) of flt1 inactivation promotes zebrafish cardiac regeneration by enhancing endothelial activity and limiting the fibrotic response
In preprints: Shh signaling activity predicts cardiac laterality in Astyanax mexicanus populations.
Part of Development, 2024
Multiple pkd and piezo gene family members are required for atrioventricular valve formation.
Part of Nature Communications, p. 214, 2023
Pathway to independence - an interview with Thomas Juan
Part of Development, 2023
Pathway to Independence: the future of developmental biology.
Part of Development, 2023
Parental mutations influence wild-type offspring via transcriptional adaptation.
Part of Science Advances, 2022
Biogenesis and function of ESCRT-dependent extracellular vesicles.
Part of Seminars in Cell and Developmental Biology, p. 66-77, 2018
Myosin1D is an evolutionarily conserved regulator of animal left-right asymmetry.
Part of Nature Communications, p. 1942, 2018
Companion Blood Cells Control Ovarian Stem Cell Niche Microenvironment and Homeostasis.
Part of Cell Reports, p. 546-560, 2015
The ESCRT complex: from endosomal transport to the development of multicellular organisms.
Part of Biologie aujourd'hui, p. 111-24, 2015