Dissecting the molecular crosstalk between mechanotransduction and primary cilia in models of congenital valvulopathies

Lead Research Organisation: Imperial College London
Department Name: Bioengineering


Primary cilia are versatile microtubule-based protrusions located at the surface of nearly every cell of the human body. In addition to important functions in adults, PC are important regulators of embryonic development. PC are considered as dynamic cellular antenna that sense environmental cues via multiple signalling pathways in different tissues and across developmental stages. Their microtubule-based axoneme can remodel by assembling, maintaining, and disassembling in response to environmental stimuli during tissue differentiation. Nevertheless, the link between PC ultrastructure and its signalling activities is unclear. Furthermore, while PC composition seems to be conserved among cell types, it is unclear why ciliary defects alter specific tissues like the retina or the heart and not others. Hence, understanding the mechanisms through which mutated proteins alter PC structure and signalling is essential to understand how ciliary defects can lead to pathologies, including CHD.

Cardiac cells sense mechanical forces through mechanotransduction. For instance, we recently found that stretch sensitive channels and mechanosensitive purinergic signalling are key to cardiogenesis. These and our further preliminary evidence prompted us to question the current paradigm of cilia related function during cardiac morphogenesis, and to formulate an alternative hypothesis: We postulate that cardiac primary cilia and cilia related proteins control cardiac cells properties required for successful morphogenesis by modulating these mechanosensitive pathways.

The proposal has two complimentary objectives:
Objective 1. To identify the mechanosensitive pathway(s) acting in the EdCs in response to mechanical forces and relationship with ciliary proteins.
Objective 2. To define the cellular functions of ciliary proteins in the process of cardiac valve formation with a specific focus on mechanosensitive processes.

We will have a particular focus on the ciliary protein Dzip1. Dzip1 is a gene involved in cardiac valvulopathy and mutations of dzip1 are responsible for ciliary defects in humans. To date, the cellular mechanism leading to defective valves in the dzip1 mutant is unknown. Our objective is to understand how DZIP1 affects cilia remodelling and regulatory functions in EdCs during cardiac valve development. We plan to tackle this question from organelle to tissue-scale in the entire organism.

Technical Summary

Cardiovascular Diseases (CVDs) are the leading causes of death in the world. Congenital heart malformations account for as many as 30% of embryos or foetuses lost before birth. To properly develop, the heart needs to generate mechanical forces during the growth of the whole structure. This, in combination with genetic information, is required for assembling a functional heart. Currently, most studies focus on how genetic programmes control cell identities and their subsequent roles in cardiac development. In contrast, the mechanical forces that are integral to the growth and assembly of the heart are much less explored. This is surprising as abnormal mechanical forces can deregulate gene expression and lead to diseases such as congenital heart disease and cardiomyopathies. Understanding how biomechanics regulates cardiac morphogenesis is thus of utmost importance. This project aims to provide a molecular and functional characterisation of primary cilia (PC) and cilia-related proteins function in a model of congenital valve disease (CVD) with a focus on mechanotransduction. We will exploit the existing advantages of live imaging and expansion light microscopy (ExM) in zebrafish (ZF) to visualize intracellular signalling and structures in tissues with unprecedented resolution. This work will contribute towards understanding and preventing Congenital Heart Diseases (CHD), which is estimated to occur in up to 10 in 1000 live births.

The overall aim of this project is to provide unprecedented insights into primary cilia and cilia related proteins function in the process of cell signalling and mechanotransduction during cardiac valve formation using advanced imaging.

The proposal has two aims divided into three work packages (Fig.2):
Aim 1. To assess PC function and activity in EdC during valvulogenesis.
Aim 2. To define the mechanosensitive pathways at work during valve morphogenesis.


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