Pilot Project 7 (2022)

Optogenetic tool for manipulating cell-cell adhesion in cultured cells and in vivo

In multicellular organisms, cells need to form stable but reversible connections with each other to allow compartmentalization of the organisms. Cell cell adhesion regulates cell migration, tissue organization, wound healing, and immune responses 1. For instance, during gastrulation, epithelial cells lose their connections, resulting in the development of the mesoderm 2. Adherens junctions (AJs), whose main components are cadherins that connect neighboring cells via homophilic interactions, are conserved throughout Bilateria 3,4. AJs are important intercellular structures that maintain and direct the assembly, recognition, and dynamics of cell adhesions, as well as controlling cytoskeletal reorganization, intracellular signaling and transcriptional regulation.

Alterations in cell-cell adhesion are related to the misregulation of cadherins or changes in their expression levels, and can lead to disruption of homeostasis and promote tumorigenesis and metastasis 5,6. There is a general loss of stabilized cell- cell adhesions between cells in a developing tumor as expression of Epithelial cadherin (E-cadherin) is down-regulated in most cancers, allowing cancer cells to acquire the migratory phenotype necessary for invasiveness and metastasis 5. The loss, reduction or dysfunction of E-cadherin is seen in most progressive, aggressive and undifferentiated carcinomas of the mammary gland and other epithelial tissues 7. Hence, understanding the mechanisms of E-cadherin-mediated cell adhesion in cancer may lead to the development of new targeted therapies.

The emergence of optogenetics in the past twenty years has enabled scientists to use light to control biological processes at high spatiotemporal resolution, in a reversible manner and with minimal side effects 8,9. Optogenetics has both improved our understanding of cellular mechanisms and signaling networks and revolutionized

neuroscience, leading to a variety of applications in biotechnology and biomedicine 10. Optogenetics is essentially based on the use of light-sensitive proteins to control and study biological functions. Optogenetic tools are genetically encoded, can be introduced into any cell type and used precisely for artificial manipulations of biological processes, as light can be delivered in well-defined spaces and time, and can cause rapid, reversible, and quantitative effects after activation of photoreceptors 9.