Biophysical Society Thematic Meeting

Mechanobiology of Disease

Thursday Speaker Abstracts

Mechanical Impact of Apoptosis in a Tissue

Yusuke Toyama

1,2,3

Mechanobiology Institute, National University of Singapore, Singapore,

Department of

Biological Sciences, National University of Singapore, Singapore,

Temasek Life Sciences

Laboratory, 1 Research Link, National University of Singapore, Singapore.

Apoptosis, or programmed cell death, is the most common mechanism of eliminating damaged

or unnecessary cells during embryonic development, tissue homeostasis, and certain pathological

conditions. It has been well known that apoptotic cell is expelled from a tissue mainly by the

formation and contraction of the actomyosin cables in the dying and the neighboring non-dying

cells. However, this was not been correlated with the dynamics of adherens junction (AJ) and the

temporal changes in tissue mechanical tension. We explored the extrusion process of apoptotic

cell in developing Drosophila pupae. Here we show that in the middle of cell extrusion, AJs

between apoptotic and non-dying cells become defective, with a reduction in the levels of AJ

components, including E-cadherin. Concurrently, tissue tension is transiently released.

Formation and contraction of a supra-cellular actomyosin cable forms in neighboring cells,

brings the non-dying cells together and further reshapes tissue tension toward the completion of

extrusion. The extrusion-associated mechanical force deforms not only the nearest-neighbor cells

but also the surrounding tissue and contributes to large-scale tissue dynamics. All together, we

conclude that a mechanical coordination between adhesion remodeling and tissue tension

reshaping represents a mechanism of apoptotic cell extrusion.

Biogeography of in vivo Microbial Biofilms

Marvin Whiteley

The University of Texas at Austin, Austin, TX, USA.

Biogeography is the study of the spatial distribution of species within an ecosystem across space

and time. The field of microbial ecology has long focused on the micron-scale biogeography and

its consequences in polymicrobial communities. For example, studies of the leaf-associated

microbiota of plants show that the arrangement of single cells in structured polymicrobial

communities is responsible for desiccation tolerance, persistence, and resistance to invading

species. The biogeography of human-associated polymicrobial communities, including those in

disease, has not been studied to similar depth. While it is now widely accepted that most

polymicrobial communities living in natural environments, including the human body, form

spatially structured consortia, the mechanisms used by microbes to form these communities is

not understood. Here I will discuss the use of a microscopic three-dimensional printing strategy

in combination with the micro-scale analytical technique scanning electrochemical microscopy

to elucidate these mechanisms. This experimental framework has allowed for the assessment of

the role of micro-scale spatial structure on bacterial interactions as well as important clinical

phenotypes including antibiotic resistance.