All-optical analysis of gap junction function in muscular pump in vivo

• Applicant: Professor Dr. Alexander Gottschalk
• Subject Area: Cell Biology ; Anatomy and Physiology ; Animal Physiology and Biochemistry ; Biophysics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 579717010

Gap junctions (GJs) consist of intercellular ion channels that mediate fast electrical signals, and which coordinate or synchronize activity in cell ensembles, e.g. in the heart or in the nervous system. Thus, GJ malfunction is often associated with diseases like epilepsy or cardiopathies. GJ channels are constituted by innexins, or in vertebrates, connexins, that form hexameric half channels. These assemble with a second half channel in the neighboring cell, thus connecting the cytoplasmata. GJ channels can be studied by single-channel electrophysiology, or as large GJ channel ensembles, sometimes comprising 10’s of thousands of channels, by whole cell patch-clamp in dissected tissues or cell culture. However, much less is known about the electrical interplay of excitable cell ensembles in vivo. Thus, we lack a holistic picture how organs like the heart orchestrate their complex function. Here, we propose to use the unique opportunity given by the animal model Caenorhabditis elegans, to achieve such a holistic picture from an intact muscular organ in vivo, the pharyngeal feeding organ. This muscular pump resembles the mammalian heart by organization and in its use of voltage gated ion channels. The expression of individual innexin GJ subunits is know for this organ down to the individual cell type. Pumping activity begins with a coordinated depolarization of the entire organ, and spatiotemporally distinct repolarization in anterior and posterior regions. In recent years, we developed all-optical methods for imaging cellular voltage, and for its manipulation using optogenetic tools, with cellular resolution, to record and control electrical activity in intact animals in vivo, in closed loop. We will use this technology to analyze all of the innexins expressed in the pharyngeal muscles and marginal cells, and assess the consequence of their lack on voltage fluctuations in the two tissues, simultaneously with two different color fluorescent voltage indicators. We will combine this analysis with electrophysiology to understand the effect of the loss of individual innexins on cellular excitability. After we identified the exact composition and properties of GJ channels expressed in the different parts of the pharynx, we will characterize them after expressing such heteromers in body wall muscles, which are accessible to single-cell optogenetic manipulation and patch-clamp electrophysiology. Last, we will use our insights to generate/modify existing mathematical models of the electrical activities in the pharynx, to understand how distinct GJs help shaping them.

• DFG Programme: Research Grants