title: The evolution of cellular functional modules and the origin of coordinated behavior in Metazoa
creator: Ruperti, Fabian
subject: ddc-500
subject: 500 Natural sciences and mathematics
subject: ddc-570
subject: 570 Life sciences
subject: ddc-590
subject: 590 Zoological sciences
description: Proteins are essential components of life. Their functions rely on intrinsic activities and specific interactions which together constitute the functional identity of a cell. Within this network of interactions, proteins (and other macromolecules) form dense and functional discernable modules that exert new, module-specific functions and are referred to here as cellular functional modules (CFMs). Examples of CFMs are protein complexes and regulatory or metabolic pathways. CFMs are evolutionary traceable, heritable and able to duplicate and diversify, and thus can be regarded independent units of selection. This opens up new avenues towards solving challenging questions in evolutionary biology, such as the origin of complex cellular traits. In particular, the nervous and muscular systems are essential for the evolution of coordinated behavior in animals, yet their origin remains obscure. This thesis summarizes my efforts investigating the evolution of CFMs, with a focus on actomyosin CFMs, using the freshwater sponge Spongilla lacustris as a model species. Sponges (Porifera) are one of the earliest-branching animals, lacking “conventional” neurons and muscle cell types, yet are shown to express neuronal and actomyosin CFMs. Strikingly, external stimuli evoke an intriguing coordinated whole-body movement which remains poorly understood. To advance on this, (1) I improved the annotation of the S. lacustris proteome by ~50%, designing a custom pipeline for protein structure-based functional transfer, termed MorF (Morpholog Finder), in a collaborative effort. This work confirmed that morphologs (= structural similar proteins) are homologs in most cases and share functions even when homology is no longer detectable with conventional sequence-based methods. Novel annotations revealed new cell-type specific CFMs. Leveraging this, (2) I specifically focused on shape changes and molecular mechanisms of the whole-body movement using live 3D imaging, pharmacological profiling, and a survey of sponge cell-type specific expression of actomyosin CFMs. I found that - in contrast to prevailing views - the movement is triggered by the relaxation of epithelial actomyosin stress fibers via an Akt/NOS/PKG pathway, conserved in vertebrate smooth musculature. These stress fibers likely present an early form of an actomyosin CFM that was ultimately incorporated into specialized myocytes. Functional proteomic profiling of the movement (3), in particular Thermal Proteome Profiling, quantitative phosphoproteomics and secretomics, reaffirmed the “smooth-muscle”-like regulation and further suggested a mechanosensory function of the stress fibers, serving both as “sensor” and “actor”. The secretion of paracrine and diffusible signals sheds new light on the whole-body coordination in an otherwise nerve-less animal. During the movement induced by mechanical stimulation, the sponge activated an inflammation-like state. This “relaxant-inflammatory” CFM represents a conserved reaction of fluid-carrying metazoan systems - such as the vertebrate vascular system - to oscillatory shear stress. Last, (4) I outline my efforts towards a sponge-specific protein-protein interactome, using Co-fractionation mass spectrometry and single cell RNAseq co-regulation, presenting preliminary sponge complex CFMs. Together, the evolutionary origin and diversification of the relaxant-inflammatory CFM in animal movement is a prime example how complex cellular functions can emerge through the step-wise integration of existing CFMs.
date: 2024
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/34103/1/thesis_Fabian_Ruperti.pdf
identifier: DOI:10.11588/heidok.00034103
identifier: urn:nbn:de:bsz:16-heidok-341037
identifier:   Ruperti, Fabian  (2024) The evolution of cellular functional modules and the origin of coordinated behavior in Metazoa.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/34103/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng