Calcium Signaling in Cellular Anabolism and Differentiation


CALL: 2014

DOMAIN: BM - Translational Biomedical Research

FIRST NAME: Alexander




HOST INSTITUTION: University of Luxembourg

KEYWORDS: Dynamic signaling; Ca2+ signaling; Encoding - decoding relation; Cell fate and Differentiation; Imaging based systems biology; Single cell analysis; Multiscale modeling and analysis; Dynamic therapy

START: 2015-05-15

END: 2018-05-14


Submitted Abstract

Ca2+ is an important and versatile second messenger in eukaryotic cells that translates extracellular signals into intracellular responses often in the form of repetitive increases of the cytosolic Ca2+ concentration. This, for many cell types, universal behavior has led to the widely accepted paradigm of Ca2+ signaling being frequency coded where changes in stimulation are assumed to modulate the oscillation period. In experiments studying the physiological relevance of these oscillations, cells were forced to exhibit specific deterministic oscillations of the cytosolic Ca2+ concentration and subsequent transcription analysis has discovered a strong relation between the Ca2+ frequency and expression levels of several genes. However, we have recently shown by comprehensive investigations that Ca2+ spiking is indeed stochastic. This challenges the current (incomplete) understanding of downstream effects including transcriptional regulation that represents a major mechanism of differentiation and cell fate. A promising new approach to cellular development triggered by Ca2+ dynamics originates from our further finding that, despite the randomness of the spiking behavior, Ca2+ signaling obeys a cell type and pathway specific signature in form of a robust relation between the standard deviation and the average period of the stochastic dynamics. While we, based on these recent observations, established a generic encoding relation of Ca2+ signaling that explains a wide range of experimental studies on Ca2+ dynamics, the impact of this signaling mechanism on downstream targets including gene expression and corresponding cell fate is not yet investigated. The intended project will address this fundamental challenge of the decoding mechanism by investigating the effect of distinct Ca2+ signatures on transcription and cell fate in medical relevant systems with a (not exclusive) focus on NF¿B. NF¿B is known to be regulated by temporal Ca2+ signals and plays a major role in many cell state transitions and differentiation processes. To investigate Ca2+ triggered cell fate dynamics and differentiation processes we will measure and manipulate Ca2+ spiking in HMLER as well as in iPS cells and characterize gene expression and cell states in dependence on spontaneous and forced Ca2+ signatures. HMLER cell cultures consist of a heterogeneous mixture of epithelial and mesenchymal populations and exhibit spontaneous epithelial to mesenchymal transitions (EMT) where the two distinct cell states are easy to identify by morphology and known cell surface markers. In addition, we will characterize the Ca2+ signaling induced cell states more functional by immunostaining of NF¿B (a major mediator of EMT) and single cell transcription analysis in collaboration with the Huang lab at the Institute of Systems Biology in Seattle (USA). While EMT corresponds to cell state transitions of mature cells, we will investigate the impact of distinct Ca2+ signatures on differentiation of iPS cells in collaboration with the Schwamborn lab at the LCSB. Thereby we will apply an analogous approach to the established differentiation process of iPS cells to neuronal stem cells (NSC) and dopaminergic neurons, which is also strongly NF¿B dependent. The shared NF¿B mechanism allows for efficient experimental multiplexing of the two model systems for cell fate and differentiation whereas the detailed single cell transcription analysis will reveal cell type specific insights. The experimental results will be utilized to extend an existing computational multiscale model of Ca2+ spiking by transcriptional dynamics enabling quantitative insights into the only poorly characterized decoding mechanism. Besides this fundamental scientific outcome, the project will generate novel insights into the cancer relevant EMT process as well as may lead to new methods to increase differentiation efficiencies of iPS cells and will therefore eventually help to optimize therapeutic approaches.

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