Calcium Dependent CAMTA1 in Adult Stem Cell Commitment to a Myocardial Lineage

Barbara Muller-Borer,Nobuyuo Maeda,Nadia N Malouf,Woohyun Woon,Rob Aldina,Neal Shepherd,Nenad Bursac,Raymond Fox,Jian Ping Jin,Gwyn Esch,Margaret L Kirby,Mary Hutson,Sylvia Hiller,Page Anderson

doi:10.1371/journal.pone.0038454

Barbara Muller-Borer, Nobuyuo Maeda + Show 12 more

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https://doi.org/10.1371/journal.pone.0038454

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Abstract

The phenotype of somatic cells has recently been found to be reversible. Direct reprogramming of one cell type into another has been achieved with transduction and over expression of exogenous defined transcription factors emphasizing their role in specifying cell fate. To discover early and novel endogenous transcription factors that may have a role in adult-derived stem cell acquisition of a cardiomyocyte phenotype, mesenchymal stem cells from human and mouse bone marrow and rat liver were co-cultured with neonatal cardiomyocytes as an in vitro cardiogenic microenvironment. Cell-cell communications develop between the two cell types as early as 24 hrs in co-culture and are required for elaboration of a myocardial phenotype in the stem cells 8–16 days later. These intercellular communications are associated with novel Ca2+ oscillations in the stem cells that are synchronous with the Ca2+ transients in adjacent cardiomyocytes and are detected in the stem cells as early as 24–48 hrs in co-culture. Early and significant up-regulation of Ca2+-dependent effectors, CAMTA1 and RCAN1 ensues before a myocardial program is activated. CAMTA1 loss-of-function minimizes the activation of the cardiac gene program in the stem cells. While the expression of RCAN1 suggests involvement of the well-characterized calcineurin-NFAT pathway as a response to a Ca2+ signal, the CAMTA1 up-regulated expression as a response to such a signal in the stem cells was unknown. Cell-cell communications between the stem cells and adjacent cardiomyocytes induce Ca2+ signals that activate a myocardial gene program in the stem cells via a novel and early Ca2+-dependent intermediate, up-regulation of CAMTA1.

Highlights

It has become well recognized that transcription factors have a crucial role in reprogramming gene expression in mammalian cells and that the process of cell differentiation can be reversed [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
Using fluorescence recovery after photobleaching (FRAP) we found that the stem cell-derived nascent cardiomyocytes were functionally coupled with adjacent cardiomyocytes through gap junctions
Began to rise soon after and continued to increase 2 days later (Figure 3). These results suggest that signaling through CAMTA1 and indirectly Ca2+/calcineurin/NFAT may be early events in the initiation of stem cell commitment into a cardiomyocyte phenotype

Summary

Introduction

It has become well recognized that transcription factors have a crucial role in reprogramming gene expression in mammalian cells and that the process of cell differentiation can be reversed [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. More recently direct reprogramming of one cell type into another, without resorting to an intermediate pluripotent stage has been achieved with over-expression of tissue specific transcription factors [13,14,15,16,17]. These findings raise the possibility that targeted manipulation of a less stringent epigenetic restrictive state in multipotent adult-derived stem cells may be achieved, so as to induce the endogenous expression of a transcriptional program that characterizes a specific cell fate. This is associated with novel Ca2+ oscillations that are synchronous with Ca2+ transients in adjacent cardiomyocytes and detected in the stem cells as early as 24–48 hrs in co-culture with the cardiomyocytes

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