Heart stem cells: hope or myth?

The search and study of endogenous heart repair remains an urgent issue in modern regenerative medicine. It is generally accepted that the human heart has a limited regenerative potential, but recent studies show that functionally significant regeneration is possible. However, the mechanisms underlying these processes remain poorly understood. In the heart, there are populations of resident mesenchymal cells that have some properties of stem cells that carry certain markers, such as c-kit+, Sca-1, etc. The ability of these cells to differentiate directly into cardiomyocytes remains controversial, but their use in clinical trials has shown improved cardiac function in patients with myocardial infarction. Currently, approaches are being developed to use, mainly, induced pluripotent stem cells as a promising regenerative therapy, but the cardioprotective role of cardiac mesenchymal cells remains the subject of active study due to their paracrine signaling

GCNA Interacts with Spartan and Topoisomerase II to Regulate Genome Stability

GCNA proteins are expressed across eukarya in pluripotent cells and have conserved functions in fertility. GCNA homologs Spartan (DVC-1) and Wss1 resolve DNA-protein crosslinks (DPCs), including Topoisomerase-DNA adducts, during DNA replication. Here, we show that GCNA mutants in mouse and C. elegans display defects in genome maintenance including DNA damage, aberrant chromosome condensation, and crossover defects in mouse spermatocytes and spontaneous genomic rearrangements in C. elegans. We show that GCNA and topoisomerase II (TOP2) physically interact in both mice and worms and colocalize on condensed chromosomes during mitosis in C. elegans embryos. Moreover, C. elegans gcna-1 mutants are hypersensitive to TOP2 poison. Together, our findings support a model in which GCNA provides genome maintenance functions in the germline and may do so, in part, by promoting the resolution of TOP2 DPCs

Gone with the wind: The evolving influence of social movements and counter movements on entrepreneurial activity in the US wind industry

Social movements can disrupt existing industries and inspire the emergence of new markets by drawing attention to problems with the status quo and promoting alternatives. We examine how the influence of social movements on entrepreneurial activity evolves as the markets they foster mature. Theoretically, we argue that the success of social movements in furthering market expansion leads to three related outcomes. First, the movement-encouraged development of market infrastructure reduces the need for continued social movement support. Second, social movements’ efforts on behalf of new markets increase the importance of resource availability for market entry. Third, market growth motivates countermovement that reduce the beneficial impact of initiator movements on entrepreneurial activity. We test these arguments by analyzing evolving social movement dynamics and entrepreneurial activity in the US wind power industry from 1992 to 2007. We discuss the implications of our findings for the study of social movements, stakeholder management, sustainability, and entrepreneurship