The involvement of DNA damage and repair in aging processes is well established. Aging is an unequivocal risk factor for chronic neurodegenerative diseases, underscoring the relevance of investigations into the role that DNA alterations may have in the pathogenesis of these diseases. Consistently, even moderate impairment of DNA repair systems facilitates the onset of pathological features typical of PD that include derangement of the dopaminergic system, mitochondrial dysfunction, and alpha-synuclein stress. The latter establishes a connection between reduced DNA repair capacity and a cardinal feature of PD, alpha-synuclein pathology. It remains to be determined, however, whether alpha-synuclein stress activates in vivo the canonical signaling cascade associated with DNA damage, which is centered on the kinase ATM and substrates such as γH2Ax and 53BP1. Addressing these issues would shed light on age-related mechanisms impinging upon PD pathogenesis and neurodegeneration in particular. We analyzed two different synucleinopathy PD mouse models based either on intranigral delivery of AAV-expressing human alpha-synuclein, or intrastriatal injection of human alpha-synuclein pre-formed fibrils. In both cases, we detected a significant increase in γH2AX and 53BP1 foci, and in phospho-ATM immunoreactivity in dopaminergic neurons, which collectively indicate DNA damage and activation of the DNA damage response. Mechanistic experiments in cell cultures indicate that activation of the DNA damage response is caused, at least in part, by pro-oxidant species because it is prevented by exogenous or endogenous antioxidants, which also rescue mitochondrial anomalies caused by proteotoxic alpha-synuclein. These in vivo and in vitro findings reveal that the cellular stress mediated by alpha-synuclein—a pathological hallmark in PD—elicits DNA damage and activates the DNA damage response. The toxic cascade leading to DNA damage involves oxidant stress and mitochondrial dysfunction The data underscore the importance of DNA quality control for preservation of neuronal integrity and protection against neurodegenerative processes.

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Coordinating the action of different enhancers is crucial to correctly specify cell fate decisions during development. Yet it remains poorly understood how the activity of multiple enhancers is choregraphed in time. To shed light on this question we used new live imaging approaches to quantify transcription and protein expression in single cells of Drosophila melanogaster embryos. We employed these tools to dissect the regulation of Fushi tarazu (Ftz), a transcription factor expressed in a series of stripes by two distinct enhancers: autoregulatory and zebra. The anterior edges of the Ftz stripes are sharply defined and specify essential signaling centers. Here, we determined the time at which each boundary cell commits to either a high-Ftz or low-Ftz fate using dynamic features of time-resolved Ftz protein traces. By following the activity of each enhancer individually, we showed that the autoregulatory enhancer does not establish this fate choice. Instead, it perpetuates the decision defined by zebra. This is contrary to the prevailing view that autoregulation drives the fate decision by causing bi-stable Ftz expression. Furthermore, we showed that the autoregulatory enhancer is not activated based on a Ftz concentration threshold, but through a timing-based mechanism. We hypothesize that this is regulated by a set of pioneer-like transcription factors, which have recently been shown to act as timers in the embryo. Our work provides new insight into the genetic mechanisms that directly regulate the dynamics of gene regulatory networks, and supports the emerging view that this regulation is vital for reliable cell fate specification.