Maintenance of Flap Endonucleases for Long-Patch Base Excision DNA Repair in Mouse Muscle and Neuronal Cells Differentiated In Vitro.

After cellular differentiation, nuclear DNA is no longer replicated, and many of the associated proteins are downregulated accordingly. These include the structure-specific endonucleases Fen1 and DNA2, which are implicated in repairing mitochondrial DNA (mtDNA). Two more such endonucleases, named MGME1 and ExoG, have been discovered in mitochondria. This category of nuclease is required for so-called "long-patch" (multinucleotide) base excision DNA repair (BER), which is necessary to process certain oxidative lesions, prompting the question of how differentiation affects the availability and use of these enzymes in mitochondria. In this study, we demonstrate that Fen1 and DNA2 are indeed strongly downregulated after differentiation of neuronal precursors (Cath.a-differentiated cells) or mouse myotubes, while the expression levels of MGME1 and ExoG showed minimal changes. The total flap excision activity in mitochondrial extracts of these cells was moderately decreased upon differentiation, with MGME1 as the predominant flap endonuclease and ExoG playing a lesser role. Unexpectedly, both differentiated cell types appeared to accumulate less oxidative or alkylation damage in mtDNA than did their proliferating progenitors. Finally, the overall rate of mtDNA repair was not significantly different between proliferating and differentiated cells. Taken together, these results indicate that neuronal cells maintain mtDNA repair upon differentiation, evidently relying on mitochondria-specific enzymes for long-patch BER.

Duchenne muscular dystrophy: disease mechanism and therapeutic strategies.

Duchenne muscular dystrophy (DMD) is a severe, progressive, and ultimately fatal disease of skeletal muscle wasting, respiratory insufficiency, and cardiomyopathy. The identification of the dystrophin gene as central to DMD pathogenesis has led to the understanding of the muscle membrane and the proteins involved in membrane stability as the focal point of the disease. The lessons learned from decades of research in human genetics, biochemistry, and physiology have culminated in establishing the myriad functionalities of dystrophin in striated muscle biology. Here, we review the pathophysiological basis of DMD and discuss recent progress toward the development of therapeutic strategies for DMD that are currently close to or are in human clinical trials. The first section of the review focuses on DMD and the mechanisms contributing to membrane instability, inflammation, and fibrosis. The second section discusses therapeutic strategies currently used to treat DMD. This includes a focus on outlining the strengths and limitations of approaches directed at correcting the genetic defect through dystrophin gene replacement, modification, repair, and/or a range of dystrophin-independent approaches. The final section highlights the different therapeutic strategies for DMD currently in clinical trials.

The primordial germ line is refractory to perturbations of actomyosin regulator function in C. elegans L1 larvae.

Cytokinesis, the separation of daughter cells at the end of mitosis, relies on the coordinated activity of several regulators of actomyosin assembly and contractility (Green et al. 2012). These include the small GTPase RhoA (RHO-1) and its guanine-nucleotide exchange factor Ect2 (ECT-2), the scaffold protein Anillin (ANI-1), the non-muscle myosin II (NMY-2), the formin CYK-1 and the centralspindlin complex components ZEN-4 and CYK-4. These regulators were also shown to be required for maintenance of C. elegans germline syncytial organization by stabilizing intercellular bridges in embryos and adults (Amini et al. 2014; Goupil et al. 2017; Green et al. 2011; Priti et al. 2018; Zhou et al. 2013). We recently demonstrated that many of these regulators are enriched at intercellular bridges in the small rachis (proto-rachis) of L1-stage larvae (Bauer et al. 2021). We sought to assess whether these contractility regulators are functionally required for stability of intercellular bridges and maintenance of the primordial germ line syncytial architecture in L1-stage C. elegans animals. Here we report that temperature-sensitive alleles, RNAi-mediated depletion and latrunculin A treatment are largely ineffective to perturb actomyosin function in the L1-stage primordial germ line.

The initial expansion of the C. elegans syncytial germ line is coupled to incomplete primordial germ cell cytokinesis.

The C. elegans germline is organized as a syncytium in which each germ cell possesses an intercellular bridge that is maintained by a stable actomyosin ring and connected to a common pool of cytoplasm, termed the rachis. How germ cells undergo cytokinesis while maintaining this syncytial architecture is not completely understood. Here, we use live imaging to characterize primordial germ cell (PGC) division in C. elegans first-stage larvae. We show that each PGC possesses a stable intercellular bridge that connects it to a common pool of cytoplasm, which we term the proto-rachis. We further show that the first PGC cytokinesis is incomplete and that the stabilized cytokinetic ring progressively moves towards the proto-rachis and eventually integrates with it. Our results support a model in which the initial expansion of the C. elegans syncytial germline occurs by incomplete cytokinesis, where one daughter germ cell inherits the actomyosin ring that was newly formed by stabilization of the cytokinetic ring, while the other inherits the pre-existing stable actomyosin ring. We propose that such a mechanism of iterative cytokinesis incompletion underpins C. elegans germline expansion and maintenance.

Studying the Fate of Tumor Extracellular Vesicles at High Spatiotemporal Resolution Using the Zebrafish Embryo.

Tumor extracellular vesicles (EVs) mediate the communication between tumor and stromal cells mostly to the benefit of tumor progression. Notably, tumor EVs travel in the bloodstream, reach distant organs, and locally modify the microenvironment. However, visualizing these events in vivo still faces major hurdles. Here, we describe an approach for tracking circulating tumor EVs in a living organism: we combine chemical and genetically encoded probes with the zebrafish embryo as an animal model. We provide a first description of tumor EVs' hemodynamic behavior and document their intravascular arrest. We show that circulating tumor EVs are rapidly taken up by endothelial cells and blood patrolling macrophages and subsequently stored in degradative compartments. Finally, we demonstrate that tumor EVs activate macrophages and promote metastatic outgrowth. Overall, our study proves the usefulness and prospects of zebrafish embryo to track tumor EVs and dissect their role in metastatic niches formation in vivo.

Meaning making, self-determination theory, and the question of wisdom in personality.

Self-determination theory (SDT) has advanced the most comprehensive model of motives for human flourishing in the field of personality psychology and beyond. In this article, we evaluate SDT relative to the process of meaning making, particularly from a narrative perspective, showing what SDT can and cannot explain about the construction of self-identity and its relation to human flourishing. On the one hand, SDT explains how subjective assessments of need fulfillment drive the process of self-determined living. The internal motives that follow such fulfillment serve as important themes in people's life stories that predict several markers of hedonic and eudaimonic well-being. On the other hand, SDT's focus on subjective fulfillment limits what SDT can explain about how wisdom, which is a canonical good of both eudaimonia and meaning making, helps people make sense of life's more difficult or unfulfilling events. SDT may facilitate a facet of wisdom that is more subjective and experiential but not the critical facet of wisdom defined by objectively more complex structures of interpretation.

What growth sounds like: Redemption, self-improvement, and eudaimonic growth across different life narratives in relation to well-being.

OBJECTIVE: We disentangled three growth-relevant concepts (redemption, self-improvement, and eudaimonic growth) in personal narratives of high, low, and turning points and tested their relations to well-being. METHOD: In two studies, participants (Study 1 n = 111, Study 2 n = 206; overall ages 17-83, 56% women, 75% white) wrote narratives of high points, low points, and turning points. Researchers coded each narrative for redemption sequences (i.e., affectively valenced changes in life from bad to good), self-improvement sequences (i.e., affectively valenced changes in oneself for the better), and themes of eudaimonic growth (i.e., values or motives for cultivating meaningful activities or relationships, helping others, or wisdom). Participants also self-reported well-being. RESULTS: Redemption sequences in low points predicted higher well-being but in high points predicted lower well-being. Self-improvement sequences and growth themes each predicted higher well-being in each life event (and interacted in high points). Growth themes consistently mediated predicted relations between both redemption and self-improvement sequences and well-being. Findings held when controlling for global narrative affect, self-reported growth motivation, and big-five traits. CONCLUSIONS: Thematic motives for eudaimonic growth were more closely tied to well-being than were affective evaluations of either changes from bad to good (redemption) or one's becoming better (self-improvement).

Eudaimonic growth: Narrative growth goals predict increases in ego development and subjective well-being 3 years later.

We examine (a) the normative course of eudaimonic well-being in emerging adulthood and (b) whether people's narratives of major life goals might prospectively predict eudaimonic growth 3 years later. We define eudaimonic growth as longitudinal increases in eudaimonic well-being, which we define as the combination of psychosocial maturity and subjective well-being (SWB). College freshmen and seniors took measures of ego development (ED; to assess maturity; Loevinger, 1976) and SWB at Time 1 (T1) and again 3 years later (Time 2). ED levels increased longitudinally across that time for men and T1 freshmen, but SWB levels did not change. Participants also wrote narratives of 2 major life goals at T1 that were coded for an explicit emphasis on specific kinds of personal growth. Participants' intellectual-growth goals (especially agentic ones) predicted increases in ED 3 years later, whereas participants' socioemotional-growth goals (especially communal ones) predicted increases in SWB 3 years later. These findings were independent of the effects of Big Five personality traits-notably conscientiousness, which on its own predicted increases in SWB. We discuss (a) emerging adulthood as the last stop for normative eudaimonic growth in modern society and (b) empirical and theoretical issues surrounding the relations among narrative identity, life planning, dispositional traits, eudaimonia, and 2 paths of personal growth.

Continuity and change in the life story: a longitudinal study of autobiographical memories in emerging adulthood.

If a person's internalized and evolving life story (narrative identity) is to be considered an integral feature of personality itself, then aspects of that story should manifest some continuity over time while also providing evidence regarding important personality change. Accordingly, college freshmen and seniors provided detailed written accounts of 10 key scenes in their life stories, and they repeated the same procedure 3 months and then 3 years later. The accounts were content analyzed for reliable narrative indices employed in previous studies of life stories: emotional tone, motivational themes (agency, communion, personal growth), and narrative complexity. The results showed substantial continuity over time for narrative complexity and positive (vs. negative) emotional tone and moderate but still significant continuity for themes of agency and growth. In addition, emerging adults (1) constructed more emotionally positive stories and showed (2) greater levels of emotional nuance and self-differentiation and (3) greater understanding of their own personal development in the 4th year of the study compared to the 1st year. The study is the first to demonstrate both temporal continuity and developmental change in narrative identity over time in a broad sampling of personally meaningful life-story scenes.

Crystallization of desire and crystallization of discontent in narratives of life-changing decisions.

Two studies of adults examined personal narratives of life-changing decisions in relation to personality and well-being. Participants whose decision narratives emphasized a crystallization of desire (i.e., approaching a desired future) rather than a crystallization of discontent (i.e., escaping an undesired past; Baumeister, 1991, 1994) reported higher well-being, fewer avoidance strivings, lower Neuroticism (in Study 1 only), and better decision outcomes (in Study 2). However, neither strivings, traits, nor outcomes accounted for the relationship between crystallization of desire and well-being. The discussion considers the roles of life-changing decisions and personal narratives in research on personality, well-being, and positive personal development.

Interpreting the good life: growth memories in the lives of mature, happy people.

In 2 studies, the authors examined autobiographical memories for the presence of 2 growth orientations that were expected to correspond differentially to maturity and well-being, which are considered to be key facets of "the good life" by L. A. King (2001). Mature participants emphasized integrative memories (conceptual integration and learning), whereas happy participants emphasized intrinsic memories (humanistic concerns). Both kinds of growth memories correlated more strongly with eudaimonic than with hedonic measures of well-being. Growth memories were largely independent of Big Five traits in relation to maturity and well-being. Finally, older participants were more likely than younger participants to have greater maturity (marginally) and well-being, but this was in part explained by older participants' greater tendency to have growth memories. The discussion considers the role of growth memories in the intentional cultivation of the good life.

Personal growth in adults' stories of life transitions.

Abstract This study identified four themes of personal growth (integrative, intrinsic, agentic, and communal) in adults' stories of life transitions in careers and religions. Specific themes were expected to relate differentially to two forms of personality development (social-cognitive maturity and social-emotional well-being) and to transition satisfaction. Integrative themes correlated primarily with social-cognitive maturity (ego development; Loevinger, 1976), whereas intrinsic themes correlated primarily with social-emotional well-being. Agentic-growth themes correlated primarily with transition satisfaction, whereas communal-growth themes correlated primarily with global well-being. Themes of agentic and communal growth also differentiated the two types of transitions studied-changes in careers and changes in religions-in ways that both supported and contradicted traditional notions of those transitions. We discuss these findings in terms of narrative meaning making, the mature and happy person, and intentional self-development via life transitions.

Growth goals, maturity, and well-being.

In 2 studies (125 college students and 51 adults), 2 forms of growth goals (exploratory and intrinsic) were compared with 2 forms of personality development (social-cognitive maturity and social-emotional well-being). Participants whose narratives of major life goals emphasized conceptual exploration were especially likely to have high levels of maturity (measured as ego development; J. Loevinger, 1976), whereas those whose goals emphasized intrinsic interests (K. M. Sheldon & T. Kasser, 1995) were especially likely to have high levels of well-being. Participants who had coherent hierarchies of growth goals on the levels of major life goals and everyday goals were especially likely to have high levels of personality development. Finally, growth goals accounted for some relationships between age and personality development. Growth goals are discussed in terms of intentional self-development and specific developmental paths.