Notch ankyrin domain: evolutionary rise of a thermodynamic sensor

Thyroid Hormones and Brain Development: A Focus on the Role of Mitochondria as Regulators of Developmental Time

Thyroid hormones (THs) regulate metabolism in a homeostatic state in an adult organism. During the prenatal period, prior to the establishment of homeostatic mechanisms, THs assume additional functions as key regulators of brain development. Here, we focus on reviewing the role of THs in orchestrating cellular dynamics in a developing brain. The evidence from the reviewed scientific literature suggests that the developmental roles of the hormones are predominantly mediated by non-genomic mitochondrial effects of THs due to attenuation of genomic effects of THs that antagonise non-genomic impacts. We argue that the key function of TH signalling during brain development is to orchestrate the tempo of self-organisation of neural progenitor cells. Further, evidence is provided that major neurodevelopmental consequences of hypothyroidism stem from an altered tempo of cellular self-organisation.

Neural differentiation in perspective: mitochondria as early programmers

Neural differentiation during development of the nervous system has been extensively studied for decades. These efforts have culminated in the generation of a detailed map of developmental events that appear to be associated with emergence of committed cells in the nervous system. In this review the landscape of neural differentiation is revisited by focusing on abiotic signals that play a role in induction of neural differentiation. Evidence is presented regarding a chimeric landscape whereby abiotic signals generated by mitochondria orchestrate early events during neural differentiation. This early stage, characterised by mitochondrial hyperactivity, in turn triggers a late stage of differentiation by reprogramming the activity of biotic signals.

Regulation of immune cell development, differentiation and function by stromal Notch ligands

In multicellular organisms, cell-to-cell communication is critical for the regulation of tissue organization. Notch signaling relies on direct interactions between Notch receptors on signal-receiving cells and Notch ligands on adjacent cells. Notch evolved to mediate local cellular interactions that are responsive to spatial cues via dosage-sensitive short-lived signals. Immune cells utilize these unique properties of Notch signaling to direct their development, differentiation, and function. In this review, we explore how immune cells interact through Notch receptors with stromal cells in specialized niches of lymphohematopoietic organs that express Notch-activating ligands. We emphasize factors that control these interactions and focus on how Notch signals communicate spatial, quantitative, and temporal information to program the function of signal-receiving cells in the immune system.

Redox-Mediated Rewiring of Signalling Pathways: The Role of a Cellular Clock in Brain Health and Disease

Metazoan signalling pathways can be rewired to dampen or amplify the rate of events, such as those that occur in development and aging. Given that a linear network topology restricts the capacity to rewire signalling pathways, such scalability of the pace of biological events suggests the existence of programmable non-linear elements in the underlying signalling pathways. Here, we review the network topology of key signalling pathways with a focus on redox-sensitive proteins, including PTEN and Ras GTPase, that reshape the connectivity profile of signalling pathways in response to an altered redox state. While this network-level impact of redox is achieved by the modulation of individual redox-sensitive proteins, it is the population by these proteins of critical nodes in a network topology of signal transduction pathways that amplifies the impact of redox-mediated reprogramming. We propose that redox-mediated rewiring is essential to regulate the rate of transmission of biological signals, giving rise to a programmable cellular clock that orchestrates the pace of biological phenomena such as development and aging. We further review the evidence that an aberrant redox-mediated modulation of output of the cellular clock contributes to the emergence of pathological conditions affecting the human brain.

Succinate Dehydrogenase, Succinate, and Superoxides: A Genetic, Epigenetic, Metabolic, Environmental Explosive Crossroad

Research focused on succinate dehydrogenase (SDH) and its substrate, succinate, culminated in the 1950s accompanying the rapid development of research dedicated to bioenergetics and intermediary metabolism. This allowed researchers to uncover the implication of SDH in both the mitochondrial respiratory chain and the Krebs cycle. Nowadays, this theme is experiencing a real revival following the discovery of the role of SDH and succinate in a subset of tumors and cancers in humans. The aim of this review is to enlighten the many questions yet unanswered, ranging from fundamental to clinically oriented aspects, up to the danger of the current use of SDH as a target for a subclass of pesticides.