A Tale of Three Systems: Toward a Neuroimmunoendocrine Model of Obesity

The prevalence of obesity is on the rise. What was once considered a simple disease of energy imbalance is now recognized as a complex condition perpetuated by neuro- and immunopathologies. In this review, we summarize the current knowledge of the neuroimmunoendocrine mechanisms underlying obesity. We examine the pleiotropic effects of leptin action in addition to its established role in the modulation of appetite, and we discuss the neural circuitry mediating leptin action and how this is altered with obesity, both centrally (leptin resistance) and in adipose tissues (sympathetic neuropathy). Finally, we dissect the numerous causal and consequential roles of adipose tissue macrophages in obesity and highlight recent key studies demonstrating their direct role in organismal energy homeostasis.

Molecular Mechanisms of Sexually Dimorphic Nervous System Patterning in Flies and Worms

Male and female brains display anatomical and functional differences. Such differences are observed in species across the animal kingdom, including humans, but have been particularly well-studied in two classic animal model systems, the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans. Here we summarize recent advances in understanding how the worm and fly brain acquire sexually dimorphic features during development. We highlight the advantages of each system, illustrating how the precise anatomical delineation of sexual dimorphisms in worms has enabled recent analysis into how these dimorphisms become specified during development, and how focusing on sexually dimorphic neurons in the fly has enabled an increasingly detailed understanding of sex-specific behaviors.

Glycocalyx Curving the Membrane: Forces Emerging from the Cell Exterior

Morphological transitions are typically attributed to the actions of proteins and lipids. Largely overlooked in membrane shape regulation is the glycocalyx, a pericellular membrane coat that resides on all cells in the human body. Comprised of complex sugar polymers known as glycans as well as glycosylated lipids and proteins, the glycocalyx is ideally positioned to impart forces on the plasma membrane. Large, unstructured polysaccharides and glycoproteins in the glycocalyx can generate crowding pressures strong enough to induce membrane curvature. Stress may also originate from glycan chains that convey curvature preference on asymmetrically distributed lipids, which are exploited by binding factors and infectious agents to induce morphological changes. Through such forces, the glycocalyx can have profound effects on the biogenesis of functional cell surface structures as well as the secretion of extracellular vesicles. In this review, we discuss recent evidence and examples of these mechanisms in normal health and disease.

From Cell Types to an Integrated Understanding of Brain Evolution: The Case of the Cerebral Cortex

With the discovery of the incredible diversity of neurons, Cajal and coworkers laid the foundation of modern neuroscience. Neuron types are not only structural units of nervous systems but also evolutionary units, because their identities are encoded in the genome. With the advent of high-throughput cellular transcriptomics, neuronal identities can be characterized and compared systematically across species. The comparison of neurons in mammals, reptiles, and birds indicates that the mammalian cerebral cortex is a mosaic of deeply conserved and recently evolved neuron types. Using the cerebral cortex as a case study, this review illustrates how comparing neuron types across species is key to reconciling observations on neural development, neuroanatomy, circuit wiring, and physiology for an integrated understanding of brain evolution. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Calcium Signaling Mechanisms Across Kingdoms

Calcium (Ca2+) is a unique mineral that serves as both a nutrient and a signal in all eukaryotes. To maintain Ca2+ homeostasis for both nutrition and signaling purposes, the toolkit for Ca2+ transport has expanded across kingdoms of eukaryotes to encode specific Ca2+ signals referred to as Ca2+ signatures. In parallel, a large array of Ca2+-binding proteins has evolved as specific sensors to decode Ca2+ signatures. By comparing these coding and decoding mechanisms in fungi, animals, and plants, both unified and divergent themes have emerged, and the underlying complexity will challenge researchers for years to come. Considering the scale and breadth of the subject, instead of a literature survey, in this review we focus on a conceptual framework that aims to introduce to readers to the principles and mechanisms of Ca2+ signaling. We finish with several examples of Ca2+-signaling pathways, including polarized cell growth, immunity and symbiosis, and systemic signaling, to piece together specific coding and decoding mechanisms in plants versus animals. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The Visual Opsin Gene Repertoires of Teleost Fishes: Evolution, Ecology, and Function

Visual opsin genes expressed in the rod and cone photoreceptor cells of the retina are core components of the visual sensory system of vertebrates. Here, we provide an overview of the dynamic evolution of visual opsin genes in the most species-rich group of vertebrates, teleost fishes. The examination of the rich genomic resources now available for this group reveals that fish genomes contain more copies of visual opsin genes than are present in the genomes of amphibians, reptiles, birds, and mammals. The expansion of opsin genes in fishes is due primarily to a combination of ancestral and lineage-specific gene duplications. Following their duplication, the visual opsin genes of fishes repeatedly diversified at the same key spectral-tuning sites, generating arrays of visual pigments sensitive from the ultraviolet to the red spectrum of the light. Species-specific opsin gene repertoires correlate strongly with underwater light habitats, ecology, and color-based sexual selection. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Dynamic Nutrient Signaling Networks in Plants

Nutrients are vital to life through intertwined sensing, signaling, and metabolic processes. Emerging research focuses on how distinct nutrient signaling networks integrate and coordinate gene expression, metabolism, growth, and survival. We review the multifaceted roles of sugars, nitrate, and phosphate as essential plant nutrients in controlling complex molecular and cellular mechanisms of dynamic signaling networks. Key advances in central sugar and energy signaling mechanisms mediated by the evolutionarily conserved master regulators HEXOKINASE1 (HXK1), TARGET OF RAPAMYCIN (TOR), and SNF1-RELATED PROTEIN KINASE1 (SNRK1) are discussed. Significant progress in primary nitrate sensing, calcium signaling, transcriptome analysis, and root–shoot communication to shape plant biomass and architecture are elaborated. Discoveries on intracellular and extracellular phosphate signaling and the intimate connections with nitrate and sugar signaling are examined. This review highlights the dynamic nutrient, energy, growth, and stress signaling networks that orchestrate systemwide transcriptional, translational, and metabolic reprogramming, modulate growth and developmental programs, and respond to environmental cues. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Biophysical and Quantitative Principles of Centrosome Biogenesis and Structure

The centrosome is a main orchestrator of the animal cellular microtubule cytoskeleton. Dissecting its structure and assembly mechanisms has been a goal of cell biologists for over a century. In the last two decades, a good understanding of the molecular constituents of centrosomes has been achieved. Moreover, recent breakthroughs in electron and light microscopy techniques have enabled the inspection of the centrosome and the mapping of its components with unprecedented detail. However, we now need a profound and dynamic understanding of how these constituents interact in space and time. Here, we review the latest findings on the structural and molecular architecture of the centrosome and how its biogenesis is regulated, highlighting how biophysical techniques and principles as well as quantitative modeling are changing our understanding of this enigmatic cellular organelle. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Nonmuscle Myosin II Regulation Directs Its Multiple Roles in Cell Migration and Division

Nonmuscle myosin II (NMII) is a multimeric protein complex that generates most mechanical force in eukaryotic cells. NMII function is controlled at three main levels. The first level includes events that trigger conformational changes that extend the complex to enable its assembly into filaments. The second level controls the ATPase activity of the complex and its binding to microfilaments in extended NMII filaments. The third level includes events that modulate the stability and contractility of the filaments. They all work in concert to finely control force generation inside cells. NMII is a common endpoint of mechanochemical signaling pathways that control cellular responses to physical and chemical extracellular cues. Specific phosphorylations modulate NMII activation in a context-dependent manner. A few kinases control these phosphorylations in a spatially, temporally, and lineage-restricted fashion, enabling functional adaptability to the cellular microenvironment. Here, we review mechanisms that control NMII activity in the context of cell migration and division. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.