Cell Death During Development of the Nervous System

The Insects has been the standard textbook in the field since the first edition published over forty years ago. Building on the strengths of Chapman's original text, this long-awaited 5th edition has been revised and expanded by a team of eminent insect physiologists, bringing it fully up-to-date for the molecular era. The chapters retain the successful structure of the earlier editions, focusing on particular functional systems rather than taxonomic groups and making it easy for students to delve into topics without extensive knowledge of taxonomy. The focus is on form and function, bringing together basic anatomy and physiology and examining how these relate to behaviour. This, combined with nearly 600 clear illustrations, provides a comprehensive understanding of how insects work. Now also featuring a richly illustrated prologue by George McGavin, this is an essential text for students, researchers and applied entomologists alike.

The insects: structure and function.

Apoptosis is a morphologically distinct form of programmed cell death that plays a major role during development, homeostasis, and in many diseases including cancer, acquired immunodeficiency syndrome, and neurodegenerative disorders. Apoptosis occurs through the activation of a cell-intrinsic suicide program. The basic machinery to carry out apoptosis appears to be present in essentially all mammalian cells at all times, but the activation of the suicide program is regulated by many different signals that originate from both the intracellular and the extracellular milieu. Genetic studies in the nematode Caenorhabditis elegans and in the fruit fly Drosophila melanogaster have led to the isolation of genes that are specifically required for the induction of programmed cell death. At least some components of the apoptotic program have been conserved among worms, insects, and vertebrates.

https://science.sciencemag.org/content/sci/267/5203/1445.full.pdf

Mechanisms and genes of cellular suicide

Activation of T cells by antigen-presenting cells (APCs) depends on the complex integration of signals that are delivered by multiple antigen receptors. Most receptor-proximal activation events in T cells were identified using multivalent anti-receptor antibodies, eliminating the need to use the more complex APCs. As the physiological membrane-associated ligands on the APC and the activating antibodies probably trigger the same biochemical pathways, it is unknown why the antibodies, even at saturating concentrations, fail to trigger some of the physiological T-cell responses. Here we study, at the level of the single cell, the responses of T cells to native ligands. We used a digital imaging system and analysed the three-dimensional distribution of receptors and intracellular proteins that cluster at the contacts between T cells and APCs during antigen-specific interactions. Surprisingly, instead of showing uniform oligomerization, these proteins clustered into segregated three-dimensional domains within the cell contacts. The antigen-specific formation of these new, spatially segregated supramolecular activation clusters may generate appropriate physiological responses and may explain the high sensitivity of the T cells to antigen.

Three-dimensional segregation of supramolecular activation clusters in T cells

CONTENTS INTRODUCTION . . . . . . . . ... . . ... . . . . . . . . . . . . . . . ... . . . . . . . . . . . ...... . ... ... . . . . . . . . . . . . . . . ... ....... ... . . . . . . . . . . . ... . . ... . . . . . 664 CELL DEATH IN CAENORHABDITIS ELEGANS .... .. ..... . . . . 664 Programmed Cell Death . ... . . . . . . . . ... . . . . . ... . . . . . . . . . . . . . . . .. . . . . . . 665 Pathological Cell Deaths ....... . ........ ... . . . . . . . . . . . . . . .. . . . . . . . .. . . . . . . . . . . . . . . . . . . ........ 669 Summary . ... . . . . . . . . . .. .. '" . . .. . . . ... .... . . . . . .... . . ..... . . . ....... . . . . . . . . . . .. . . . . . . . . . . . . ...... 670 CELL DEATH IN OTHER ANIMALS .. . .. . . . . . . . . . . . . . . . . . . . . . . .. .. .. . ... . . . ... . . . ... . . ... . . . . . . . .. ... . . . . ... . . . ... ...... 670 Cell Death During the Metamorphosis of Moths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . 671 Deaths of Vertebrate Neurons Deprived of Growth Factors . . . ...... .... . . . . . ...... ... . 673 Cell Death ol'lhymocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . ... . . . . . . . . . . . . ..... . ... . . . . . . . . . . . . . . . . . . .. . ... . . . . . ... 675 Cell Death in the Regressing Rat Prostate ........ . 678 FUNCTIONS OF CELL DEATH 679 Cells That Appear to Have No Function .. ..... . . .... . . . . .... . ...... 680 Cells That Are Generated in Excess ......... ......... . . . . . . . . . . . 683 Cells That Develop Improperly . .. . . . .. . . . . . . . . . . . . . . . . . . . . ....... . . . . . . . . . . . . . . . . .. .. . . ....... ... .. . ... . . ...... 684 Cells That Have Completed Their Functions . . . . . . . . . .... . . ... . . . . . . . . . . . ... . . . . . . ... ... .. . . .. ... .. . . ... . 684 Cells That Are Harmful 685 MECHANISMS OF CELL DEATH 685 Cell Death Is an Active Process . . . .. . . ... . . . . . . . . ... . ...... . . .. 685 Control of the Cell Death Process ....... . 686 Mechanisms That Kill Cells . . . ... . . ... . ... . . . . . . . . . ... . . ... . ... . . . . . . .. . . . .. .. .... . . . . . . . .. 687 Engulfment of Dead Cells . . . ....... . . . . . . . 689 Degradation of Dead Cells. . . . . . . ... ... . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 690 Future Prospects 690

Mechanisms and Functions of Cell Death

Spatial and temporal patterns of neurogenesis in the central nervous system of Drosophila melanogaster

Publisher Summary This chapter discusses the ecdysone receptors and their biological actions. It also summarizes the insect endocrinology and the roles of these steroids in the molting and metamorphosis. Natural hormones that lead to molting and metamorphosis are ecdysones. Molecules whose structures resemble those of the natural hormones are called ecdysteroids. The receptor for ecdysone is a member of the nuclear receptor superfamily that acts as a ligand-dependent transcription factor. The vertebrate steroid hormone receptors act as homodimers whereas the functional ecdysone receptor is always a heterodimer of receptor for ecdysone (EcR) with another member of the nuclear receptor (NR) superfamily, Ultraspiracle, the insect homolog of the vertebrate retinoid X receptor (RXR). Two new technologies promise to transform the environment for investigations of insect hormones, ecdysone receptor, and metamorphosis. The microarrays of expressed sequence tags are constructed (ESTs) and used hybridization to catalog changes in gene expression during metamorphosis. The first technological achievement is reviewed: the complete sequence of the Drosophila genome is obtained and is about to be released. It will be the first complete insect sequence and also the first genomic sequence from an organism that has served as a model for nuclear receptor endocrinology.

Ecdysone receptors and their biological actions.

The Role of the Prothoracic Gland in Determining Critical Weight for Metamorphosis in Drosophila melanogaster

The ability to specify the expression levels of exogenous genes inserted in the genomes of transgenic animals is critical for the success of a wide variety of experimental manipulations. Protein production can be regulated at the level of transcription, mRNA transport, mRNA half-life, or translation efficiency. In this report, we show that several well-characterized sequence elements derived from plant and insect viruses are able to function in Drosophila to increase the apparent translational efficiency of mRNAs by as much as 20-fold. These increases render expression levels sufficient for genetic constructs previously requiring multiple copies to be effective in single copy, including constructs expressing the temperature-sensitive inactivator of neuronal function Shibirets1, and for the use of cytoplasmic GFP to image the fine processes of neurons.

https://www.pnas.org/content/pnas/109/17/6626.full.pdf

Using translational enhancers to increase transgene expression in Drosophila

Pruning is important for sculpting neural circuits, as it removes excessive or inaccurate projections. Here we show that the removal of sensory neuron dendrites during pruning in Drosophila melanogaster is directed by local caspase activity. Suppressing caspase activity prevented dendrite removal, whereas a global activation of caspases within a neuron caused cell death. A new genetically encoded caspase probe revealed that caspase activity is confined to the degenerating dendrites of pruning neurons.

http://cnc.cj.uc.pt/BEB/private/pdfs/DeathSuvSig0607/Williams2006.pdf

James W. Truman

Papers

Spatial and temporal patterns of neurogenesis in the central nervous system of Drosophila melanogaster

Ecdysone receptors and their biological actions.

The Role of the Prothoracic Gland in Determining Critical Weight for Metamorphosis in Drosophila melanogaster

Using translational enhancers to increase transgene expression in Drosophila

Local caspase activity directs engulfment of dendrites during pruning