High-throughput RNAi screening for germline apoptosis genes in Caenorhabditis elegans

Classes of Drugs that Mitigate Radiation Syndromes

We previously reported several vignettes on types and classes of drugs able to mitigate acute and, in at least one case, late radiation syndromes in mice. Most of these had emerged from high throughput screening (HTS) of bioactive and chemical drug libraries using ionizing radiation-induced lymphocytic apoptosis as a readout. Here we report the full analysis of the HTS screen of libraries with 85,000 small molecule chemicals that identified 220 "hits." Most of these hits could be allocated by maximal common substructure analysis to one of 11 clusters each containing at least three active compounds. Further screening validated 23 compounds as being most active; 15 of these were cherry-picked based on drug availability and tested for their ability to mitigate acute hematopoietic radiation syndrome (H-ARS) in mice. Of these, five bore a 4-nitrophenylsulfonamide motif while 4 had a quinoline scaffold. All but two of the 15 significantly (p < 0.05) mitigated H-ARS in mice. We had previously reported that the lead 4-(nitrophenylsulfonyl)-4-phenylpiperazine compound (NPSP512), was active in mitigating multiple acute and late radiation syndromes in mice of more than one sex and strain. Unfortunately, the formulation of this drug had to be changed for regulatory reasons and we report here on the synthesis and testing of active analogs of NPSP512 (QS1 and 52A1) that have increased solubility in water and in vivo bioavailability while retaining mitigator activity against H-ARS (p < 0.0001) and other radiation syndromes. The lead quinoline 057 was also active in multiple murine models of radiation damage. Taken together, HTS of a total of 150,000 bioactive or chemical substances, combined with maximal common substructure analysis has resulted in the discovery of diverse groups of compounds that can mitigate H-ARS and at least some of which can mitigate multiple radiation syndromes when given starting 24 h after exposure. We discuss what is known about how these agents might work, and the importance of formulation and bioavailability.

Generation and Analysis of CCM Phenotypes in C. elegans

This chapter presents methods for exploiting the powerful tools available in the nematode worm Caenorhabditis elegans to understand the in vivo functions of cerebral cavernous malformation (CCM) genes and the organization of their associated signaling pathways. Included are methods for assessing phenotypes caused by loss-of-function mutations in the worm CCM genes kri-1 and ccm-3, CRISPR-based gene editing techniques, and protocols for conducting high-throughput forward genetic and small molecule screens.

Analysis of apoptosis in Caenorhabditis elegans

The nematode worm Caenorhabditis elegans has provided researchers with a wealth of information on the molecular mechanisms controlling programmed cell death (apoptosis). Its genetic tractability, optical clarity, and relatively short lifespan are key advantages for rapid assessment of apoptosis in vivo. The use of forward and reverse genetics methodology, coupled with in vivo imaging, has provided deep insights into how a multicellular organism orchestrates the self-destruction of specific cells during development and in response to exogenous stresses. Strains of C. elegans carrying mutations in the core elements of the apoptotic pathway, or in tissue-specific regulators of apoptosis, can be used for genetic analyses to reveal conserved mechanisms by which apoptosis is regulated in the somatic and reproductive (germline) tissue. Here we present an introduction to the study of apoptosis in C. elegans, including current techniques for visualization, analysis, and screening.

Fluorescent visualization of germline apoptosis in living Caenorhabditis elegans

Visualization of apoptosis using fluorescent tools is quite straightforward in living Caenorhabditis elegans. Several transgenic lines are available that mark dying cells with fluorescent proteins, making it possible to quantify kinetics at various stages of the apoptotic process. Proteins required for the engulfment of cell corpses are particularly useful for detecting early apoptotic stages using this approach. For example, expression of the engulfment protein CED-1 fused to green fluorescent protein (CED-1::GFP) creates a halo around cells during early apoptosis, before their refractile morphology can be detected by differential interference contrast (DIC) optics. In addition, vital dyes such as acridine orange (AO) and SYTO-12 are selectively retained in apoptotic cells and can be used to visualize apoptosis in the germlines of living animals. It is also possible to use vital dyes in combination with transgenic strains expressing fluorescent markers of cell corpses to examine, in detail, multiple stages of apoptosis in vivo. Because of the high optical contrast of fluorescent reagents, apoptosis can be visualized even at low magnification, facilitating the use of screening platforms to identify apoptosis regulators. This protocol describes multiple uses of fluorescent reagents for visualization of germline apoptosis in living C. elegans, including AO staining, time-course studies using fluorescent proteins, and low-throughput screening of cell death genes using RNA interference (RNAi).