Successful drug discovery from a phenotypic screening is not necessarily impeded by a lack of molecular insight. Phenotypic screening is usually more physiologically relevant and embraces the ability to study pleiotropic effects. This can be, as clinical practice demonstrates, applied to the discovery of new drugs especially against illnesses where our understanding of the underlying mechanisms is low, such as in the case of common psychosomatic conditions or neurological diseases.
Modern phenotypic assays should capture key aspects of the physiological process such as relevant cell types, cell-cell interactions, growth factors, signal transduction pathways, and molecular targets while utilizing in vitro systems amenable to rigorous statistical validation and high throughput operations. An appropriate cellular screening model is chosen according to the type of screening library and the phenotype of interest. Screening libraries can be divided into three classes: small molecule compound libraries, knockdown or deletion libraries, or overexpression libraries. Knockdown or deletion libraries contain either siRNA, shRNA, or gRNA for CRISPR screens. For CRISPR screens, the chosen cell type requires the expression of Cas9 endonuclease. Cells can also express a disease gene that causes the phenotype of interest (e.g., overexpression of tau, α-synuclein, or Htt fragments) and/or a reporter gene (e.g., GFP-labelled LC3 to visualize autophagic flux, a minigene to assess splicing, a luciferase-labeled transgene to visualize up-or downregulation of protein levels).
Fig.1 Schematic of phenotypic screening approaches. (Brown, 2020)
Phenotypic screens in neurodegeneration are being facilitated by advances in screening models all the way from primitive organisms such as yeast to complex 3D cell models. The outcome of a screen is critically dependent on the design of the assay, the nature of the screening collection, the concentrations of the test molecules, and an appropriate triage effort to confirm the hits. Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and frontotemporal dementia (FTD) are debilitating disorders, and there are currently no disease-modifying therapies available to patients. Many of these diseases share common mechanisms and phenotypes (e.g., aberrant protein aggregation, impaired autophagic flux, excitotoxicity, mitochondrial dysfunction). Phenotypic screens are being used to interrogate these and other disease mechanisms in a variety of model systems. Recent examples in ALS, Huntington's disease, Parkinson's disease, and Alzheimer's disease illustrate that a diverse range of techniques can be used to identify hits and lead chemical series that mitigate neurodegeneration-associated phenotypes.
Fig.2 Overview of cell models used in phenotypic screening for neurodegeneration. (Brown, 2020)
With years of experience focusing on neuroscience, Creative Biolabs has gradually optimized our technology platform with advanced facilities and professional specialists. We are now capable of providing a variety of basic neuroscience assay services, including high-throughput phenotypic screen services. The strong foundations, professional expertise, and Ph.D. level scientists consist of the powerful guarantee of the quality of our services. If you are looking for high-throughput phenotypic screen services or you have any other requirements, please don't hesitate to contact us for more information.
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