Monitoring Neuronal Survival via Longitudinal Fluorescence Microscopy

Summary

Here, we present a protocol to monitor survival on a single-cell basis and identify variables that significantly predict cell death.

Abstract

Standard cytotoxicity assays, which require the collection of lysates or fixed cells at multiple time points, have limited sensitivity and capacity to assess factors that influence neuronal fate. These assays require the observation of separate populations of cells at discrete time points. As a result, individual cells cannot be followed prospectively over time, severely limiting the ability to discriminate whether subcellular events, such as puncta formation or protein mislocalization, are pathogenic drivers of disease, homeostatic responses, or merely coincidental phenomena. Single-cell longitudinal microscopy overcomes these limitations, allowing the researcher to determine differences in survival between populations and draw causal relationships with enhanced sensitivity. This video guide will outline a representative workflow for experiments measuring single-cell survival of rat primary cortical neurons expressing a fluorescent protein marker. The viewer will learn how to achieve high-efficiency transfections, collect and process images enabling the prospective tracking of individual cells, and compare the relative survival of neuronal populations using Cox proportional hazards analysis.

Introduction

Abnormal cell death is a driving factor in many diseases, including cancer, neurodegeneration, and stroke¹. Robust and sensitive assays for cell death are essential to the characterization of these disorders, as well as the development of therapeutic strategies for extending or reducing cellular survival. There are currently dozens of techniques for measuring cell death, either directly or through surrogate markers². For example, cell death can be assessed visually with the help of vital dyes that selectively stain dead or living cells³, or by monitoring the appearance of specific phospholipids on....

Protocol

All vertebrate animal work was approved by the Committee on the Use and Care of Animals at the University of Michigan (protocol # PRO00007096). Experiments are carefully planned to minimize the number of animals sacrificed. Pregnant female wild-type (WT), non-transgenic Long Evans rats (Rattus norvegicus) are housed singly in chambers equipped with environmental enrichment, and cared for by the Unit for Laboratory Animal Medicine (ULAM) at the University of Michigan, in accordance with the NIH-supported Guide for the Care and Use of Laboratory Animals. All rats were kept in routine housing for as little time as possible prior to euthanasia, consistent with th....

Results

Using the transfection procedure described here, DIV4 rat cortical neurons were transfected with a plasmid encoding the fluorescent protein mApple. Beginning 24 h post-transfection, cells were imaged by fluorescence microscopy every 24 h for 10 consecutive days. The resultant images were organized as indicated in Figure 2, then stitched, stacked, and scored for cell death (Figure 1). Figure 3 shows a.......

Discussion

Here, methodology to directly monitor neuronal survival on a single-cell basis is presented. In contrast to traditional assays for cell death that are limited to discrete time points and entire populations of cells, this method allows for the continuous assessment of a variety of factors such as cellular morphology, protein expression, or localization, and can determine how each factor influences cellular survival in a prospective manner.

This methodology can be modified to fit a wide array of.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Neurobasal Medium	GIBCO	21103-049
Opti-MEM	GIBCO	31985-070
CompactPrep Plasmid Maxi Kit	Qiagen	12863
Magnesium chloride Hexahydrate	Sigma	M9272
Kynurenic Acid Hydrate	TCI	H0303
Poly D-Lysine	Millipore	A-003-E
Glutamax	GIBCO	35050-061
Lipofectamine 2000	Invitrogen	52887
B27 supplement	Thermo Fisher	A3582801
Penicillin/Streptomycin	GIBCO	15140122
96 well plates	TPP	0876