Two-color fluorescent in situ hybridization in the embryonic zebrafish brain using differential detection systems

Abstract

BackgroundWhole-mount in situ hybridization (WISH) is extensively used to characterize gene expression patterns in developing and adult brain and other tissues. To obtain an idea whether a novel gene might be involved in specification of a distinct brain subdivision, nucleus or neuronal lineage, it is often useful to correlate its expression with that of a known regional or neuronal marker gene. Two-color fluorescent in situ hybridization (FISH) can be used to compare different transcript distributions at cellular resolution. Conventional two-color FISH protocols require two separate rounds of horseradish peroxidase (POD)-based transcript detection, which involves tyramide signal amplification (TSA) and inactivation of the first applied antibody-enzyme conjugate before the second detection round.ResultsWe show here that the alkaline phosphatase (AP) substrates Fast Red and Fast Blue can be used for chromogenic as well as fluorescent visualization of transcripts. To achieve high signal intensities we optimized embryo permeabilization properties by hydrogen peroxide treatment and hybridization conditions by application of the viscosity-increasing polymer dextran sulfate. The obtained signal enhancement allowed us to develop a sensitive two-color FISH protocol by combining AP and POD reporter systems. We show that the combination of AP-Fast Blue and POD-TSA-carboxyfluorescein (FAM) detection provides a powerful tool for simultaneous fluorescent visualization of two different transcripts in the zebrafish brain. The application of different detection systems allowed for a one-step antibody detection procedure for visualization of transcripts, which significantly reduced working steps and hands-on time shortening the protocol by one day. Inactivation of the first applied reporter enzyme became unnecessary, so that false-positive detection of co-localization by insufficient inactivation, a problem of conventional two-color FISH, could be eliminated.ConclusionSince POD activity is rather quickly quenched by substrate excess, less abundant transcripts can often not be efficiently visualized even when applying TSA. The use of AP-Fast Blue fluorescent detection may provide a helpful alternative for fluorescent transcript visualization, as the AP reaction can proceed for extended times with a high signal-to-noise ratio. Our protocol thus provides a novel alternative for comparison of two different gene expression patterns in the embryonic zebrafish brain at a cellular level. The principles of our method were developed for use in zebrafish but may be easily included in whole-mount FISH protocols of other model organisms.

Genome-wide analysis of the bHLH gene family in planarians identifies factors required for adult neurogenesis and neuronal regeneration

“…For γ-irradiation treatments, animals were exposed to 100 Gy in a JL Shepherd Mark I Cesium-137 irradiator and fixed 6 days after treatment. To visualize bHLH transcripts by multiple fluorescent in situ hybridization (FISH), we used horseradish peroxidase substrates as described previously (Pearson et al, 2009) or the alkaline phosphatase (AP) substrate Fast Blue (Lauter et al, 2011;Currie and Pearson, 2013). For Fast Blue staining, animals were developed in 0.25 mg/ml Fast Blue BB (Sigma F3378) and NAMP (Sigma 855) in AP staining buffer (0.1 M Tris-HCl pH 8.2, containing 50 mM MgCl 2 , 100 mM NaCl, 0.1% Tween 20) (Hauptmann, 2001;Lauter et al, 2011).…”

Planarian yorkie/YAP functions to integrate adult stem cell proliferation, organ homeostasis and maintenance of axial patterning

“…Immunolabeling, TUNEL and in situ hybridizations (ISH) Whole-mount ISH (WISH), double fluorescent ISH (dFISH) and immunostainings were performed as previously described (Lauter et al, 2011;Pearson et al, 2009). Colorimetric WISH stains were imaged on a Leica M165 fluorescence dissecting microscope.…”

Multi-target Chromogenic Whole-mount <em>In Situ</em> Hybridization for Comparing Gene Expression Domains in <em>Drosophila</em> Embryos

“…Another possibility is to take advantage of the fluorescent properties of azo dyes. Fast Red can be visualized using rhodamine filter sets 27 , while Fast Blue can be observed with far-red filters 28,29 . Comparison or overlay of chromogenic and fluorescent images can reveal the site of co-distribution.Using this approach, BCIP/NBT signal development has to be stopped in time, so that it does not become too dense and quench the fluorescent signal of the azo dye reaction product.…”