An Electrochemiluminescence-Based Assay for MeCP2 Protein Variants

Summary

The electrochemiluminescence immunoassay (ECLIA) is a novel approach for quantitative detection of endogenous and exogenously applied MeCP2 protein variants, which produces highly quantitative, accurate and reproducible measurements with low intra- and inter-assay error over a wide working range. Here, the protocol for the MeCP2-ECLIA in a 96-well format is described.

Abstract

The ECLIA is a versatile method which is able to quantify endogenous and recombinant protein amounts in a 96-well format. To demonstrate ECLIA efficiency, this assay was used to analyze intrinsic levels of MeCP2 in mouse brain tissue and the uptake of TAT-MeCP2 in human dermal fibroblasts. The MeCP2-ECLIA produces highly accurate and reproducible measurements with low intra- and inter-assay error. In summary, we developed a quantitative method for the evaluation of MeCP2 protein variants that can be utilized in high-throughput screens.

Introduction

The electrochemiluminescence immunoassay (ECLIA) is based on a process that utilizes labels designed to emit luminescence when electrochemically stimulated. It is a broadly applicable technique for the quantitative detection of biological analytes in basic industry and academic research, food industry as well as in clinical diagnostics¹. Commonly, a disposable 96-well plate with carbon ink electrodes is used. These electrodes act as a solid-phase carrier for the immunoassay. A secondary antibody is conjugated to an electrochemiluminescent label and when electricity is applied to the system, light emission of the chemical label is triggered. An ....

Protocol

Approval for skin biopsy procurement for research purposes was obtained from the Human Research Ethics Committee of the Children’s Hospital at Westmead, Australia. Consent for animal experiments was obtained from the Austrian Federal Ministry of Science, Research and Economy, which were performed in accordance with local animal welfare regulations (GZ: 66.009/0218-II/3b/2015).

NOTE: The principle of the ECLIA system is depicted in Figure 1.

1. Antibody selection

1. Evaluate the signal-to-noise ratio for a range of various MeCP2 antibodies and identify the best signal s....

Results

The principle of the ECLIA system is described in Figure 1. Standard curves for two MeCP2 variants are shown in Figure 2. Accurate quantification was possible over a wide range of concentrations (1−1,800 ng/mL). In Figure 3, MeCP2 levels of lysates derived from mouse brain and HDFs were analyzed. MeCP2 expression in brain nuclear lysates from heterozygous, wildtype and knockout mice were compared in Figure.......

Discussion

To measure endogenous MeCP2, recombinant MeCP2 and TAT-MeCP2 levels, a 96-well plate ECLIA was developed. It has been shown that loss of MeCP2 protein function leads to RTT syndrome⁶, for which treatment is currently limited to symptom management and physical therapy. One promising treatment avenue is the so-called protein replacement therapy, where MeCP2 levels can be titrated up to their needed concentration^12,13,

Materials

Name	Company	Catalog Number	Comments
1,4-Dithiothreitol (DTT)	Sigma-Aldrich	D9779	Hypotonic lysis reagent, Extraction Buffer
Bio-Rad Protein Assay Dye Reagent Concentrate	Bio-Rad Laboratories Inc.	500-0006	Sample preperation
Detection AB SULFO-TAG labeled anti-rabbit	Meso Scale Diagnostics	R32AB-1	Antibody
Discovery workbench 4.0	Meso Scale Discovery		Software
DMEM (1X)	gibco by Life Technologies	41966-029	Sample preperation
Dulbecco’s PBS (sterile)	Sigma-Aldrich	D8537-500ML	Sample preperation, Washing solution, Coating solution
EDTA	Sigma-Aldrich	EDS	Extraction Buffer
Fetal Bovine Serum	Sigma-Aldrich	F9665	Sample preperation
Glycerol	Sigma-Aldrich	G2025	Extraction Buffer
Gold Read Buffer T (1x) with surfactant	Meso Scale Diagnostics	R92TG	MeCP2 ECLIA protocol
HEPES	Sigma-Aldrich	H3375	Hypotonic lysis reagent, Extraction Buffer
KIMBLE Dounce tissue grinder set	Sigma-Aldrich	D8938	Sample preperation
Laboratory Shaker, rocking motion (low speed)	GFL	3014	MeCP2 ECLIA protocol
Magnesium chloride hexahydrate (MgCl*6H20)	Sigma-Aldrich	M2670	Hypotonic lysis reagent, Extraction Buffer
MeCP2 (Human) Recombinant Protein (P01)	Abnova Corporation	H00004204-P01	Cell treatment
Microseal B seal	Bio-Rad Laboratories Inc.	MSB1001	for plate sealing
Monoclonal Anti-MeCP2, produced in mouse, clone Mec-168, purified immunoglobulin	Sigma-Aldrich	M6818-100UL; RRID:AB_262075	Antibody, Coating solution
MSD Blocker A	Meso Scale Diagnostics	R93BA-4	Blocker
MSD SECTOR Imager 2400	Meso Scale Diagnostics	I30AA-0	MeCP2 ECLIA protocol
Multi-Array 96-well Plate	Meso Scale Diagnostics	L15XB-3/L11BX-3	MeCP2 ECLIA protocol
Penicillin-Streptomycin	gibco by Life Technologies	15140122	Sample preperation
Polyclonal Anti-MeCP2, produced in rabbit	Eurogentec S.A.	custom-designed	Antibody
Potassium chloride (KCl)	Merck KGaA	1049361000	Hypotonic lysis reagent
Primary AB Mouse, anti-MeCP2 (1B11)	Sigma-Aldrich	SAB1404063; RRID:AB_10737296	Antibody
Primary AB Mouse, anti-MeCP2 (4B6)	Sigma-Aldrich	WH0004204M1; RRID:AB_1842411	Antibody
Primary AB Mouse, anti-MeCP2 (Mec-168)	Sigma-Aldrich	M6818; RRID:AB_262075	Antibody
Primary AB Mouse, anti-MeCP2 (Men-8)	Sigma-Aldrich	M7443; RRID:AB_477235	Antibody
Primary AB Rabbit, anti-MeCP2 (D4F3)	Cell Signaling Technology	3456S; RRID:AB_2143849	Antibody
Protease Inhibitor Cocktail (100X)	Sigma-Aldrich	8340	Hypotonic lysis reagent, Extraction Buffer
Secondary AB, Rabbit, anti-MeCP2	Eurogentec S.A.	custom	Antibody
Secondary AB, Rabbit, anti-MeCP2	Merck	07-013	Antibody
Sodium chloride (NaCl)	Sigma-Aldrich	S3014	Extraction Buffer
SULFO-TAG Labeled Anti-Rabbit Antibody (goat)	Meso Scale Diagnostics	W0015528S	Antibody
TAT-MeCP2 fusion protein	in-house production		Cell treatment
Trypsin EDTA 0.25% (1X)	gibco by Life Technologies	25200-056	Cell treatment
Tween 20	Sigma-Aldrich	P9416	Washing solution