24 Nov 2004

Surveying the protein profile of a tissue or body fluid by traditional methods—separating proteins by 2D gels and then analyzing the spots by mass spectrometry—has not proven a very efficient way to detect changes in protein levels in neurodegenerative diseases, according to Jonas Bergquist and his colleagues at Uppsala University in Sweden.

In an article published 12 November 2004 in the journal Proteomics, Bergquist and colleagues report that an alternative approach can distinguish protein profiles of the cerebrospinal fluid of patients with amyotrophic lateral sclerosis (ALS) from those of control subjects. The method uses liquid chromatography (LC) and capillary electrophoresis to separate proteins and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to detect protein peaks. The data is then analyzed to detect peptide patterns.

The traditional methods have not yielded any insights into proteome changes of the CSF in ALS, but first author Margareta Ramstrom and colleagues took note of the fact that LC-FT-ICR MS had proven at least as accurate in a number of studies of different animal tissues and fluids. As a first trial run of the method, and their pattern recognition algorithm, the authors showed that they could detect different concentrations (1.4 and 0.14 micromolar) of horse myoglobin added to human CSF to mimic upregulation of a protein.

Ramstrom and colleagues then evaluated chromatograms from 12 ALS patients and 10 control subjects. Perhaps because of the low number of samples, the researchers were unable to identify a particular protein whose CSF levels were altered in the disease relative to control. However, their pattern recognition algorithm was able to correctly classify four of five blinded samples as being from ALS patients, and the fifth was believed to be misclassified because of a known anomaly in the patient's spinal cord.

Regarding this technique, which might be useful both for diagnosis and etiologic research, the authors write that "An advantage of the method is the low sample consumption required for the analysis; a volume corresponding to only 16 microliters of CSF is needed for one LC-experiment. Also, the mass chromatogram is collected during approximately 1 [hour] and the total time for sample preparation prior to MS is another hour, except for the overnight incubation.”—Hakon Heimer