Profound influence of microarray scanner characteristics on gene expression ratios: analysis and procedure for...

Area of Science:

• Genomics
• Bioinformatics
• Biotechnology

Background:

• Gene expression data is collected using spotted cDNA microarrays and fluorescence scanners.
• Scanner settings like laser power and photomultiplier tube (PMT) voltage influence spot intensities.
• Accurate gene expression ratios must be independent of these scanner settings.

Purpose of the Study:

• Investigate the relationship between PMT voltage, spot intensities, and expression ratios.
• Define an optimal scanning procedure for microarray data acquisition.
• Develop methods to improve the accuracy and reliability of gene expression data.

Main Methods:

• Analyzed spot intensities and expression ratios across different scanners at varying PMT voltages.
• Identified a limited usable intensity range (200-50,000 mean spot intensity) where ratios are independent of PMT voltage.
• Developed an algorithm to correct for saturated pixel intensities within spots.

Main Results:

• Expression ratios were only independent of PMT voltage within a specific, limited intensity range.
• High and low intensities outside this range led to significant errors in expression ratios.
• The developed algorithm successfully corrected saturated spot intensities, extending the usable data range.

Conclusions:

• Recommended increasing PMT voltage to capture weaker spots, allowing brighter spots to saturate.
• Proposed acquiring a second image set with lower PMT settings to correct saturated spots using the algorithm.
• This dual-scan approach enhances data accuracy and increases the number of reliable data points per experiment.