Interpretation of multiple probe sets mapping to the same gene in Affymetrix GeneChips

Area of Science:

• Genomics
• Molecular Biology
• Bioinformatics

Background:

• Affymetrix GeneChip technology allows simultaneous measurement of thousands of genes.
• Accurate probe set annotations are crucial for reliable biological inferences from gene expression data.
• Discrepancies exist where probe sets expected to represent the same gene show dissimilar expression patterns.

Purpose of the Study:

• To investigate the reliability of probe set annotations for gene expression analysis.
• To identify instances where probe sets may detect multiple transcripts or splice variants.
• To assess the impact of annotation discrepancies on differential expression studies.

Main Methods:

• Case study of mouse Surf4 using Affymetrix MOE430A array data.
• Analysis of probe set expression patterns in public-domain microarray experiments.
• Investigation of probe sets assigned to the same LocusID on the RAE230A array.

Main Results:

• Five out of eight probe sets for mouse Surf4 accurately detected Surf4 transcripts; two detected Surf2 variants.
• Expression patterns of Surf4 and Surf2 transcripts were correlated within their respective genes but not between them.
• High variance in differential expression for probe sets with the same LocusID indicated alternative splicing, alternative polyadenylation, or annotation errors.

Conclusions:

• Some probe sets do not uniquely measure a single transcript, as individual probes can map to multiple transcripts depending on biological context.
• Care must be taken when evaluating groups of probe sets intended to measure the same transcript to avoid erroneous conclusions.