normalize450K

normalize450K normalizes Illumina Infinium HumanMethylation450 BeadChip (450K) data to correct dye- and signal intensity–related biases and produce accurate beta-values for DNA methylation profiling across approximately 485,000 CpG sites.

Key Features:

• Local regression normalization: Applies a local regression–based normalization to correct biases related to dye intensity and probe methylation levels.
• Dye-bias correction: Corrects fluorescence dye bias that can affect methylation measurements on microarrays.
• Signal intensity and probe-specific adjustment: Adjusts for biases associated with signal intensity and probe-specific methylation levels to improve beta-value precision.
• No probe-type bias adjustment: Deliberately does not adjust for probe type bias to avoid compromising the accuracy of beta-values despite potential precision trade-offs.

Scientific Applications:

• Epigenetic DNA methylation profiling: Supports analysis of DNA methylation measured by the 450K BeadChip for epigenetic studies.
• Reproducibility assessment: Improves correlation between technical replicates, demonstrated using 21 pairs of replicates.
• Differential methylation detection: Assists detection of differential methylation across samples for epigenetic association studies.
• Correlation with phenotype: Enhances correlation between methylation at smoking-associated CpG sites and smoking behavior in a cohort of 655 participants.

Methodology:

The method applies local regression normalization and corrections for dye bias and signal intensity while explicitly not adjusting for probe type bias.