Reference Gene Sequences for Expression Normalization
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Solution Overview
Problem
Current methods for comparing gene expression levels across different cells and samples face challenges due to differential expression of 'housekeeping genes' and the need for consistent reference genes that remain unchanged under varying conditions.
Innovation Solution
Identification and utilization of eight specific gene sequences that are consistently expressed across various tumor types and their corresponding normal tissues, serving as normalization references for comparing gene expression levels, allowing for accurate classification and comparison of tumor samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional housekeeping genes (e.g., actin, glyceraldehyde-3-phosphate dehydrogenase) are used for normalization, then gene expression levels can be compared across samples, but the expression levels of these genes vary under different conditions and tissue types, reducing measurement accuracy
Solution Approach 1:
The patent extracts and identifies specific gene sequences (e.g., TBP, B2M, GAPDH variants) that exhibit stable expression patterns across different tissue types and experimental conditions. These sequences are selected and validated as reference genes, separating them from traditional housekeeping genes that show variable expression. The extraction process involves screening multiple candidate genes and selecting those with minimal expression variation.
Solution Approach 2:
The patent changes the selection criteria for reference genes from traditional housekeeping genes to genes with demonstrated stable expression across diverse conditions. This parameter change involves evaluating genes based on expression consistency metrics rather than assuming all housekeeping genes are equally stable. The selected reference genes show minimal expression variation across different tissue types, treatments, and experimental conditions.
2Ease of operation
If gene expression levels are compared without normalization, then the comparison process is simpler, but the results cannot be reliably compared across different cells, samples, or experiments
Solution Approach 1:
The patent introduces stable reference gene sequences as intermediary elements that mediate the comparison between different gene expression measurements. These reference genes serve as a common baseline across all samples, allowing indirect comparison through ratio calculations. The intermediary reference genes bridge the gap between samples processed under different conditions, enabling reliable cross-sample and cross-experiment comparisons.
3Measurement precision
If multiple reference genes are used for normalization, then the accuracy of gene expression determination improves, but the complexity of the assay increases
Solution Approach 1:
The patent segments the normalization process by identifying and validating multiple independent reference gene sequences with different expression patterns. This segmentation allows the use of multiple reference genes to compensate for condition-specific variations that any single gene might exhibit. The segmented approach divides the normalization task across several stable genes rather than relying on a single reference gene.
Solution Approach 2:
The patent merges the expression data from multiple stable reference genes to create a composite normalization factor. This combining approach integrates information from several reference genes, providing a more robust normalization baseline that accounts for variations across different conditions. The merged reference gene expression profile offers improved stability and reliability compared to using individual reference genes alone.
Data Source
AI summary
This invention provides gene sequence identities and methods for the determination of cellular gene expression and the comparison of expression levels between different gene sequences and between different cells. The gene sequences may be used as reference, normalization, or "housekeeping" gene sequences, the expression of which remains consistent in individual cells, even under different conditions, as well as among cells from different samples and origins.