Biomedical genomics resource · BEGINNER LESSON
GTEx
GTEx, short for Genotype-Tissue Expression, is a research project and data resource that studies how DNA differences are linked to gene expression across human tissues. It also provides tissue samples and molecular data for scientists to analyze these links.
What GTEx is and what it measures
GTEx is a large research project that built a database and tissue bank for studying how genetic variation, meaning differences in DNA sequence, relates to gene expression, meaning how much a gene’s RNA product is made in a tissue. It also supports other molecular phenotypes, which are measurable molecular traits such as RNA levels or protein-related features. The project uses many post-mortem human donors so that many tissues can be collected from the same person and compared across the body.
[1] The Genotype-Tissue Expression (GTEx) project - PMC - NIH [2] Principles of gene regulation across tissues - Nature Reviews Genetics [3] The Enhancing Gtex Project
How the project works
Researchers genotype each donor, meaning they measure the donor’s DNA variants, and then profile gene expression in many tissues, mainly by sequencing RNA. The DNA results are compared with expression levels to find expression quantitative trait loci, or eQTLs. An eQTL is a DNA variant associated with changed gene expression. GTEx was designed to make these data available to the scientific community through a database and data portal.
[1] The Genotype-Tissue Expression (GTEx) project - PMC - NIH [2] Principles of gene regulation across tissues - Nature Reviews Genetics
What the main patterns mean
GTEx separates two broad kinds of eQTLs. Cis-eQTLs affect nearby genes, usually within 1 megabase (1 Mb, about one million DNA letters) of the gene’s start site. Trans-eQTLs affect genes at long distance, sometimes on different chromosomes. The sources report that cis-eQTLs were found for many genes across many tissues, while trans-eQTLs were harder to detect and may often work indirectly through local control of another gene, such as a transcription factor, which then influences other genes.
[1] The Genotype-Tissue Expression (GTEx) project - PMC - NIH [2] Principles of gene regulation across tissues - Nature Reviews Genetics
Why it matters and where it falls short
GTEx helps connect non-coding DNA variants, which do not change protein sequence, to possible target genes and tissues. This matters because many variants linked to complex traits and diseases lie outside protein-coding regions. A limitation is that some tissues are hard to collect from living people, so the project relies on post-mortem donation. Another limitation is statistical power: rare variants and trans effects are harder to detect, so some real signals may be missed.
[1] The Genotype-Tissue Expression (GTEx) project - PMC - NIH [2] Principles of gene regulation across tissues - Nature Reviews Genetics [3] The Enhancing Gtex Project
SEE THE IDEA
How GTEx links DNA to tissue gene activity
Measure genetic variants from each donor
Collect RNA and other samples from multiple body tissues
Match variants with expression differences across tissues
Identify cis or trans links between variant and gene activity
DNA variation is compared with tissue expression data to find variant–gene associations.
GTEx connects donor genotypes to tissue-specific gene expression patterns.
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Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.