Horvath 353-CpG Clock
Definition
A pan-tissue epigenetic age clock built on the methylation values of 353 CpG sites from the Illumina 450K array; developed by Steve Horvath and published in 2013. Requires microgram-quantity DNA and array-based measurement.
- Developer
- Steve Horvath
- Publication year
- 2013
- CpG sites used
- 353
- Platform
- Illumina 450K methylation array
Common questions
How does the Horvath clock estimate a person's age from DNA?+
It applies a mathematical model to the methylation levels measured at 353 specific CpG sites across the genome, since methylation at these sites changes with age in a fairly predictable, tissue-independent pattern.
What practical limitation makes this clock harder to apply to typical crime scene samples?+
It needs microgram quantities of DNA and array-based measurement, both of which are demanding for the trace, degraded, or low-template samples common in forensic casework, unlike targeted PCR-based methylation age assays developed for such samples.
Related terms
- Bisulphite Conversion
- A chemical treatment that deaminates unmethylated cytosines to uracil, converting them to thymine upon PCR amplification; methylated cytosines are protected. Allows methylation...
- Cell-Free DNA (cfDNA)
- Short DNA fragments (~166 bp) circulating extracellularly in body fluids, shed from apoptotic and necrotic cells. In plasma, predominantly hematopoietic; in pregnancy,...
- CpG Methylation
- Addition of a methyl group to cytosine in a CpG dinucleotide. Methylation at age-associated CpGs increases or decreases with chronological age in...
- ELOVL2 Clock
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- EPIC Array (Illumina)
- The Infinium MethylationEPIC v2.0 microarray measuring methylation beta values at approximately 935,000 CpG sites genome-wide; the current standard instrument for multi-CpG age-clock...
- EpiTYPER
- Agena Bioscience (formerly Sequenom) reagent system for quantitative methylation analysis via bisulphite PCR and MALDI-TOF mass spectrometry; used for multi-CpG methylation profiling...
- HIrisPlex-S
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- MiRNA (microRNA)
- A small non-coding RNA (21-23 nt) that regulates gene expression post-transcriptionally. Different tissues and body fluids express different miRNA sets; forensic miRNA...