MiRNA (microRNA)
Definition
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 panels exploit this tissue specificity for body-fluid identification.
- Length
- 21 to 23 nucleotides
- Function
- Post-transcriptional regulation of gene expression
- Coding status
- Non-coding RNA
- Forensic use
- Tissue and body fluid identification
Common questions
Why is miRNA useful for body fluid identification when mRNA markers already exist?+
MiRNA is smaller and more chemically stable than messenger RNA, so it tends to survive environmental degradation, ageing, and processing better, which makes it attractive for identifying body fluids in older or compromised forensic samples where mRNA has broken down.
How does a miRNA panel actually distinguish between body fluids like blood and saliva?+
Different tissues and fluids express distinct, characteristic combinations of miRNA species. A panel measures the relative abundance of several tissue-specific miRNAs together, and the resulting expression profile is compared to reference patterns established for each fluid type.
Is miRNA-based body fluid identification as established in casework as STR profiling?+
No, it remains a comparatively newer, emerging technique alongside DNA methylation and phenotyping markers, and is not yet as standardised or as widely validated across accredited laboratories as core STR-based DNA profiling.
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
- A forensic age-estimation system based on bisulphite pyrosequencing of 5 CpG sites in the ELOVL2 gene promoter; validated in multiple independent European...
- 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
- A 41-SNP externally visible characteristics (EVC) panel for simultaneous prediction of eye, hair, and skin colour, developed at Erasmus MC Rotterdam by...
- Horvath 353-CpG Clock
- A pan-tissue epigenetic age clock built on the methylation values of 353 CpG sites from the Illumina 450K array; developed by Steve...