Laser Capture Microdissection (LCM)
Definition
A UV-laser instrument technique for physically isolating individual cells or clusters of cells from a stained slide into a capture tube, without manual contact. Used for sperm isolation in azoospermic or very-low-sperm-count cases.
- Energy source
- UV laser
- Sample form
- Stained slide
- Key use case
- Sperm isolation in azoospermic or very-low-count samples
- Advantage
- Isolates targeted cells without manual manipulation
Common questions
Why use LCM instead of standard differential extraction for sperm cells?+
Differential extraction relies on chemically lysing epithelial cells while sperm resist lysis, but when sperm counts are extremely low or absent chemically, that separation fails to yield enough target DNA. LCM instead visually identifies and physically excises individual sperm cells from a stained slide.
What limits LCM's use in routine sexual-assault casework?+
It requires specialized microscopy equipment, is labour intensive, and works cell by cell, so it is generally reserved for cases where standard differential extraction has failed to yield a usable male profile, not as a first-line technique.
Related terms
- Differential Extraction
- A two-step DNA extraction procedure used when a stain contains both sperm cells and non-sperm epithelial cells. The first step lyses epithelial...
- DTT (Dithiothreitol)
- A reducing agent that cleaves the disulphide bonds in the sperm protamine matrix, allowing proteinase K and SDS to lyse the sperm...
- Erase Sperm Isolation Kit
- An immunomagnetic sperm-cell isolation system using paramagnetic beads coated with antibodies against sperm-specific surface antigens. Achieves greater than 99% sperm recovery with...
- Female Fraction
- The lysate produced by the first (no-DTT) lysis step of differential extraction. Contains DNA from epithelial cells and other non-sperm cellular material...
- Male Fraction (Sperm Fraction)
- The lysate produced by the second (DTT + proteinase K) lysis step after washing the sperm pellet. Ideally contains predominantly the suspect's...
- Protamine
- Small arginine-rich proteins that replace histones in the nuclei of spermatozoa during spermatogenesis, producing a hyper-compacted chromatin structure approximately six times denser...