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Method for recovering sperm nucleic acid from a forensic sample

A sample and sperm technology, applied in the field of sperm nucleic acid recovery from forensic samples, can solve the problems of sperm cell loss, limit the accurate identification of criminals, hinder accurate sperm analysis, etc., and achieve the effect of reducing the number

Active Publication Date: 2013-12-11
APPL BIOSYSTEMS INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Additional washing steps required to remove epithelial DNA also contribute to the loss of sperm cells
[0012] Lysis or presence of epithelial cells or other contaminating cell types such as leukocytes may prevent accurate sperm analysis
The presence of DNA from damaged non-sperm cells in forensic samples can contaminate the cells (most likely by binding to the sperm cell surface), which may limit the precise identification of perpetrators, especially when the number of recovered sperm cells is low
[0013] The inventors discovered that while techniques exist for the differential extraction of one nucleic acid type from heterogeneous cell populations (from individual cell types), residual contaminating nucleic acids remain a problem for warranting more accurate extraction methods

Method used

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  • Method for recovering sperm nucleic acid from a forensic sample
  • Method for recovering sperm nucleic acid from a forensic sample
  • Method for recovering sperm nucleic acid from a forensic sample

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0113] Example 1 - Comparative Differential Extraction Procedure: Prior Art Wash Solution (1×PBS) vs. MgCl 2 washing solution

[0114] 500 μL MgCl 2 Wash solution (260 mM final concentration in 1X PBS) or 1X PBS was added to the cell suspension sample containing 50 μL of a heterogeneous cell suspension containing approximately 10,000 epithelial cells, 1,000 sperm cells and impurities including residual DNA. The samples and wash solutions were then transferred to spin filter tubes (Corning spinX Costar 8160, pore size 220 nm). The tubes were centrifuged at 14,000 RPM in a Beckman Coulter Microfuge 18 centrifuge after which time the filtrate was discarded.

[0115] will contain 875mM NaCl 2 and 85 mM dTT, 200 μL of selective sperm lysis buffer diluted in 1×PBS were added to the spin filter tube. The sperm cells were then lysed by mixing for about 5 minutes. The tubes were centrifuged at 14,000 RPM in a Beckman Coulter Microfuge 18 centrifuge to separate sperm lysate from i...

Embodiment 2

[0120] Example 2 - MgCl 2 Wash solution reduces exogenous epithelial DNA from epithelial cell samples

[0121] It has been found that MgCl in the concentration range of 0-260mM 2 Efficiently removes surface-bound DNA, more so than when using the classic wash solution 1X PBS ( image 3 ). Epithelial cell samples were first treated with MgCl 2 Wash, dilute with 1x PBS, and mix. Wash buffer is removed and cells are incubated with selective sperm lysis buffer. Lysis was performed for 5 minutes, after which time the samples were filtered, and the DNA in the filtrate was purified and quantified. Because the lysis buffer is selective, what remains in the filtrate is residual epithelial cell DNA that was originally present in the sample. Depend on image 3 Visible, compared with 1×PBS control, with as low as 30mM MgCl 2 Concentration reduces the amount of residual DNA. Depend on image 3 Obviously, the best MgCl 2 The concentration is between 160mM and 260mM.

Embodiment 3

[0122] Example 3 - Comparing Differential Extraction Steps: DNase-Free Wash vs. DNase Wash

[0123] 500 μL MgCl 2 Wash solution (260 mM final concentration in 1×PBS) was added to the cell suspension samples containing 50 μL of the post-coitus samples. After mixing and incubating at room temperature for 5 minutes, the samples and wash solutions were transferred to spin filter tubes (Corning spinX Costar 8160, pore size 220 nm), the tubes were centrifuged at 14,000 RPM in a Beckman Coulter Microfuge 18 centrifuge, after which the filters were discarded. over liquid.

[0124] 100 μL of DNase wash solution containing 10 units of Turbo DNase (AM2238, Applied Biosystems, Foster City, CA) was added to one of the two samples in the spin filter tube. A DNase wash was performed at 37°C for 5 minutes. The tubes were centrifuged at 14,000 RPM in a Beckman Coulter Microfuge 18 centrifuge after which time the filtrate was discarded. Two washing solutions (MgCl 2 and DNase) correspondin...

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Abstract

A method for selectively recovering nucleic acid from a sperm cell in a sample containing cells of at least a sperm cell and an epithelial cell, and a cell suspension medium comprising extracellular impurities, is provided. The method entails introducing a sample into a vessel, sequestering the cells from the remaining sample components, washing the cells with a washing solution either before or after sequestration, removing the impurities-containing cell suspension medium from the vessel while retaining the cells; lysing selectively cells of the first cell type; and isolating the nucleic acid from the lysed cells. Methods for recovering nucleic acid from the second cell type are also provided.

Description

[0001] related application [0002] This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60 / 961,734, filed July 23, 2007. field of invention [0003] The present invention relates to the field of isolating cells from samples containing cellular and non-cellular impurities and further isolating nucleic acids from specific cell types. [0004] More specifically, the invention relates to the field of isolating sperm cells from a sample containing extracellular impurities and at least one other type of contaminating cell (e.g. epithelial cells) and recovering DNA from sperm cells and non-sperm cells, For various purposes, including forensic purposes. Background of the invention [0005] Forensic DNA analysis of sexual assault evidence often includes analysis of the DNA of sperm cells as well as the DNA of other cells such as epithelial cells. Sperm cells are generally obtained from rape victims by swabbing mucous membranes. Samples from...

Claims

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Application Information

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IPC IPC(8): C12N15/10
CPCC12N15/1003C12Q1/6806
Inventor Y·刘
Owner APPL BIOSYSTEMS INC