Circulating DNA in systemic lupus erythematosus. Isolation and characterization

Area of Science:

• Molecular Biology
• Immunology
• Genetics

Background:

• Double-stranded DNA (dsDNA) is found in circulation in a subset of systemic lupus erythematosus (SLE) patients.
• The characteristics and origin of this circulating dsDNA are not fully understood.

Purpose of the Study:

• To characterize the nucleotide base composition and sequence homology of circulating dsDNA in SLE patients.
• To determine the proportion of circulating dsDNA that shares sequences with human genomic DNA.

Main Methods:

• Isolation of dsDNA from plasma of 10 SLE patients using proteolysis, phenol extraction, and hydroxylapatite adsorption.
• Radiolabeling of isolated dsDNA and characterization via ultracentrifugation and S1-endonuclease digestion.
• Renaturation experiments comparing plasma DNA with human and nonhuman genomic DNA.

Main Results:

• Plasma-derived dsDNA exhibited essential identity in nucleotide base composition with human genomic DNA.
• A minimum of 47% of plasma DNA sequences were found to be present in human genomic DNA.
• 10-20% of plasma DNA showed reduced renaturation with human DNA, suggesting sequence differences or alterations.

Conclusions:

• Persistently circulating dsDNA in this SLE patient group primarily consists of sequences found in human genomic DNA.
• A distinct subfraction of circulating DNA with altered renaturation behavior was identified, but its significance remains unclear.