Screening for mutations by RNA single-strand conformation polymorphism (rSSCP): comparison with DNA-SSCP

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Single-strand conformation polymorphism (SSCP) is a DNA mutation detection method with variable sensitivity.
• The detection rate of SSCP for single-base mutations, especially in longer DNA fragments, requires optimization.
• Factor IX gene mutations are a common cause of hemophilia B.

Purpose of the Study:

• To evaluate and optimize conditions for DNA-based SSCP in detecting factor IX gene mutations.
• To investigate the potential of RNA-based SSCP (rSSCP) as a more sensitive mutation detection technique.
• To compare the diagnostic utility of SSCP, rSSCP, and direct genomic sequencing in patients with hemophilia B.

Main Methods:

• Optimization of electrophoresis conditions (temperature, buffer, acrylamide ratios, cooling) for DNA SSCP.
• Development of rSSCP by incorporating phage promoter sequences for in vitro RNA transcription.
• Comparative analysis of SSCP, rSSCP, and direct genomic sequencing in a blinded study of 28 hemophilia B patients.

Main Results:

• DNA SSCP detected 10-11/12 mutations in a 183 bp segment and 11-14/22 mutations in a 307 bp segment, with sensitivity varying by condition.
• rSSCP demonstrated superior performance compared to DNA SSCP, especially for the 307 bp segment.
• In a blinded study, rSSCP detected 70% of sequence changes, while SSCP detected only 35%, compared to direct genomic sequencing which identified all 20 sites.

Conclusions:

• rSSCP offers enhanced sensitivity and broader applicability for mutation detection compared to standard DNA SSCP.
• The nonradioactive, rapid detection capability of rSSCP makes it a valuable tool for genetic diagnostics.
• rSSCP represents a significant improvement for identifying mutations in the factor IX gene and potentially other genetic disorders.