DNA technology in the clinical laboratory

Rolling-circle amplification in DNA diagnostics: the power of simplicity

Due to its robustness and simplicity, the rolling replication of circular DNA probes holds a distinct position in DNA diagnostics among other isothermal methods of target, probe or signal amplification. Major rolling-circle amplification approaches to DNA detection via posthybridization probe/signal turn-by-turn enhancement are briefly overviewed here with an emphasis on the new concepts and latest progress in the field, including the single-molecule and single-mutation detection assays as exemplary applications. Underlying mechanisms, current controversies and principal advantages of rolling-circle amplification are also considered. Possible future directions for the further advancement of this diagnostic methodology are outlined.

Validation of Sixteen Leukemia and Lymphoma Cell Lines as Controls for Molecular Gene Rearrangement Assays

Background: Assays for rearrangement of the immunoglobulin, T-cell receptor, bcr/abl, and bcl-2 genes are valuable tools to aid in the diagnosis of leukemias and lymphomas and are now offered by many pathology laboratories. However, there is a lack of well-characterized and validated calibrators and positive controls for these assays. We therefore evaluated 16 readily available leukemia and lymphoma cell lines for their potential use as controls.

Methods: DNA and RNA were isolated from each cell line and analyzed by Southern blot and PCR or reverse transcription-PCR (RT-PCR). Rearrangements in the IgJH, IgJκ, TcR-β or TcR-γ, bcr/abl, and bcl-2 genes were detected by commercially available probes and primers. Cell lineages were confirmed by immunophenotyping.

Results: Immunoglobulin and T-cell receptor gene rearrangements were identified in five B- and three T-cell lines, respectively. Two cell lines tested positive for the bcr/abl gene, and one was positive for the bcl-2 gene rearrangement by Southern blot.

Conclusions: The 16 cell lines studied can be used as positive controls in molecular detection assays for gene rearrangements. The parallel processing of these cell lines with clinical samples can serve to quality control the experimental procedures from the first step of DNA or RNA extraction to the final step of result analysis.