Simultaneous SIL‐TAL1 RT‐PCR detection of all tal d deletions and identification of novel tal d variants

Site‐specific deletions of the 5′ part of the TAL1 gene ( tal d ) are among the most frequent non‐random genetic abnormalities in T‐cell acute lymphoblastic leukaemia (T‐ALL). They are usually detected by PCR from DNA with several primer pairs or by Southern blot analysis. Since tal d lead to expression of a SIL‐TAL1 fusion transcript, irrespective of the genomic breakpoint, we have used a single monoplex RT‐PCR reaction to screen 55 T‐ALL patients at diagnosis. SIL‐TAL1 transcripts were demonstrated in 12 (22%) cases, including 7/27 (26%) children 20 years. SIL‐TAL1 RT‐PCR was preferrable to tal d DNA PCR since it allowed the simultaneous detection of tal d1 , tal d2 and two previously undescribed tal d variants. SIL‐TAL1 RT‐PCR screening should therefore increase the detection rate of tal d by approximately 15–20%, with an at least comparable sensitivity to tal d genomic PCR, and represents a more practical and economic alternative to multiple DNA PCRs or Southern blotting when incorporated into molecular screening for multiple transcripts at diagnosis.