Loss of the TEL/ETV6 gene by a second translocation in ALL patients with t(12;21)

Inactivation of the non translocated TEL/ETV6 gene is commonly associated w ith translocation (12;21) of acute lymphoblastic leukemia (ALL). Translocat ions involving the short arm of chromosome 12 were analysed in two children with t(12;21) ALL. Fluorescence in situ hybridation studies showed that th ese associated translocations resulted in loss of TEL/ETV6. While hybridiza tion with a YAC probe covering TEL/ETV6 was positive in one patient, analys is with cosmid probes covering the gene demonstrated that the gene was in f act deleted. It is concluded that deletions involving TEL/ETV6 can remain u ndetected by FISH using only YAC probes. (C) 1999 Elsevier Science Ltd. All rights reserved.