Map of the ETV6 gene between exon 5 and 6 containing the ETV6 breakpoint cluster region (bcr). Chromosomal orientation from telomere to centromere is as indicated. Exons 5 and 6 are shown as solid boxes. The breakpoints in the different patients are shown as downward arrows with the patient identification numbers marked above. Patients 41 and 44 have two breakpoints each, designated 41a and 41b, and 44a and 44b, respectively. The portion of the gene between these breakpoints is deleted in each patient. Only the derivative 21 was cloned from patients 23 and 55. The 0.3-kb area in the ETV6 gene, shown as a speckled box, represents a pu/py repeat region. The 0.7-kb region depicted by the triangle is a deletion/insertion polymorphism in theETV6 gene. Restriction enzyme sites are B,BamHI; G, BglII; R, EcoRI; S, SstI; M, MluI; H,HindIII and X, XbaI. The 1.3-kbSstI-XbaI probe used to identify the deletion/insertion polymorphism on Southern blot is indicated .