Fluorescence in situ hybridization analysis of chromosome 1 abnormalities in hematopoietic disorders:: rearrangements of DNA satellite II and new recurrent translocations

Using fluorescence in situ hybridization analysis, breakpoints involving the long arm of chromosome 1 (Iq) were localized in 36 patients with various hematopoietic disorders and rearrangements of the proximal part of Iq, as ascertained with banding techniques. The breakpoint was localized within the satellite Il(sat II) domain in 14 patients with Various abnormalities, between the sat II domain and the BCL9 locus in eight, between the BCL9 and ARNT loci in two, between sat II and ARNT in two others, and distal to ARNT in seven. A dicentric chromosome 1 was present in two patients. A high incidence of heterochromatin heteromorphism of chromosome 1 was present in this series. Two recurrent translocations were identified, t(1;2)(q12;q37) in three patients suffering from three different acute leukemia subtypes, and t(1;16)(q12;q24) in two patients with different diseases. Two patients had jumping translocations. Most of the rearrangements of Iq were secondary abnormalities, included in complex karyotypes. The roles of methylation, interactions with the proteins interfering with heterochromatin and possible gene silencing due to heterochromatin rearrangements are discussed.