CBFA2, FREQUENTLY REARRANGED IN LEUKEMIA, IS NOT RESPONSIBLE FOR A FAMILIAR LEUKEMIA SYNDROME

We have identified a family with an autosomal dominant platelet disord er with a predisposition for developing myeloid malignancies and have previously demonstrated linkage of this trait to chromosome 21q22.1-22 .2. The nearest flanking markers, D21S1265 and D21S167, define the fam ilial platelet disorder (FPD) critical region at a genetic distance of approximately 15.2 centimorgans and physical distance of approximatel y 6 megabases. This locus is of particular interest as it has previous ly been implicated in the pathogenesis of acute myelogenous leukemia ( AML) and acute lymphoblastic leukemia (ALL) through the (8;21), (3;21) and (12;21) chromosomal translocations. In each of these cases, the C BFA2 gene is rearranged. As well, there is a potential association of this locus with the hematologic abnormalities seen in Down syndrome (t risomy 21). To identify the mutant gene in this pedigree, a positional cloning strategy has been undertaken. Several candidate genes map to this locus including: CBFA2, IFNAR1, IFNAR2, CRFB4, GART, SON, KCNE1, SCL5A3 and ATP50. CBFA2, as well as IFNAR1 and CRFB4, were the focus o f initial mutational analysis efforts. In this report, we exclude CBFA 2 as a candidate by Northern and Southern blotting, RNase protection, single-strand conformational polymorphism (SSCP), direct sequencing an d gel-shift analysis. Exons of the IFNAR1 and CRFB4 genes were also an alyzed by SSCP and demonstrated no evidence of mutation. SSCP analysis identified a new polymorphism in the second exon of the CRFB4 gene an d confirmed a previously described polymorphism in the fourth exon of IFNAR1. Efforts are currently underway to delimit further the FPD crit ical region and to analyze the other known candidate genes, as well as novel candidate genes, which map to this locus.