Leukemia (1997) 11, 2111–2119 1997 Stockton Press All rights reserved 0887-6924/97 $12.00 CBFA2, frequently rearranged in leukemia, is not responsible for a familial leukemia syndrome RD Legare1,DLu1, M Gallagher1,CHo1, X Tan1, G Barker1, K Shimizu2, M Ohki2, N Lenny3, S Hiebert3 and DG Gilliland1,4 1Department of Medicine, Division of Hematology/Oncology, Harvard Medical School, Boston, MA, USA; 2Division of Radiobiology, National Cancer Center Research Institute, Tokyo, Japan; 3Department of Tumor Cell Biology, St Jude Children’s Research Hospital, Memphis, TN; and 4Howard Hughes Medical Institute, Brigham and Women’s Hospital, Harvard Institute of Medicine, Boston, MA, USA We have identified a family with an autosomal dominant platelet The placement of the FPD critical region on chromosome disorder with a predisposition for developing myeloid malig- 21q22 is of particular interest as this locus has been previously nancies and have previously demonstrated linkage of this trait to chromosome 21q22.1-22.2. The nearest flanking markers, implicated in AML and acute lymphoblastic leukemia (ALL) D21S1265 and D21S167, define the familial platelet disorder through the (8;21), (3;21) and (12;21) chromosomal translo- (FPD) critical region at a genetic distance of approximately 15.2 cations.4–6 As well, there is a potential association between centimorgans and physical distance of approximately 6 mega- the FPD gene and the hematologic abnormalities seen in bases. This locus is of particular interest as it has previously Down syndrome (trisomy 21), including an approximate 15- been implicated in the pathogenesis of acute myelogenous leu- fold increased risk of developing AML.7,8 kemia (AML) and acute lymphoblastic leukemia (ALL) through the (8;21), (3;21) and (12;21) chromosomal translocations. In As there is no discernible, constitutional cytogenetic abnor- each of these cases, the CBFA2 gene is rearranged. As well, mality in this pedigree, a positional cloning strategy has been there is a potential association of this locus with the hemato- undertaken to identify the mutant gene responsible for this logic abnormalities seen in Down syndrome (trisomy 21). To phenotype. Several known candidate genes map to this locus, identify the mutant gene in this pedigree, a positional cloning including CBFA2,4 IFNAR1,9 IFNAR2,10 CRFB4,11 GART,12 strategy has been undertaken. Several candidate genes map to SON,13 KCNE1,14 SCL5A315 and ATP50 (Antonarakis, per- this locus including: CBFA2, IFNAR1, IFNAR2, CRFB4, GART, SON, KCNE1, SCL5A3 and ATP50. CBFA2, as well as IFNAR1 sonal communication). We have first undertaken mutation and CRFB4, were the focus of initial mutational analysis efforts. analysis of three of these candidate genes: CBFA2, IFNAR1 In this report, we exclude CBFA2 as a candidate by Northern and CRFB4 for involvement in FPD. and Southern blotting, RNase protection, single-strand confor- CBFA2 (PEBP2␣A; AML13,4,6,16–26 encodes a subunit of the mational polymorphism (SSCP), direct sequencing and gel- heterodimeric transcription factor polyomavirus enhancer- shift analysis. Exons of the IFNAR1 and CRFB4 genes were binding protein 2 (PEBP2), also known as core binding factor also analyzed by SSCP and demonstrated no evidence of (CBF) and is involved in both DNA binding and protein– mutation. SSCP analysis identified a new polymorphism in the 16,23,25 second exon of the CRFB4 gene and confirmed a previously protein interaction. CBFA2 is the fusion partner on chro- described polymorphism in the fourth exon of IFNAR1. Efforts mosome 21 involved in the t(8;21) translocation seen in the are currently underway to delimit further the FPD critical region M2 subtype of AML,4,17,18,22 as well as as the t(3;21) translo- and to analyze the other known candidate genes, as well as cation associated with myelodysplastic syndrome, chronic novel candidate genes, which map to this locus. myelogenous leukemia in blast crisis, and therapy-related Keywords: AML; familial leukemia; CBFA2 (AML1) gene; positional 5,21,24 cloning; candidate gene; platelet disorder AML, and in t(12;21) associated with acute lymphoid malignancy.6,27 Several myeloid leukemia-associated fusion partners have been identified for CBFA2.17,19,20,21,24,26 A com- mon feature for each of these translocations is expression of Introduction the DNA binding domain of CBFA2 and disruption of the transactivating domain by the respective fusion partners. It has Analysis of the molecular basis of human tumors has provided been shown that the DNA binding domain then has dominant evidence for the multistep pathogenesis1 of many of these negative activity in precluding normal transactivation of genes malignancies, including acute myelogenous leukemia (AML). by CBFA2.28 It is therefore possible that an inherited missense However, it has been difficult to identify early mutations in or frameshift mutation which disrupts the CBFA2 transactivat- AML, due in part to the rarity of pedigrees with an inherited ing domain could lead to abnormal hematopoiesis in the pedi- predisposition to develop leukemias. In 1985, Dowton et al2 gree. This is an attractive hypothesis, because FPD is an auto- reported on a large kindred with an autosomal dominant bone somal dominant disorder in which there is one normal and marrow disorder, consisting of qualitative and quantitative one mutant allele; the phenotype could therefore be a conse- defects in platelet function and a propensity to develop AML. quence of a dominant negative mutant. Moreover, evidence Of 29 affected family members, eight have developed AML is mounting that the alternatively spliced species which con- or myelodysplastic syndrome (MDS). We have recently estab- tain the runt domain without the transactivation domain, may lished linkage of this disorder to chromosome 21q22.1-22.2.3 act in a similar fashion to decrease transactivation of the full The nearest flanking markers, D21S1265 and D21S167 define length transcript (unpublished data). the familial platelet disorder (FPD) critical region at a genetic The interferon ␣/␤ receptor (IFNAR1) gene encodes one of distance of approximately 15.2 centimorgans and physical the components of the fully functional interferon ␣/␤ receptor distance of approximately 6 megabases. and has been assigned to 21q22.1.9 IFNAR1 is a member of the cytokine/growth hormone/prolactin/interferon receptor family, and is a reasonable candidate gene based on its known Correspondence: DG Gilliland, Howard Hughes Medical Institute, function. Interferon mediates a variety of effects in hematopo- Brigham and Women’s Hospital, Harvard Institute of Medicine, 4 Blackfan Circle, Room 421, Boston, MA 02115, USA; Fax: 617 525 ietic cells through interaction with its receptor, including 5530 induction of expression of interferon regulatory factor 1 (IRF- Received 7 April 1997; accepted 13 August 1997 1), which has been implicated in pathogenesis of myelodys- CBFA2 is not responsible for a familial leukemia syndrome RD Legare et al 2112 plastic syndromes.29 CRFB4 is located approximately 35 kb Single-strand conformational polymorphism (SSCP) from IFNAR1 on chromosome 21.30 Analysis of the extracellu- analysis lar domain indicates that CRFB4 is a typical member of the class II cytokine receptor family, which includes IFNAR, PCR-SSCP analysis was performed using a modification of a ␥ human tissue factor gene, and interferon- receptor gene. previously reported method,37 and using PCR conditions as Although the function and pattern of expression of the CRFB4 previously described.38 gene is unknown, it appears to be a gene duplication of IFNAR1 and by analogy may also play a role in hematopo- iesis. In this report we describe the analysis of CBFA2, IFNAR1 and CRFB4 and show that no mutation can be identified in RNA-based PCR these genes using standard mutational analysis. Screening of the other known candidate genes and characterization and First-strand cDNA was synthesized as previously described,6 analysis of novel candidate genes which map to this locus using 1 ␮g of RNA and Moloney murine leukemia virus is ongoing. reverse transcriptase (GIBCO-BRL, Gaithersburg, MD, USA) according to the manufacturer’s instructions. To amplify the CBFA2 coding region, CBFA2 sense and antisense primers Materials and methods were generated from the AML1b coding region (GenBank accession U19601). Generation of lymphoblastoid cell lines and isolation of DNA and RNA Lymphoblastoid cell lines (LBCL) were established as pre- Cloning and DNA sequencing viously described.31 DNA was extracted from lymphoblastoid cell lines according to the manufacturer’s instructions (DNA cDNA amplified by PCR was purified, cloned, miniprepped STAT 60; Tel-Test, Friendwood, TX, USA). Total RNA was and sequenced as previously described.6 PCR products gener- extracted from lymphoblastoid cells by the acid guanidinium ated from exon 4 of IFNAR1 and exon 2 of CRFB4 were simi- thiocyanate/phenol/chloroform method,32 according to the larly cloned and sequenced. manufacturer’s instructions (RNA STAT 60; Tel-Test). Electrophoretic mobility shift assays Pulsed-field gel electrophoresis and Southern hybridization Cell extracts were prepared from 1 × 107 lymphoblastoid cells Southern blotting was performed according to standard as previously described.20 Lysates were clarified by high speed methods33 using LBCL DNA or genomic DNA obtained from centrifugation and 20 ␮g of cell lysate was used in EMSA. peripheral blood as previously described.34 Restriction endo- DNA-binding site selection and EMSA were performed