GENOMICS 35, 118–128 (1996) ARTICLE NO. 0330 Physical Mapping of the Bloom Syndrome Region by the Identification of YAC and P1 Clones from Human Chromosome 15 Band q26.1 J OEL S TRAUGHEN,* S USAN C IOCCI,† T IAN-Z HANG YE ,† DAVID N. L ENNON,† M ARIA P ROYTCHEVA,† BECKY ALHADEFF ,† P ETER GOODFELLOW,‡ J AMES GERM AN,† NATHAN A. E LLIS ,† AND J OANNA GRODEN* ,1 * Department of Molecular Genetics, Biochemistry and Microbiology, The University of Cincinnati College of Medicine, 231 Bethesda Avenue, Cincinnati, Ohio 45267-0524; †Laboratory of Human Genetics, New York Blood Center, 310 East 67th Street, New York, New York 10021; and ‡Department of Genetics, University of Cambridge, Downing Street, Cambridge, United Kingdom CB2 3EH Received October 6, 1995; accepted February 12, 1996 fold increase in locus-specific mutations (German, The gene for Bloom syndrome (BLM) has been 1993). The hypermutability of BS cells is responsible mapped to human chromosome 15 band q26.1 by homo- for a major complication in persons affected with BS, zygosity mapping. Further refinement of the location namely the emergence of benign and malignant neo- of BLM has relied upon linkage-disequilibrium map- plasms at unusually early ages and in excessive num- ping and somatic intragenic recombination. In combi- bers (German, 1993). Thus, BS is considered the pro- nation with these mapping approaches and to identify totype of a class of human diseases referred to as the novel DNA markers and probes for the BLM candidate somatic mutational disorders. region, a contiguous representation of the 2-Mb region Complementation analyses have established that a that contains the BLM gene was generated and is pre- single locus, designated BLM, appears to be mutated sented here. YAC and P1 clones from the region have in BS (Weksberg et al., 1988). McDaniel and Schultz been identified and ordered by using previously avail- (1992) localized BLM to chromosome 15 by microcell- able genetic markers in the region along with newly mediated chromosome transfer; this localization was developed sequence-tagged sites from radiation-re- confirmed and refined to band q26.1 by demonstrating duced hybrids, polymorphic dinucleotide repeat loci, linkage of BLM to the FES proto-oncogene in 21 con- and end sequences of YACs and P1s. A long-range re- sanguineous BS families (German et al., 1994). FES striction map of the 2-Mb region that allowed estima- had been mapped previously by in situ hybridization tion of the distance between polymorphic microsatel- (Jhanwar et al., 1984). Additional polymorphic markers lite loci is also reported. This map and the DNA mark- have been identified in the region around FES; the use ers derived from it were instrumental in the recent of homozygosity mapping has been extended to include identification of the BLM gene.  1996 Academic Press, Inc. these markers. In addition, the map position of BLM has been refined by using two other genetic approaches: INTRODUCTION linkage-disequilibrium mapping in Ashkenazi Jews with BS (Ellis et al., 1994) and analysis of cell lines in Bloom syndrome (BS) 2 is a rare, autosomal reces- which intragenic recombination has occurred within sive disorder characterized clinically by growth retar- BLM (Ellis et al., 1995a). This second and novel ap- dation, a sun-sensitive facial skin lesion, immunode- proach relies upon the detection of reduction to homo- ficiency, and male infertility (German, 1993). Somatic zygosity of all loci distal to BLM. BLM was localized cells from persons with BS display excessive genomic within a very small region immediately proximal to instability, and they exhibit an increased frequency FES and more recently has been isolated from this of microscopically visible chromosome abnormalities same region (Ellis et al., 1995b). (breaks, gaps, and rearrangements), inter- and in- The construction of a physical map of the BLM-con- trachromosomal chromatid exchanges, and a many- taining region on 15q26 initially was undertaken to facilitate the identification of new genetic markers in this region of the genome and ultimately to clone the 1 To whom correspondence should be addressed. Telephone: (513) 558-0088. Fax: (513) 558-8474. BLM gene. We report the identification of YACs and 2 Abbreviations used: Bloom syndrome, BS; fluorescence in situ P1 clones that form a contiguous representation of a hybridization, FISH; polymerase chain reaction, PCR; pulsed-field 2-Mb region flanking the BLM gene, as well as the gel electrophoresis, PFGE; sequence-tagged site, STS; sister-chroma- tid exchange, SCE; yeast artificial chromosome, YAC. construction of a long-range restriction map of the re- 118 0888-7543/96 $18.00 Copyright  1996 by Academic Press, Inc. All rights of reproduction in any form reserved.