Shwachman-Diamond Syndrome with Exocrine Pancreatic Dysfunction and Bone Marrow Failure Maps to the Centromeric Region of Chromosome 7
2001; Elsevier BV; Volume: 68; Issue: 4 Linguagem: Inglês
10.1086/319505
ISSN1537-6605
AutoresSharan Goobie, M. Popović, Jodi Morrison, Lynda Ellis, Hedy Ginzberg, Graeme R.B. Boocock, Nadia Ehtesham, Christine Bétard, Carl G. Brewer, Nicole M. Roslin, Thomas J. Hudson, Kenneth Morgan, Takuya Fujiwara, Peter R. Durie, Johanna M. Rommens,
Tópico(s)Pneumocystis jirovecii pneumonia detection and treatment
ResumoShwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by exocrine pancreatic insufficiency and hematologic and skeletal abnormalities. A genomewide scan of families with SDS was terminated at ∼50% completion, with the identification of chromosome 7 markers that showed linkage with the disease. Finer mapping revealed significant linkage across a broad interval that included the centromere. The maximum two-point LOD score was 8.7, with D7S473, at a recombination fraction of 0. The maximum multipoint LOD score was 10, in the interval between D7S499 and D7S482 (5.4 cM on the female map and 0 cM on the male map), a region delimited by recombinant events detected in affected children. Evidence from all 15 of the multiplex families analyzed provided support for the linkage, consistent with a single locus for SDS. However, the presence of several different mutations is suggested by the heterogeneity of disease-associated haplotypes in the candidate region. Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by exocrine pancreatic insufficiency and hematologic and skeletal abnormalities. A genomewide scan of families with SDS was terminated at ∼50% completion, with the identification of chromosome 7 markers that showed linkage with the disease. Finer mapping revealed significant linkage across a broad interval that included the centromere. The maximum two-point LOD score was 8.7, with D7S473, at a recombination fraction of 0. The maximum multipoint LOD score was 10, in the interval between D7S499 and D7S482 (5.4 cM on the female map and 0 cM on the male map), a region delimited by recombinant events detected in affected children. Evidence from all 15 of the multiplex families analyzed provided support for the linkage, consistent with a single locus for SDS. However, the presence of several different mutations is suggested by the heterogeneity of disease-associated haplotypes in the candidate region. Shwachman-Diamond syndrome (SDS [MIM 260400]), also known as "Shwachman syndrome," "Shwachman-Bodian syndrome," or "congenital lipomatosis of the pancreas," is a rare disorder first reported in 1964 (Bodian et al. Bodian et al., 1964Bodian M Sheldon W Lightwood R Congenital hypoplasia of the exocrine pancreas.Acta Paediatr. 1964; 53: 282-293Crossref PubMed Scopus (139) Google Scholar; Shwachman et al. Shwachman et al., 1964Shwachman H Diamond LK Oski FA Khaw K-T The syndrome of pancreatic insufficiency and bone marrow dysfunction.J Pediatr. 1964; 65: 645-663Abstract Full Text PDF PubMed Scopus (368) Google Scholar). Multiple organs are affected, and there is a broad range in severity of presentation even among affected siblings (Burke et al. Burke et al., 1967Burke V Colebatch JH Anderson CM Simons MJ Association of pancreatic insufficiency and chronic neutropenia in childhood.Arch Dis Child. 1967; 42: 147-157Crossref PubMed Scopus (73) Google Scholar; Shmerling et al. Shmerling et al., 1969Shmerling DH Prader A Hitzig WH Giedion A Hadorn ZB Kühni M The syndrome of exocrine pancreatic insufficiency, neutropenia, metaphyseal dysostosis and dwarfism.Helvetica Paediatr Acta. 1969; 24: 547-575PubMed Google Scholar; Aggett et al. Aggett et al., 1980Aggett PJ Cavanagh NP Matthew DJ Pincott JR Sutcliffe J Harries JT Shwachman's syndrome: a review of 21 cases.Arch Dis Child. 1980; 55: 331-347Crossref PubMed Scopus (200) Google Scholar; Savilahti and Rapola Savilahti and Rapola, 1984Savilahti E Rapola J Frequent myocardial lesions in Shwachman's syndrome: eight fatal cases among 16 Finnish patients.Acta Paediatr Scand. 1984; 73: 642-651Crossref PubMed Scopus (50) Google Scholar), although impaired exocrine pancreatic function and hematologic abnormalities with depressed myeloid cell lineages are the most consistent features (Ginzberg et al. Ginzberg et al., 1999Ginzberg H Shin J Ellis L Morrison J Ip W Dror Y Freedman M Heitlinger LA Belt MA Corey M Rommens JM Durie PR Shwachman syndrome: phenotypic manifestations of sibling sets and isolated cases in a large patient cohort are similar.J Pediatr. 1999; 135: 81-88Abstract Full Text Full Text PDF PubMed Scopus (165) Google Scholar). Exocrine pancreatic insufficiency typically manifests in infancy, although some improvement may be seen with age (Hill et al. Hill et al., 1982Hill RE Durie PR Gaskin KJ Davidson GP Forstner GG Steatorrhea and pancreatic insufficiency in Shwachman syndrome.Gastroenterology. 1982; 83: 22-27PubMed Scopus (45) Google Scholar; Mack et al. Mack et al., 1996Mack DR Forstner GG Wilschanski M Freedman MH Durie PR Shwachman syndrome: exocrine pancreatic dysfunction and variable phenotypic expression.Gastroenterology. 1996; 111: 1593-1602Abstract Full Text PDF PubMed Scopus (134) Google Scholar). In addition to persistent or intermittent neutropenia and an increased susceptibility to infections, hematologic problems also can include anemia, thrombocytopenia, and pancytopenia (Smith et al. Smith et al., 1996Smith OP Hann IM Chessells JM Reeves BR Milla P Haematological abnormalities in Shwachman-Diamond syndrome.Br J Haematol. 1996; 94: 279-284Crossref PubMed Scopus (166) Google Scholar). SDS is considered to be a genetic bone marrow–failure syndrome; patients with SDS are at increased risk of development of myelodysplasia and hematologic malignancy—in particular, acute myelogenous leukemia (Huijgens et al. Huijgens et al., 1977Huijgens PC van der Veen EA Meijer S Muntinghe OG Syndrome of Shwachman and leukaemia.Scand J Haematol. 1977; 18: 20-24Crossref PubMed Scopus (33) Google Scholar; Woods et al. Woods et al., 1981Woods WG Roloff JS Lukens JN Krivit W The occurrence of leukemia in patients with the Shwachman syndrome.J Pediatr. 1981; 99: 425-428Abstract Full Text PDF PubMed Scopus (92) Google Scholar; Smith et al. Smith et al., 1996Smith OP Hann IM Chessells JM Reeves BR Milla P Haematological abnormalities in Shwachman-Diamond syndrome.Br J Haematol. 1996; 94: 279-284Crossref PubMed Scopus (166) Google Scholar). Skeletal abnormalities include delayed maturation, metaphyseal chondrodysplasia of the long bones, and thoracic-cage abnormalities with costochondral thickening (Aggett et al. Aggett et al., 1980Aggett PJ Cavanagh NP Matthew DJ Pincott JR Sutcliffe J Harries JT Shwachman's syndrome: a review of 21 cases.Arch Dis Child. 1980; 55: 331-347Crossref PubMed Scopus (200) Google Scholar; Dhar and Anderton Dhar and Anderton, 1994Dhar S Anderton JM Orthopaedic features of Shwachman syndrome: A report of two cases.J Bone Joint Surg Am. 1994; 76: 278-282PubMed Google Scholar; Mack et al. Mack et al., 1996Mack DR Forstner GG Wilschanski M Freedman MH Durie PR Shwachman syndrome: exocrine pancreatic dysfunction and variable phenotypic expression.Gastroenterology. 1996; 111: 1593-1602Abstract Full Text PDF PubMed Scopus (134) Google Scholar). Short stature occurs in 50% of patients (Ginzberg et al. Ginzberg et al., 1999Ginzberg H Shin J Ellis L Morrison J Ip W Dror Y Freedman M Heitlinger LA Belt MA Corey M Rommens JM Durie PR Shwachman syndrome: phenotypic manifestations of sibling sets and isolated cases in a large patient cohort are similar.J Pediatr. 1999; 135: 81-88Abstract Full Text Full Text PDF PubMed Scopus (165) Google Scholar). Other common anomalies include hepatomegaly and abnormal liver-biochemical tests, both found in younger patients (Aggett et al. Aggett et al., 1980Aggett PJ Cavanagh NP Matthew DJ Pincott JR Sutcliffe J Harries JT Shwachman's syndrome: a review of 21 cases.Arch Dis Child. 1980; 55: 331-347Crossref PubMed Scopus (200) Google Scholar; Ginzberg et al. Ginzberg et al., 1999Ginzberg H Shin J Ellis L Morrison J Ip W Dror Y Freedman M Heitlinger LA Belt MA Corey M Rommens JM Durie PR Shwachman syndrome: phenotypic manifestations of sibling sets and isolated cases in a large patient cohort are similar.J Pediatr. 1999; 135: 81-88Abstract Full Text Full Text PDF PubMed Scopus (165) Google Scholar). Behavioral and learning difficulties have also been reported in some patients (Aggett et al. Aggett et al., 1980Aggett PJ Cavanagh NP Matthew DJ Pincott JR Sutcliffe J Harries JT Shwachman's syndrome: a review of 21 cases.Arch Dis Child. 1980; 55: 331-347Crossref PubMed Scopus (200) Google Scholar; Kent et al. Kent et al., 1990Kent A Murphy GH Milla P Psychological characteristics of children with Shwachman syndrome.Arch Dis Child. 1990; 65: 1349-1352Crossref PubMed Scopus (37) Google Scholar). An unusual combination of organs are affected in SDS, and, to date, the basic pathophysiological defect is unknown. Segregation analysis of an international collection of families supports an autosomal recessive mode of inheritance (Ginzberg et al. Ginzberg et al., 2000Ginzberg H Shin J Ellis L Goobie S Morrison J Corey M Durie PR Rommens JM Segregation analysis in Shwachman-Diamond syndrome: evidence for recessive inheritance.Am J Hum Genet. 2000; 66: 1413-1416Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar). Molecular analysis (Ikegawa et al. Ikegawa et al., 1999Ikegawa S Masuno M Kumano Y Okawa A Isomura M Koyama K Okui K Makita Y Sasaki M Kohdera U Okuda M Koyama H Ohashi H Tajiri H Imaizumi K Nakamura Y Cloning of translocation breakpoints associated with Shwachman syndrome and identification of a candidate gene.Clin Genet. 1999; 55: 466-472Crossref PubMed Scopus (10) Google Scholar) and family studies (Goobie et al. Goobie et al., 1999Goobie S Morrison J Ginzberg H Ellis L Corey M Masuno M Imaizumi K Kuroki Y Fujiwara TM Morgan K Durie PR Rommens JM Exclusion of linkage of Shwachman-Diamond syndrome to chromosome regions 6q and 12q implicated by a de novo translocation.Am J Med Genet. 1999; 85: 171-174Crossref PubMed Scopus (11) Google Scholar) have excluded those regions of chromosomes 6 and 12 that were pinpointed in a study of the one patient known to have a constitutional chromosomal abnormality in the form of the balanced de novo translocation t(6;12)(q16.2:q21.2) (Masuno et al. Masuno et al., 1995Masuno M Imaizumi K Nishimura G Nakamura M Saito I Akagi K Kuroki Y Shwachman syndrome associated with de novo reciprocal translocation t(6;12)(q16.2;q21.2).J Med Genet. 1995; 32: 894-895Crossref PubMed Scopus (21) Google Scholar). In the present study, linkage analysis was used to establish the chromosomal location for SDS. Most of the families with SDS included in the present study have been described elsewhere, and additional families have been obtained through ongoing recruitment (Ginzberg et al. Ginzberg et al., 1999Ginzberg H Shin J Ellis L Morrison J Ip W Dror Y Freedman M Heitlinger LA Belt MA Corey M Rommens JM Durie PR Shwachman syndrome: phenotypic manifestations of sibling sets and isolated cases in a large patient cohort are similar.J Pediatr. 1999; 135: 81-88Abstract Full Text Full Text PDF PubMed Scopus (165) Google Scholar; Goobie et al. Goobie et al., 1999Goobie S Morrison J Ginzberg H Ellis L Corey M Masuno M Imaizumi K Kuroki Y Fujiwara TM Morgan K Durie PR Rommens JM Exclusion of linkage of Shwachman-Diamond syndrome to chromosome regions 6q and 12q implicated by a de novo translocation.Am J Med Genet. 1999; 85: 171-174Crossref PubMed Scopus (11) Google Scholar). Diagnosis was rigorously determined for all patients; the criterion for inclusion was the presence of both exocrine pancreatic dysfunction and hematologic abnormalities, including neutropenia and other bone marrow failure–associated problems. Consent was obtained from all participating families, and procedural approval was obtained from the human subjects review board of The Hospital for Sick Children, Toronto (HSC). Genomic DNA was extracted either from Epstein-Barr virus–transformed lymphoblastoid cell lines or directly from peripheral white-blood-cell pellets, as described by Miller et al. (Miller et al., 1988Miller SA Dykes DD Polesky HF A simple salting out procedure for extracting DNA from human nucleated cells.Nucleic Acids Res. 1988; 16: 1215Crossref PubMed Scopus (17175) Google Scholar). A panel of simple sequence length polymorphic markers from the Cooperative Human Linkage Center Human Screening Set, version 6.0 (Dubovsky et al. Dubovsky et al., 1995Dubovsky J Sheffield VC Duyk GM Weber JL Sets of short tandem repeat polymorphisms for efficient linkage screening of the human genome.Hum Mol Genet. 1995; 4: 449-452Crossref PubMed Scopus (77) Google Scholar), supplemented with selected Généthon markers (Dib et al. Dib et al., 1996Dib C Fauré S Fizames C Samson D Drouot N Vignal A Millasseau P Marc S Hazan J Seboun E Lathrop M Gyapay G Morrissette J Weissenbach J A comprehensive genetic map of the human genome based on 5,264 microsatellites.Nature. 1996; 380: 152-154Crossref PubMed Scopus (2668) Google Scholar), was used to initiate a genomewide scan of 13 multiplex and 8 simplex families. The markers had an average heterozygosity of .75 and an average intermarker distance of 12 cM. In brief, PCRs were set up, with DNA from each family member, with fluorescently labeled oligonucleotides (Research Genetics). Amplified products of an average of eight markers were pooled into groups based on expected allele sizes and labels. Products were analyzed, after separation by electrophoresis on an ABI 377 sequencer (PE Biosystems), as described by Rioux et al. (Rioux et al., 1998Rioux JD Stone VA Daly MJ Cargill M Green T Nguyen H Nutman T Zimmerman PA Tucker MA Hudson T Goldstein AM Lander E Lin AY Familial eosinophilia maps to the cytokine gene cluster on human chromosomal region 5q31-q33.Am J Hum Genet. 1998; 63: 1086-1094Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). Linkage was analyzed under the assumption that SDS is a completely penetrant autosomal recessive trait. We estimated the disease-allele frequency to be .0036, based on an incidence of 1/76,563. The incidence of SDS was obtained by multiplying the cystic fibrosis (CF) incidence (1/2,500) by the ratio of the number of patients with SDS (N=24) to the number of patients with CF (N=735), cared for at HSC during a recent 21-year period. We assumed that levels of ascertainment were the same for both diseases. Marker-allele frequencies were estimated from the genotypes of the founders in the pedigrees, by PEDMANAGER, version 0.9 (M. J. Daly, personal communication). Linkage analysis was performed by the FASTLINK, version 4.1P, of the LINKAGE programs (Lathrop et al. Lathrop et al., 1984Lathrop GM Lalouel JM Julier C Ott J Strategies for multilocus linkage analysis in humans.Proc Natl Acad Sci USA. 1984; 81: 3443-3446Crossref PubMed Scopus (2173) Google Scholar; Cottingham et al. Cottingham et al., 1993Cottingham Jr, RW Idury RM Schäffer AA Faster sequential genetic linkage computations.Am J Hum Genet. 1993; 53: 252-263PubMed Google Scholar; Schäffer et al. Schäffer et al., 1994Schäffer AA Gupta SK Shriram K Cottingham Jr, RW Avoiding recomputation in linkage analysis.Hum Hered. 1994; 44: 225-237Crossref PubMed Scopus (610) Google Scholar). Two-point LOD scores were computed by MLINK, under the assumption that there is no sex difference in recombination rates. After 228 markers were genotyped, the genomewide scan was terminated because one locus, D7S1830, had a two-point LOD score of 4.2 at a recombination fraction (θ) of .05. Two proximal loci, D7S817 and D7S1808, also gave positive LOD scores, of 0.9 and 1.8, respectively, at θ=.1. To map the putative SDS locus more precisely, 27 additional chromosome 7 markers, spanning 40 cM (sex-averaged map), were genotyped in families with either two or three affected children (fig. 1 and table 1). Markers were selected from public resources, with a preference for those included in recently assembled genetic maps (Broman et al. Broman et al., 1998Broman KW Murray JC Sheffield VC White RL Weber JL Comprehensive human genetic maps: individual and sex-specific variation in recombination.Am J Hum Genet. 1998; 63: 861-869Abstract Full Text Full Text PDF PubMed Scopus (892) Google Scholar). PCRs were set up to use either α[35S]-dATP (Goobie et al. Goobie et al., 1999Goobie S Morrison J Ginzberg H Ellis L Corey M Masuno M Imaizumi K Kuroki Y Fujiwara TM Morgan K Durie PR Rommens JM Exclusion of linkage of Shwachman-Diamond syndrome to chromosome regions 6q and 12q implicated by a de novo translocation.Am J Med Genet. 1999; 85: 171-174Crossref PubMed Scopus (11) Google Scholar) or γ[33P]-dATP (Amersham Pharmacia Biotech) end-labeled oligonucleotides (Hudson et al. Hudson et al., 1997Hudson TJ Clark CD Gschwend M Justice-Higgins E PCR methods of genotyping.in: Dracopoli NC Haines JL Korf BR Moir DT Morton CC Seidman CE Seidman JG Smith DR Boyle AL Current protocols in human genetics. John Wiley & Sons, New York1997: 2.5.1-2.5.23Google Scholar), after optimization for MgCl2 levels (1–1.5 mM) and annealing temperatures. Alleles were assigned after electrophoreses of PCR products on 6% polyacrylamide gels and autoradiography (Goobie et al. Goobie et al., 1999Goobie S Morrison J Ginzberg H Ellis L Corey M Masuno M Imaizumi K Kuroki Y Fujiwara TM Morgan K Durie PR Rommens JM Exclusion of linkage of Shwachman-Diamond syndrome to chromosome regions 6q and 12q implicated by a de novo translocation.Am J Med Genet. 1999; 85: 171-174Crossref PubMed Scopus (11) Google Scholar). Maximum-likelihood estimates of sex-specific θ values were computed by ILINK. A maximum LOD score of 8.7 was obtained with D7S473, at θ=0 (table 1). LOD scores >3 were obtained over a large region (35 cM on the female map and 8.6 cM on the male map) that includes the centromere. We have no evidence of SDS locus heterogeneity; in each of the 15 families, the expected LOD scores (Leal and Ott Leal and Ott, 1990Leal SM Ott J Expected lod scores in linkage analysis of autosomal recessive traits for affected and unaffected offspring.Am J Hum Genet Suppl. 1990; 47: A188Google Scholar) at θ=0 were obtained for at least one marker in the candidate chromosome 7 centromeric region.Table 1Two-Point Linkage between the SDS Locus and Chromosome 7 LociDistance on Genetic MapaFrom the Center for Medical Genetics Web site, in Kosambi centimorgans (Broman et al. 1998); D7S473 and D7S494 were ordered by recombination in one family, and D7S2512 and D7S2549 were ordered by YAC/BAC mapping. The occurrence of satellite-repeat sequences (D7Z2) localizes the centromere near D7S2429, as indicated in The Genetic Location Database Web site (Collins et al. 1996). D7S793-D7S499 and D7S482-D7S1839-D7S2503, which flank the block of eight nonrecombinant loci, were ordered according to the composite location in The Genetic Location Database. No recombination was observed between the SDS locus and D7S506; D7S506 was not informative in one of the two potentially informative families and was not typed in the other. The sex-averaged genetic map was used for the multipoint analysis by GENEHUNTER 2.0; increments of 0.1 cM were added for subsequent loci assigned to the same position. A locus not included on the Center for Medical Genetics map was ordered according to The Genetic Location Database and was positioned, by linear interpolation, between the closest flanking loci on the Center for Medical Genetics map. (cM)LocusAverageFemaleMaleMaximum LOD Score ( θˆf/ θˆm)bθˆf = maximum-likelihood estimate of the female recombination fraction; θˆm = maximum-likelihood estimate of the male recombination fraction.Radiation-Hybrid–Map PositioncFrom the G3 radiation-hybrid map (version 2.0) of the Stanford Human Genome Center Web site, selected for LINKMAP multipoint analysis. The markers were assigned to different bins in the same block, in a physical order consistent with genetic mapping. D7S2483 was placed 0.1 cM distal to D7S502 on the female map. Although the average map distance per centiray (cR) along chromosome 7 is 20 kb, the accurate sizes of the bins at the centromere are unknown (Stewart et al. 1997). Both long-range mapping (Wevrick and Willard 1991) and our effort to establish a physical map support a large physical size of the centromeric region of chromosome 7. (cR10000)D7S180841.6943.5939.841.49 (.200/.061)D7S81750.2954.4246.272.20 (.104/.055)D7S2206………1.64 (.238/.060)D7S69163.6770.5456.972.58 (.224/0)D7S67969.0381.2956.973.46 (.193/0)D7S66569.5681.2958.043.34 (.240/0)D7S250669.5681.2958.045.00 (.068/0)D7S181869.5681.2958.043.77 (.071/0)D7S242272.7887.7458.043.95 (.100/0)D7S1830dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).72.7887.7458.044.61 (.170/0)D7S50673.8489.8858.047.16 (0/0)D7S255274.3890.9458.043.95 (.052/0)2442EGFRdFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).………5.32 (.053/0)D7S2550dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).75.4493.0858.045.91 (.041/0)2458D7S793dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).………4.20 (.068/0)D7S499dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).75.9894.1558.046.26 (.085/0)2495D7S659dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).75.9894.1558.047.19 (0/0)D7S473dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).76.7195.6258.048.74 (0/0)D7S494dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).76.7195.6258.048.57 (0/0)D7S2429dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).76.7195.6258.047.11 (0/0)2741D7S2512dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).77.9198.0358.047.16 (0/0)D7S2549dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).77.9198.0358.045.92 (0/0)2836D7S663dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).78.6599.5058.047.71 (0/0)D7S502dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).78.6599.5058.047.13 (0/0)2907D7S482dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).78.6599.5058.043.56 (.103/0)D7S1839dFifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1).78.6599.5058.047.08 (.072/0)D7S250378.6599.5058.044.61 (.058/0)D7S248378.6599.5058.045.01 (.068/0)2960D7S181683.99105.9262.344.13 (.165/0)D7S220490.95116.6465.533.64 (.366/0)a From the Center for Medical Genetics Web site, in Kosambi centimorgans (Broman et al. Broman et al., 1998Broman KW Murray JC Sheffield VC White RL Weber JL Comprehensive human genetic maps: individual and sex-specific variation in recombination.Am J Hum Genet. 1998; 63: 861-869Abstract Full Text Full Text PDF PubMed Scopus (892) Google Scholar); D7S473 and D7S494 were ordered by recombination in one family, and D7S2512 and D7S2549 were ordered by YAC/BAC mapping. The occurrence of satellite-repeat sequences (D7Z2) localizes the centromere near D7S2429, as indicated in The Genetic Location Database Web site (Collins et al. Collins et al., 1996Collins A Frezal J Teague J Morton NE A metric map of humans: 23,500 loci in 850 bands.Proc Natl Acad Sci USA. 1996; 93: 14771-14775Crossref PubMed Scopus (243) Google Scholar). D7S793-D7S499 and D7S482-D7S1839-D7S2503, which flank the block of eight nonrecombinant loci, were ordered according to the composite location in The Genetic Location Database. No recombination was observed between the SDS locus and D7S506; D7S506 was not informative in one of the two potentially informative families and was not typed in the other. The sex-averaged genetic map was used for the multipoint analysis by GENEHUNTER 2.0; increments of 0.1 cM were added for subsequent loci assigned to the same position. A locus not included on the Center for Medical Genetics map was ordered according to The Genetic Location Database and was positioned, by linear interpolation, between the closest flanking loci on the Center for Medical Genetics map.b θˆf = maximum-likelihood estimate of the female recombination fraction; θˆm = maximum-likelihood estimate of the male recombination fraction.c From the G3 radiation-hybrid map (version 2.0) of the Stanford Human Genome Center Web site, selected for LINKMAP multipoint analysis. The markers were assigned to different bins in the same block, in a physical order consistent with genetic mapping. D7S2483 was placed 0.1 cM distal to D7S502 on the female map. Although the average map distance per centiray (cR) along chromosome 7 is 20 kb, the accurate sizes of the bins at the centromere are unknown (Stewart et al. Stewart et al., 1997Stewart EA McKusick KB Aggarwal A Bajorek E Brady S Chu A Fang N et al.An STS-based radiation hybrid map of the human genome.Genome Res. 1997; 7: 422-433Crossref PubMed Scopus (276) Google Scholar). Both long-range mapping (Wevrick and Willard Wevrick and Willard, 1991Wevrick R Willard HF Physical map of the centromeric region of human chromosome 7: relationship between two distinct alpha satellite arrays.Nucleic Acids Res. 1991; 19: 2295-2301Crossref PubMed Scopus (77) Google Scholar) and our effort to establish a physical map support a large physical size of the centromeric region of chromosome 7.d Fifteen families were included in the linkage analysis (12 families were included for the remaining loci; see fig. 1). Open table in a new tab Multipoint linkage analysis, by GENEHUNTER, version 2.0 (Kruglyak et al. Kruglyak et al., 1996Kruglyak L Daly MJ Reeve-Daly MP Lander ES Parametric and nonparametric linkage analysis: a unified multipoint approach.Am J Hum Genet. 1996; 58: 1347-1363PubMed Google Scholar; Kruglyak and Lander Kruglyak and Lander, 1998Kruglyak L Lander ES Faster multipoint linkage analysis using Fourier transforms.J Comput Biol. 1998; 5: 1-7Crossref PubMed Scopus (185) Google Scholar), using the marker order and sex-averaged map in table 1, indicated a maximum LOD score of 10 in the most likely interval, between D7S499 and D7S482 (fig. 2). The next-most-likely interval, which includes D7S506, had a multipoint LOD score of 5.3. It is noteworthy that male recombination is markedly suppressed (table 1) in the centromeric region, over a female genetic distance of ∼20 cM, with a peak ratio of distance in females to distance in males (female:male distance ratio) of ∼8 at the centromere (Broman et al. Broman et al., 1998Broman KW Murray JC Sheffield VC White RL Weber JL Comprehensive human genetic maps: individual and sex-specific variation in recombination.Am J Hum Genet. 1998; 63: 861-869Abstract Full Text Full Text PDF PubMed Scopus (892) Google Scholar). Thus, we selected seven markers (table 1) encompassing the candidate region, for multipoint analysis by the LINKMAP program in the FASTLINK package, which allows for sex differences in recombination rates. The maximum multipoint LOD score with a sliding window of five markers was 10, and there were only small ( 50 gene/expressed-sequence–tag clusters or transcription units that map across the interval delimited by D7S499 and D7S482 (5.4 cM in the female map and 0 cM on the male map) have been identified. Of the known genes—including GBAS, GUSB, CCT6A, and FKBP9, among others—that have been confirmed, by complementary methods, to map to the SDS gene region, none have biological function or defined expression patterns that suggest that they are obvious candidates for the SDS gene. Many of the remaining cDNA clusters are presently insufficiently characterized for direct assessment, but some have recognizable transcription-factor motifs and warrant prioritization in more-detailed investigations. On chromosome 7, there are local variations in female and male genetic distances, with the most pronounced difference being at the centromere (Broman et al. Broman et al., 1998Broman KW Murray JC Sheffield VC White RL Weber JL Comprehensive human genetic maps: individual and sex-specific variation in recombination.Am J Hum Genet. 1998; 63: 861-869Abstract Full Text Full Text PDF PubMed Scopus (892) Google Scholar). In the families included in the present study, we did not observe male recombination with any of the 21 markers assigned to the same position on the male map (table 1), consistent with an absence of male recombination in the families used to build the genetic map (Broman et al. Broman et al., 1998Broman KW Murray JC Sheffield VC White RL Weber JL Comprehensive human genetic maps: individual and sex-specific variation in recombination.Am J Hum Genet. 1998; 63: 861-869Abstract Full Text Full Text PDF PubMed Scopus (892) Google Scholar). From the perspective of bone marrow failure and hematopoietic-cell chromosomal abnormalities, the mapping of the SDS locus to the centromeric region of chromosome 7 is provocative. Both myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML) are serious complications of SDS, with indications of risk as high as 30%–35% (Smith et al. Smith et al., 1996Smith OP Hann IM Chessells JM Reeves BR Milla P Haematological abnormalities in Shwachman-Diamond syndrome.Br J Haematol. 1996; 94: 279-284Crossref PubMed Scopus (166) Google Scholar). Monosomy 7 and deletion of 7q are acquired changes frequently seen in the bone marrow cells of patients with either MDS or AML (Luna-Fineman et al. Luna-Fineman et al., 1995Luna-Fineman S Shannon KM Lange BJ Childhood monosomy 7: epidemiology, biology and mechanistic implications.Blood. 1995; 85: 1985-1999Crossref PubMed Google Scholar; Mitelman et al. Mitelman et al., 1997Mitelman F Mertens F Johansson B A breakpoint map of recurrent chromosomal rearrangements in human neoplasia.Nat Genet. 1997; 15: 417-474Crossref PubMed Scopus (617) Google Scholar); isochromosome 7 formation has also been reported (Mertins et al. Mertins et al., 1994Mertins F Johansson B Mitelman F Isochromosomes in neoplasia.Genes Chromosom Cancer. 1994; 10: 221-230Crossref PubMed Scopus (157) Google Scholar). Although chromosomal changes generally predict a poor prognosis, both their role in the development of cancer, and patients' susceptibility to their formation, are unknown. Formation of isochromosome 7q has been reported in five patients with SDS; one of these patients has neither MDS nor AML (Dror et al. Dror et al., 1998Dror Y Squire J Durie P Freedman MH Malignant myeloid transformation with isochromosome 7q in Shwachman-Diamond syndrome.Leukemia. 1998; 12: 1591-1595Crossref PubMed Scopus (56) Google Scholar; Maserati et al. Maserati et al., 2000Maserati E Minelli A Olivieri C Bonvini L Marchi A Bozzola M Danesino C Scappaticci S Pasquali F Isochromosome (7)(q10) in Shwachman Syndrome without MDS/AML and role of chromosome 7 anomalies in myeloproliferative disorders.Cancer Genet Cytogenet. 2000; 121: 167-171Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar). It is tempting to speculate that mutations in the SDS gene may increase susceptibility to somatic chromosomal changes. However, the way in which this may occur is not readily predictable. Acquired chromosome 7–associated changes of the bone marrow cells are not unique to SDS, nor are there any direct indications that SDS carriers are at increased risk for hematologic problems. Furthermore, some observed alterations to chromosome 7, such as non–whole arm translocations, do not appear to involve the centromere directly. A finding that does hint at events associated with the centromere is the report of chromosome 7 centromeric heteromorphism in bone marrow cells from a patient with SDS who showed no evidence of either MDS or AML (Sokolic et al. Sokolic et al., 1999Sokolic RA Ferguson W Mark HF Discordant detection of monosomy 7 by GTG-banding and FISH in a patient with Shwachman-Diamond syndrome without evidence of myelodysplastic syndrome or acute myelogenous leukemia.Cancer Genet Cytogenet. 1999; 115: 106-113Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar). The heteromorphism occurred in an otherwise intact chromosome and was sustained for >6 mo. Although there is one other report of chromosome 7 heteromorphism, involving the bone marrow cells of a 25-year-old woman (without SDS) in remission from pre-B lymphoblastic leukemia (Duval et al. Duval et al., 2000Duval A Feneux D Sutton L Tchernia G Leonard C Spurious monosomy 7 in leukemia due to centromeric heteromorphism.Cancer Genet Cytogenet. 2000; 119: 67-69Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar), the true occurrence of centromeric heteromorphism in bone marrow cells is unknown, since whole-chromosome and centromeric analyses are not necessarily performed simultaneously. Heteromorphism may be due to deletions of centromeric repeat sequences, as a result of misalignment and unequal crossing over, but it has not been found for chromosome 7, either in cells of peripheral blood or in established lymphoblastoid lines (Lo et al. Lo et al., 1999Lo AW Liao GC Rocchi M Choo KH Extreme reduction of chromosome-specific alpha-satellite array is unusually common in human chromosome 21.Genome Res. 1999; 9: 895-908Crossref PubMed Scopus (51) Google Scholar). More information is needed to understand whether the SDS locus plays any role in the development of abnormal chromosomes or changes in chromosome numbers. The identification of a locus for SDS provides the starting point for the identification, by positional cloning, of a gene with SDS-causing mutations and for the application of genetic diagnosis in families at risk. Studies directed toward an understanding of the function of the gene should help explain the variability of disease symptoms and should provide insight into the development of bone marrow failure and of the preleukemic and leukemic states. We thank M. Corey, Ph.D., for discussions and for registry information on patients with CF. We thank S. Clark and C. Darmond-Zwaig, for technical assistance, and J C. Loredo-Osti, for helpful discussions on linkage analysis. We are grateful for the cooperation of the patients with SDS, their families, and their physicians. We also acknowledge support from Shwachman-Diamond Canada, Shwachman Support of Great Britain, The Harrison Wright Appeal, Shwachman-Diamond Support of Australia, Shwachman-Diamond Support International, and the Canadian Institutes of Health Research (CIHR). T.J.H., K.M., and J.M.R. are members of the Networks of Centres of Excellence–Canadian Genetic Diseases Network (CGDN). T.J.H. holds a Clinician Scientist Award from the CIHR. T.M.F. is supported by a gift to McGill University from Alcan Aluminum, Limitée. S.G. was a recipient of a graduate studentship from the Natural Sciences and Engineering Research Council of Canada. M.P. is a recipient of studentships from the Ontario Graduate Program and from the Joint Hospital for Sick Children–CGDN Program. H.G. received Duncan Gordon and Canadian Association of Gastroenterology/Janssen fellowships.
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