Comparison of constitutional and tumor-associated 11;22 translocations: nonidentical breakpoints on chromosomes 11 and 22

Ocular manifestations of Emanuel syndrome

Emanuel syndrome is caused by a supernumerary der(22)t(11;22) and typically manifests with intellectual disability and craniofacial dysmorphism. Ocular abnormalities have infrequently been described. We report a 36-year-old man with severe intellectual disability, aphasia, and facial dysmorphism, with high myopia and juvenile open angle glaucoma (JOAG). Microarray analysis results included 47,XY,+der(22)t(11;22)(q23;q11.2), and a 269 kb deletion of 7q31.33(125,898,014-126,166,829). Two candidate genes were identified as possible etiologies for the ocular pathologies in our patient: a MFRP duplication on chromosome 11, which may play a role in high myopia and dysregulation of emmetropization, and a GRM8 deletion on chromosome 7, which may cause glutamate-induced excitotoxicity and therefore have a role in the development of JOAG, unrelated to the Emanuel syndrome genotype. We provide the first detailed description these ocular abnormalities in a patient with Emmanuel syndrome.

Review of Ets1 structure, function, and roles in immunity

The Ets1 transcription factor is a member of the Ets gene family and is highly conserved throughout evolution. Ets1 is known to regulate a number of important biological processes in normal cells and in tumors. In particular, Ets1 has been associated with regulation of immune cell function and with an aggressive behavior in tumors that express it at high levels. Here we review and summarize the general features of Ets1 and describe its roles in immunity and autoimmunity, with a focus on its roles in B lymphocytes. We also review evidence that suggests that Ets1 may play a role in malignant transformation of hematopoietic malignancies including B cell malignancies.

Renal cell carcinoma and a constitutional t(11;22)(q23;q11.2): case report and review of the potential link between the constitutional t(11;22) and cancer

We observed a t(11;22)(q23-24;q11.2-12) and monosomy 3 in renal tumor cells from a 72-year-old man. The hypothesis of a primitive peripheral neuroectodermal tumor (PPNET) located in the kidney was promptly excluded: Histologically, the tumor was a clear cell renal cell carcinoma (RCC) and we did not observe an EWSR1 gene rearrangement. The constitutional origin of this alteration was established. We report on the second case of RCC in a patient with a constitutional t(11;22). The t(11;22)(q23;q11.2) is the main recurrent germline translocation in humans. Unbalanced translocation can be transmitted to the progeny and can cause Emanuel syndrome. Our observation alerts cancer cytogeneticists to the fortuitous discovery of the constitutional t(11;22) in tumor cells. This translocation appears grossly similar to the t(11;22)(q24;q12) of PPNET and should be evoked if present in all cells of a tumor other than PPNET. This is important when providing appropriate genetic counseling. Moreover, the potential oncogenic role of the t(11;22) and its predisposing risk of cancer are under debate. The family history of the patient revealed a disabled brother who died at an early age from colon cancer and a sister with breast cancer. This observation reopens the issue of a link between the constitutional t(11;22) and cancer, and the utility of cancer prevention workups for t(11;22) carriers.

Phenotypic delineation of Emanuel syndrome (supernumerary derivative 22 syndrome): Clinical features of 63 individuals

Emanuel syndrome is characterized by multiple congenital anomalies and developmental disability. It is caused by the presence of a supernumerary derivative chromosome that contains material from chromosomes 11 and 22. The origin of this imbalance is 3:1 malsegregation of a parental balanced translocation between chromosomes 11 and 22, which is the most common recurrent reciprocal translocation in humans. Little has been published on the clinical features of this syndrome since the 1980s and information on natural history is limited. We designed a questionnaire to collect information from families recruited through an international online support group, Chromosome 22 Central. Data gathered include information on congenital anomalies, medical and surgical history, developmental and behavioral issues, and current abilities. We received information on 63 individuals with Emanuel syndrome, ranging in age from newborn to adulthood. As previously recognized, congenital anomalies were common, the most frequent being ear pits (76%), micrognathia (60%), heart malformations (57%), and cleft palate (54%). Our data suggest that vision and hearing impairment, seizures, failure to thrive and recurrent infections, particularly otitis media, are common in this syndrome. Psychomotor development is uniformly delayed, however the majority of individuals (over 70%) eventually learn to walk with support. Language development and ability for self-care are also very impaired. This study provides new information on the clinical spectrum and natural history of Emanuel syndrome for families and physicians caring for these individuals.

Constitutional chromosome aberrations as pathogenetic events in hematologic malignancies

A predisposition to tumor development is associated with some constitutional chromosomal abnormalities. Investigations of families with an apparent hereditary cancer and constitutional chromosome rearrangements have led to the molecular identification of tumor suppressor genes. Under the somatic mutation theory for the development of cancer, two mutational events are required. The first step may be a constitutional event and the second an acquired genetic mutation. Cytogenetic studies were performed on 5633 bone marrow specimens from patients with hematologic malignancies from a single institution. Fifty cases of constitutional chromosome aberrations were detected. Data collected from the literature and from our series are reviewed and compared with the incidence of specific constitutional chromosome aberrations in the newborn population. Possible mechanisms that may predispose individuals with constitutional chromosome aberrations to the development of a hematologic malignancy are reviewed.

Cytogenetic characterization of Ewing tumors using fine needle aspiration samples. a 10-year experience and review of the literature

Chromosomal analysis was performed in fine needle aspiration samples of 98 primary Ewing tumors (ETs) prior to treatment. Among the 58 (59.18%) successful cultures, t(11;22)(q24;q12) was observed in 87.9% and 6.8% had abnormalities other than t(11;22), viz., del(22)(q12), der(16)t(1;16)(q12;q11), and variant t(8;22)(q24;q12). Involvement of breakpoints 1q21, 1q22, 3p14, 16q22, and 17p13 was also observed. Numerical abnormalities such as trisomies 8 and 12 were found in 29.3% and 20.6% and trisomy 18 in 17.2%. An attempt was made to evaluate the role of these additional changes in the process of tumor development, metastasis, and progression of the disease. This is the largest cytogenetic study on ET from a single center using a simple and reliable technique of fine-needle aspiration culture. The literature on cytogenetics of ET is reviewed.

Long-range mapping and construction of a YAC contig within the cat eye syndrome critical region

Cat eye syndrome (CES) is typically associated with a supernumerary bisatellited marker chromosome derived from human chromosome 22pter to 22q11.2. The region of 22q duplicated in the typical CES marker chromosome extends between the centromere and locus D22S36. We have constructed a long-range restriction map of this region using pulsed-field gel electrophoresis and probes to 10 loci (11 probes). The map covers -3.6 Mb. We have also used 15 loci to construct a yeast artificial chromosome contig, which encompasses about half of the region critical to the production of the CES phenotype (centromere to D22S57). Thus, the CES critical region has been mapped and a substantial portion of it cloned in preparation for the isolation of genes in this region.

Prostate cancer--biology of metastasis and its clinical implications

Prostate cancer is one of the most commonly diagnosed cancers and is a major cause of cancer death in men. Although the majority of the diagnosed prostate cancers will remain localized and never produce clinical symptoms during the lifetime of the host, a subset of these cancers will progress to a more malignant state requiring therapeutic intervention. Acquisition of metastatic ability by prostatic cancer cells is the most lethal aspect of prostatic cancer progression. Once this has occurred, definitive therapy is required before the initially localized metastatic cells escape from the prostate. At present, metastatic prostate cancer is incurable. Therefore, there is an urgent need to develop molecular markers that can be used to predict the metastatic potential of prostate cancers. Using somatic cell hybridization, we have demonstrated that acquisition of metastatic ability requires both the loss of metastasis-suppressor function(s) and the activation of oncogenes. In further studies using micro-cell-mediated chromosomal transfer, we located genes on human chromosome, 8, 10cen-q23, 11p11.2-13, and 17pter-q23, which, when introduced into rat prostatic cancer cells, are capable of suppressing their metastatic ability without affecting their tumorigenicity or growth rate in vivo. Initially we focused upon the human chromosome 11p11.2-13 region to clone metastasis-suppressor gene(s) positionally. One such gene, termed KAI-1, encodes a membrane glycoprotein. KAI-1 has been mapped to the p11.2 region of human chromosome 11 by fluorescence in-situ hybridization analysis. Expression of KAI-1 has been detected in all normal human tissues thus far tested, including prostate tissue. When introduced into rat metastatic prostatic cancer cells, KAI-1 significantly suppressed the metastasis without affecting the tumor growth rate. KAI-1 expression is high in human normal prostate and benign prostatic hyperplasia but is dramatically lower in cancer cell lines derived from metastatic prostate tumors.

Predisposition for breast cancer in carriers of constitutional translocation 11q;22q

A translocation between the long arms of chromosomes 11 and 22, t(11;22)(q23;q11), is the most frequent constitutional reciprocal translocation in man. This chromosome abnormality has not previously been reported to be associated with an increased risk for neoplasia. The observation of one patient with a constitutional translocation t(11q;22q) and breast cancer prompted us to study the relationship between these two conditions. The incidence of breast cancer was determined in carriers of t(11q;22q). The karyotypes were determined by QFQ-banding, and the breakpoints were then further characterized by fluorescent in situ hybridization. Eight families with a total of 22 balanced carriers were found. In five of these families there was one case of breast cancer each. In another family a case of an unknown malignancy was reported in one member. No other malignancies were found among these patients. The number of breast cancer cases was significantly higher than expected among the translocation carriers (P < .001). The chromosomal breakpoints showed the same localization with the markers used, in the seven families studied. The association of constitutional translocation t(11q;22q) and breast cancer identifies a subset of patients with a highly increased risk for breast cancer who would benefit from counseling and screening. It also suggests the involvement of genes on 11q and/or 22q, in the tumorigenesis of breast cancer.

Variant translocations of chromosome 22 in Ewing's sarcoma

Relatively few variant translocations have been reported in primary Ewing's sarcomas (ES). We report two new variant translocations, both of which involve chromosomal rearrangements of 22q12. Cytogenetic studies of tumor cells from a 12-year-old girl revealed a variant translocation, t(7;22)(p22;q12), the second example reported of a simple variant of the 22q12 reciprocal translocation in this type of sarcoma. The identity of this rearrangement was confirmed by in situ hybridization. In addition, a complex translocation was identified in a dysmorphic 15-year-old girl, t(4;11;22)(q21;q24;q12). No previous cases of variant translocations in ES have involved band 7p22 or 4q21, and there are no previous reports of an association between congenital abnormalities and unusual karyotype abnormalities in ES. Both variant translocations conserve the junction on the der (22), providing additional cytogenetic evidence that the sequences on chromosome 22 are critical.

Identification and regional localization of a highly polymorphic dinucleotide repeat D11S614 to the interval in 11q23.3 flanked by recurrent translocation breakpoints

A highly informative dinucleotide repeat polymorphism has been identified at the D11S614 locus on chromosome 11q23. Ten different alleles have been observed at this locus, and the heterozygosity frequency is approximately 85%. Physical localization of this marker in a panel of somatic cell hybrids containing chromosome 11 translocations showed that it maps to 11q23.3, within the interval between the recurrent t(4;11) leukaemia breakpoint and the t(11;22) Ewing's sarcoma breakpoint. This physical mapping data is consistent with the genetic mapping which indicates tight linkage to other markers in the q23.3 region including PBGD, CD3D and D11S29. Regional localization of highly informative markers such as D11S614 will facilitate integration of the genetic and physical maps.

Expression of the cholecystokinin gene in pediatric tumors

We have examined a wide range of cultured human tumor cell lines and found that a specific subset of tumors expresses the cholecystokinin (CCK) gene. All neuroepitheliomas (eight) and Ewing sarcoma (eight) cell lines that were tested express CCK RNA. In addition, two of six rhabdomyosarcoma cell lines also express the CCK gene, suggesting that rhabdomyosarcomas are probably heterogenous and that a subset may be similar to Ewing sarcoma and neuroepithelioma. Very few of the positive tumors express completely processed immunoreactive CCK. However, we have used a radioimmunoassay that detects the CCK precursor to demonstrate synthesis of CCK precursor-like peptides by all of the Ewing sarcoma and neuroepithelioma lines that were tested and by the rhabdomyosarcoma cell line that expresses CCK mRNA. These data demonstrate a consistent association of CCK gene expression with a specific group of human neoplasms. The data also add credence to the theory that Ewing sarcoma and neuroepithelioma are derived from the same transformed cell type. Finally, our results suggest that CCK gene expression may serve as a marker to distinguish these tumors, which are considered to be small-round-cell tumors of childhood, from other pediatric tumors.

Mapping of 262 DNA markers into 24 intervals on human chromosome 11

We have extended our mapping effort on human chromosome 11 to encompass a total of 262 DNA markers, which have been mapped into 24 intervals on chromosome 11; 123 of the markers reveal RFLPs. These clones are scattered throughout the chromosome, although some clustering occurs in R-positive bands (p15.1, p11.2, q13, and q23.3). Fifty-two of the markers were found to contain DNA sequences conserved in Chinese hamster, and some of these 52 also cross-hybridized with DNA from other mammals and/or chicken. As the length of chromosome 11 is estimated at nearly 130 cM, the average distance between RFLP markers is roughly 1 cM. The large panel of DNA markers on our map should contribute to investigations of hereditary diseases on this chromosome, and it will also provide reagents for constructing either fine-scale linkage and physical maps or contig maps of cosmids or yeast artificial chromosomes.

Molecular localization of the t(11;22)(q24;q12) translocation of Ewing sarcoma by chromosomal in situ suppression hybridization

Chromosome translocations are associated with a variety of human leukemias, lymphomas, and solid tumors. To localize molecular markers flanking the t(11;22) (q24;q12) breakpoint that occurs in virtually all cases of Ewing sarcoma and peripheral neuroepithelioma, high-resolution chromosomal in situ suppression hybridization was carried out using a panel of cosmid clones localized and ordered on chromosome 11q. The location of the Ewing sarcoma translocation breakpoint was determined relative to the nearest two cosmid markers on 11q, clones 23.2 and 5.8, through the analysis of metaphase chromosome hybridization. By in situ hybridization to interphase nuclei, the approximate physical separation of these two markers was determined. In both Ewing sarcoma and peripheral neuroepithelioma, cosmid clone 5.8 is translocated from chromosome 11q24 to the derivative chromosome 22 and a portion of chromosome 22q12 carrying the leukemia inhibitory factor gene is translocated to the derivative chromosome 11. The physical distance between the flanking cosmid markers on chromosome 11 was determined to be in the range of 1000 kilobases, and genomic analysis using pulsed-field gel electrophoresis showed no abnormalities over a region of 650 kilobases in the vicinity of the leukemia inhibitory factor gene on chromosome 22. This approach localizes the Ewing sarcoma breakpoint to a small region on chromosome 11q24 and provides a rapid and precise technique for the molecular characterization of chromosomal aberrations.

Isolation and mapping of 62 new RFLP markers on human chromosome 11

To obtain new RFLP markers on human chromosome 11 for a high-resolution map, we constructed a cosmid library from a Chinese hamster x human somatic hybrid cell line that retains only human chromosome 11 in a Chinese hamster genomic background. A total of 3,500 cosmids were isolated by colony hybridization with labeled human genomic DNA. DNA was prepared from 130 of these cosmid clones and examined for RFLP. In 62 of them, polymorphism was detected with one or more enzymes; four RFLPs were VNTR systems. All polymorphic clones were assigned to one of 22 intervals obtained by mapping on a deletion panel of 15 somatic hybrid cell lines containing parts of chromosome 11; 11 clones were finely mapped by in situ hybridization. Although RFLP markers were scattered on the whole chromosome, they were found predominantly in the regions of R-banding. These DNA markers will contribute to fine mapping of genes causing inherited disorders and tumor-suppressor genes that reside on chromosome 11. Furthermore, as one-third of the cosmid clones revealed a band or bands in Chinese hamster DNA, indicating sequence conservation, this subset of clones may be useful for isolating biologically important genes on chromosome 11.

Nonhomologous chromatid exchange in hereditary and sporadic renal cell carcinomas

For the development of renal cell carcinomas, it has been suggested that a germ-line or somatic mutation occurs on one of the homologous chromosomes 3p, and subsequently the other 3p segment is lost. We have examined the karyotype and/or the allelic combination on chromosomes 3 and 5 by restriction fragment length polymorphism analysis in normal kidney and tumor samples from 28 renal cell carcinomas that developed in two patients with von Hippel-Lindau disease; we then compared the results to those of sporadic tumors. An unbalanced translocation between chromosome 3p and 5q or other chromosomes was found to be the most common aberration. We developed a model of nonhomologous chromatid exchange involving breakpoint clusters at chromosomes 3p13, 3p11.2, 5q22, and 8q11.2. Subsequent chromatid segregation may result in net loss of the 3p segment either (i) in one step or (ii) after a nondisjunctional loss of the derivative chromosome carrying the 3p segment. This general mechanism could also be implicated to explain genetic changes occurring in other types of solid tumors.

Simultaneous localization of cosmids and chromosome R-banding by fluorescence microscopy: application to regional mapping of human chromosome 11

A technique for nonradioactive in situ hybridization on human metaphase chromosomes has been developed to localize human cosmid clones. The simple procedure using two fluorescent dyes (fluorescein and propidium iodide) allows the simultaneous identification of chromosomal R-bands and hybridization signal in a single screening of the slides. This technique has been used for rapid correlation of the genetic and physical map of chromosome 11q13-qter in the region of genes responsible for ataxia-telangiectasia and tuberous sclerosis.

Human central nervous system primitive neuroectodermal tumor expressing nerve growth factor receptors: CHP707m

A primitive neuroectodermal tumor (PNET) presented as a cerebral hemispheric mass in a 33-year-old man. Bone marrow metastases were discovered 11 months later. A cell line (CHP707m) was derived from these metastases. In culture, the cells showed features of neuronal differentiation, forming short neurites and synthesizing low-molecular-weight neurofilament protein. Northern blotting showed the tumor cells express nerve growth factor (NGF) receptor messenger RNA, and fluorescence-activated cell-sorting demonstrated NGF receptors on the cell surface. Western blotting showed CHP707m NGF receptors are truncated. The receptors are functional; they bind iodine 125-labeled mouse NGF with an affinity of 1.6 x 10(-9) M, and short-term treatment with NGF induces expression by the tumor cells of the proto-oncogene, c-fos. Although CHP707m is the first central nervous system PNET cell line proven to express NGF receptors, immunohistological survey of tissue sections prepared from human central nervous system PNETs showed that 13 of 35 contained NGF receptor-positive tumor cells. Thus, more than one-third of such tumors might be responsive to the effects of NGF.

t(11;22) in three cases of peripheral neuroepithelioma

Short-term cultures of three cases of peripheral neuroepitheliomas were studied using G-banding technique. A t(11;22)(q24;q12) was recognized in all three tumors. The results strengthen the hypothesis of a common histogenesis for neuroepithelioma, Ewing's sarcoma, and the Askin tumor.

Primary skeletal Ewing's sarcoma in Down syndrome

Primary skeletal Ewing's sarcoma that occurred in two teenage patients with Down syndrome are reported. Cytogenetic analysis of one of these tumors showed the 11;22 translocation characteristic of Ewing's sarcoma as well as other complex karyotypic changes. The possible role of constitutional trisomy 21 in development of these sarcomas is discussed.

The ataxia-telangiectasia gene (ATA) on chromosome II is distinct from the ETS-1 gene

We have studied the segregation of an RFLP detected with a human ETS-1 genomic probe in 25 families containing members affected with ataxia-telangiectasia (AT) and in 27 families from the Centre d'Etude du Polymorphisme Humain (CEPH) panel. We have recently mapped a gene for AT to 11q22-23 by linkage to the markers THY1 and D11S144. Multipoint linkage analysis of the CEPH families indicated that ETS-1 is located on chromosome 11q approximately 19.2 centimorgans telomeric to THY1. Analysis of the segregation of ETS-1 alleles in AT families yields strongly negative LOD scores, excluding an AT gene from a region extending 15 cM to either side of ETS-1. Multipoint mapping of ETS-1, D11S144, THY1, and AT also excludes the possibility that an AT gene is telomeric to ETS-1.

Establishment and characterization of a small round cell sarcoma cell line, SCCH-196, with t(11;22)(q24;q12)

A cell line designated SCCH-196 was established from an extraskeletal small round cell sarcoma developed in a 16-year-old Japanese girl. The cells grew as a monolayer, and have been continuously propagated by serial subcultures during the past 26 months. Cells from the primary tumor and those from the SCCH-196 cell line at passage 10 both showed the same karyotype, 51,XX, +8, +20, +21, t(11;22)(q24;q12), +i(1q), +i(1q). Histologically the primary tumor was difficult to classify as either Ewing's sarcoma (ES) or peripheral neuroepithelioma (NE). Neuron-specific enolase-positive cells in the primary tumor and the occurrence in the upper extremity were in favor of NE, while positive reaction of SCCH-196 cells to an ES-specific monoclonal antibody 5C11 suggested a diagnosis of ES. The SCCH-196 cell line may be useful for basic studies on differentiation of neuroectodermal tumors, and for future cloning of still unidentified genes which may be located at the breakpoints of the 11;22 translocation.

Molecular differential pathology of rhabdomyosarcoma

Tumors of the soft tissues are classified histogenetically according to their phenotypic resemblance to normal adult tissue. Here we describe molecular approaches that make it possible to distinguish between one class of these tumors, rhabdomyosarcoma, and other small-, round-cell tumors. We show that the ascertainment of specific genotypic changes can be used to distinguish further between the embryonal and alveolar subtypes of rhabdomyosarcoma. We tested our model in two ways: first, in a retrospective analysis of diagnostically problematic cases of undifferentiated, small-cell tumors and, second, in a blind study of pediatric tumors. Rhabdomyosarcoma was correctly identified in all cases using this strategy alone. The underlying simplicity of the strategy used to define rhabdomyosarcoma subtypes with molecular markers suggests a model by which tumors can be unequivocally identified, which may apply equally well to other human solid tumors.

Comparative mapping of the constitutional and tumor-associated 11;22 translocations

The reciprocal t(11;22)(q23;q11) is the most common non-Robertsonian constitutional translocation in humans. The tumor-associated 11;22 rearrangement of Ewing sarcoma (ES) and peripheral neuroepithelioma (NE) is cytologically very similar to the 11;22 constitutional rearrangement. Using immunoglobulin light-chain constant region, ETS1 probes, and the technique of in situ hybridization, we previously were able to show that the constitutional and ES/NE breakpoints are different. As a first step toward isolating these translocation junctions and to further distinguish between them, we have made somatic cell hybrids. Cells from a constitutional 46,XX,inv(9),t(11;22) carrier and from an ES cell line with a t(11;22) were separately fused to a hypoxanthine-guanine phosphoribosyltransferase-deficient Chinese hamster cell line (RJK88). Resulting clones were screened with G-banding and Southern hybridization. Hybrid clones derived from the constitutional t(11;22) were established which contained the der(22) and both the der(22) and the der(11). Hybrid clones derived from the ES cell line containing the der(11) were isolated. Using the technique of Southern hybridization we have sublocalized the loci; ApoA1/C3, CD3D, ETS1, PBGD, THY1, D11S29, D11S34, and D11S147 to the region between the two breakpoints on chromosome 11 and V lambda I, V lambda VI, V lambda VII, and D22S10 to the region between the breakpoints on chromosome 22. Using anonymous DNA probes, we found that D22S9 and D22S24 map proximal to the constitutional breakpoint and that D22S15 and D22S32 map distal to the ES breakpoint on chromosome 22.

Physical mapping of complex genomes by cosmid multiplex analysis

A rapid and powerful approach for linking individual clones of a cosmid library and the assembly of a large physical map is presented, which depends on the simultaneous analysis of many cosmid clones for overlapping regions. This method uses cosmid vectors that contain endogenous bacteriophage T3 and T7 promoters to allow for the identification of overlapping clones through the synthesis of end-specific RNA probes. A genomic library is constructed and organized as an ordered matrix such that each clone is assigned an identifying coordinate. DNA from mixtures of cosmid clones is pooled such that each pool contains only one common member with any other pool, RNA probes are prepared from mixtures of cosmid clones, and groups of clones overlapping with the constituents of the mixtures are determined by hybridization. Pooled probes are most simply prepared by grouping clones according to the rows and columns of the library matrix. The pairwise comparison of data generated by the hybridization of mixed probes can be decoded by using simple algorithms that predict the order and linkage of all clones in the collection and organize them into predicted contigs. To demonstrate the feasibility of multiplexed analysis of cosmids, a genomic library was prepared from a mouse-human somatic cell hybrid that contains a portion of the long arm of human chromosome 11. Preparation, arrangement on a matrix, and analysis of pooled cosmid clones from this collection resulted in the detection of 1099 linked pairs of cosmids, which could be assembled into 315 contigs. Thus, with a minimal amount of effort, a substantial portion of this genomic region has been linked in multiple overlapping contigs. This method may have practical applications in the large-scale mapping and sequencing of mammalian genomes.

Cancer in relatives of leukemic patients with chromosomal rearrangements at rare (heritable) fragile-site locations in their malignant cells

The cancer occurrence in relatives (N = 407) of 40 case probands (who had leukemia and rearrangements at the same chromosomal location as at least one of 23 recognized rare [heritable] autosomal fragile sites [Sutherland and Mattei 1987]) was compared both to cancer occurrence in relatives (N = 390) of 40 control probands (who had leukemia or other hematologic illness but no recognized chromosomal rearrangements) and to cancer incidence in the general population of the United States. Fragile-site carrier status was not determined in case or control probands. No significant excess of cancer in case relatives, compared with either control relatives or to general (SEER) population expectancies, was found. Furthermore, there was neither evidence of cancer at younger ages, when cases were compared with control relatives, nor an excess of cancer at multiple sites. Male relatives of cases did, however, show a small excess of cancer, especially in older age groups. There was a slight, but not statistically significant, excess of lung cancer in case relatives, with this deviation occurring almost exclusively in relatives of probands having rearrangements at 11q23 and having lymphoid leukemia. It is possible that heritable tendency to chromosomal rearrangement--and thus to cancer--is expressed in such a small proportion of family members that cancer excess in these families could not be detected with the numbers of relatives analyzed in this study, although there was no significant evidence for a hereditary predisposition to cancer in the families of probands with leukemia and with chromosomal rearrangements at the same apparent chromosomal location as rare fragile sites.

Primary peripheral neuroepithelioma of the orbit with intracranial extension

A 7-year-old girl with clinical signs limited to moderate unilateral proptosis of 2 weeks duration and ipsilateral disc edema was found to have a contiguous orbital and subfrontal intracranial tumor best characterized as a peripheral neuroepithelioma by recent studies. Previously this tumor would have been called an extraosseous Ewing's sarcoma. The tumor had a significant lobular component on either side of the orbital roof. The patient is still alive 24 months posttreatment with multimodal excisional surgery, radiation, and chemotherapy.

Recurrent t(11;22) breakpoint mapping by chromosome flow sorting and spot-blot hybridization

The breakpoint of the recurrent t(11;22) translocation, one of the most frequent chromosome anomalies encountered in human population, always involves bands 11q23.2 and 22q11.2. The involvement of the C lambda locus of the immunoglobulin lambda gene cluster on chromosome 22 has been suggested: however, in situ hybridization experiments have yielded conflicting results. In order to solve these discrepancies by another approach, we have used bivariate flow sorting to separate the chromosomes of interest and to map the specific breakpoints by direct spot-blot hybridization with the gene-specific radiolabelled DNA probes, Alu, V lambda, ets. The results showed unambiguously that in the t(11;22) patient analysed, a set of C lambda and V lambda genes was translocated to the der(11) chromosome. Since V lambda genes are situated proximally to C lambda genes, we demonstrate that, in the case studied here, the chromosome 22 breakpoint is not located within or even immediately close to the C lambda region.

Further localization of ETS1 indicates that the chromosomal rearrangement in Ewing sarcoma does not occur at fra(11)(q23)

A genomic probe homologous to 5.4 kb of the c-ets-1 gene was hybridized in situ to chromosomes expressing fra(11)(q23). This probe hybridized distal to the fragile site, which is just distal to the midpoint of band 11q23.3. This result localizes ETS1 from the FRA11B locus to 11q24. The result also distinguishes the FRA11B locus from the site of translocation at 11q23-q24 in the Ewing sarcoma- and peripheral neuroepithelioma-specific t(11;22), indicating that the chromosomes of a previously reported patient heterozygous for fra(11)(q23) did not rearrange at this fragile site to give rise to Ewing sarcoma. This adds to the mounting evidence against individuals with fragile sites being predisposed to developing cancer.

Poorly differentiated, neuron-specific enolase positive round cell tumor with two translocations t(11;22) and t(21;22)

The authors describe a highly malignant, disseminated round cell tumor originating in the ninth rib of a 14-year-old boy. Extensive studies by means of light and electron microscopic examination, histocytochemistry and immunocytochemistry and cytogenetic analysis revealed an undifferentiated, neuron-specific enolase positive round cell tumor with a unique karyotype: 45,XY,-21,t(11;22)(q23;q11), der(22)t(21;22)(q11.2;p11). Thus, despite the absence of definite morphologic features, such as Homer-Wright rosettes, neurosecretory granules and cytoplasmatic processes, these findings suggest a neuroectodermal origin of this bone tumor.

Assignment of the human gamma-glutamyl transferase gene to the long arm of chromosome 22

We have determined the chromosomal location of the human gene for gamma-glutamyltransferase (GGT). This study was done by in situ hybridization of human metaphase spreads with a rat cDNA probe specific for this enzyme and constructed from two clones previously characterized in our laboratory. The final construct had a 1.6-kb-long insert covering 92% of the coding sequence for GGT. The new insert was also freed of any GC tails introduced for the cDNA cloning, because we observed that these sequences were responsible for a high background. Using this probe for the analysis of 136 human metaphase spreads, we observed a strong specific signal on chromosome 22 at the interface of q111-112 and a minor peak in q131. Thus GGT might represent a new marker for the study of certain diseases which have chromosomal abnormalities at these loci.

Human chromosome 22

The acrocentric chromosome 22, one of the shortest human chromosomes, carries about 52 000 kb of DNA. The short arm is made up essentially of heterochromatin and, as in other acrocentric chromosomes, it contains ribosomal RNA genes. Ten identified genes have been assigned to the long arm, of which four have already been cloned and documented (the cluster of lambda immunoglobulin genes, myoglobin, the proto-oncogene c-sis, bcr). In addition, about 10 anonymous DNA segments have been cloned from chromosome 22 specific DNA libraries. About a dozen diseases, including at least four different malignancies, are related to an inherited or acquired pathology of chromosome 22. They have been characterised at the phenotypic or chromosome level or both. In chronic myelogenous leukaemia, with the Ph1 chromosome, and Burkitt's lymphoma, with the t(8;22) variant translocation, the molecular pathology is being studied at the DNA level, bridging for the first time the gap between cytogenetics and molecular genetics.