The phenotypic effects of chromosome rearrangement involving bands 7q21.3 and 22q13.3.

We report a family in which the proband has a direct insertion of band 7q21.3 into chromosome 22 at 22q13.3, karyotype 46,XX,dir ins(22;7)(q13.3;q21.2q22.1). Two of her children have unbalanced chromosome rearrangements involving 7q21.3, with one girl monosomic for the region and a boy trisomic for the region. The child monosomic for band 7q21.3 has a split hand/split foot (SHSF) anomaly and her clinical features are consistent with the 7q21-q22 contiguous gene deletion syndrome. In situ hybridisation studies have shown that the proband and her son have a submicroscopic deletion of chromosome band 22q13.3. Interstitial deletions of this chromosome band have rarely been reported.     

Deletions at chromosome regions 7q11.23 and 7q36 in a patient with Williams syndrome

We report on a patient with Williams syndrome and a complex de novo chromosome rearrangement, including microdeletions at 7q11.23 and 7q36 and additional chromosomal material at 7q36. The nature of this additional material was elucidated by spectral karyotyping and first assigned to chromosome 22. Subsequent fluorescence in situ hybridization (FISH) experiments showed that it consisted of satellite material only. Refinement of the 7q36 breakpoint was performed with several FISH probes, showing a deletion distal to the triphalangeal thumb (TPT) region. The phenotype of the patient principally results from the microdeletion of the 7q11.23; the small deletion at 7qter and the extra satellite material may not be of clinical significance.     

Molecular and cytogenetic analysis of chromosome 7 in uterine leiomyomas

Uterine leiomyomas are benign tumors that arise clonally from smooth muscle cells of the myometrium. Cytogenetic studies of uterine leiomyomas have shown that about 40% have chromosome abnormalities and that deletion of 7q is a common finding. The observations suggest the possible location of a growth-suppressor gene within the 7q21-q22 region. Molecular genetic analysis of cytogenetically normal tumors has frequently shown somatic loss of specific tumor suppressor genes detected by loss of heterozygosity in the critical region. To test the hypothesis that chromosome region 7q21-q22 contains a growth-suppressor gene involved in the development of leiomyomas, we examined 92 leiomyomas for allelic loss of 7q markers spanning the cytogenetically defined critical region. Forty tumors with cytogenetically defined 7q deletion, 45 tumors without cytogenetically visible 7q deletion, and seven tumors with no cytogenetic information were examined for allelic loss of loci D7S489, D7S440, D7S492, D7S518, D7S471, D7S466, and D7S530. Loss of heterozygosity for one or more of these loci was observed in 23 of 40 (57.5%) of the tumors with deletion of 7q and in 2 of 45 cases without a cytogenetically visible deletion. The tumors with cytogenetic deletion of 7q, but no loss of 7q21-q22 markers, were mosaics, with only a minority of cells containing the cytogenetic deletion. The critical region of loss is defined by the markers D7S518 and D7S471, each showing loss in approximately 50% of informative cases. These markers define a 10 cM region of 7q21-q22 that is consistent with the cytogenetically defined smallest region of overlap and exclude loss of the MET oncogene locus and WNT1, the murine mammary tumor-virus integration site, from the critical region. Our results further define a region that is consistently lost in leiomyomas with cytogenetic deletion of chromosome arm 7q. This region may contain a tumor suppressor gene involved in the development of a subset of leiomyomas.     

Derivative (7)t(7;8)(q34;q21). a new additional cytogenetic abnormality in acute promyelocytic leukemia

Cytogenetic abnormalities in acute myelocytic leukemia (AML) have been identified as one of the most important prognostic factors. The t(15;17) is associated with high rates of complete remission and event-free survival. Secondary chromosomal changes are also present in approximately one third of patients with newly diagnosed acute promyelocytic leukemia (APL). Indeed, the gain of whole chromosome 8 may be involved in the course of APL under C-MYC gene dosage effect theory. Complete or partial loss of the long arm of chromosome 7 region has been recognized in preleukemic myelodysplasia or unfavorable AML. We report here two original APL cases in which a new additional chromosomal abnormality, der(7)t(7;8)(q34;q21), is associated with the t(15;17)(q22;q21). This recurrent abnormality results in a partial loss of 7q associated with a partial 8q trisomy. As the 7q and 8q breakpoints were similar in both cases, the involvement of these critical regions in the pathogenesis and outcome of APL disease has to be determined.     

Delineation of multiple deleted regions in 7q in myeloid disorders.

Loss of chromosome material due to deletions of the long arm of chromosome 7, del(7q), is a consistent finding in all types of myeloid disorders, invariably associated with a poor prognosis. Two different segments, 7q22 and 7q32-q33, have been implicated as critical regions of gene loss associated with these disorders. In the present study, we used fluorescence in situ hybridization (FISH) to characterize the 7q22 breakpoint of an apparently balanced t(7;7)(p13;q22) in an acute myeloid leukemia patient. FISH analysis on bone marrow metaphases from this patient revealed that the sequence corresponding to a series of three ordered cosmids from 7q22 was deleted from one of the der(7) chromosomes. These cosmids contain the human homologue of the Drosophila homeobox gene cut (CUTL1) and span a region of approximately 150 kb. Although the proximal boundary of the deleted segment could not be exactly defined, we estimate the size of this deletion to be approximately 500 kb. Subsequently, we carried out FISH studies using the CUTL1 cosmids on a further 16 patients with deletions of 7q and myeloid disorders. The sequence corresponding to at least two of the cosmids was deleted from the del(7q) in 11 out of 14 cases with a proximal breakpoint within 7q22. Further detailed FISH mapping in this series of 17 patients has identified two other nonoverlapping commonly deleted segments at 7q31-q32 and 7q33, respectively. These data confirm and refine other studies, implying that several different genes on 7q may be involved in the pathogenesis of myeloid diseases. Genes Chromosomes Cancer 25:384-392, 1999.     

Structural aberrations of chromosome 7 revealed by a combination of molecular cytogenetic techniques in myeloid malignancies

In bone marrow cells of 33 patients with myelodysplastic syndrome and acute myeloid leukemia, structural rearrangements of chromosome 7 were found with conventional G-banding: 8 with deletions 7q and 25 with translocations. In 29 of the patients, complex karyotypes were confirmed using multicolor fluorescence in situ hybridization (mFISH). Commercial probes (Abbot Molecular) were used for 7q22, 7q31, and 7q35, the regions most frequently deleted in myeloid malignancies. In three cases without deletions, high-resolution multicolor banding (mBAND) for chromosome 7 revealed other aberrations. Five groups of chromosomal rearrangements were established: (a) deletion 7q as a sole aberration (2 cases), (b) deletion 7q and complex karyotypes (6 cases), (c) combined translocations and deletions of 7q (17 cases), (d) combined translocation and deletion 7p (5 cases), and (e) translocation of chromosomes 7 without deletion 7p or 7q (3 cases). Deletions of all three FISH-screened regions were the most frequent, with heterogeneous breakpoints. The region 7p13.2 approximately p15.2 was most commonly deleted. Most of the deletions were cryptic, not detectable with conventional cytogenetics. Aberrations of chromosome 7 are associated with a very poor outcome; survival time in our cohort was short (median 7 months).     

Spectral karyotypic study of the HL-60 cell line: detection of complex rearrangements involving chromosomes 5, 7, and 16 and delineation of critical region of deletion on 5q31.1.

Interstitial deletions of the q arm of chromosome 5 have been associated with acute myelogenous leukemia (AML); therefore, accurate identification of rearrangements of this chromosome in a model cell line, HL-60, is important for understanding the critical genes involved in this disease. In this study, we employed a newly developed technology termed spectral karyotyping to delineate chromosomal rearrangements in this cell line. Our study revealed a derivative of chromosome 7 that resulted from translocations of chromosome arms 5q and 16q to 7q; that is, der(7)t(5;7)(?;q?)t(5;16)(?;q?). Interestingly, both chromosomes 5 and 7 were also involved in translocations with chromosome 16 in der(16) t(5;16)(q?;q?22-24) and der(16)t(7;16)(?;q?22-24), respectively. Other notable chromosomal abnormalities that were not previously reported in the HL-60 included an insertion of chromosome 8 in the q arm of chromosome 11, a translocation between chromosomes 9 and 14, and a translocation between chromosomes 14 and 15. In an attempt to define the loss of the 5q31.1 region in HL-60, we performed fluorescence in situ hybridization analysis by utilizing bacterial artificial chromosomes BAC1 and BAC2 that spanned the IL9 and EGR1 gene interval, which was previously shown to be a critical region of loss in AML. We showed that a copy of both BAC1 (spanning the D5S399 locus) and BAC2 (spanning the D5S393 locus centromeric to BAC1) were present in the normal chromosome 5, but a second copy of BAC1 was lost and a second copy of BAC2 was inserted in the der(16)t(7;16) chromosome. Thus, not only was this study the first to use the new 24-color karyotyping technique to identify several novel chromosomal rearrangements in HL-60, but it also narrowed the 5q31.1 critical region of deletion to the region represented by BAC1.     

Ring chromosome 6 may represent a cytogenetic subgroup in benign thymoma

Abnormalities of chromosome 7 are a frequent finding in myelocytic malignancies and are associated with a poor prognosis. Based on chromosome banding analysis, two critical regions have been identified: one in band 7q22 and the second in region 7q32 approximately q35. The chromosomal breakpoint in band 7q22 appears to be heterogeneous and may involve tumor suppressor gene(s). Constitutional rearrangements of 7q22 have rarely been reported in myeloid malignancies. To our knowledge, this is the first report in the literature of a myeloproliferative disorder with a constitutional t(1;7)(q42;q22).     

Frequent loss of heterozygosity in the region of the D7S523 locus in advanced ovarian cancer

Loss of heterozygosity (LOH) of the long arm of chromosome 7 occurs frequently in many types of primary cancers. We analyzed 22 primary ovarian cancers for LOH of chromosome arm 7q using a set of 16 microsatellite markers in order to determine the location of a putative tumor suppressor gene (TSG). Eleven samples (50%) showed LOH at least at one locus on chromosome arm 7q. We identified the smallest commonly deleted region to be at 7q31.1, which includes D7S523. LOH of chromosome arm 7q was more frequent in advanced stages (III–IV) (7/9, 78%) than in early stages (I–II) (4/13, 31%) of ovarian cancer (P<0.05). These data suggest that alteration of a TSG at 7q31.1 gene plays an important role in advanced ovarian cancer. Genes Chromosom. Cancer 19:1–5, 1997. © 1997 Wiley-Liss, Inc.     

Atypical (7;19) translocation in acute myelomonocytic leukemia.

Chromosome studies were carried out after a 24-hour harvest of unstimulated bone marrow aspirate cell cultures from a 75-year-old male with a clinical diagnosis of acute myelomonocytic leukemia (FAB M4). Analysis of nine cells after trypsin-Giemsa banding (GTG) revealed two cell lines with a mosaic chromosome pattern, 46,XY/46,XY,t(7;19)(q22;p13.3). A review of the recent literature reveals one case of childhood ALL with a 46,XY/46,XY,t(7;19)(q11;q13) chromosome pattern [1] and a 46,XY,t(3q;11q),t(7q;19p),t(15;17)(q26;q22) in one patient with ANLL (FAB M3) [2]. The t(7;19)(q22;p13.3) seen in our case has not been reported as the sole specific clonal chromosome rearrangement in myeloid neoplasia. Interestingly, the plasminogen activator inhibitor type I, multi-drug resistance, and erythropoietin genes are located at band 7q22 and the insulin receptor gene is located at band 19p13.3. Both sites contain fragile site loci. The possible role of these fragile sites, genes, or other genes in the rearrangement can only be surmised.     

Comparative mapping of the region of human chromosome 7 deleted in williams syndrome.

Williams syndrome (WS) is a complex developmental disorder resulting from the deletion of a large (approximately 1.5-2 Mb) segment of human chromosome 7q11.23. Physical mapping studies have revealed that this deleted region, which contains a number of known genes, is flanked by several large, nearly identical blocks of DNA. The presence of such highly related DNA segments in close physical proximity to one another has hampered efforts to elucidate the precise long-range organization of this segment of chromosome 7. To gain insight about the structure and evolutionary origins of this important and complex genomic region, we have constructed a fully contiguous bacterial artificial chromosome (BAC) and P1-derived artificial chromosome (PAC) contig map encompassing the corresponding region on mouse chromosome 5. In contrast to the difficulties encountered in constructing a clone-based physical map of the human WS region, the BAC/PAC-based map of the mouse WS region was straightforward to construct, with no evidence of large duplicated segments, such as those encountered in the human WS region. To confirm this difference, representative human and mouse BACs were used as probes for performing fluorescence in situ hybridization (FISH) to metaphase and interphase chromosomes. Human BACs derived from the nonunique portion of the WS region hybridized to multiple, closely spaced regions on human chromosome 7q11.23. In contrast, corresponding mouse BACs hybridized to a single site on mouse chromosome 5. Furthermore, FISH analysis revealed the presence of duplicated segments within the WS region of various nonhuman primates (chimpanzee, gorilla, orangutan, and gibbon). Hybridization was also noted at the genomic locations corresponding to human chromosome 7p22 and 7q22 in human, chimpanzee, and gorilla, but not in the other animal species examined. Together, these results indicate that the WS region is associated with large, duplicated blocks of DNA on human chromosome 7q11.23 as well as the corresponding genomic regions of other nonhuman primates. However, such duplications are not present in the mouse.     

Molecular cloning of a constitutional t(7;22) translocation associated with risk of hematological malignancy

We report the molecular characterization of a reciprocal constitutional translocation t(7;22)(p13;q11.2) carried by three family members who have each developed a hematological malignancy. The chromosome 7 breakpoint was localized to a single BAC clone, RP11-571N3, by sequential fluorescence in situ hybridization analysis of clones selected from the NCBI chromosome 7 map. This was further refined to a 739-bp region by Southern blot analysis of DNA from the two cell lines 1193 and 1194 digested with EcoRI, HindIII, PstI, and PvuII. A 2.8-kb fragment spanning the der(22) breakpoint was amplified by long-range inverse PCR. The sequence of this fragment was used to predict the composition of the der(7) breakpoint, and a 1.3-kb fragment was amplified by use of primers from both chromosomes 7 and 22 based on this prediction. The breakpoint on chromosome 22 is located between the 3rd and 4th V regions of the immunoglobulin lambda (IGL) locus, and the breakpoint on chromosome 7 is located 122 kb proximal to the insulin-like growth factor binding protein (IGFBP) 3 gene. Examination of both reciprocal junctions showed that four bases were lost from chromosome 22, whereas 75 bases were lost from chromosome 7. Small insertions of 46 bases and 13 bases were found at the der(22) and the der(7) junctions, respectively. As a consequence of this event, the entire IGL locus, less the first three Vlambda elements, is translocated to chromosome 7, whereas the three remaining Vlambda elements on the der(22) are juxtaposed with IGFBP3 and IGFBP1.     

Uncommon cytogenetic findings in a case of splenic marginal zone lymphoma with aggressive clinical course

The majority of splenic marginal zone lymphoma (SMZL) patients experience an indolent clinical course; however, some cases transform to a high-grade lymphoma. Cytogenetic analyses have shown that chromosome 7 is the most frequently altered chromosome and, in some cases, 7q deletion has been found as a single aberration, suggesting its association with the development of SMZL. We studied one patient showing clinical features of SMZL with an aggressive course. Immunophenotypic, conventional and molecular cytogenetic techniques were applied to support the diagnosis. The immunophenotype of peripheral blood mononuclear cells showed the presence of 90% B-lymphocytes. Cytogenetic analysis indicated the presence of a stem-line lacking normal chromosomes 7, but showing a der(7) and a ring, and a side-line with additional aberrations: t(2;22), add(8). Fluorescence in situ hybridization analysis revealed a loss of the 7q32 region. Nonclonal rearrangements involving chromosome 7 were also detected. Chromosome 7 rearrangements were studied to investigate their evolution during the development of the pathology. We have shown that in this patient both chromosomes 7 underwent different rearrangements leading to a loss of the 7q32 region and that the ring chromosome originated from chromosome 7 and was associated with a t(7;7) (p22;q31). We conclude that not only the 7q deletion but also the proneness of chromosome 7 to rearrange might have played a role in the progression of this SMZL.     

A de novo complex chromosomal rearrangement with a translocation 7;9 and 8q insertion in a male carrier with no infertility

A de novo complex chromosomal rearrangement (CCR) involving chromosomes 7, 8 and 9 in a male carrier was ascertained through his healthy wife's recurrent spontaneous abortions. Six pregnancies over eight years resulted in four spontaneous abortions and two livebirths who died perinatally due to abnormal vital signs. Cytogenetic analyses utilizing high resolution chromosome banding technique showed a deletion of band in a der(7) chromosome and an extra band inserting at 8q21.2. Another extra band was also observed at the band 9p24, but it could not be karyotypically determined. Fluorescent in-situ hybridization using chromosome 7 and 8 specific microdissected library as probes confirmed the insertion of a segment from the translocated chromosome 7 into a chromosome 8, and additionally revealed a translocation between chromosomes 7 and 9. The karyotype of the CCR carrier was determined as 46,XY,t(7;9)(q22;p24),ins(8;7)(q21.2;q22q32).ish der(9)(wcp7+);ins(8;7)(wcp8+,wcp7+). Comparing with previously reported male CCR carriers with our case, we conclude that male CCR carriers may not always present with infertility or subfertility phenotypes. This may suggest that rare transmission of male carriers could result from abnormal chromosomal rearrangements during meiosis and gametogenesis in addition to frequent infertility.     

Bilateral split hand/foot malformation and inv(7)(p22q21.3).

A boy with typical tetramelic split hands and feet is described. In addition, there was a large arteriovenous malformation of the right arm. Chromosome studies showed a pericentric inversion of chromosome 7: 46,XY,inv(7)(p22q21.3). Inspection of the extremities and chromosome studies in the parents were normal. This case confirms the suggested localisation of a locus, important for early limb differentiation, on the long arm of chromosome 7, most probably in the chromosomal region 7q21.2-7q21.3. Previously reported cases are reviewed briefly.     

Functional evidence from microcell-mediated chromosome transfer of myeloid leukemia suppressor genes on human chromosomes 7 and 11

The long arm of human chromosome 7 between 7q22 and 7q36 has been identified as a region harboring one or more tumor-suppressor genes (TSGs) inactivated in acute myeloid leukemia (AML). Additional TSGs mapping to other chromosomes may well be involved in the etiology of this disease. For example, experiments using a mouse model system have indicated the possible presence of an AML TSG at 11p11-12. Microcell-mediated chromosome transfer (MMCT) has been used to introduce human chromosomes 7 and 11 into a murine myeloid leukemia cell line. A proportion of MMCT hybrid clones containing either whole chromosome 7 or fragments of chromosome 11 showed a significant delay in leukemogenic onset when injected into syngeneic mice. Screening of hybrid clones did not associate any human microsatellite markers with decreased leukemogenic potential in vivo. However, preliminary evidence was obtained of allelic loss at chromosomal regions homologous with human 7q22 in murine F1 hybrid AMLs. Our data provide functional evidence of AML-associated TSGs localized to human chromosomes 7 and 11 in support of previously published studies on cytogenetic and allelic losses associated with AML development.     

Split hand/split foot anomaly in a family segregating a balanced translocation with breakpoint on 7q22.1

An apparently balanced translocation, t(2;7)(q21.1;q22.1) was detected in a female patient with bilateral split hand and right split foot. Split hand/split foot (SHSF) segregated as an autosomal dominant character with low penetrance in her family. The translocation was present in 6 of 13 additional relatives investigated, one of whom also had split hand on right. This observation provides further confirmation of the presence of a locus for SHSF on 7q and narrows the critical region to band 7q22.1. Defects caused by alterations of this chromosome region are variable and include manifestations of both syndromal and non-syndromal SHSF. Review of SHSF cases associated with chromosome 7 abnormalities showed a preferential involvement of the lower limbs and of the right side, suggesting the action of locally restricted developmental resistance mechanisms. © 1993 Wiley-Liss, Inc.     

De novo inverted duplication of chromosome 7q

We report a fetus with a de novo inverted duplication of the long arm of chromosome 7, karyotype 46,XX, inv dup(7) (pter→q36.1::q36.1→q22::q36.1→qter).     

Refined localization and yeast artificial chromosome (YAC) contig--mapping of genes and DNA segments in the 7q21-q32 region

The chromosome localizations for 159 gene and DNA segments havebeen refined to one of five intervals in the 7q21–q32region through hybridization analysis with a panel of somaticcell hybrid lines. Seventy-two of these chromosome 7 markersare also mapped on common or overlapping yeast artificial chromosome(YAC) clones. In addition, the breakpoints of chromosome rearrangmentcontained in five of the somatic cell hybrid lines have beendefined by flanking probes within YAC contigs. To provide aframework for further mapping of the 7q21–q32 region,we have established the physical order of a set of referencemarkers: cen-(COL1A2-D7S15-CYP3A4-PON)-D7S456-(breakpoint containedin cell hybrid 1EF2/3/K017)-GUSB-D7S186-ASL-(PGY1-PGY3-GNB2-EPO-ACHE)-D7S238-(proximalbreakpoint in GM1059-Rag5)-D7S240-(CUTL1-PLANHI)-(breakpointsin 1CF2/5/K016 and 2068Rag22–2)-(PRKAR2B-D7S13)-LAMB1-(breakpointin JSR-17S)-DLD-D7S16-MET-WNT2-CFTR-D7S8-tel.     

Discordant phenotypes in a mother and daughter with mosaic supernumerary ring chromosome 19 explained by a de novo 7q36.2 deletion and 7p22.1 duplication

We report on a patient with severe intellectual disability, microcephaly, short stature, and dysmorphic features who, based on standard karyotyping, has two cytogenetic abnormalities: an apparently balanced paracentric inversion of chromosome 7, inv(7)(q31.2q36), and a small supernumerary ring chromosome derived entirely of material from chromosome 19. While the inversion was detected in all cells, mosaicism was observed for the ring chromosome. Interestingly, apparently identical cytogenetic abnormalities were detected in the patient's mother, who presented with normal stature, few dysmorphic features, and normal cognition without microcephaly. While the level of mosaicism could not adequately explain the phenotypic discordance, comparative genome hybridization revealed a de novo terminal deletion of chromosome 7, del(7)(q36.2), and a terminal duplication of chromosome 7, dup(7)(p22.1) in the patient. Additional cytogenetic investigation revealed that the patient inherited a recombinant chromosome derived from a cryptic maternal pericentric inversion: inv(7)(p22q36). The patient's distinctive features are consistent with the wide phenotypic spectrum reported in 7p duplication and 7q terminal deletion syndromes. These chromosomal regions contain several candidate genes of clinical significance, including SHH, EN2, and FAM20C. Our findings strongly suggest that our patient's phenotype is largely attributable to partial 7pter trisomy and partial 7qter monosomy rather than mosaic supernumerary ring chromosome 19.