AID-associated DNA repair pathways regulate malignant transformation in a murine model of BCL6-driven diffuse large B-cell lymphoma.

Somatic hypermutation and class-switch recombination of the immunoglobulin (Ig) genes occur in germinal center (GC) B cells and are initiated through deamination of cytidine to uracil by activation-induced cytidine deaminase (AID). Resulting uracil-guanine mismatches are processed by uracil DNA glycosylase (UNG)-mediated base-excision repair and MSH2-mediated mismatch repair (MMR) to yield mutations and DNA strand lesions. Although off-target AID activity also contributes to oncogenic point mutations and chromosome translocations associated with GC and post-GC B-cell lymphomas, the role of downstream AID-associated DNA repair pathways in the pathogenesis of lymphoma is unknown. Here, we show that simultaneous deficiency of UNG and MSH2 or MSH2 alone causes genomic instability and a shorter latency to the development of BCL6-driven diffuse large B-cell lymphoma (DLBCL) in a murine model. The additional development of several BCL6-independent malignancies in these mice underscores the critical role of MMR in maintaining general genomic stability. In contrast, absence of UNG alone is highly protective and prevents the development of BCL6-driven DLBCL. We further demonstrate that clonal and nonclonal mutations arise within non-Ig AID target genes in the combined absence of UNG and MSH2 and that DNA strand lesions arise in an UNG-dependent manner but are offset by MSH2. These findings lend insight into a complex interplay whereby potentially deleterious UNG activity and general genomic instability are opposed by the protective influence of MSH2, producing a net protective effect that promotes immune diversification while simultaneously attenuating malignant transformation of GC B cells.

Comprehensive high-resolution genomic profiling and cytogenetics of human chondrocyte cultures by GTG-banding, locus-specific FISH, SKY and SNP array.

In the development of cell-based medicinal products, it is crucial to guarantee that the application of such an advanced therapy medicinal product (ATMP) is safe for the patients. The consensus of the European regulatory authorities is: "In conclusion, on the basis of the state of art, conventional karyotyping can be considered a valuable and useful technique to analyse chromosomal stability during preclinical studies". 408 chondrocyte samples (84 monolayers and 324 spheroids) from six patients were analysed using trypsin-Giemsa staining, spectral karyotyping and fluorescence in situ hybridisation, to evaluate the genetic stability of chondrocyte samples from non-clinical studies. Single nucleotide polymorphism (SNP) array analysis was performed on chondrocyte spheroids from five of the six donors. Applying this combination of techniques, the genetic analyses performed revealed no significant genetic instability until passage 3 in monolayer cells and interphase cells from spheroid cultures at different time points. Clonal occurrence of polyploid metaphases and endoreduplications were identified associated with prolonged cultivation time. Also, gonosomal losses were observed in chondrocyte spheroids, with increasing passage and duration of the differentiation phase. Interestingly, in one of the donors, chromosomal aberrations that are also described in extraskeletal myxoid chondrosarcoma were identified. The SNP array analysis exhibited chromosomal aberrations in two donors and copy neutral losses of heterozygosity regions in four donors. This study showed the necessity of combined genetic analyses at defined cultivation time points in quality studies within the field of cell therapy.

Novel mouse model recapitulates genome and transcriptome alterations in human colorectal carcinomas.

Human colorectal carcinomas are defined by a nonrandom distribution of genomic imbalances that are characteristic for this disease. Often, these imbalances affect entire chromosomes. Understanding the role of these aneuploidies for carcinogenesis is of utmost importance. Currently, established transgenic mice do not recapitulate the pathognonomic genome aberration profile of human colorectal carcinomas. We have developed a novel model based on the spontaneous transformation of murine colon epithelial cells. During this process, cells progress through stages of pre-immortalization, immortalization and, finally, transformation, and result in tumors when injected into immunocompromised mice. We analyzed our model for genome and transcriptome alterations using ArrayCGH, spectral karyotyping (SKY), and array based gene expression profiling. ArrayCGH revealed a recurrent pattern of genomic imbalances. These results were confirmed by SKY. Comparing these imbalances with orthologous maps of human chromosomes revealed a remarkable overlap. We observed focal deletions of the tumor suppressor genes Trp53 and Cdkn2a/p16. High-level focal genomic amplification included the locus harboring the oncogene Mdm2, which was confirmed by FISH in the form of double minute chromosomes. Array-based global gene expression revealed distinct differences between the sequential steps of spontaneous transformation. Gene expression changes showed significant similarities with human colorectal carcinomas. Pathways most prominently affected included genes involved in chromosomal instability and in epithelial to mesenchymal transition. Our novel mouse model therefore recapitulates the most prominent genome and transcriptome alterations in human colorectal cancer, and might serve as a valuable tool for understanding the dynamic process of tumorigenesis, and for preclinical drug testing. © 2016 Wiley Periodicals, Inc.

Establishment and characterization of BHD-F59RSVT, an immortalized cell line derived from a renal cell carcinoma in a patient with Birt-Hogg-Dubé syndrome.

Hereditary renal cell carcinomas (RCCs) are life-threatening disorders not only for the patients but also for their relatives. Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant disorder caused by germline mutations in the folliculin gene (FLCN). The protein product, FLCN, functions as a tumor suppressor, and the affected patients have high risks of developing multiple RCCs. The carcinogenic mechanisms stemming from FLCN dysfunction have been investigated using rodent models and human RCC tissues. However, very limited information has been available about in vitro signaling of human renal cells with genetically mutant FLCN. Herein, we established a new cell line, BHD-F59RSVT, from a BHD patient's chromophobe RCC by transfecting SV40 large T antigen. We investigated FLCN mutations, chromosome profiles, and cytopathologic characteristics of the cell line. BHD-F59RSVT reflected the patient's FLCN germline mutation, a 3-nt deletion in exon 13 (c.1528_1530delGAG). Neither somatic mutation nor loss of heterozygosity of FLCN was detectable. Chromosome 17p11.2 of the FLCN proximal region demonstrated a trimodal pattern. Genome-wide chromosomal analysis revealed a loss of chromosome 16 and mosaic segmental gains in chromosome 7. BHD-F59RSVT cells were positive when immunostained for cytokeratin 7, supporting their origin from distal convoluted tubules. Western blotting analysis demonstrated severely suppressed FLCN expression at the protein level. The collective findings indicate that the established cell line will be suitable for functional analysis of the typical phenotype of BHD-associated RCC with suppressed FLCN expression.

Multicolor Spectral Analyses of Mitotic and Meiotic Mouse Chromosomes Involved in Multiple Robertsonian Translocations. II. The NMRI/CD and CD/TA Hybrid Strains.

Multicolor spectral analyses (spectral karyotyping) were performed on mitotic chromosomes of NMRI, CD, and TA mice and on male meiotic chromosomes (diakineses) of NMRI/CD and CD/TA hybrids. All chromosomes, including the various centric (robertsonian) fusions, could be unequivocally identified. Apart from the robertsonian translocations, which were previously detected by conventional banding analyses, no other interchromosomal rearrangements were found in these mice. In both the CD and TA mice, the autosomes 19 and the XY sex chromosomes are not involved in robertsonian translocations. In diakineses of male meiosis of the NMRI/CD hybrid, the 9 expected trivalents were present, whereas in those of the CD/TA hybrids a stable large meiotic multivalent, formed by 15 robertsonian fusion chromosomes and 2 terminally located normal chromosomes, was observed. The specific sequential order of the robertsonian fusion chromosomes found within this meiotic chain was as theoretically predicted. In the majority of diakineses of the NMRI/CD and CD/TA hybrids, the free autosomal bivalent 19 and the XY sex bivalent formed noticeable tight spatial associations.

Identification of Small and Non-Small Cell Lung Cancer Markers in Peripheral Blood Using Cytokinesis-Blocked Micronucleus and Spectral Karyotyping Assays.

Small cell lung cancer (SCLC) is a highly aggressive form of lung cancer. There is an urgent need to develop tools to identify individuals at high risk of developing SCLC. We have previously reported that the cytokinesis-blocked micronucleus (CBMN) assay is a strong predictor of non-small cell lung cancer (NSCLC). Here, we investigate the sensitivity of the CBMN endpoints as predictors of SCLC risk. We conducted the CBMN assay on SCLC patients (n = 216), NSCLC patients (n = 173), and healthy controls (n = 204). Per sample, 1,000 binucleated cells (BN) were scored, and 3 endpoints, micronuclei (BN-MN), nucleoplasmic bridges (BN-NPB), and nuclear buds(BN-BUD), were recorded. Spectral karyotyping was also conducted on SCLC patients (n = 116) and NSCLC patients (n = 137) to identify genomic regions unique to each disease. Significantly higher levels of CBMN endpoints were observed in both cancer groups compared to controls. BN-NPBs were significantly higher among SCLC patients compared to NSCLC patients (p < 0.001). Chromosomes 5 and 17 were associated with BN-MN, and chromosomes 5, 18, 20, and 22 were associated with BN-NPBs in SCLC patients. Given the high frequency of chromosome aberrations observed in SCLC, events such as reinsertion of the micronucleus and chromothripsis may be potential mechanisms for the genetic instability in these patients.

Coexpression of NUP98/TOP1 and TOP1/NUP98 in de novo Acute Myeloid Leukemia with t(11;20)(p15;q12) and t(2;5)(q33;q31).

The t(11;20)(p15;q11∼12) translocation is a very rare but recurrent cytogenetic aberration that occurs in myelodysplastic syndrome/acute myeloid leukemia (MDS/AML). This translocation was shown to form a fusion gene between NUP98 at 11p15 and TOP1 at 20q12. Here, we describe a new case of de novo AML M2 with t(11;20) which was associated with another balanced translocation. An 81-year-old man was admitted to undergo salvage therapy for relapsed AML. G-banding and spectral karyotyping showed 46,XY,t(2;5)(q33;q31),t(11;20)(p15;q12)[20]. Expression of the NUP98/TOP1 fusion transcript was confirmed: NUP98 exon 13 was in-frame fused with TOP1 exon 8. The reciprocal TOP1/NUP98 fusion transcript was also detected: TOP1 exon 7 was fused with NUP98 exon 14. After achieving hematological complete remission, the karyotype converted to 46,XY,t(2;5)(q33;q31)[19]/46,sl,t(11;20)(p15;q12)[1]. FISH analysis demonstrated that the 5q31 breakpoint of t(2;5) was centromeric to EGR1. In all 10 cases described in the literature, the NUP98 exon 13/TOP1 exon 8 fusion transcript was expressed, indicating that it may be responsible for the pathogenesis of MDS/AML with t(11;20). On the other hand, the TOP1/NUP98 transcript was coexpressed in 4 cases of de novo AML, but not in 3 cases of therapy-related MDS. Thus, this reciprocal fusion may be associated with progression to AML.

Hyperspectral backscatter imaging: a label-free approach to cytogenetics.

Current techniques for chromosome analysis need to be improved for rapid, economical identification of complex chromosomal defects by sensitive and selective visualisation. In this paper, we present a straightforward method for characterising unstained human metaphase chromosomes. Backscatter imaging in a dark-field setup combined with visible and short near-infrared spectroscopy is used to monitor morphological differences in the distribution of the chromosomal fine structure in human metaphase chromosomes. The reasons for the scattering centres in the fine structure are explained. Changes in the scattering centres during preparation of the metaphases are discussed. FDTD simulations are presented to substantiate the experimental findings. We show that local scattering features consisting of underlying spectral modulations of higher frequencies associated with a high variety of densely packed chromatin can be represented by their scatter profiles even on a sub-microscopic level. The result is independent of the chromosome preparation and structure size. This analytical method constitutes a rapid, cost-effective and label-free cytogenetic technique which can be used in a standard light microscope. Graphical abstract Hyperspectral backscatter imaging for label-free characterization.

Multicolor Spectral Analyses of Mitotic and Meiotic Mouse Chromosomes Involved in Multiple Robertsonian Translocations. I. The CD/Cremona Hybrid Strain.

Multicolor spectral analysis (spectral karyotyping) was applied to mitotic and male diakinetic chromosomes of hybrid mice carrying a unique system of 18 autosomal Robertsonian translocation chromosomes with alternating arm homologies. Only the autosomes 19 and the XY sex chromosomes are excluded from these Robertsonian translocations. The translocations, previously identified by conventional banding analyses, could be verified by spectral karyotyping. Besides the Robertsonian translocations, no other interchromosomal rearrangements were detected. In diakineses of male meiosis, the 18 metacentric Robertsonian translocation chromosomes form a very large meiotic 'superring'. The predictable, specific order of the chromosomes along this 'superring' was completely confirmed by multicolor spectral analysis. In the majority of diakineses analyzed, the free autosomal bivalent 19 and the XY sex bivalent form a conspicuous complex which tightly associates with the 12;14 Robertsonian translocation chromosome in the 'superring'.

NUP214-RAC1 and RAC1-COL12A1 Fusion in Complex Variant Translocations Involving Chromosomes 6, 7 and 9 in an Acute Myeloid Leukemia Case with DEK-NUP214.

DEK-NUP214 gene fusion in acute myeloid leukemia (AML) is associated with poor prognosis. It is most often a sole translocation and more rarely observed as complex chromosomal forms. We describe an AML case with complex karyotype abnormalities involving chromosome bands 6p23, 6q13, 7p22, and 9q34. RNA sequencing analysis revealed that exon 17 of NUP214 (9q34) was fused to exon 2 of RAC1 (7p22). We also detected that the 5'-end of intron 1 of RAC1 was fused with the antisense strand of intron 5 of COL12A1 (6q13). RT-PCR analysis confirmed the expression of DEK-NUP214, NUP214-RAC1, RAC1-COL12A1, NUP214, and RAC1. These results suggest that the 5'- and 3'-ends of NUP214 from the breakpoint in the same locus were fused to RAC1 and DEK, respectively, and the 5'-end of RAC1 was fused to COL12A1. The reading frame of NUP214 was not matched with RAC1; however, high expression of the RAC1 protein was detected by Western blotting. This study identifies the variant complex fusion genesNUP214-RAC1 and RAC1- COL12A1 in a case of AML.

Mosaic variegated aneuploidy in mouse BubR1 deficient embryos and pregnancy loss in human.

Chromosome aberrations (aneuploidies mostly) are the cause of the majority of spontaneous abortions in humans. However, little is known about defects in the underlying molecular mechanisms resulting in chromosome aberrations and following failure of preimplantation embryo development, initiation of implantation and postimplantation pregnancy loss. We suggest that defects of the spindle assembly checkpoint (SAC) are responsible for aneuploidy and the following abortions. To develop our hypothesis, we modeled this process in the mouse after inactivation of protein BubR1, one of the key players of SAC. We found that soon after implantation, more than 50 % of cells of BubR1 (-/-) embryos were aneuploid and had an increased level of premature sister chromatid separation (PSCS). Aneuploid cells do not have a predominant gain or loss of some specific chromosomes, but they have mosaic variegated aneuploidy (MVA), which is characterised by random mixture of different chromosomes. MVA leads to growth retardation, stochastic massive apoptosis, disruption of bilateral symmetry, and embryo death between embryonic days 7.5 to 13.5. Analysis published human data revealed that human recurrent pregnancy loss (RPL) embryos and rare infant patients carrying BubR1 mutations that have been described so far have the PSCS and MVA as in BubR1 deficient/insufficient mice. Based on this data, we predict that deficiency/insufficiency of BubR1 and other components of the SAC in human are responsible for a significant fraction of both early and late RPLs.

Three gangliogliomas: results of GTG-banding, SKY, genome-wide high resolution SNP-array, gene expression and review of the literature.

According to the World Health Organization gangliogliomas are classified as well-differentiated and slowly growing neuroepithelial tumors, composed of neoplastic mature ganglion and glial cells. It is the most frequent tumor entity observed in patients with long-term epilepsy. Comprehensive cytogenetic and molecular cytogenetic data including high-resolution genomic profiling (single nucleotide polymorphism (SNP)-array) of gangliogliomas are scarce but necessary for a better oncological understanding of this tumor entity. For a detailed characterization at the single cell and cell population levels, we analyzed genomic alterations of three gangliogliomas using trypsin-Giemsa banding (GTG-banding) and by spectral karyotyping (SKY) in combination with SNP-array and gene expression array experiments. By GTG and SKY, we could confirm frequently detected chromosomal aberrations (losses within chromosomes 10, 13 and 22; gains within chromosomes 5, 7, 8 and 12), and identify so far unknown genetic aberrations like the unbalanced non-reciprocal translocation t(1;18)(q21;q21). Interestingly, we report on the second so far detected ganglioglioma with ring chromosome 1. Analyses of SNP-array data from two of the tumors and respective germline DNA (peripheral blood) identified few small gains and losses and a number of copy-neutral regions with loss of heterozygosity (LOH) in germline and in tumor tissue. In comparison to germline DNA, tumor tissues did not show substantial regions with significant loss or gain or with newly developed LOH. Gene expression analyses of tumor-specific genes revealed similarities in the profile of the analyzed samples regarding different relevant pathways. Taken together, we describe overlapping but also distinct and novel genetic aberrations of three gangliogliomas.

G1 checkpoint establishment in vivo during embryonic liver development.

BACKGROUND: The DNA damage-mediated cell cycle checkpoint is an essential mechanism in the DNA damage response (DDR). During embryonic development, the characteristics of cell cycle and DNA damage checkpoint evolve from an extremely short G1 cell phase and lacking G1 checkpoint to lengthening G1 phase and the establishment of the G1 checkpoint. However, the regulatory mechanisms governing these transitions are not well understood. In this study, pregnant mice were exposed to ionizing radiation (IR) to induce DNA damage at different embryonic stages; the kinetics and mechanisms of the establishment of DNA damage-mediated G1 checkpoint in embryonic liver were investigated. RESULTS: We found that the G2 cell cycle arrest was the first response to DNA damage in early developmental stages. Starting at E13.5/E15.5, IR mediated inhibition of the G1 to S phase transition became evident. Concomitantly, IR induced the robust expression of p21 and suppressed Cdk2/cyclin E activity, which might involve in the initiation of G1 checkpoint. The established G1 cell cycle checkpoint, in combination with an enhanced DNA repair capacity at E15.5, displayed biologically protective effects of repairing DNA double-strand breaks (DSBs) and reducing apoptosis in the short term as well as reducing chromosome deletion and breakage in the long term. CONCLUSION: Our study is the first to demonstrate the establishment of the DNA damage-mediated G1 cell cycle checkpoint in liver cells during embryogenesis and its in vivo biological effects during embryonic liver development.

Block of T cell development in P53-deficient mice accelerates development of lymphomas with characteristic RAG-dependent cytogenetic alterations.

Mice deficient in the DNA damage sensor P53 display normal T cell development but eventually succumb to thymic lymphomas. Here, we show that inactivation of the TCR beta gene enhancer (E beta) results in a block of T cell development at stages where recombination-activating genes (RAG) are expressed. Introduction of the E beta mutation into p53-/- mice dramatically accelerates the onset of lethal thymic lymphomas that harbor RAG-dependent aberrant rearrangements, chromosome 14 and 12 translocations, and amplification of the chromosomal region 9A1-A5.3. Phenotypic and genetic analyses suggest that lymphomas emerge through a normal thymocyte development pathway. These findings provide genetic evidence that block of lymphocyte development at stages with RAG endonuclease activity can provoke lymphomagenesis on a background with deficient DNA damage responses.

Histone methyltransferase Suv39h1 deficiency prevents Myc-induced chromosomal instability in murine myeloid leukemias.

Suv39h1 mediates heterochromatin formation in pericentric and telomeric regions by trimethylation of lysine 9 of histone 3 (H3K9me3). Yet, its role in the induction of chromosomal instability is poorly understood. We established a leukemia model by retrovirally expressing Myc in wild-type and histone methyltransferase Suv39h1-deficient hematopoietic cells and characterized the resulting leukemias for chromosomal instability. All mice that received cells overexpressing Myc developed myeloid leukemia with a median survival of 44 days posttransplantation. Myc-overexpressing wild-type leukemias demonstrated clones with numerical chromosomal aberrations (5/16). In secondary transplantations of these leukemic cells, structural changes, mostly end-to-end fusions of chromosomes, appeared (10/12). In contrast, leukemic cells overexpressing Myc with reduced or no Suv39h1 expression had a normal karyotype in primary, secondary, and tertiary transplantations (16/16). Myc-transduced Suv39h1-deficient cells showed less critically short telomeres (P < 0.05) compared with Myc-transduced wild-type bone marrow cells. Gene expression analysis showed upregulation of genes involved in the alternative lengthening of telomeres (ALT) mechanism. Thus, we hypothesize that loss of Suv39h1 implies activation of the ALT mechanism, in turn ensuring telomere length and stability. Our data show for the first time that Suv39h1 deficiency may prevent chromosomal instability by more efficient telomere stabilization in hematopoietic bone marrow cells overexpressing Myc.

Aneuploidy, oncogene amplification and epithelial to mesenchymal transition define spontaneous transformation of murine epithelial cells.

Human epithelial cancers are defined by a recurrent distribution of specific chromosomal aneuploidies, a trait less typical for murine cancer models induced by an oncogenic stimulus. After prolonged culture, mouse epithelial cells spontaneously immortalize, transform and become tumorigenic. We assessed genome and transcriptome alterations in cultures derived from bladder and kidney utilizing spectral karyotyping, array CGH, FISH and gene expression profiling. The results show widespread aneuploidy, yet a recurrent and tissue-specific distribution of genomic imbalances, just as in human cancers. Losses of chromosome 4 and gains of chromosome 15 are common and occur early during the transformation process. Global gene expression profiling revealed early and significant transcriptional deregulation. Chromosomal aneuploidy resulted in expression changes of resident genes and consequently in a massive deregulation of the cellular transcriptome. Pathway interrogation of expression changes during the sequential steps of transformation revealed enrichment of genes associated with DNA repair, centrosome regulation, stem cell characteristics and aneuploidy. Genes that modulate the epithelial to mesenchymal transition and genes that define the chromosomal instability phenotype played a dominant role and were changed in a directionality consistent with loss of cell adhesion, invasiveness and proliferation. Comparison with gene expression changes during human bladder and kidney tumorigenesis revealed remarkable overlap with changes observed in the spontaneously transformed murine cultures. Therefore, our novel mouse models faithfully recapitulate the sequence of genomic and transcriptomic events that define human tumorigenesis, hence validating them for both basic and preclinical research.

A hypomorphic Artemis human disease allele causes aberrant chromosomal rearrangements and tumorigenesis.

The Artemis gene encodes a DNA nuclease that plays important roles in non-homologous end-joining (NHEJ), a major double-strand break (DSB) repair pathway in mammalian cells. NHEJ factors repair general DSBs as well as programmed breaks generated during the lymphoid-specific DNA rearrangement, V(D)J recombination, which is required for lymphocyte development. Mutations that inactivate Artemis cause a human severe combined immunodeficiency syndrome associated with cellular radiosensitivity. In contrast, hypomorphic Artemis mutations result in combined immunodeficiency syndromes of varying severity, but, in addition, are hypothesized to predispose to lymphoid malignancy. To elucidate the distinct molecular defects caused by hypomorphic compared with inactivating Artemis mutations, we examined tumor predisposition in a mouse model harboring a targeted partial loss-of-function disease allele. We find that, in contrast to Artemis nullizygosity, the hypomorphic mutation leads to increased aberrant intra- and interchromosomal V(D)J joining events. We also observe that dysfunctional Artemis activity combined with p53 inactivation predominantly predisposes to thymic lymphomas harboring clonal translocations distinct from those observed in Artemis nullizygosity. Thus, the Artemis hypomorphic allele results in unique molecular defects, tumor spectrum and oncogenic chromosomal rearrangements. Our findings have significant implications for disease outcomes and treatment of patients with different Artemis mutations.

Post-transplantation B cell function in different molecular types of SCID.

PURPOSE: Severe combined immunodeficiency (SCID) is a syndrome of diverse genetic cause characterized by profound deficiencies of T, B and sometimes NK cell function. Non-ablative HLA-identical or rigorously T cell-depleted haploidentical parental bone marrow transplantation (BMT) results in thymus-dependent genetically donor T cell development in the recipients, leading to a high rate of long-term survival. However, the development of B cell function has been more problematic. We report here results of analyses of B cell function in 125 SCID recipients prior to and long-term after non-ablative BMT, according to their molecular type. METHODS: Studies included blood immunoglobulin measurements; antibody titers to standard vaccines, blood group antigens and bacteriophage Φ X 174; flow cytometry to examine for markers of immaturity, memory, switched memory B cells and BAFF receptor expression; B cell chimerism; B cell spectratyping; and B cell proliferation. RESULTS: The results showed that B cell chimerism was not required for normal B cell function in IL7Rα-Def, ADA-Def and CD3-Def SCIDs. In X-linked-SCID, Jak3-Def SCID and those with V-D-J recombination defects, donor B cell chimerism was necessary for B cell function to develop. CONCLUSION: The most important factor determining whether B cell function develops in SCID T cell chimeras is the underlying molecular defect. In some types, host B cells function normally. In those molecular types where host B cell function did not develop, donor B cell chimerism was necessary to achieve B cell function. 236 words.

PARK2 deletions occur frequently in sporadic colorectal cancer and accelerate adenoma development in Apc mutant mice.

In 100 primary colorectal carcinomas, we demonstrate by array comparative genomic hybridization (aCGH) that 33% show DNA copy number (DCN) loss involving PARK2, the gene encoding PARKIN, the E3 ubiquitin ligase whose deficiency is responsible for a form of autosomal recessive juvenile parkinsonism. PARK2 is located on chromosome 6 (at 6q25-27), a chromosome with one of the lowest overall frequencies of DNA copy number alterations recorded in colorectal cancers. The PARK2 deletions are mostly focal (31% approximately 0.5 Mb on average), heterozygous, and show maximum incidence in exons 3 and 4. As PARK2 lies within FRA6E, a large common fragile site, it has been argued that the observed DCN losses in PARK2 in cancer may represent merely the result of enforced replication of locally vulnerable DNA. However, we show that deficiency in expression of PARK2 is significantly associated with adenomatous polyposis coli (APC) deficiency in human colorectal cancer. Evidence of some PARK2 mutations and promoter hypermethylation is described. PARK2 overexpression inhibits cell proliferation in vitro. Moreover, interbreeding of Park2 heterozygous knockout mice with Apc(Min) mice resulted in a dramatic acceleration of intestinal adenoma development and increased polyp multiplicity. We conclude that PARK2 is a tumor suppressor gene whose haploinsufficiency cooperates with mutant APC in colorectal carcinogenesis.

Partial proximal trisomy 14: identification and molecular characterization in a girl with global developmental delay.

Chromosomal rearrangements associated with a disease play a significant role in the phenotypic manifestation. Here we report a 9-month-old girl with de novo partial proximal trisomy 14 with seizures and global developmental delay. Cytogenetic investigations revealed a karyotype of 47,XX+marker. The marker was approximately the size of G-group chromosomes and almost mistaken as chromosome 22 due to its banding pattern but the trisomy 22 was ruled out considering its lethality. To find out the origin of the marker chromosome, Spectral karyotyping (SKY) was performed which showed the marker to be of chromosome 14 origin. Further Molecular cytogenetic analysis with whole chromosome 14 confirmed the marker as a derivative 14. Fluorescence in situ hybridization (FISH) with centromeric probe 14 also showed 3 signals. Further fine mapping with three Bacterial Artificial Chromosome clones helped us to tentatively find the extent of the break point regions. The use of SKY and FISH permitted the characterization of this cytogenetic abnormality. The clinical data of the present case are compared with other published cases in the literature. This helps in better genetic counseling and also in the genotype/phenotype correlation. The impact of the extra chromosomal part in relation with the phenotype of the patient is also discussed.