A full-coverage, high-resolution human chromosome 22 genomic microarray for clinical and research applications

Label-Free Sample Preparation for Single-Cell Proteomics

In recent years, single-cell proteomics (SCP) has become a valuable addition to other single-cell omics technologies for studying cellular heterogeneity. The amount of protein in a single cell is very limited, and in contrast to sequencing techniques, there are currently no means for protein amplification. Therefore, most single-cell proteomics approaches aim to maximize sample preparation efficiency while minimizing peptide loss. By reducing processing volumes to sub-microliters and avoiding manual transfer steps that could lead to peptide loss, peptide recovery, and the robustness of SCP workflows have been significantly improved. In this chapter, we describe a protocol for label-free SCP sample preparation using the cellenONE® platform and the proteoCHIP LF 48 substrate prior to analysis with high-performance liquid chromatography-mass spectrometry.

Roles of Skeletal Muscle in Development: A Bioinformatics and Systems Biology Overview

The ability to assess various cellular events consequent to perturbations, such as genetic mutations, disease states and therapies, has been recently revolutionized by technological advances in multiple "omics" fields. The resulting deluge of information has enabled and necessitated the development of tools required to both process and interpret the data. While of tremendous value to basic researchers, the amount and complexity of the data has made it extremely difficult to manually draw inference and identify factors key to the study objectives. The challenges of data reduction and interpretation are being met by the development of increasingly complex tools that integrate disparate knowledge bases and synthesize coherent models based on current biological understanding. This chapter presents an example of how genomics data can be integrated with biological network analyses to gain further insight into the developmental consequences of genetic perturbations. State of the art methods for conducting similar studies are discussed along with modern methods used to analyze and interpret the data.

Novel applications of array comparative genomic hybridization in molecular diagnostics

INTRODUCTION

In 2004, the implementation of array comparative genomic hybridization (array comparative genome hybridization [CGH]) into clinical practice marked a new milestone for genetic diagnosis. Array CGH and single-nucleotide polymorphism (SNP) arrays enable genome-wide detection of copy number changes in a high resolution, and therefore microarray has been recognized as the first-tier test for patients with intellectual disability or multiple congenital anomalies, and has also been applied prenatally for detection of clinically relevant copy number variations in the fetus. Area covered: In this review, the authors summarize the evolution of array CGH technology from their diagnostic laboratory, highlighting exonic SNP arrays developed in the past decade which detect small intragenic copy number changes as well as large DNA segments for the region of heterozygosity. The applications of array CGH to human diseases with different modes of inheritance with the emphasis on autosomal recessive disorders are discussed. Expert commentary: An exonic array is a powerful and most efficient clinical tool in detecting genome wide small copy number variants in both dominant and recessive disorders. However, whole-genome sequencing may become the single integrated platform for detection of copy number changes, single-nucleotide changes as well as balanced chromosomal rearrangements in the near future.

Computational Methods for the Analysis of Array Comparative Genomic Hybridization

Array comparative genomic hybridization (array CGH) is a technique for assaying the copy number status of cancer genomes. The widespread use of this technology has lead to a rapid accumulation of high throughput data, which in turn has prompted the development of computational strategies for the analysis of array CGH data. Here we explain the principles behind array image processing, data visualization and genomic profile analysis, review currently available software packages, and raise considerations for future software development.

Evolution of Dermatofibrosarcoma Protuberans to DFSP-Derived Fibrosarcoma: An Event Marked by Epithelial-Mesenchymal Transition-like Process and 22q Loss

Dermatofibrosarcoma protuberans (DFSP) is a rare and indolent cutaneous sarcoma. At times, a fibrosarcomatous transformation marked by a more aggressive clinical behavior may be present. We investigated the natural history and the molecular bases of progression from classic DFSP to the fibrosarcomatous form (FS-DFSP), looking, retrospectively, at the outcome of all patients affected by primary DFSP treated at our institution from 1993 to 2012 and analyzing the molecular profile of 5 DFSPs and 5 FS-DFSPs by an integrated genomics approach (whole transcriptome sequencing, copy number analysis, FISH, qRT-PCR, IHC). The presence of fibrosarcomatous features was identified in 20 (7.6%) patients out of 263 DFSP. All cases were treated with macroscopic complete surgery. A local relapse occurred in 4 of 23 patients who received a microscopic marginal surgery (2 classic DFSP, 2 FS-DFSP), while metastasis affected 2 patients, both FS-DFSP (10% of FS-DFSP), being the first event. DFSP evolution to FS-DFSP was paralleled by a transcriptional reprogramming. The recurrent loss of chromosome 22q appeared to contribute to this phenomenon by promoting the expression of epigenetic regulators, such as EZH2. Loss of the p16/CDKN2A/INK4A locus at 9p was also observed in two FS-DFSP metastatic cases.

IMPLICATIONS

FS-DFSP is a rare subgroup among DFSP, with a 10% metastatic risk, that was independent from local recurrence and that was not observed in DFSP, that were all cured by wide surgery. Chromosome 22q deletion might play a role in FS-DFSP, and p16 loss may convey a poor outcome. EZH2 dysregulation was also found and represents a druggable target. Mol Cancer Res; 14(9); 820-9. ©2016 AACR.

Atypical amplification of chromosome region 22q12 in melanoma: A case report

Morphological, ultrastructural and immunohistochemical characteristics of clear cell sarcoma (CCS) of the soft tissue frequently overlap with those of malignant melanoma. Thus, the differential diagnosis between the two lesions represents an important diagnostic dilemma. However, a number of genetic factors can be used to differentiate the two tumors; in particular, the t(12;22)(q13;q12) chromosomal translocation is typical of CCS, resulting in fusion of the EWSR1 gene on chromosome 22q12 and the ATF1 gene on chromosome 12q13. The detection of this molecular alteration has proved useful in the differential diagnosis of the two lesions. The present study reports the case of a 71-year-old male patient with a suspicious lymph node mass. Immunohistochemical analysis of the lesion indicated a diagnosis of metastatic melanoma, however, cytogenetic analysis using fluorescence in situ hybridization was additionally performed to investigate the chromosomal rearrangements of the 22q12 region and completely exclude the possibility of CCS. The current case did not demonstrate the presence of the translocation, supporting the diagnosis of melanoma. However, a clear orange amplification signal was observed relative to an ~500-kb region adjacent to the EWSR1 gene in the centromeric direction of chromosome 22q12. To the best of our knowledge, this is the first description of a 22q12 chromosomal alteration in melanoma. Furthermore, despite the presence of numerous genes in this region, their amplification has not previously been associated with the pathogenesis of melanoma.

Exploitation of rolling circle amplification for the construction of large phage-display antibody libraries

Phage display antibody libraries have proven to have a significant role in the discovery of therapeutic antibodies and polypeptides with desired biological and physicochemical properties. Obtaining a large and diverse phage display antibody library, however, is always a challenging task. Various steps of this technique can still undergo optimization in order to obtain an efficient library. In the construction of a single chain fragment variable (scFv) phage display library, the cloning of the scFv fragments into a phagemid vector is of crucial importance. An efficient restriction enzyme digestion of the scFv DNA leads to its proper ligation with the phagemid followed by its successful cloning and expression. Here, we are reporting a different approach to enhance the efficiency of the restriction enzyme digestion step. We have exploited rolling circle amplification (RCA) to produce a long strand of DNA with tandem repeats of scFv sequences, which is found to be highly susceptible to restriction digestion. With this important modification, we are able to construct a large phage display antibody library of naive SJL/J mice. The size of the library is estimated as ~10(8) clones. The number of clones containing a scFv fragment is estimated at 90%. Hence, the present results could considerably aid the utilization of the phage-display technique in order to get an efficiently large antibody library.

Evolution of prenatal genetics: from point mutation testing to chromosomal microarray analysis

Molecular genetic testing involves DNA analysis using various methods for the purpose of diagnosing genetic disorders. In the prenatal DNA diagnostic setting, fetal DNA is usually tested for a specific single-gene disorder for which the fetal risk is 25% or more. In contrast, cytogenetic testing is often used to detect fetal chromosomal abnormalities in cases that involve a wider range of indications. Classic cytogenetic and DNA-based testing methods provide a range of aberrations detected with different levels of genomic resolution. More recently developed molecular cytogenetic methods provide powerful tools to bridge the technical divide between these related areas. One such hybrid method is microarray-based comparative genomic hybridization. Chromosomal microarray analysis has been applied to clinical testing for unbalanced gains or losses of genomic regions associated with genetic disorders. This technology is poised to have a substantial impact on clinical genetics, including prenatal genetic testing.

Microarray and its applications

Microarray is one of the most recent advances being used for cancer research; it provides assistance in pharmacological approach to treat various diseases including oral lesions. Microarray helps in analyzing large amount of samples which have either been recorded previously or new samples; it even helps to test the incidence of a particular marker in tumors. Till recently, microarray's usage in dentistry has been very limited, but in future, as the technology becomes affordable, there may be increase in its usage. Here, we discuss the various techniques and applications of microarray or DNA chip.

Delineation of commonly deleted chromosomal regions in meningiomas by high-density single nucleotide polymorphism genotyping arrays

Despite recent advances in the identification of the cytogenetic profiles of meningiomas, a significant group of tumors still show normal karyotypes or few chromosomal changes. The authors analyzed the cytogenetic profile of 50 meningiomas using fluorescence in situ hybridization and high-density (500 K) single nucleotide polymorphism (SNP) arrays. Our results confirm that del(22q) (52%) and del(1p) (16%) (common deleted regions: 22q11.21-22q13.3. and 1p31.2-p36.33) are the most frequent alterations. Additionally, recurrent monosomy 14 (8%), del(6q) (10%), del(7p) (10%), and del(19q) (4%) were observed, while copy number patterns consistent with recurrent chromosomal gains, gene amplification, and copy number neutral loss of heterozygosity (cnLOH) were either absent or rare. Based on their overall SNP profiles, meningiomas could be classified into: (i) diploid cases, (ii) meningiomas with a single chromosomal change [e.g., monosomy 22/del(22q)] and (iii) tumors with ≥2 altered chromosomes. In summary, our results confirm and extend on previous observations showing that the most recurrent chromosomal abnormalities in meningiomas correspond to chromosome losses localized in chromosomes 1, 22 and less frequently in chromosomes 6, 7, 14, and 19, while chromosomal gains and cnLOH are restricted to a small proportion of cases. Finally, a set of cancer-associated candidate genes associated with the TP53, MYC, CASP3, HDAC1, and TERT signaling pathways was identified, in cases with coexisting monosomy 14 and del(1p).

Strategies for genotyping

The identification of genomic loci linked to or associated with human disease has been greatly facilitated by the evolution of genotyping strategies and techniques. The success of these strategies continues to be based upon clear clinical assessment, accurate sample handling, and careful data management, but also increasingly upon experimental design. Technological advances in the field of genotyping have permitted increasingly complex and large population studies to be performed. An understanding of publicly available genetic variation databases, including an awareness of the limitations of these data, and an appreciation of the strategic approaches that should be used to exploit this information will provide tremendous insight for researchers are aiming to utilize this accessible technology. As genome-wide association studies (GWAS) and Next Generation (NextGen) sequencing become the mainstays of genetic analyses, it is important that their technical strengths and limitations, as well as their impact on study design, be understood before use in a linkage or genetic association study.

Common pathogenetic mechanism involving human chromosome 18 in familial and sporadic ileal carcinoid tumors

Serotonin producing endocrine carcinoma of small intestine (ileal carcinoid) is a clinically distinct endocrine tumor. It is generally considered as a sporadic disease and its molecular etiology is poorly understood. We report comprehensive clinical and molecular studies of 55 sporadic and familial patients diagnosed with this condition. Nine pedigrees encompassing 23 affected subjects were established, consistent with autosomal dominant mode of inheritance. Familial and sporadic patients demonstrated indistinguishable clinical pictures. Molecular analyses of 61 tumors from 45 individuals, including eight familial and 37 sporadic patients, aimed at determination of global copy number aberrations using BAC and Illumina SNP arrays and gene expression profiling by Affymetrix chips. Chromosome 18 aberrations were identified in both sporadic and in familial tumors; 100% vs. 38%, respectively. Other, less frequent aberrations were also common for both groups. Global expression profiles revealed no differentially expressed genes. Frequent gain of chromosome 7 was exclusively observed in metastases, when patient matched primary tumors and metastases were compared. Notably, the latter aberration correlated with solid growth pattern morphology (P < 0.01), a histopathological feature that has previously been related to worse prognosis. The clinical and molecular similarities identified between sporadic and familial cases suggest a common pathogenetic mechanism involved in tumor initiation. The familial variant of ileal carcinoid represents a previously unrecognized autosomal dominant inherited tumor disease, which we propose to call Familial Ileal Endocrine Carcinoma (FIEC). Our findings indicate the location of a FIEC tumor suppressor gene near the telomere of 18q, involved in development of inherited and sporadic tumors.

Integrative epigenomic and genomic analysis of malignant pheochromocytoma

Epigenomic and genomic changes affect gene expression and contribute to tumor development. The histone modifications trimethylated histone H3 lysine 4 (H3K4me3) and lysine 27 (H3K27me3) are epigenetic regulators associated to active and silenced genes, respectively and alterations of these modifications have been observed in cancer. Furthermore, genomic aberrations such as DNA copy number changes are common events in tumors. Pheochromocytoma is a rare endocrine tumor of the adrenal gland that mostly occurs sporadic with unknown epigenetic/genetic cause. The majority of cases are benign. Here we aimed to combine the genome-wide profiling of H3K4me3 and H3K27me3, obtained by the ChIP-chip methodology, and DNA copy number data with global gene expression examination in a malignant pheochromocytoma sample. The integrated analysis of the tumor expression levels, in relation to normal adrenal medulla, indicated that either histone modifications or chromosomal alterations, or both, have great impact on the expression of a substantial fraction of the genes in the investigated sample. Candidate tumor suppressor genes identified with decreased expression, a H3K27me3 mark and/or in regions of deletion were for instance TGIF1, DSC3, TNFRSF10B, RASSF2, HOXA9, PTPRE and CDH11. More genes were found with increased expression, a H3K4me3 mark, and/or in regions of gain. Potential oncogenes detected among those were GNAS, INSM1, DOK5, ETV1, RET, NTRK1, IGF2, and the H3K27 trimethylase gene EZH2. Our approach to associate histone methylations and DNA copy number changes to gene expression revealed apparent impact on global gene transcription, and enabled the identification of candidate tumor genes for further exploration.

Focal amplifications are associated with high grade and recurrences in stage Ta bladder carcinoma

Urinary bladder cancer is a heterogeneous disease with tumors ranging from papillary noninvasive (stage Ta) to solid muscle infiltrating tumors (stage T2+). The risk of progression and death for the most frequent diagnosed type, Ta, is low, but the high incidence of recurrences has a significant effect on the patients' quality of life and poses substantial costs for health care systems. Consequently, the purpose of this study was to search for predictive factors of recurrence on the basis of genetic profiling. A clinically well characterized cohort of Ta bladder carcinomas, selected by the presence or absence of recurrences, was evaluated by an integrated analysis of DNA copy number changes and gene expression (clone-based 32K, respectively, U133Plus2.0 arrays). Only a few chromosomal aberrations have previously been defined in superficial bladder cancer. Surprisingly, the profiling of Ta tumors with a high-resolution array showed that DNA copy alterations are relatively common in this tumor type. Furthermore, we observed an overrepresentation of focal amplifications within high-grade and recurrent cases. Known (FGFR3, CCND1, MYC, MDM2) and novel candidate genes were identified within the loci. For example, MYBL2, a nuclear transcription factor involved in cell-cycle progression; YWHAB, an antiapoptotic protein; and SDC4, an important component of focal adhesions represent interesting candidates detected within two amplicons on chromosome 20, for which DNA amplification correlated with transcript up-regulation. The observed overrepresentation of amplicons within high-grade and recurrent cases may be clinically useful for the identification of patients who will benefit from a more aggressive therapy.

Characterization of novel and complex genomic aberrations in glioblastoma using a 32K BAC array

Glioblastomas (GBs) are malignant CNS tumors often associated with devastating symptoms. Patients with GB have a very poor prognosis, and despite treatment, most of them die within 12 months from diagnosis. Several pathways, such as the RAS, tumor protein 53 (TP53), and phosphoinositide kinase 3 (PIK3) pathways, as well as the cell cycle control pathway, have been identified to be disrupted in this tumor. However, emerging data suggest that these aberrations represent only a fraction of the genetic changes involved in gliomagenesis. In this study, we have applied a 32K clone-based genomic array, covering 99% of the current assembly of the human genome, to the detailed genetic profiling of a set of 78 GBs. Complex patterns of aberrations, including high and narrow copy number amplicons, as well as a number of homozygously deleted loci, were identified. Amplicons that varied both in number (three on average) and in size (1.4 Mb on average) were frequently detected (81% of the samples). The loci encompassed not only previously reported oncogenes (EGFR, PDGFRA, MDM2, and CDK4) but also numerous novel oncogenes as GRB10, MKLN1, PPARGC1A, HGF, NAV3, CNTN1, SYT1, and ADAMTSL3. BNC2, PTPLAD2, and PTPRE, on the other hand, represent novel candidate tumor suppressor genes encompassed within homozygously deleted loci. Many of these genes are already linked to several forms of cancer; others represent new candidate genes that may serve as prognostic markers or even as therapeutic targets in the future. The large individual variation observed between the samples demonstrates the underlying complexity of the disease and strengthens the demand for an individualized therapy based on the genetic profile of the patient.

Design, Construction and Validation of Targeted BAC Array-Based CGH Test for Detecting the Most Commons Chromosomal Abnormalities

We designed a targeted-array called GOLD (Gain or Loss Detection) Chip consisting of 900 FISH-mapped non-overlapping BAC clones spanning the whole genome to enhance the coverage of 66 unique human genomic regions involved in well known microdeletion/microduplication syndromes. The array has a 10 Mb backbone to guarantee the detection of the aneuploidies, and has an implemented resolution for telomeres, and for regions involved in common genomic diseases. In order to evaluate clinical diagnostic applicability of GOLDChip, analytical validity was carried-out via retrospective analysis of DNA isolated from a series of cytogenetically normal amniocytes and cytogenetically abnormal DNA obtained from cultured amniocytes, peripheral blood and/or cell lines. We recruited 47 DNA samples corresponding to pathologies with significant frequencies (Cri du Chat syndrome, Williams syndrome, Prader Willi/Angelman syndromes, Smith-Magenis syndrome, DiGeorge syndrome, Miller-Dieker syndrome, chromosomes 13, 18 and 21 trisomies). We set up an experimental protocol that allowed to identify chromosomal rearrangements in all the DNA samples analyzed. Our results provide evidence that our targeted BAC array can be used for the identification of the most common microdeletion syndromes and common aneuploidies.

Identification of copy number variants defining genomic differences among major human groups

Background

Understanding the genetic contribution to phenotype variation of human groups is necessary to elucidate differences in disease predisposition and response to pharmaceutical treatments in different human populations.

Methodology/Principal Findings

We have investigated the genome-wide profile of structural variation on pooled samples from the three populations studied in the HapMap project by comparative genome hybridization (CGH) in different array platforms. We have identified and experimentally validated 33 genomic loci that show significant copy number differences from one population to the other. Interestingly, we found an enrichment of genes related to environment adaptation (immune response, lipid metabolism and extracellular space) within these regions and the study of expression data revealed that more than half of the copy number variants (CNVs) translate into gene-expression differences among populations, suggesting that they could have functional consequences. In addition, the identification of single nucleotide polymorphisms (SNPs) that are in linkage disequilibrium with the copy number alleles allowed us to detect evidences of population differentiation and recent selection at the nucleotide variation level.

Conclusions

Overall, our results provide a comprehensive view of relevant copy number changes that might play a role in phenotypic differences among major human populations, and generate a list of interesting candidates for future studies.

Fluorescence in situ hybridization techniques in medical diagnostics

BACKGROUND

Fluorescence in situ hybridization (FISH) has become a well-established method in medical diagnostics. FISH methods complement conventional cytogenetic banding techniques and offer extra clinical applications. FISH is based on the binding of complementary, single-stranded fluorescence-labeled nucleic acid sequences to the fixed and denatured target DNA of metaphases, interphase nuclei or isolated DNA sequences (BACs, oligonucleotides).

OBJECTIVE

The intent of this article is to review the development of molecular cytogenetic techniques available at present and to summarize the most efficient and appropriate use of these techniques in medical diagnostics. The technical aspects and most important applications of FISH assays are described.

CONCLUSION

FISH is bridging the gap between conventional cytogenetic banding analysis and molecular genetic DNA studies. The use of FISH techniques enhances the correct interpretation of numerical and structural chromosome aberrations.

Somatic mosaicism for copy number variation in differentiated human tissues

Two major types of genetic variation are known: single nucleotide polymorphisms (SNPs), and a more recently discovered structural variation, involving changes in copy number (CNVs) of kilobase- to megabase-sized chromosomal segments. It is unknown whether CNVs arise in somatic cells, but it is, however, generally assumed that normal cells are genetically identical. We tested 34 tissue samples from three subjects and, having analyzed for each tissue < or =10(-6) of all cells expected in an adult human, we observed at least six CNVs, affecting a single organ or one or more tissues of the same subject. The CNVs ranged from 82 to 176 kb, often encompassing known genes, potentially affecting gene function. Our results indicate that humans are commonly affected by somatic mosaicism for stochastic CNVs, which occur in a substantial fraction of cells. The majority of described CNVs were previously shown to be polymorphic between unrelated subjects, suggesting that some CNVs previously reported as germline might represent somatic events, since in most studies of this kind, only one tissue is typically examined and analysis of parents for the studied subjects is not routinely performed. A considerable number of human phenotypes are a consequence of a somatic process. Thus, our conclusions will be important for the delineation of genetic factors behind these phenotypes. Consequently, biobanks should consider sampling multiple tissues to better address mosaicism in the studies of somatic disorders.

From cytogenetics to next-generation sequencing technologies: advances in the detection of genome rearrangements in tumorsThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Systems and Chemical Biology, and has undergone the Journal's usual peer review process

Genome rearrangements have long been recognized as hallmarks of human tumors and have been used to diagnose cancer. Techniques used to detect genome rearrangements have evolved from microscopic examinations of chromosomes to the more recent microarray-based approaches. The availability of next-generation sequencing technologies may provide a means for scrutinizing entire cancer genomes and transcriptomes at unparalleled resolution. Here we review the methods that have been used to detect genome rearrangements and discuss the scope and limitations of each approach. We end with a discussion of the potential that next-generation sequencing technologies may offer to the field.

Clinical array comparative genomic hybridization: a new paradigm

BACKGROUND

Although the clinical utility of array comparative genomic hybridization (aCGH) is undisputed, the implementation of this technology is a unique experience for each laboratory.

OBJECTIVE

Endeavors to construct a bacterial artificial chromosome (BAC)-based CGH microarray targeting microdeletion and duplication syndromes related to mental retardation and developmental delay are described.

METHOD

Covering each chromosome at the 650-band level, the array comprises 1360 BAC clones with emphasis on the subtelomeric and pericentromeric regions and enrichment of genomic hot spots containing genes associated with specific constitutional disorders. During development of the array, fluorescence in situ hybridization (FISH) and end-sequencing analysis eliminated 24% of BACs that were mismapped or cross-hybridized, underscoring the need rigorously to assess arrayed elements. Performance of the BACs was tested further with chromosome-specific add-in experiments.

CONCLUSION

Of the first 500 clinical cases, 54 (11%) showed chromosome abnormalities, which were confirmed by FISH with BACs from the aberrant loci or by conventional cytogenetics. Array CGH is a powerful tool that is now being implemented in the realm of diagnostic testing.

Phenotypically concordant and discordant monozygotic twins display different DNA copy-number-variation profiles

The exploration of copy-number variation (CNV), notably of somatic cells, is an understudied aspect of genome biology. Any differences in the genetic makeup between twins derived from the same zygote represent an irrefutable example of somatic mosaicism. We studied 19 pairs of monozygotic twins with either concordant or discordant phenotype by using two platforms for genome-wide CNV analyses and showed that CNVs exist within pairs in both groups. These findings have an impact on our views of genotypic and phenotypic diversity in monozygotic twins and suggest that CNV analysis in phenotypically discordant monozygotic twins may provide a powerful tool for identifying disease-predisposition loci. Our results also imply that caution should be exercised when interpreting disease causality of de novo CNVs found in patients based on analysis of a single tissue in routine disease-related DNA diagnostics.

Representational oligonucleotide microarray analysis (ROMA) and comparison of binning and change-point methods of analysis: application to detection of del22q11.2 (DiGeorge) syndrome

DiGeorge (del22q11.2) syndrome is estimated to occur in 1:4,000 births, is the most common contiguous-gene deletion syndrome in humans, and is caused by autosomal dominant deletions in the 22q11.2 DiGeorge syndrome critical region (DGCR). Multiple microarray methods have been developed recently for analyzing such copy number changes, but data analysis and accurate deletion detection remains challenging. Clinical use of these microarray methods would have many advantages, particularly when the possibility of a chromosomal disorder cannot be determined simply on the basis of history and physical examination data alone. We investigated the use of the microarray technique, representational oligonucleotide microarray analysis (ROMA), in the detection of del22q11.2 syndrome. Genomic DNA was isolated from three well-characterized cell lines with 22q11.2 DGCR deletions and from the blood of a patient suspected of having del22q11.2 syndrome, and analyzed using both the binning and change-point model algorithms. Though the 22q11.2 deletion was easily identified with either method, change-point models provide clearer identification of deleted regions, with the potential for fewer false-positive results. For circumstances in which a clear, a priori, copy-number change hypothesis is not present, such as in many clinical samples, change-point methods of analysis may be easier to interpret.

Autoantibodies to glutathione S-transferase theta 1 in patients with primary sclerosing cholangitis and other autoimmune diseases

Primary sclerosing cholangitis (PSC) is an enigmatic disorder with a suggested autoimmune basis. A variety of autoantigens have been suggested but no specific or highly directed epitope has been identified. To address this issue, we constructed a cDNA library from normal human choledochus and screened expressing clones with serum from a patient with PSC and inflammatory bowel disease (IBD). Based on this screening, glutathione S-transferase theta 1 (GSTT1) was identified as a potential autoantigenic target. To study the specificity of GSTT1, we determined immunoreactivity using a panel of 58 patients with PSC, with and without IBD, 57 patients with IBD, 31 patients with Hashimoto's thyroiditis, 30 patients with primary biliary cirrhosis (PBC), 20 patients with insulin dependent diabetes mellitus, 22 patients with autoimmune polyendocrine syndrome type I, 10 patients with systemic lupus erythematosus (SLE), 20 patients with Sjögren's syndrome, 12 patients with autoimmune pancreatitis, 28 patients with Addison's disease, 27 patients with Grave's disease, 17 with myasthenia gravis, and 118 healthy controls. Reactivity against GSTT1 was found with PSC and IBD as well as some patients with other autoimmune pathology, indicating that this population of antibodies is neither specific nor a sensitive serologic marker for PSC, but the frequency was clearly higher in autoimmune patients than controls. GSTT1-antibodies have been described in persons with GSTT1-null genotype and are suggested to develop as an alloimmune response to blood transfusions from GSTT1-positive donors or pregnancies with GSTT1-positive children. Therefore, two IBD patients with and 15 PSC patients without GSTT1-antibodies were genotyped for GSTT1 to investigate if the presence of GSTT1-antibodies was associated with the GSTT1-null genotype and possibly caused by an alloimmune response. Both IBD patients and three of the PSC patients were of the GSTT1-null genotype. We note that the frequency of GSTT1-antibodies in this study is more than 100-fold higher than the frequency described earlier in patients with autoimmune diseases. We also observe an increased frequency of GSTT1-antibodies in patients with autoimmune diseases compared to healthy controls. This increased frequency can be explained by an autoimmune phenotype which increases susceptibility to such autoantibodies, or by a high frequency of the GSTT1-null genotype in autoimmune disease.

A patient with 22q11.2 deletion and Opitz syndrome-like phenotype has the same deletion as velocardiofacial patients

Five patients were previously described with the Opitz (GBBB) syndrome (OMIM 145410) phenotype and 22q11.2 deletion determined by FISH but the precise limits of their deletions have not been determined. Since one locus for Opitz syndrome maps to 22q11.2 and chromosomal arrangements are frequently complex and could inactivate such a locus, we performed high-resolution array-based comparative genomic hybridization (CGH) on a new Opitz syndrome-like phenotype patient with a 22q11.2 deletion. He shares the same deletion as patients with velocardiofacial and DiGeorge syndrome.

Oligonucleotide arrays for high-resolution analysis of copy number alteration in mental retardation/multiple congenital anomalies

Genetic diseases arising from microdeletions and microduplications lead to copy number alterations of genomic regions containing one or more genes. Clinically, these rearrangements may be detected by routine cytogenetic testing, which may include karyotype analysis, subtelomeric analysis with fluorescence in situ hybridization, and/or fluorescence in situ hybridization directed at known chromosomal rearrangement-based disorders. The major limitations of these tests are low resolution and limited coverage of the genome. Array-based comparative genomic hybridization has recently become a widely used approach in the genome-wide analysis of copy number alterations in children with mental retardation and/or multiple congenital anomalies. Oligonucleotide-based arrays provide a genome-wide coverage at a much higher resolution than microarrays currently used in clinical diagnostics, greatly improving the rate of detection of submicroscopic copy number alterations in children with mental retardation and/or multiple congenital anomalies.

Cellular functions of 14-3-3 zeta in apoptosis and cell adhesion emphasize its oncogenic character

14-3-3 proteins are relevant to cancer biology as they are key regulators of major cellular processes such as proliferation, differentiation, senescence and apoptosis. So far, the sigma isoform (14-3-3sigma) has most directly been implicated in carcinogenesis and was recognized as a tumour-suppressor gene. The other six members of the mammalian 14-3-3 gene family likely behave as oncogenes, although direct evidence supporting this view is largely circumstantial. In this report, we show that knockdown of 14-3-3zeta induces at least two isoform-specific phenotypes that are consistent with a potential oncogenic activity during tumorigenesis. Firstly, downregulation of 14-3-3zeta sensitized cells to stress-induced apoptosis and JNK/p38 signalling and secondly, it enforced cell-cell contacts and expression of adhesion proteins. Apparently, the zeta isoform restrains both cell adhesion and the cellular propensity for apoptosis, two activities that are also restrained during carcinogenesis. The assumption that 14-3-3zeta has oncogenic properties was substantiated with a web-based meta-analysis (Oncomine), revealing that 14-3-3zeta is overexpressed in various types of carcinomas. As the highly conserved human 14-3-3 gene family encodes proteins with either tumour-promoting or tumour-suppressing activities, we infer that the cellular balance between the various 14-3-3 isoforms is crucial for the proper functioning of cells.

Construction and use of spotted large-insert clone DNA microarrays for the detection of genomic copy number changes

Microarray-based comparative genomic hybridization has become a widespread method for the analysis of DNA copy number changes across the human genome. Initial methods for microarray construction using large-insert clones required the preparation of DNA from large-scale cultures. This rapidly became an expensive and time-consuming process when expanded to the number of clones needed for higher resolution arrays. To overcome this problem, several PCR-based strategies have been developed to enable array construction from small amounts of cloned DNA. Here, we describe the construction of microarrays composed of human-specific large-insert clones (40-200 kb) using a specific degenerate oligonucleotide PCR strategy. In addition, we also describe array hybridization using manual and automated procedures and methods for array analysis. The technology and protocols described in this article can easily be adapted for other species dependent on the availability of clone libraries. According to our protocols, the procedure will take approximately 3 days from labeling the DNA to scanning the hybridized slides.

Mechanism of chimera formation during the Multiple Displacement Amplification reaction

Background

Multiple Displacement Amplification (MDA) is a method used for amplifying limiting DNA sources. The high molecular weight amplified DNA is ideal for DNA library construction. While this has enabled genomic sequencing from one or a few cells of unculturable microorganisms, the process is complicated by the tendency of MDA to generate chimeric DNA rearrangements in the amplified DNA. Determining the source of the DNA rearrangements would be an important step towards reducing or eliminating them.

Results

Here, we characterize the major types of chimeras formed by carrying out an MDA whole genome amplification from a single E. coli cell and sequencing by the 454 Life Sciences method. Analysis of 475 chimeras revealed the predominant reaction mechanisms that create the DNA rearrangements. The highly branched DNA synthesized in MDA can assume many alternative secondary structures. DNA strands extended on an initial template can be displaced becoming available to prime on a second template creating the chimeras. Evidence supports a model in which branch migration can displace 3'-ends freeing them to prime on the new templates. More than 85% of the resulting DNA rearrangements were inverted sequences with intervening deletions that the model predicts. Intramolecular rearrangements were favored, with displaced 3'-ends reannealing to single stranded 5'-strands contained within the same branched DNA molecule. In over 70% of the chimeric junctions, the 3' termini had initiated priming at complimentary sequences of 2–21 nucleotides (nts) in the new templates.

Conclusion

Formation of chimeras is an important limitation to the MDA method, particularly for whole genome sequencing. Identification of the mechanism for chimera formation provides new insight into the MDA reaction and suggests methods to reduce chimeras. The 454 sequencing approach used here will provide a rapid method to assess the utility of reaction modifications.

Development of a high-density pericentromeric region BAC clone set for the detection and characterization of small supernumerary marker chromosomes by array CGH

PURPOSE

Small supernumerary marker chromosomes are centric chromosomal segments that, by definition, cannot be characterized unambiguously by conventional chromosome banding. Marker chromosomes are of particular interest in clinical cytogenetics because they are nearly 10 times more frequent in individuals with mental retardation (0.426%) than in the normal population (0.043%). However, they are often found in only a small percentage of cells, making them difficult to detect and characterize in a diagnostic setting. We designed, constructed, and employed a bacterial artificial chromosome (BAC)-based microarray to demonstrate the utility of array-based comparative genomic hybridization (array CGH) for detecting and characterizing marker chromosomes in clinical diagnostic specimens.

METHODS

We constructed a high-density microarray using 974 BAC clones that were mapped by fluorescence in situ hybridization and cover approximately 5 Mb of the most proximal unique sequence adjacent to the centromere on all 43 unique pericentromeric regions of the human genome (excluding the acrocentric short arms). This array was used to further characterize 20 previously identified marker chromosomes that were originally found with either conventional chromosome analysis or a targeted microarray.

RESULTS

The enhanced coverage of this pericentromeric array not only identified the chromosomal origin of each marker in 15 cases, it also distinguished between the involvement of the short arm and/or the long arm of each chromosome, defined the sizes of many of the markers, and revealed complex rearrangements or multiple markers in single individuals. However, in five cases, the markers could not be identified by this assay, most likely because of very low levels of mosaicism and/or their small size and lack of detectable euchromatin. The expanded coverage of the pericentromeric regions represented on the array was adequate to refine the breakpoints in two-thirds of all cases in which a marker chromosome was identified by this assay.

CONCLUSIONS

This study demonstrates the utility of array CGH in the detection and characterization of mosaic marker chromosomes. Because approximately one-third of the markers characterized in this study involved more unique sequence than that represented on this array, additional pericentromeric coverage may be even more valuable. We anticipate that this will allow detailed characterization of small supernumerary marker chromosomes that will greatly facilitate phenotype/genotype correlations and play a valuable role in the diagnosis and medical management of both pre- and postnatal cases in which marker chromosomes have been identified.

Role of cytogenetics and molecular cytogenetics in the diagnosis of genetic imbalances

Five decades ago, Tijo and Levan (1956) first recognized the correct chromosome number in man to be 46. Shortly thereafter, several chromosome aneuploid syndromes were identified. In the early 1970s, various chromosomal-banding techniques were developed that allowed the recognition of individual chromosomes and deletions and duplications as etiologies for numerous chromosome syndromes. Slightly more than 10 years ago, fluorescence in situ hybridization (FISH) procedures, using fluorescent-labeled DNA sequences were developed and clinical use of this technique allowed for the identification of cryptic chromosome abnormalities associated with microdeletions and microduplications. The use of subtelomere region-specific FISH probes further led to the identification of deletions and other unbalanced rearrangements in individuals with mental retardation with an apparently normal karyotype. More recently, microarray comparative genomic hybridization was developed, and the technique has recently become incorporated into the clinical cytogenetics laboratory for the identification of submicrosopic deletions and duplications that are associated with developmental delay. The intent of this article is to review the cytogenetic and molecular cytogenetic techniques currently available for the diagnosis of individuals with neurologic disease and genetic imbalances that result in neurologic disturbances and to summarize the most efficient and appropriate use of these techniques in clinical practice.

Array-based comparative genomic hybridization in clinical diagnosis

The sequencing of the human genome and development of high-throughput microarray technologies have enhanced the detection of copy number alterations in cancer research and the study of constitutional chromosomal abnormalities. Microarray-based comparative genomic hybridization (array CGH) has integrated molecular and traditional cytogenetics and has begun to impact the clinician's approach to medical genetics. Clinical applications of array CGH may define new genetic syndromes, expand the phenotype of existing syndromes and characterize a genomic signature of some cancers. As array CGH becomes the initial diagnostic approach for the investigation of constitutional and acquired chromosomal abnormalities, the combination of bioinformatics, robotics and microarray technology will set the stage for a new generation of high-resolution and high-throughput tools for genetic analysis, diagnosis and gene discovery.

Application of array-based comparative genomic hybridization to clinical diagnostics

Microarray-based comparative genomic hybridization (array CGH) is a revolutionary platform that was recently adopted in the clinical laboratory. This technology was first developed as a research tool for the investigation of genomic alterations in cancer. It allows for a high-resolution evaluation of DNA copy number alterations associated with chromosome abnormalities. Array CGH is based on the use of differentially labeled test and reference genomic DNA samples that are simultaneously hybridized to DNA targets arrayed on a glass slide or other solid platform. In this review, we examine the technology and its transformation from a research tool into a maturing diagnostic instrument. We also evaluate the various approaches that have shaped the current platforms that are used for clinical applications. Finally, we discuss the advantages and shortcomings of "whole-genome" arrays and compare their diagnostic use to "targeted" arrays. Depending on their design, microarrays provide distinct advantages over conventional cytogenetic analysis because they have the potential to detect the majority of microscopic and submicroscopic chromosomal abnormalities. This new platform is poised to revolutionize modern cytogenetic diagnostics and to provide clinicians with a powerful tool to use in their increasingly sophisticated diagnostic capabilities.

Comprehensive genetic and epigenetic analysis of sporadic meningioma for macro-mutations on 22q and micro-mutations within the NF2 locus

BACKGROUND

Meningiomas are the most common intracranial neoplasias, representing a clinically and histopathologically heterogeneous group of tumors. The neurofibromatosis type 2 (NF2) tumor suppressor is the only gene known to be frequently involved in early development of meningiomas. The objective of this study was to identify genetic and/or epigenetic factors contributing to the development of these tumors. A large set of sporadic meningiomas were analyzed for presence of 22q macro-mutations using array-CGH in order to identify tumors carrying gene dosage aberrations not encompassing NF2. The NF2 locus was also comprehensively studied for point mutations within coding and conserved non-coding sequences. Furthermore, CpG methylation within the NF2 promoter region was thoroughly analyzed.

RESULTS

Monosomy 22 was the predominant finding, detected in 47% of meningiomas. Thirteen percent of the tumors contained interstitial/terminal deletions and gains, present singly or in combinations. We defined at least two minimal overlapping regions outside the NF2 locus that are small enough (approximately 550 kb and approximately 250 kb) to allow analysis of a limited number of candidate genes. Bialleinactivationo the NF2 gne was detected in 36% of meningiomas. Among the monosomy 22 cases, no additional NF2 mutations could be identified in 35% (17 out of 49) of tumors. Furthermore, the majority of tumors (9 out of 12) with interstitial/terminal deletions did not have any detectable NF2 mutations. Methylation within the NF2 promoter region was only identified at a single CpG site in one tumor sample.

CONCLUSION

We confirmed previous findings of pronounced differences in mutation frequency between different histopathological subtypes. There is a higher frequency of biallelic NF2 inactivation in fibroblastic (52%) compared to meningothelial (18%) tumors. The presence of macro-mutations on 22q also shows marked differences between fibroblastic (86%) and meningothelial (39%) subtypes. Thus, inactivation of NF2, often combined with the presence of macro-mutation on 22q, is likely not as important for the development of the meningothelial subtype, as opposed to the fibroblastic form. Analysis of 40 CpG sites distributed within 750 bp of the promoter region suggests that NF2 promoter methylation does not play a major role in meningioma development.

Array-CGH and multipoint FISH to decode complex chromosomal rearrangements

Background

Recently, several high-resolution methods of chromosome analysis have been developed. It is important to compare these methods and to select reliable combinations of techniques to analyze complex chromosomal rearrangements in tumours. In this study we have compared array-CGH (comparative genomic hybridization) and multipoint FISH (mpFISH) for their ability to characterize complex rearrangements on human chromosome 3 (chr3) in tumour cell lines. We have used 179 BAC/PAC clones covering chr3 with an approximately 1 Mb resolution to analyze nine carcinoma lines. Chr3 was chosen for analysis, because of its frequent rearrangements in human solid tumours.

Results

The ploidy of the tumour cell lines ranged from near-diploid to near-pentaploid. Chr3 locus copy number was assessed by interphase and metaphase mpFISH. Totally 53 chr3 fragments were identified having copy numbers from 0 to 14. MpFISH results from the BAC/PAC clones and array-CGH gave mainly corresponding results. Each copy number change on the array profile could be related to a specific chromosome aberration detected by metaphase mpFISH. The analysis of the correlation between real copy number from mpFISH and the average normalized inter-locus fluorescence ratio (ANILFR) value detected by array-CGH demonstrated that copy number is a linear function of parameters that include the variable, ANILFR, and two constants, ploidy and background normalized fluorescence ratio.

Conclusion

In most cases, the changes in copy number seen on array-CGH profiles reflected cumulative chromosome rearrangements. Most of them stemmed from unbalanced translocations. Although our chr3 BAC/PAC array could identify single copy number changes even in pentaploid cells, mpFISH provided a more accurate analysis in the dissection of complex karyotypes at high ploidy levels.

Strategies for the detection of copy number and other structural variants in the human genome

Advances in genome scanning technologies are revealing that copy number variants (CNVs) and polymorphisms, ranging from a few kilobases to several megabases in size, are present in genomes at frequencies much greater than previously known. Discoveries of additional forms of genomic variation, including inversions, insertions, deletions and complex rearrangements, are also occurring at an increased rate. Along with CNVs, these sequence alterations are collectively known as structural variants, and their discovery has had an immediate impact on the interpretation of basic research and clinical diagnostic data. This paper discusses different methods, experimental strategies and technologies that are currently available to study copy number variation and other structural variants in the human genome.

Genomic Alterations in Ectopic and Eutopic Endometria of Women with Endometriosis

BACKGROUND/AIMS

Ectopic and eutopic endometria of women with endometriosis have been shown to contain genomic alterations. In this study, we sought to identify genomic alterations in both ectopic and eutopic endometria of 5 women with endometriosis and to examine whether the two tissues share any genomic alterations. We also attempted to classify tissue samples based on the alteration profiles.

METHODS

Laser capture microdissection was used to harvest epithelial cells. High-resolution comparative genomic hybridization microarrays were used to identify genomic alterations in eutopic and ectopic endometria from 5 women with endometriosis. The results were validated by real-time RT-PCR and loss of heterozygosity analysis.

RESULTS

All 5 patients had genomic alterations in their eutopic and ectopic endometria. The ectopic and eutopic endometria shared a sizable portion of genomic alterations. Cluster analysis of the genomic alteration profile correctly and consistently classified tissue samples from the 5 patients into two groups: peritoneal implants and ovarian cysts.

CONCLUSIONS

The correct classification of tissue samples into two groups suggests that these two subtypes of endometriosis may have distinct genomic alteration profiles and are thus distinct entities, as previously proposed. The shared alterations are likely the ones that harbor genes responsible for an increased propensity of endometrial debris to implant to the ectopic sites and for early events that lead to the establishment of lesions. Alternatively, these shared alterations may harbor genes that are dysregulated in both eutopic and ectopic endometria. The identified genomic alterations should help to zero in genes involved in the pathogenesis of endometriosis in future studies.

Recent advances in array comparative genomic hybridization technologies and their applications in human genetics

Array comparative genomic hybridization (array CGH) is a method used to detect segmental DNA copy number alterations. Recently, advances in this technology have enabled high-resolution examination for identifying genetic alterations and copy number variations on a genome-wide scale. This review describes the current genomic array platforms and CGH methodologies, highlights their applications for studying cancer genetics, constitutional disease and human variation, and discusses visualization and analytical software programs for computational interpretation of array CGH data.

Array-based comparative genome hybridization in clinical genetics

Abnormalities in DNA copy number are frequently found in patients with multiple anomaly syndromes and mental retardation. Array-based comparative genomic hybridization (array-CGH) is a high-resolution, whole-genome technology that improves detection of submicroscopic aberrations underlying these syndromes. Eight patients with mental disability, multiple congenital anomalies, and dysmorphic features were screened for submicroscopic chromosomal imbalances using the GenoSensor Array 300 Chip. Subtelomeric aberrations previously detected by fluorescence in situ hybridization (FISH) analysis were confirmed in two patients, and accurate diagnosis was provided in two previously undiagnosed complex cases. Microdeletions at 15q11.2-q13 in a newborn with hypotonia, cryptorchidism, and hypopigmentation were detected with few discrepancies between the array results and FISH analysis. Contiguous microdeletion of GSCL, HIRA and TBX1 genes at 22q11.2 was identified in a previously undiagnosed boy with an unusual presentation of the VCF/DiGeorge spectrum. In a newborn with aniridia, a borderline false-negative WT1 deletion was observed, most probably because of differences between the size of the genomic deletion and the microarray probe. A false-positive rate of 0.2% was calculated for clone-by-clone analysis, whereas the per patient false-positive rate was 20%. Array-CGH is a powerful tool for the rapid and accurate detection of genetic disorders associated with copy number abnormalities and can significantly improve clinical genetic diagnosis and care.

Tapping diversity lost in transformations--in vitro amplification of ligation reactions

Molecular evolution is a powerful means of engineering proteins. It usually requires the generation of a large recombinant DNA library of variants for cloning into a phage or plasmid vector, and the transformation of a host organism for expression and screening of the variant proteins. However, library size is often limited by the low yields of circular DNA and the poor transformation efficiencies of linear DNA. Here we have overcome this limitation by amplification of recombinant circular DNA molecules directly from ligation reactions. The amplification by bacteriophage Phi29 polymerase increased the number of transformants; thus from a nanogram-scale ligation of DNA fragments comprising two sub-libraries of variant antibody domains, we succeeded in amplifying a highly diverse and large combinatorial phage antibody library (>10(9) transformants in Escherichia coli and 10(5)-fold more transformants than without amplification). From the amplified library, but not from the smaller un-amplified library, we could isolate several antibody fragments against a target antigen. It appears that amplification of ligations with Phi29 polymerase can help recover clones and molecular diversity otherwise lost in the transformation step. A further feature of the method is the option of using PCR-amplified vectors for ligations.

Analysis of copy number variation in the normal human population within a region containing complex segmental duplications on 22q11 using high-resolution array-CGH

A previously detected copy number polymorphism (Ep CNP) in patients affected with neuroectodermal tumors led us to investigate its frequency and length in the normal population. For this purpose, a program called Sequence Allocator was developed and applied for the construction of an array that consisted of unique and duplicated fragments, allowing the assessment of copy number variation within regions of segmental duplications. The average resolution of this array was 11 kb and we determined the size of the Ep CNP to be 290 kb. Analysis of normal controls identified 7.7 and 7.1% gains in peripheral blood and lymphoblastoid cell line (LCL) DNA, respectively, while deletions were found only in the LCL group (7.1%). This array platform allows the detection of DNA copy number variation within regions of pronounced genomic complexity, which constitutes an improvement over available technologies.

Identification of limited regions of genetic aberrations in patients affected with Wilms' tumor using a tiling-path chromosome 22 array

Wilms' tumor (WT) is one of the most common solid tumors of childhood. The genetics of this disorder is complex and few studies have suggested allelic loss of chromosome 22 as a frequent aberration. To assess tumor- and possible germline-specific regions affected with gene copy number variations on this chromosome, we applied a high-resolution genomic clone-based chromosome 22 array to a series of 28 WT samples and the paired blood-derived DNA of the patients. The group of tumors was enriched for cases with metastases, relapse or fatal outcome, criteria that were expected to yield a higher number of alterations on chromosome 22. Overall, the array-based form of comparative genomic hybridization (array-CGH) analysis revealed genomic changes in 53% (15 out of 28) of cases. We identified hemizygous deletion of the whole arm of 22q in 3 tumors (11%). Furthermore, a complex amplifier genotype was detected in 8 samples, presenting regions of gain along the chromosome, which defined 7 distinct minimal overlapping segments. The distribution of aberrations in 4 additional cases displaying regional genomic imbalances delimited 2 tumor suppressor/oncogene candidate loci, 1 in the proximal and the other in the terminal part of 22q. Analysis of these regions revealed the presence of several candidate genes that may play a role in the development of WT. These findings demonstrate the power of array-CGH in the determination of DNA copy number alterations and further strength the notion that WT-associated genes exist on this chromosome.

Microarray-based survey of CpG islands identifies concurrent hyper- and hypomethylation patterns in tissues derived from patients with breast cancer

Maintenance of CpG island methylation in the genome is crucial for cellular homeostasis and this balance is disrupted in cancer. Our rationale was to compare the methylation of CpG islands in tissues (tumor, healthy breast and blood) from patients with breast cancer. We studied 72 genes in 103 samples using microarray hybridization and bisulfite sequencing. We observed tumor specific hyper- or hypomethylation of five genes; COL9A1, MT1A, MT1J, HOXA5 and FLJ45983. A general drop of methylation in COL9A1 was apparent in tumors, when compared with blood and healthy breast tissue. Furthermore, one tumor displayed a complete loss of methylation of all five genes, suggesting overall impairment of methylation. The downstream, evolutionary conserved island of HOXA5 showed hypomethylation in 18 tumors and complete methylation in others. This CpG island also displayed a semimethylated state in the majority of normal breast samples, when compared to complete methylation in blood. Distinct methylation patterns were further seen in MT1J and MT1A, belonging to the metallothionein gene family. The CpG islands of these genes are spaced by 2 kb, which shows selective methylation of two structurally and functionally related genes. The promoters of FLJ45983 and MT1A were methylated above 25% in 18 primary and metastatic tumors. Concurrently, there was also >10% methylation of healthy breast tissue in 11 and 5 samples, respectively. This suggests that the methylation process for the latter two genes takes place already in normal breast cells. Our results also point to a considerable heterogeneity of epigenetic disturbance in breast cancer. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

BAC-based PCR fragment microarray: high-resolution detection of chromosomal deletion and duplication breakpoints

The introduction of molecular techniques in conjunction with classical cytogenetic methods has in recent years greatly improved the diagnostic potential for chromosomal abnormalities. In particular, microarray-comparative genomic hybridization (CGH) based on the use of BAC clones promises a sensitive strategy for the detection of DNA copy-number changes on a genomewide scale, offering a resolution as high as >30,000 "bands" (as defined by the number of BACs within the currently highest-density BAC array) [Ishkanian et al., 2004]. We have tested the possibility of further increasing this resolution using PCR fragments generated from individual BAC clones. Using this approach, we have efficiently defined the proximal and distal breakpoints in two cytogenetic cases, one duplication and one deletion, to within 5-20 kb. The results support the potential use of BAC-based PCR fragments to further improve the resolution of the microarray-CGH strategy by an order of magnitude.

Identification of disease genes by whole genome CGH arrays

Small, submicroscopic, genomic deletions and duplications (1 kb to 10 Mb) constitute up to 15% of all mutations underlying human monogenic diseases. Novel genomic technologies such as microarray-based comparative genomic hybridization (array CGH) allow the mapping of genomic copy number alterations at this submicroscopic level, thereby directly linking disease phenotypes to gene dosage alterations. At present, the entire human genome can be scanned for deletions and duplications at over 30,000 loci simultaneously by array CGH ( approximately 100 kb resolution), thus entailing an attractive gene discovery approach for monogenic conditions, in particular those that are associated with reproductive lethality. Here, we review the present and future potential of microarray-based mapping of genes underlying monogenic diseases and discuss our own experience with the identification of the gene for CHARGE syndrome. We expect that, ultimately, genomic copy number scanning of all 250,000 exons in the human genome will enable immediate disease gene discovery in cases exhibiting single exon duplications and/or deletions.

Detection of genomic imbalances by array based comparative genomic hybridisation in fetuses with multiple malformations

BACKGROUND

Malformations are a major cause of morbidity and mortality in full term infants and genomic imbalances are a significant component of their aetiology. However, the causes of defects in many patients with multiple congenital malformations remain unexplained despite thorough clinical examination and laboratory investigations.

METHODS

We used a commercially available array based comparative genomic hybridisation method (array CGH), able to screen all subtelomeric regions, main microdeletion syndromes, and 201 other regions covering the genome, to detect submicroscopic chromosomal imbalances in 49 fetuses with three or more significant anomalies and normal karyotype.

RESULTS

Array CGH identified eight genomic rearrangements (16.3%), all confirmed by quantitative multiplex PCR of short fluorescent fragments. Subtelomeric and interstitial deletions, submicroscopic duplications, and a complex genomic imbalance were identified. In four de novo cases (15qtel deletion, 16q23.1-q23.3 deletion, 22q11.2 deletion, and mosaicism for a rearranged chromosome 18), the genomic imbalance identified clearly underlay the pathological phenotype. In one case, the relationship between the genotype and phenotype was unclear, since a subtelomeric 6q deletion was detected in a mother and her two fetuses bearing multiple malformations. In three cases, a subtelomeric 10q duplication, probably a genomic polymorphism, was identified.

CONCLUSIONS

The detection of 5/49 causative chromosomal imbalances (or 4/49 if the 6qtel deletion is not considered as causative) suggests wide genome screening when standard chromosome analysis is normal and confirms that array CGH will have a major impact on pre and postnatal diagnosis as well as providing information for more accurate genetic counselling.

Allelic Losses of Chromosome 10 in Glioma Tissues Detected by Quantitative Single-Strand Conformation Polymorphism Analysis

Background: Detection of loss of heterozygosity (LOH) in clinical tissue samples is frequently difficult because samples are usually contaminated with noncancerous cells or because tumor cells in single tissues have genetic heterogeneity, and the precision of available techniques is insufficient for reliable analysis in such materials. We hypothesized that single-strand conformation polymorphism (SSCP) analysis can precisely quantify the gene dosage in mixed samples and is suitable for detection of LOH in clinical tissue samples.

Methods: We assessed the accuracy of a fluorescent SSCP method for the quantification of single-nucleotide polymorphism (SNP) alleles, using DNAs that were composed of cancerous DNA mixed with noncancerous DNA at various ratios. We applied this method to precisely characterize LOH in glioma tissue samples, using 96 SNPs that were evenly distributed throughout chromosome 10.

Results: LOH could be detected even in the cancerous DNA heavily contaminated (up to 80%) with noncancerous DNA. Using this method, we obtained LOH profiles of 56 gliomas with resolution at the SNP level (i.e., 1.5-Mbp interval). Anaplastic astrocytomas exhibited both 10p and 10q LOH, whereas diffuse astrocytomas frequently (63% of the cases) exhibited loss of 10p alone. We also found a possible new LOH region (around 10p13) in gliomas.

Conclusions: The present method is effective for precise mapping of LOH region in surgically obtained tumor tissues and could be applicable to the genetic diagnosis of cancers other than gliomas.

Comparative Genomic Hybridization by Microarray for the Detection of Cytogenetic Imbalance

Chromosomal abnormalities often result in the improper dosage of genes in a particular chromosome or chromosome segment, which may cause specific and complex clinical phenotypes. Comparative genomic hybridization by microarray (array CGH) is a high-throughput and high-resolution method for the detection of microscopic and submicroscopic chromosome abnormalities, some of which may not be detectable by conventional cytogenetic techniques. In addition, with the human genome sequenced and publicly available, array CGH allows for the direct correlation between chromosomal anomalies and genomic sequence. Properly constructed, microarrays have the potential to be a valuable tool for the detection of chromosomal abnormalities in cancer and genetic disease.