Comparative Genomic Hybridization Approach Research Articles

Satellitome analysis on the pale-breasted thrush Turdus leucomelas (Passeriformes; Turdidae) uncovers the putative co-evolution of sex chromosomes and satellite DNAs

Do all birds' sex chromosomes follow the same canonical one-way direction of evolution? We combined cytogenetic and genomic approaches to analyze the process of the W chromosomal differentiation in two selected Passeriform species, named the Pale-breasted Thrush Turdus leucomelas and the Rufous-bellied thrush T. rufiventris. We characterized the full catalog of satellite DNAs (satellitome) of T. leucomelas, and the 10 TleSatDNA classes obtained together with 16 microsatellite motifs were in situ mapped in both species. Additionally, using Comparative Genomic Hybridization (CGH) assays, we investigated their intragenomic variations. The W chromosomes of both species did not accumulate higher amounts of both heterochromatin and repetitive sequences. However, while T. leucomelas showed a heterochromatin-poor W chromosome with a very complex evolutionary history, T. rufiventris showed a small and partially heterochromatic W chromosome that represents a differentiated version of its original autosomal complement (Z chromosome). The combined approach of CGH and sequential satDNA mapping suggest the occurrence of a former W-autosomal translocation event in T. leucomelas, which had an impact on the W chromosome in terms of sequence gains and losses. At the same time, an autosome, which is present in both males and females in a polymorphic state, lost sequences and integrated previously W-specific ones. This putative W-autosomal translocation, however, did not result in the emergence of a multiple-sex chromosome system. Instead, the generation of a neo-W chromosome suggests an unexpected evolutionary trajectory that deviates from the standard canonical model of sex chromosome evolution.

Newly discovered genomic mutation patterns in radiation-induced small intestinal tumors of ApcMin/+ mice.

Among the small intestinal tumors that occur in irradiated mice of the established mouse model B6/B6-Chr18MSM-F1 ApcMin/+, loss of heterozygosity analysis can be utilized to estimate whether a deletion in the wild-type allele containing the Adenomatous polyposis coli (Apc) region (hereafter referred to as Deletion), a duplication in the mutant allele with a nonsense mutation at codon 850 of Apc (Duplication), or no aberration (Unidentified) has occurred. Previous research has revealed that the number of Unidentified tumors tends to increase with the radiation dose. In the present study, we investigated the molecular mechanisms underlying the development of an Unidentified tumor type in response to radiation exposure. The mRNA expression levels of Apc were significantly lower in Unidentified tumors than in normal tissues. We focused on epigenetic suppression as the mechanism underlying this decreased expression; however, hypermethylation of the Apc promoter region was not observed. To investigate whether deletions occur that cannot be captured by loss of heterozygosity analysis, we analyzed chromosome 18 using a customized array comparative genomic hybridization approach designed to detect copy-number changes in chromosome 18. However, the copy number of the Apc region was not altered in Unidentified tumors. Finally, gene mutation analysis of the Apc region using next-generation sequencing suggested the existence of a small deletion (approximately 3.5 kbp) in an Unidentified tumor from a mouse in the irradiated group. Furthermore, nonsense and frameshift mutations in Apc were found in approximately 30% of the Unidentified tumors analyzed. These results suggest that radiation-induced Unidentified tumors arise mainly due to decreased Apc expression of an unknown regulatory mechanism that does not depend on promoter hypermethylation, and that some tumors may result from nonsense mutations which are as-yet undefined point mutations.

FNBtools: A Software to Identify Homozygous Lesions in Deletion Mutant Populations

Deletion mutagenesis such as fast neutron bombardment (FNB) has been widely used for forward and reverse genetics studies in functional genomics. Traditionally, the time-consuming map-based cloning is used to locate causal deletions in deletion mutants. In recent years, comparative genomic hybridization (CGH) has been used to speed up and scale up the lesion identification process in deletion mutants. However, limitations of low accuracy and sensitivity for small deletions in the CGH approach are apparent. With the next generation sequencing (NGS) becoming affordable for most users, NGS-based bioinformatics tools are more appealing. Although several deletion callers are available, these tools are not efficient in detecting small deletions. Population-scale deletion callers that can identify both small and large deletions are rare. We were motivated to create a population-scale deletion detection tool, called FNBtools, to identify homozygous causal deletions in mutant populations by using NGS data. FNBtools is a tool to call deletions at a population-scale and to achieve high accuracy at different levels of coverage. In addition, FNBtools can detect both small and large deletions with the ability to identify unique deletions in a mutant pool by filtering deletions that exist in a wild-type or control pool. Furthermore, FNBtools is also able to visualize all identified deletions in a genome-wide scope by using Circos. From simulated data analysis, FNBtools outperforms four existing popular deletion callers in detecting small deletions at different coverage levels. To test the usefulness of FNBtools in real biological applications, we used it to analyze a salt-tolerant mutant in Medicago truncatula and identified the unique deletion locus that is tightly linked with this trait. The causal deletion in the mutant was confirmed by PCR amplification, sequencing and genetic linkage analyses. FNBtools can be used for homozygous deletion identification in any species with reference genome sequences. FNBtools is publicly available at: https://github.com/noble-research-institute/fnbtools.

A tiling array-based comparative genomic hybridization approach to predict copy number variations between Plasmodium falciparum field isolates from the Indian Sub-continent

Background: There are several techniques to analyse copy number variation in both research and clinical settings, such as whole genome amplification (sWGA), SNP arrays and one of the most commonly used techniques, array based comparative genomic hybridization (aCGH). In the latter, copy number comparison is obtained between differentially labelled target and reference DNAs by measuring ratio of fluorescence intensity of probes indicating loss or gain in the chromosomal region. Methods: Here we carry out a comparative analysis between two Plasmodium falciparum parasite isolates (Pf-isolate-2 and Pf-isolate-1) causing malaria using array CGH. The array contains approximately 418,577, 60mer custom-designed probes with an average probe spacing of 56 bp. The significant major variations (amplifications and deletions) copy number variations (CNV) in Pf-isolate-2 (Pf-2) in comparison with Pf-isolate-1 (Pf-1), are reported. Results: CNVs have been seen in all the chromosomes in Pf-2, most of the deletions have been seen mostly in sub-telomeric and telomeric regions of the chromosomes that comprises of variant surface antigen family genes. Apart from the subtelomeric regions other parts of the chromosomes have also shown CNVs. Novel variations , like continuous amplification of 28kb region (249817-278491) of chromosome-8, which covers for 3 genes two of which codes for conserved Plasmodium proteins with unknown function (MAL8P1.139, PF08_0122) and tRNA pseudouridine synthase, putative (PF08_0123). Amplifications in regions harboring genes like GTP cyclohydrolase I (GCH-1, PFL1155W) and ribosomal protein, L24, putative (PFL1150C) of chromosome 12 were seen. Conclusion: Other than known variations reported earlier, some novel variations have also been seen in the chromosomes of Pf-2. This is an experimental case study reporting major amplifications and deletions in Pf-isolate-2 in comparison with Pf-isolate-1 using a tiling array based comparative genomic hybridization approach.

Sequence Polymorphisms and Structural Variations among Four Grapevine (Vitis vinifera L.) Cultivars Representing Sardinian Agriculture.

The genetic diversity among grapevine (Vitis vinifera L.) cultivars that underlies differences in agronomic performance and wine quality reflects the accumulation of single nucleotide polymorphisms (SNPs) and small indels as well as larger genomic variations. A combination of high throughput sequencing and mapping against the grapevine reference genome allows the creation of comprehensive sequence variation maps. We used next generation sequencing and bioinformatics to generate an inventory of SNPs and small indels in four widely cultivated Sardinian grape cultivars (Bovale sardo, Cannonau, Carignano and Vermentino). More than 3,200,000 SNPs were identified with high statistical confidence. Some of the SNPs caused the appearance of premature stop codons and thus identified putative pseudogenes. The analysis of SNP distribution along chromosomes led to the identification of large genomic regions with uninterrupted series of homozygous SNPs. We used a digital comparative genomic hybridization approach to identify 6526 genomic regions with significant differences in copy number among the four cultivars compared to the reference sequence, including 81 regions shared between all four cultivars and 4953 specific to single cultivars (representing 1.2 and 75.9% of total copy number variation, respectively). Reads mapping at a distance that was not compatible with the insert size were used to identify a dataset of putative large deletions with cultivar Cannonau revealing the highest number. The analysis of genes mapping to these regions provided a list of candidates that may explain some of the phenotypic differences among the Bovale sardo, Cannonau, Carignano and Vermentino cultivars.

A comparative genomic hybridization approach to study gene copy number variations among chinese hamster cell lines

Chinese Hamster Ovary (CHO) cells are aneuploid in nature. The genome of recombinant protein producing CHO cell lines continuously undergoes changes in its structure and organization. We analyzed nine cell lines, including parental cell lines, using a comparative genomic hybridization (CGH) array focused on gene-containing regions. The comparison of CGH with copy-number estimates from sequencing data showed good correlation. Hierarchical clustering of the gene copy number variation data from CGH data revealed the lineage relationships between the cell lines. On analyzing the clones of a clonal population, some regions with altered genomic copy number status were identified indicating genomic changes during passaging. A CGH array is thus an effective tool in quantifying genomic alterations in industrial cell lines and can provide insights into the changes in the genomic structure during cell line derivation and long term culture. Biotechnol. Bioeng. 2017;114: 1903-1908. © 2017 Wiley Periodicals, Inc.

Genomic answers for recurrent spontaneous abortion in Saudi Arabia: An array comparative genomic hybridization approach

To study the genomics/genetic factors associated with recurrent spontaneous abortion (RSA), as ∼50% of RSA are unexplained. However, chromosome abnormalities have been reported to play major role in RSA. We performed whole genome array-CGH based genomic analysis of forty four Saudi RSA patients to identify potential molecular and chromosomal abnormalities. We identified a total of 845 alterations, usually not detected by classic cytogenetic methods, in different genomic regions using a cut off value of −0.25 and 0.25 for structural loss and gain, whereas −1.0 and 0.58 were used for single copy number deletion and duplication respectively. We identified frequent (present at least in 10% of patients) alterations including three macro-alteration at 8p23.1, 10q11.21-q11.22 and 15q11.2 as well as large numbers of micro-deletions/amplifications with affected genes including 22q11.23 (GSTT1), 3p22.2 (CTDSPL), 6p21.32 (HLA), and 8p22 (MSR1). Pathway analysis of genes located in detected CNVs regions revealed the allograft rejection signaling, IL-4 signaling, and autoimmune thyroid disease signaling as the most significant canonical pathways associated with RSA. Whole genome array CGH technique can be used to identify potential genes, biofunctions and chromosomal abnormalities associated with RSA which is supported by our findings of a number of novel CNVs/genes (22q11.23/GSTT1, 3p22.2/CTDSPL, 6p21.32/HLA, 8p22/MSR1, and 14q32.33/AKT1) and pathways in patients affected with RSA. To improve diagnosis and treatment of RSA, a comprehensive procedure is needed for identification and validation of causative genes.

Oligonucleotide Array-based Comparative Genomic Hybridization Approach in Hematologic Malignancies With Normal/Failed Conventional Cytogenetics and Fluorescent In Situ Hybridization.

Oligonucleotide array-based comparative genomic hybridization (oaCGH) was used to investigate 60 cases of hematologic malignancies, mainly acute myeloid leukemias and myelodysplastic syndromes, in order to evaluate its sensitivity and specificity and to search for genomic alterations undetected by previous investigation with conventional cytogenetics (CC) and fluorescent in situ hybridization (FISH). On the basis of CC and FISH results, we subdivided the series into group A (36 cases with a normal karyotype after CC and/or FISH testing) and group B (24 cases with anomalies detected by CC and/or FISH). oaCGH did not show alterations in 21 cases of the group A (58.3%); in the remaining 15 cases (41.7%), it detected 19 new abnormalities (14 amplifications and 5 deletions). In the group B, oaCGH confirmed 32/55 aneuploidies detected by FISH (58.1%). The sensitivity increased at 27/33 confirmed aneuploidies (81.8%) by placing as a cutoff a mosaic of 50%. Moreover, in the cases of this group oaCGH revealed 36 new alterations (15 amplifications and 21 deletions). From these results it is possible to assess a strong overlap between results obtained by FISH and oaCGH. However, oaCGH is a reliable alternative where CC and FISH are not feasible and is able to identify new alterations unexplored by FISH.

Oncogenic mutations and chromosomal aberrations in primary extranodal diffuse large b-cell lymphomas of the thyroid – A study of 21 cases

Context: Primary extranodal diffuse large B-cell lymphomas of the thyroid (ptDLBCL) constitute a rare entity, which until now was not fully explored. Objective: Due to recently published data genetically linking ptDLBCL to a subset of thyroid carcinoma, we assessed the occurrence of oncogenic mutations and copy number alterations. Design: A high-resolution array-based comparative genomic hybridization approach was applied to quantify genomic aberrations in a study population of 21 ptDLBCL patients. In addition, we investigated the frequency of mutations involving the BRAF, NRAS, and MYD88 genes in correlation with immunohistochemical data. Results: Chromosomal gains were recurrently detected at 6p21.33-p21.31, 6p22.2, 12p13.31, 14q31.1, 14q32.33, 19p13.3, and 22q11.22; numeric losses were most frequently observed at 6p21.3-p21.31, 10q26.3, 19p13.3, 20q13.33, and 21q11.2. Aberrations affecting 6p22.2 and 14q32.33 as well as 22q11.22 differed slightly between germinal center B-cell (GCB) and non-GCB groups....

Oncogenic mutations and chromosomal aberrations in primary extranodal diffuse large B-cell lymphomas of the thyroid--a study of 21 cases.

Primary extranodal diffuse large B-cell lymphomas of the thyroid (ptDLBCL) constitute a rare entity, which until now was not fully explored. Due to recently published data genetically linking ptDLBCL to a subset of thyroid carcinoma, we assessed the occurrence of oncogenic mutations and copy number alterations. A high-resolution array-based comparative genomic hybridization approach was applied to quantify genomic aberrations in a study population of 21 ptDLBCL patients. In addition, we investigated the frequency of mutations involving the BRAF, NRAS, and MYD88 genes in correlation with immunohistochemical data. Chromosomal gains were recurrently detected at 6p21.33-p21.31, 6p22.2, 12p13.31, 14q31.1, 14q32.33, 19p13.3, and 22q11.22; numeric losses were most frequently observed at 6p21.3-p21.31, 10q26.3, 19p13.3, 20q13.33, and 21q11.2. Aberrations affecting 6p22.2 and 14q32.33 as well as 22q11.22 differed slightly between germinal center B-cell (GCB) and non-GCB groups. Statistically significant deviations were detected at 20q13.33 and 21q11.2. These specific alterations do not seem to occur in thyroid carcinomas or other DLBCL, according to previously published literature. Analysis of BRAF and NRAS showed mutation frequencies of 4.8 and 9.5%, respectively. No MYD88 mutations could be detected in any of the analyzed cases. Fluorescence in situ hybridization demonstrated breakage events involving the BCL2, BCL6, and cMYC locus in 14.3, 9.5, and 9.5%, respectively. Our study revealed ptDLBCL to be predominantly composed of the GCB type, harboring no MYD88 mutations and showing infrequent mutations in the BRAF and NRAS genes. Additionally, array comparative genomic hybridization showed no overlapping alterations between ptDLBCL and thyroid carcinomas or other nodal or extranodal DLBCL.

Genomic landscape of pancreatic neuroendocrine tumors

To investigate the prognostic role of genomic stability and copy number alterations (CNAs) pancreatic neuroendocrine tumors (PanNETs). A high-resolution array-based comparative genomic hybridization approach was utilized in order to investigate and quantify chromosomal aberrations in a panel of 37 primary PanNET and 11 metastatic samples. DNA samples were extracted from formalin-fixed and paraffin-embedded tumor specimen. Genomic findings were correlated with histopathological and immunohistochemical data. Moreover, the dataset was subjected to employing an unsupervised hierarchical clustering analysis approach utilizing Euclidean distance and average linkage and associations between genomically defined tumor groups and recurrent CNAs or clinicopathological features of the study group were assessed. Numerous chromosomal aberrations were recurrently detected in both, primary tumor samples and metastases. Copy number gains were most frequently observed at 06p22.2-p22.1 (27.1%), 17p13.1 (20.8%), 07p21.3-p21.2 (18.8%), 09q34.11 (18.8%). Genomic losses were significantly less frequent and the only recurrent aberration affected 08q24.3 (6.3%). Moreover, we detected a high degree of genomic heterogeneity between primary tumors and metastatic lesions. Unsupervised hierarchical clustering of loci affected by CNAs in more than 3 primary tumor samples revealed two genetically distinct tumor groups as well as two chromosomal clusters of genomic imbalances indicating a small subset of tumors with common molecular features (13.5%). Aberrations affecting 6p22.2-22.1, 8q24.3, 9q34.11 and 17p13.1 (P = 0.011; 0.003; 0.003; 0.001), were significantly associated with a poorer survival prognosis. This study suggests that several frequent CNAs in numerous candidate regions are involved in the pathogenesis and metastatic progression of PanNET.

Genomic Heterogeneity and Structural Variation in Soybean Near Isogenic Lines

Near isogenic lines (NILs) are a critical genetic resource for the soybean research community. The ability to identify and characterize the genes driving the phenotypic differences between NILs is limited by the degree to which differential genetic introgressions can be resolved. Furthermore, the genetic heterogeneity extant among NIL sub-lines is an unaddressed research topic that might have implications for how genomic and phenotypic data from NILs are utilized. In this study, a recently developed high-resolution comparative genomic hybridization (CGH) platform was used to investigate the structure and diversity of genetic introgressions in two classical soybean NIL populations, respectively varying in protein content and iron deficiency chlorosis (IDC) susceptibility. There were three objectives: assess the capacity for CGH to resolve genomic introgressions, identify introgressions that are heterogeneous among NIL sub-lines, and associate heterogeneous introgressions with susceptibility to IDC. Using the CGH approach, introgression boundaries were refined and previously unknown introgressions were revealed. Furthermore, heterogeneous introgressions were identified within seven sub-lines of the IDC NIL “IsoClark.” This included three distinct introgression haplotypes linked to the major iron susceptible locus on chromosome 03. A phenotypic assessment of the seven sub-lines did not reveal any differences in IDC susceptibility, indicating that the genetic heterogeneity among the lines does not have a significant impact on the primary NIL phenotype.

Highly significant improvement in embryo implantation and increased live birth rate achieved after comprehensive chromosomal screening: implications for single embryo transfer

OBJECTIVE: To improve the identification of viable embryos for uterine transfer with a view to increasing implantation and birth rates. DESIGN: Prospective clinical trial. MATERIALS AND METHODS: Comparative genomic hybridization (CGH) was used to screen all 23 pairs of chromosomes for aneuploidy in over 500 blastocysts derived from 115 patients. The patients were of advanced maternal age (mean 39 years) and in most cases had at least one previous failed IVF attempt (mean failed cycles 2). RESULTS: The CGH approach underwent extensive validation prior to clinical application, confirming concordance between the biopsied trophectoderm (TE) cells and the inner cell mass. A full chromosome screen was obtained for 93% of blastocysts tested. Almost all patients (96%) had at least one normal embryo available for transfer. Currently, 42 patients have had their blastocysts transferred, with the remaining patients scheduled to receive transfers in the coming weeks. The clinical pregnancy rate stands at 86% (36/42). Fifteen cycles have now gone to term, giving a birth rate per cycle of 80% (versus 60% in control blastocyst transfer cycles). Even more impressive was the implantation rate (fetal heart detected) which was increased from 28% in controls to 66% (54/82) in cases with CGH screening (2.4 fold increase, P<0.0003). CONCLUSIONS: We report the first births following comprehensive chromosome screening of blastocyst stage embryos. The sampling of several TE cells led to a robust diagnosis, less susceptible to problems such as chromosomal mosaicism than previous screening methods. Implantation and birth rates were exceptional (66% per embryo and 80% per cycle started respectively). These results were especially good given the poor reproductive history of the patients and were significantly better than cycles without chromosome screening. The dramatic improvement in implantation rate provides a clear indication that methods such as this will allow high pregnancy and birth rates in cycles involving single embryo transfer.

Identification of Copy Number Abnormalities and Inactivating Mutations in Two Negative Regulators of Nuclear Factor-κB Signaling Pathways in Waldenström's Macroglobulinemia

Waldenström's macroglobulinemia (WM) is a distinct clinicobiological entity defined as a B-cell neoplasm characterized by a lymphoplasmacytic infiltrate in bone marrow (BM) and IgM paraprotein production. Cytogenetic analyses were historically limited by difficulty in obtaining tumor metaphases, and the genetic basis of the disease remains poorly defined. Here, we performed a comprehensive analysis in 42 WM patients by using a high-resolution, array-based comparative genomic hybridization approach to unravel the genetic mechanisms associated with WM pathogenesis. Overall, 83% of cases have chromosomal abnormalities, with a median of three abnormalities per patient. Gain of 6p was the second most common abnormality (17%), and its presence was always concomitant with 6q loss. A minimal deleted region, including MIRN15A and MIRN16-1, was delineated on 13q14 in 10% of patients. Of interest, we reported biallelic deletions and/or inactivating mutations with uniparental disomy in tumor necrosis factor (TNF) receptor-associated factor 3 and TNFalpha-induced protein 3, two negative regulators of the nuclear factor-kappaB (NF-kappaB) signaling pathway. Furthermore, we confirmed the association between TRAF3 inactivation and increased transcriptional activity of NF-kappaB target genes. Mutational activation of the NF-kappaB pathway, which is normally activated by ligand receptor interactions within the BM microenvironment, highlights its biological importance, and suggests a therapeutic role for inhibitors of NF-kappaB pathway activation in the treatment of WM.

High-Resolution Genomic Analysis in Waldenström's Macroglobulinemia Identifies Disease-Specific and Common Abnormalities with Marginal Zone Lymphomas

Cytogenetic analyses have been historically limited in Waldenström's macroglobulinemia (WM) by the difficulty to obtain tumor metaphases. Thus, few recurrent karyotypic abnormalities have been reported and the molecular consequences of these imbalances are largely unknown. We used an array-based comparative genomic hybridization approach to better characterize the recurrent chromosome abnormalities associated with WM pathogenesis and to compare them with the publicly available findings in other B-cell neoplasias. The majority of the recurrent chromosome abnormalities identified in WM were shared with marginal zone lymphomas (MZL), as deletions of 6q23 and 13q14 and gains of 3q13-q28, 6p and 18q. On the other hand, gains of 4q and 8q were recurrently identified in WM but have not been described as being common abnormalities in MZL. The genetic consequences of these specific abnormalities remain elusive and further studies are critical to refine the search and to precise the molecular pathways affected by these abnormalities.

High pregnancy rate after comprehensive chromosomal screening of blastocysts

OBJECTIVE: Traditionally, preimplantation genetic screening has involved the biopsy of a single blastomere at the cleavage stage followed by limited chromosomal assessment using fluorescent in situ hybridization (FISH). The objective of this study was to clinically apply a novel strategy for aneuploidy detection, based upon comprehensive chromosome screening of trophectoderm (TE) cells biopsied at the blastocyst stage. DESIGN: Clinical evaluation of a new approach for embryo viability assessment. MATERIALS AND METHODS: All 23 pairs of chromosomes were screened for aneuploidy in 106 blastocysts derived from 17 patients. The patients were of advanced maternal age (mean 37 years), with a history of multiple failed IVF attempts and/or multiple abortions. 3-10 TE cells were biopsied from each blastocyst and subjected to whole genome amplification and comparative genomic hybridization (CGH). Blastocysts were cryopreserved using vitrification while CGH analysis took place. Chromosomally normal blastocysts were warmed and transferred in a subsequent FET. RESULTS: The CGH approach underwent extensive validation prior to clinical application, confirming accuracy and cytogenetic concordance between the TE and inner cell mass. Clinically, CGH succeeded in producing a full chromosome screen for 91% of blastocysts tested. The aneuploidy rate was 43.8%. Embryo survival after biopsy and warming were excellent (100%). To date, 10 patients have undergone blastocyst FET, resulting in an implantation rate of 55% per embryo and an ongoing clinical pregnancy rate (fetal heart) of 70% per cycle. Further transfers are in progress. CONCLUSIONS: We report the first clinical application of a novel approach for preimplantation genetic screening, involving assessment of all chromosomes at the blastocyst stage. The sampling of several cells resulted in a robust diagnosis and greatly reduces the risk of misdiagnosis due to chromosomal mosaicism. Implantation and clinical pregnancy rates were high (55% and 70%), especially given the poor reproductive history of the patients, and compare very favorably with non-PGS cycles matched for maternal age (30% and 60% respectively). Despite the high implantation potential of blastocysts it is clear that many still harbor lethal aneuploidies. It is likely that accurate, comprehensive chromosomal screening will significantly improve embryo selection and may be key to maintaining high pregnancy rates in cycles involving elective single blastocyst transfer.

Detection of exonic copy-number changes using a highly efficient oligonucleotide-based comparative genomic hybridization-array method

Genomic copy-number variations (CNVs) involving large DNA segments are known to cause many genetic disorders. Depending on the changes, they are predicted to lead either to decreased or an increased gene expression. However, the ability to detect smaller exonic copy-number changes has not been explored. Here we describe a new oligonucleotide-based comparative genomic hybridization (CGH)-array approach for high-throughput detection of exonic deletions or duplications and its application to deletion/duplication analyses of the genes encoding CFTR, six sarcoglycans (SGCA, SGCB, SGCG, SGCD, SGCE, and SGCZ), and DMD. In this work we show the successful development of an array format containing 158 exons that collectively span eight genes and its clinical application for the rapid screening of deletions and duplications in a diagnostic setting. We have analyzed a series of 35 DNA samples from patients affected with cystic fibrosis (CF), Duchenne and Becker muscular dystrophies (DMD/BMD), or sarcoglycanopathies, and have characterized exonic copy-number changes that have been validated with other methods. Interestingly, even heterozygous deletions and duplications of only one exon, as well as mosaic deletions, were detected by this CGH approach. Our results showed that the resolution is very high, as abnormalities of about 1.5-2 kb could be detected. Since this approach is completely scalable, this new molecular tool will allow the screening of combinations of genes involved in a particular group of clinically and genetically heterogeneous disorders such as mental retardation, muscular dystrophies and brain malformations.

Array CGH analysis of copy number variation identifies 1284 new genes variant in healthy white males: implications for association studies of complex diseases

The discovery of copy number variation in healthy individuals is far from complete, and owing to the resolution of detection systems used, the majority of loci reported so far are relatively large ( approximately 65%>10 kb). Applying a two-stage high-resolution array comparative genomic hybridization approach to analyse 50 healthy Caucasian males from northern France, we discovered 2208 copy number variants (CNVs) detected by more than one consecutive probe. These clustered into 1469 CNV regions (CNVRs), of which 721 are thought to be novel. The majority of these are small (median size 4.4 kb) and most have common boundaries, with a coefficient of variation less than 0.1 for 83% of endpoints in those observed in multiple samples. Only 6% of the CNVRs analysed showed evidence of both copy number losses and gains at the same site. A further 6089 variants were detected by single probes: 48% of these were observed in more than one individual. In total, 2570 genes were seen to intersect variants: 1284 in novel loci. Genes involved in differentiation and development were significantly over-represented and approximately half of the genes identified feature in the Online Mendelian Inheritance in Man database. The biological importance of many genes affected, along with the well-conserved nature of the majority of the CNVs, suggests that they could have important implications for phenotype and, thus, be useful for association studies of complex diseases.

A Microarray Based Genomic Hybridization Method for Identification of New Genes in Plants: Case Analyses of Arabidopsis and Oryza

AbstractTo systematically estimate the gene duplication events in closely related species, we have to use comparative genomic approaches, either through genomic sequence comparison or comparative genomic hybridization (CGH). Given the scarcity of complete genomic sequences of plant species, in the present study we adopted an array based CGH to investigate gene duplications in the genus Arabidopsis. Fragment genomic DNA from four species, namely Arabidopsis thaliana, A. lyrata subsp. lyrata, A. lyrata subsp. petraea, and A. halleri, was hybridized to Affymetrix (Santa Clara, CA, USA) tiling arrays that are designed from the genomic sequences of A. thaliana. Pairwise comparisons of signal intensity were made to infer the potential duplicated candidates along each phylo‐genetic branch. Ninety‐four potential candidates of gene duplication along the genus were identified. Among them, the majority (69 of 94) were A. thaliana lineage specific. This result indicates that the array based CGH approach may be used to identify candidates of duplication in other plant genera containing closely related species, such as Oryza, particularly for the AA genome species. We compared the degree of gene duplication through retrotransposon between O. sativa and A. thaliana and found a strikingly higher number of chimera retroposed genes in rice. The higher rate of gene duplication through retroposition and other mechanisms may indicate that the grass species is able to adapt to more diverse environments.

Chromosomal aberrations in angioimmunoblastic T‐cell lymphoma and peripheral T‐cell lymphoma unspecified: A matrix‐based CGH approach

Angioimmunoblastic T-cell lymphoma (AILT) is a histopathologically well-defined entity. However, despite a number of cytogenetic studies, the genetic basis of this lymphoma entity is not clear. Moreover, there is an overlap to some cases of peripheral T-cell lymphoma unspecified (PTCL-u) in respect to morphological and genetic features. We used array-based comparative genomic hybridization (CGH) to study genetic imbalances in 39 AILT and 20 PTCL-u. Array-based CGH revealed complex genetic imbalances in both AILT and PTCL-u. Chromosomal imbalances were more frequent in PTCL-u than in AILT and gains exceeded the losses. The most recurrent changes in AILT were gains of 22q, 19, and 11p11-q14 (11q13) and losses of 13q. The most frequent changes in PTCL-u were gains of 17 (17q11-q25), 8 (involving the MYC locus at 8q24), and 22q and losses of 13q and 9 (9p21-q33). Interestingly, gains of 4q (4q28-q31 and 4q34-qtel), 8q24, and 17 were significantly more frequent in PTCL-u than in AILT. The regions 6q (6q16-q22) and 11p11 were predominantly lost in PTCL-u. Moreover, we could identify a recurrent gain of 11q13 in both AILT and PTCL-u, which has previously not been described in AILT. Trisomies 3 and 5, which have been described as typical aberrations in AILT, were identified only in a small number of cases. In conclusion, CGH revealed common genetic events in peripheral T-cell lymphomas as well as peculiar differences between AILT and PTCL-u.