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1.  Prediction of Cochlear Implant Performance by Genetic Mutation: The Spiral Ganglion Hypothesis 
Hearing research  2012;292(1-2):51-58.
Up to 7% of patients with severe-to-profound deafness do not benefit from cochlear implantation. Given the high surgical implantation and clinical management cost of cochlear implantation (> $1 million lifetime cost), prospective identification of the worst performers would reduce unnecessary procedures and healthcare costs. Because cochlear implants bypass the membranous labyrinth but rely on the spiral ganglion for functionality, we hypothesize that cochlear implant (CI) performance is dictated in part by the anatomic location of the cochlear pathology that underlies the hearing loss. As a corollary, we hypothesize that because genetic testing can identify sites of cochlear pathology, it may be useful in predicting CI performance.
29 adult CI recipients with idiopathic adult-onset severe-to-profound hearing loss were studied. DNA samples were subjected to solution-based sequence capture and massively parallel sequencing using the OtoSCOPE® platform. The cohort was divided into three CI performance groups (good, intermediate, poor) and genetic causes of deafness were correlated with audiometric data to determine whether there was a gene-specific impact on CI performance.
The genetic cause of deafness was determined in 3/29 (10%) individuals. The two poor performers segregated mutations in TMPRSS3, a gene expressed in the spiral ganglion, while the good performer segregated mutations in LOXHD1, a gene expressed in the membranous labyrinth. Comprehensive literature review identified other good performers with mutations in membranous labyrinth-expressed genes; poor performance was associated with spiral ganglion-expressed genes.
Our data support the underlying hypothesis that mutations in genes preferentially expressed in the spiral ganglion portend poor CI performance while mutations in genes expressed in the membranous labyrinth portend good CI performance. Although the low mutation rate in known deafness genes in this cohort likely relates to the ascertainment characteristics (postlingual hearing loss in adult CI recipients), these data suggest that genetic testing should be implemented as part of the CI evaluation to test this association prospectively.
PMCID: PMC3461332  PMID: 22975204
Cochlear implant performance; spiral ganglion; hearing loss; genetic testing; massively parallel sequencing
2.  High Frequency of PIK3R1 and PIK3R2 Mutations in Endometrial Cancer Elucidates a Novel Mechanism for Regulation of PTEN Protein Stability 
Cancer discovery  2011;1(2):170-185.
We demonstrate that phosphatidylinositol 3-kinase (PI3K) pathway aberrations occur in >80% of endometrioid endometrial cancers, with coordinate mutations of multiple PI3K pathway members being more common than predicted by chance. PIK3R1 (p85α) mutations occur at a higher rate in endometrial cancer than in any other tumor lineage, and PIK3R2 (p85β), not previously demonstrated to be a cancer gene, is also frequently mutated. The dominant activation event in the PI3K pathway appears to be PTEN protein loss. However, in tumors with retained PTEN protein, PI3K pathway mutations phenocopy PTEN loss, resulting in pathway activation. KRAS mutations are common in endometrioid tumors activating independent events from PI3K pathway aberrations. Multiple PIK3R1 and PIK3R2 mutations demonstrate gain of function including disruption of a novel mechanism of pathway regulation wherein p85α dimers bind and stabilize PTEN. Taken together, the PI3K pathway represents a critical driver of endometrial cancer pathogenesis and a novel therapeutic target.
PMCID: PMC3187555  PMID: 21984976
Endometrial Cancer; PTEN; PIK3CA; PIK3R1; PIK3R2
3.  A genetic map of Xenopus tropicalis 
Developmental Biology  2011;354(1-2):1-8.
We present a genetic map for Xenopus tropicalis, consisting of 2886 Simple Sequence Length Polymorphism (SSLP) markers. Using a bioinformatics-based strategy, we identified unique SSLPs within the X. tropicalis genome. Scaffolds from X. tropicalis genome assembly 2.0 (JGI) were scanned for Simple Sequence Repeats (SSRs); unique SSRs were then tested for amplification and polymorphisms using DNA from inbred Nigerian and Ivory Coast individuals. Thus identified, the SSLPs were genotyped against a mapping cross panel of DNA samples from 190 F2 individuals. Nearly 4000 SSLPs were genotyped, yielding a 2886-marker genetic map consisting of 10 major linkage groups between 73 and 132 cM in length, and 4 smaller linkage groups between 7 and 40 cM. The total effective size of the map is 1658 cM, and the average intermarker distance for each linkage group ranged from 0.27 to 0.75 cM. Fluorescence In Situ Hybridization (FISH) was carried out using probes for genes located on mapped scaffolds to assign linkage groups to chromosomes. Comparisons of this map with the X. tropicalis genome Assembly 4.1 (JGI) indicate that the map provides representation of a minimum of 66% of the X. tropicalis genome, incorporating 758 of the approximately 1300 scaffolds over 100,000 bp. The genetic map and SSLP marker database constitute an essential resource for genetic and genomic analyses in X. tropicalis.
Research highlights
► A genetic map of 2886 Simple Sequence Length Polymorphisms for Xenopus tropicalis. ► 10 major linkage groups corresponding to the 10 chromosomes, plus 4 minor linkage groups. ► Linkage groups are cytogenetically mapped to chromosomes by Fluorescence In Situ Hybridization.
PMCID: PMC3098391  PMID: 21458440
Xenopus; X. tropicalis; Genetic map; Genome; Simple sequence length polymorphism
4.  Compound and Digenic Heterozygosity Contributes to Arrhythmogenic Right Ventricular Cardiomyopathy 
To define the genetic basis of arrhythmogenic right ventricular cardiomyopathy.
Arrhythmogenic right ventricular cardiomyopathy (ARVC), characterized by right ventricular fibrofatty replacement and arrhythmias, causes sudden death. Autosomal dominant Inheritance, reduced penetrance, and 7 desmosome-encoding causative genes are known. The basis of low penetrance is poorly understood.
ARVC probands and family members were enrolled, blood obtained, lymphoblastoid cell lines immortalized, DNA extracted, PCR amplification of desmosome-encoding genes performed, PCR products sequenced and diseased tissue samples studied for intercellular junction protein distribution using confocal immunofluorescence microscopy and antibodies against key proteins.
We identified 21 variants in plakophilin-2 (PKP2) in 38 of 198 probands (19%), including missense, nonsense, splice site, and deletion/insertion mutations. Pedigrees showed wide intra-familial variability (severe early-onset disease to asymptomatic individuals). In 9/38 probands, PKP2 variants were identified that were encoded in trans (compound heterozygosity). The 38 probands hosting PKP2 variants were screened for other desmosomal genes mutations; second variants (digenic heterozygosity) were identified in 16/38 subjects with PKP2 variants (42%) including desmoplakin (DSP, n=6), desmoglein-2 (DSG2, n=5), plakophilin-4 (PKP4, n=1), and desmocollin-2 (DSC2, n=1). Heterozygous mutations in non-PKP 2desmosomal genes occurred in 14/198 subjects (7%), including DSP (n=4), DSG2 (n=5), DSC2 (n=3), and junctional plakoglobin (JUP, n=2). All variants occurred in conserved regions; none were identified in 700 ethnic-matched controls.
Immunohistochemical analysis demonstrated abnormalities of protein architecture.
These data suggest that the genetic basis of ARVC includes reduced penetrance with compound and digenic heterozygosity. Disturbed junctional cytoarchitecture in subjects with desmosomal mutations confirms that ARVC is a disease of the desmosome and cell junction.
PMCID: PMC2852685  PMID: 20152563
Arrhythmias; Cardiomyopathies; Desmosomes; Intercalated Disks; Genetic Mutations
5.  Identification of genetic risk variants for deep vein thrombosis by multiplexed next-generation sequencing of 186 hemostatic/pro-inflammatory genes 
Next-generation DNA sequencing is opening new avenues for genetic association studies in common diseases that, like deep vein thrombosis (DVT), have a strong genetic predisposition still largely unexplained by currently identified risk variants. In order to develop sequencing and analytical pipelines for the application of next-generation sequencing to complex diseases, we conducted a pilot study sequencing the coding area of 186 hemostatic/proinflammatory genes in 10 Italian cases of idiopathic DVT and 12 healthy controls.
A molecular-barcoding strategy was used to multiplex DNA target capture and sequencing, while retaining individual sequence information. Genomic libraries with barcode sequence-tags were pooled (in pools of 8 or 16 samples) and enriched for target DNA sequences. Sequencing was performed on ABI SOLiD-4 platforms. We produced > 12 gigabases of raw sequence data to sequence at high coverage (average: 42X) the 700-kilobase target area in 22 individuals. A total of 1876 high-quality genetic variants were identified (1778 single nucleotide substitutions and 98 insertions/deletions). Annotation on databases of genetic variation and human disease mutations revealed several novel, potentially deleterious mutations. We tested 576 common variants in a case-control association analysis, carrying the top-5 associations over to replication in up to 719 DVT cases and 719 controls. We also conducted an analysis of the burden of nonsynonymous variants in coagulation factor and anticoagulant genes. We found an excess of rare missense mutations in anticoagulant genes in DVT cases compared to controls and an association for a missense polymorphism of FGA (rs6050; p = 1.9 × 10-5, OR 1.45; 95% CI, 1.22-1.72; after replication in > 1400 individuals).
We implemented a barcode-based strategy to efficiently multiplex sequencing of hundreds of candidate genes in several individuals. In the relatively small dataset of our pilot study we were able to identify bona fide associations with DVT. Our study illustrates the potential of next-generation sequencing for the discovery of genetic variation predisposing to complex diseases.
PMCID: PMC3305575  PMID: 22353194
Deep vein thrombosis; venous thromboembolism; next-generation sequencing; target capture; multiplexing; FGA; rs6025; heamostateome; DVT; VTE
6.  Understanding the development of human bladder cancer by using a whole-organ genomic mapping strategy 
The search for the genomic sequences involved in human cancers can be greatly facilitated by maps of genomic imbalances identifying the involved chromosomal regions, particularly those that participate in the development of occult preneoplastic conditions that progress to clinically aggressive invasive cancer. The integration of such regions with human genome sequence variation may provide valuable clues about their overall structure and gene content. By extension, such knowledge may help us understand the underlying genetic components involved in the initiation and progression of these cancers. We describe the development of a genome-wide map of human bladder cancer that tracks its progression from in situ precursor conditions to invasive disease. Testing for allelic losses using a genome-wide panel of 787 microsatellite markers was performed on multiple DNA samples, extracted from the entire mucosal surface of the bladder and corresponding to normal urothelium, in situ preneoplastic lesions, and invasive carcinoma. Using this approach, we matched the clonal allelic losses in distinct chromosomal regions to specific phases of bladder neoplasia and produced a detailed genetic map of bladder cancer development. These analyses revealed three major waves of genetic changes associated with growth advantages of successive clones and reflecting a stepwise conversion of normal urothelial cells into cancer cells. The genetic changes map to six regions at 3q22–q24, 5q22–q31, 9q21–q22, 10q26, 13q14, and 17p13, which may represent critical hits driving the development of bladder cancer. Finally, we performed high-resolution mapping using single nucleotide polymorphism markers within one region on chromosome 13q14, containing the model tumor suppressor gene RB1, and defined a minimal deleted region associated with clonal expansion of in situ neoplasia. These analyses provided new insights on the involvement of several non-coding sequences mapping to the region and identified novel target genes, termed forerunner (FR) genes, involved in early phases of cancer development.
PMCID: PMC2849658  PMID: 18458673
forerunner genes; whole-organ histologic and genetic mapping; high-resolution mapping with SNPs; dual-track pathway of bladder cancer development; apoptosis
7.  Somatic mutations affect key pathways in lung adenocarcinoma 
Ding, Li | Getz, Gad | Wheeler, David A. | Mardis, Elaine R. | McLellan, Michael D. | Cibulskis, Kristian | Sougnez, Carrie | Greulich, Heidi | Muzny, Donna M. | Morgan, Margaret B. | Fulton, Lucinda | Fulton, Robert S. | Zhang, Qunyuan | Wendl, Michael C. | Lawrence, Michael S. | Larson, David E. | Chen, Ken | Dooling, David J. | Sabo, Aniko | Hawes, Alicia C. | Shen, Hua | Jhangiani, Shalini N. | Lewis, Lora R. | Hall, Otis | Zhu, Yiming | Mathew, Tittu | Ren, Yanru | Yao, Jiqiang | Scherer, Steven E. | Clerc, Kerstin | Metcalf, Ginger A. | Ng, Brian | Milosavljevic, Aleksandar | Gonzalez-Garay, Manuel L. | Osborne, John R. | Meyer, Rick | Shi, Xiaoqi | Tang, Yuzhu | Koboldt, Daniel C. | Lin, Ling | Abbott, Rachel | Miner, Tracie L. | Pohl, Craig | Fewell, Ginger | Haipek, Carrie | Schmidt, Heather | Dunford-Shore, Brian H. | Kraja, Aldi | Crosby, Seth D. | Sawyer, Christopher S. | Vickery, Tammi | Sander, Sacha | Robinson, Jody | Winckler, Wendy | Baldwin, Jennifer | Chirieac, Lucian R. | Dutt, Amit | Fennell, Tim | Hanna, Megan | Johnson, Bruce E. | Onofrio, Robert C. | Thomas, Roman K. | Tonon, Giovanni | Weir, Barbara A. | Zhao, Xiaojun | Ziaugra, Liuda | Zody, Michael C. | Giordano, Thomas | Orringer, Mark B. | Roth, Jack A. | Spitz, Margaret R. | Wistuba, Ignacio I. | Ozenberger, Bradley | Good, Peter J. | Chang, Andrew C. | Beer, David G. | Watson, Mark A. | Ladanyi, Marc | Broderick, Stephen | Yoshizawa, Akihiko | Travis, William D. | Pao, William | Province, Michael A. | Weinstock, George M. | Varmus, Harold E. | Gabriel, Stacey B. | Lander, Eric S. | Gibbs, Richard A. | Meyerson, Matthew | Wilson, Richard K.
Nature  2008;455(7216):1069-1075.
Determining the genetic basis of cancer requires comprehensive analyses of large collections of histopathologically well-classified primary tumours. Here we report the results of a collaborative study to discover somatic mutations in 188 human lung adenocarcinomas. DNA sequencing of 623 genes with known or potential relationships to cancer revealed more than 1,000 somatic mutations across the samples. Our analysis identified 26 genes that are mutated at significantly high frequencies and thus are probably involved in carcinogenesis. The frequently mutated genes include tyrosine kinases, among them the EGFR homologue ERBB4; multiple ephrin receptor genes, notably EPHA3; vascular endothelial growth factor receptor KDR; and NTRK genes. These data provide evidence of somatic mutations in primary lung adenocarcinoma for several tumour suppressor genes involved in other cancers—including NF1, APC, RB1 and ATM—and for sequence changes in PTPRD as well as the frequently deleted gene LRP1B. The observed mutational profiles correlate with clinical features, smoking status and DNA repair defects. These results are reinforced by data integration including single nucleotide polymorphism array and gene expression array. Our findings shed further light on several important signalling pathways involved in lung adenocarcinoma, and suggest new molecular targets for treatment.
PMCID: PMC2694412  PMID: 18948947
8.  Finishing a whole-genome shotgun: Release 3 of the Drosophila melanogaster euchromatic genome sequence 
Genome Biology  2002;3(12):research0079.1-79.14.
The Drosophila melanogaster genome was the first metazoan genome to be sequenced by whole-genome shotgun. Now, the sequence has been finished in a process designed to close gaps, improve sequence quality and validate the assembly.
The Drosophila melanogaster genome was the first metazoan genome to have been sequenced by the whole-genome shotgun (WGS) method. Two issues relating to this achievement were widely debated in the genomics community: how correct is the sequence with respect to base-pair (bp) accuracy and frequency of assembly errors? And, how difficult is it to bring a WGS sequence to the accepted standard for finished sequence? We are now in a position to answer these questions.
Our finishing process was designed to close gaps, improve sequence quality and validate the assembly. Sequence traces derived from the WGS and draft sequencing of individual bacterial artificial chromosomes (BACs) were assembled into BAC-sized segments. These segments were brought to high quality, and then joined to constitute the sequence of each chromosome arm. Overall assembly was verified by comparison to a physical map of fingerprinted BAC clones. In the current version of the 116.9 Mb euchromatic genome, called Release 3, the six euchromatic chromosome arms are represented by 13 scaffolds with a total of 37 sequence gaps. We compared Release 3 to Release 2; in autosomal regions of unique sequence, the error rate of Release 2 was one in 20,000 bp.
The WGS strategy can efficiently produce a high-quality sequence of a metazoan genome while generating the reagents required for sequence finishing. However, the initial method of repeat assembly was flawed. The sequence we report here, Release 3, is a reliable resource for molecular genetic experimentation and computational analysis.
PMCID: PMC151181  PMID: 12537568

Results 1-8 (8)