Suiyuan Zhang

Exome sequencing of serous endometrial tumors identifies recurrent somatic mutations in chromatin-remodeling and ubiquitin ligase complex genes

Endometrial cancer is the sixth most commonly diagnosed cancer in women worldwide, causing ∼74,000 deaths annually. Serous endometrial cancers are a clinically aggressive subtype with a poorly defined genetic etiology. We used whole-exome sequencing to comprehensively search for somatic mutations within ∼22,000 protein-encoding genes in 13 primary serous endometrial tumors. We subsequently resequenced 18 genes, which were mutated in more than 1 tumor and/or were components of an enriched functional grouping, from 40 additional serous tumors. We identified high frequencies of somatic mutations in CHD4 (17%), EP300 (8%), ARID1A (6%), TSPYL2 (6%), FBXW7 (29%), SPOP (8%), MAP3K4 (6%) and ABCC9 (6%). Overall, 36.5% of serous tumors had a mutated chromatin-remodeling gene, and 35% had a mutated ubiquitin ligase complex gene, implicating frequent mutational disruption of these processes in the molecular pathogenesis of one of the deadliest forms of endometrial cancer.

Predisposition to Cancer Caused by Genetic and Functional Defects of Mammalian Atad5

ATAD5, the human ortholog of yeast Elg1, plays a role in PCNA deubiquitination. Since PCNA modification is important to regulate DNA damage bypass, ATAD5 may be important for suppression of genomic instability in mammals in vivo. To test this hypothesis, we generated heterozygous (Atad5+/m) mice that were haploinsuffficient for Atad5. Atad5+/m mice displayed high levels of genomic instability in vivo, and Atad5+/m mouse embryonic fibroblasts (MEFs) exhibited molecular defects in PCNA deubiquitination in response to DNA damage, as well as DNA damage hypersensitivity and high levels of genomic instability, apoptosis, and aneuploidy. Importantly, 90% of haploinsufficient Atad5+/m mice developed tumors, including sarcomas, carcinomas, and adenocarcinomas, between 11 and 20 months of age. High levels of genomic alterations were evident in tumors that arose in the Atad5+/m mice. Consistent with a role for Atad5 in suppressing tumorigenesis, we also identified somatic mutations of ATAD5 in 4.6% of sporadic human endometrial tumors, including two nonsense mutations that resulted in loss of proper ATAD5 function. Taken together, our findings indicate that loss-of-function mutations in mammalian Atad5 are sufficient to cause genomic instability and tumorigenesis.

The Zebrafish Insertion Collection (ZInC): a web based, searchable collection of zebrafish mutations generated by DNA insertion

ZInC (Zebrafish Insertional Collection, http://research.nhgri.nih.gov/ZInC/) is a web-searchable interface of insertional mutants in zebrafish. Over the last two decades, the zebrafish has become a popular model organism for studying vertebrate development as well as for modeling human diseases. To facilitate such studies, we are generating a genome-wide knockout resource that targets every zebrafish protein-coding gene. All mutant fish are freely available to the scientific community through the Zebrafish International Resource Center (ZIRC). To assist researchers in finding mutant and insertion information, we developed a comprehensive database with a web front-end, the ZInC. It can be queried using multiple types of input such as ZFIN (Zebrafish Information Network) IDs, UniGene accession numbers and gene symbols from zebrafish, human and mouse. In the future, ZInC may include data from other insertional mutation projects as well. ZInC cross-references all integration data with the ZFIN (http://zfin.org/).

A Systems Genetics Approach Identifies CXCL14, ITGAX, and LPCAT2 as Novel Aggressive Prostate Cancer Susceptibility Genes

Although prostate cancer typically runs an indolent course, a subset of men develop aggressive, fatal forms of this disease. We hypothesize that germline variation modulates susceptibility to aggressive prostate cancer. The goal of this work is to identify susceptibility genes using the C57BL/6-Tg(TRAMP)8247Ng/J (TRAMP) mouse model of neuroendocrine prostate cancer. Quantitative trait locus (QTL) mapping was performed in transgene-positive (TRAMPxNOD/ShiLtJ) F2 intercross males (n = 228), which facilitated identification of 11 loci associated with aggressive disease development. Microarray data derived from 126 (TRAMPxNOD/ShiLtJ) F2 primary tumors were used to prioritize candidate genes within QTLs, with candidate genes deemed as being high priority when possessing both high levels of expression-trait correlation and a proximal expression QTL. This process enabled the identification of 35 aggressive prostate tumorigenesis candidate genes. The role of these genes in aggressive forms of human prostate cancer was investigated using two concurrent approaches. First, logistic regression analysis in two human prostate gene expression datasets revealed that expression levels of five genes (CXCL14, ITGAX, LPCAT2, RNASEH2A, and ZNF322) were positively correlated with aggressive prostate cancer and two genes (CCL19 and HIST1H1A) were protective for aggressive prostate cancer. Higher than average levels of expression of the five genes that were positively correlated with aggressive disease were consistently associated with patient outcome in both human prostate cancer tumor gene expression datasets. Second, three of these five genes (CXCL14, ITGAX, and LPCAT2) harbored polymorphisms associated with aggressive disease development in a human GWAS cohort consisting of 1,172 prostate cancer patients. This study is the first example of using a systems genetics approach to successfully identify novel susceptibility genes for aggressive prostate cancer. Such approaches will facilitate the identification of novel germline factors driving aggressive disease susceptibility and allow for new insights into these deadly forms of prostate cancer.

CRISPRz: a database of zebrafish validated sgRNAs

CRISPRz (http://research.nhgri.nih.gov/CRISPRz/) is a database of CRISPR/Cas9 target sequences that have been experimentally validated in zebrafish. Programmable RNA-guided CRISPR/Cas9 has recently emerged as a simple and efficient genome editing method in various cell types and organisms, including zebrafish. Because the technique is so easy and efficient in zebrafish, the most valuable asset is no longer a mutated fish (which has distribution challenges), but rather a CRISPR/Cas9 target sequence to the gene confirmed to have high mutagenic efficiency. With a highly active CRISPR target, a mutant fish can be quickly replicated in any genetic background anywhere in the world. However, sgRNAs vary widely in their activity and models for predicting target activity are imperfect. Thus, it is very useful to collect in one place validated CRISPR target sequences with their relative mutagenic activities. A researcher could then select a target of interest in the database with an expected activity. Here, we report the development of CRISPRz, a database of validated zebrafish CRISPR target sites collected from published sources, as well as from our own in-house large-scale mutagenesis project. CRISPRz can be searched using multiple inputs such as ZFIN IDs, accession number, UniGene ID, or gene symbols from zebrafish, human and mouse.

Sequencing of Candidate Chromosome Instability Genes in Endometrial Cancers Reveals Somatic Mutations in ESCO1, CHTF18, and MRE11A

Most endometrial cancers can be classified histologically as endometrioid, serous, or clear cell. Non-endometrioid endometrial cancers (NEECs; serous and clear cell) are the most clinically aggressive of the three major histotypes and are characterized by aneuploidy, a feature of chromosome instability. The genetic alterations that underlie chromosome instability in endometrial cancer are poorly understood. In the present study, we used Sanger sequencing to search for nucleotide variants in the coding exons and splice junctions of 21 candidate chromosome instability genes, including 19 genes implicated in sister chromatid cohesion, from 24 primary, microsatellite-stable NEECs. Somatic mutations were verified by sequencing matched normal DNAs. We subsequently resequenced mutated genes from 41 additional NEECs as well as 42 endometrioid ECs (EECs). We uncovered nonsynonymous somatic mutations in ESCO1, CHTF18, and MRE11A in, respectively, 3.7% (4 of 107), 1.9% (2 of 107), and 1.9% (2 of 107) of endometrial tumors. Overall, 7.7% (5 of 65) of NEECs and 2.4% (1 of 42) of EECs had somatically mutated one or more of the three genes. A subset of mutations are predicted to impact protein function. The co-occurrence of somatic mutations in ESCO1 and CHTF18 was statistically significant (P = 0.0011, two-tailed Fishers exact test). This is the first report of somatic mutations within ESCO1 and CHTF18 in endometrial tumors and of MRE11A mutations in microsatellite-stable endometrial tumors. Our findings warrant future studies to determine whether these mutations are driver events that contribute to the pathogenesis of endometrial cancer.

Somatic mutation profiles of clear cell endometrial tumors revealed by whole exome and targeted gene sequencing

The molecular pathogenesis of clear cell endometrial cancer (CCEC), a tumor type with a relatively unfavorable prognosis, is not well defined. We searched exome‐wide for novel somatically mutated genes in CCEC and assessed the mutational spectrum of known and candidate driver genes in a large cohort of cases.

Mutational analysis of the tyrosine kinome in serous and clear cell endometrial cancer uncovers rare somatic mutations in TNK2 and DDR1

BackgroundEndometrial cancer (EC) is the 8th leading cause of cancer death amongst American women. Most ECs are endometrioid, serous, or clear cell carcinomas, or an admixture of histologies. Serous and clear ECs are clinically aggressive tumors for which alternative therapeutic approaches are needed. The purpose of this study was to search for somatic mutations in the tyrosine kinome of serous and clear cell ECs, because mutated kinases can point to potential therapeutic targets.MethodsIn a mutation discovery screen, we PCR amplified and Sanger sequenced the exons encoding the catalytic domains of 86 tyrosine kinases from 24 serous, 11 clear cell, and 5 mixed histology ECs. For somatically mutated genes, we next sequenced the remaining coding exons from the 40 discovery screen tumors and sequenced all coding exons from another 72 ECs (10 clear cell, 21 serous, 41 endometrioid). We assessed the copy number of mutated kinases in this cohort of 112 tumors using quantitative real time PCR, and we used immunoblotting to measure expression of these kinases in endometrial cancer cell lines.ResultsOverall, we identified somatic mutations in TNK2 (tyrosine kinase non-receptor, 2) and DDR1 (discoidin domain receptor tyrosine kinase 1) in 5.3% (6 of 112) and 2.7% (3 of 112) of ECs. Copy number gains of TNK2 and DDR1 were identified in another 4.5% and 0.9% of 112 cases respectively. Immunoblotting confirmed TNK2 and DDR1 expression in endometrial cancer cell lines. Three of five missense mutations in TNK2 and one of two missense mutations in DDR1 are predicted to impact protein function by two or more in silico algorithms. The TNK2P761Rfs*72 frameshift mutation was recurrent in EC, and the DDR1R570Q missense mutation was recurrent across tumor types.ConclusionsThis is the first study to systematically search for mutations in the tyrosine kinome in clear cell endometrial tumors. Our findings indicate that high-frequency somatic mutations in the catalytic domains of the tyrosine kinome are rare in clear cell ECs. We uncovered ten new mutations in TNK2 and DDR1 within serous and endometrioid ECs, thus providing novel insights into the mutation spectrum of each gene in EC.

De Novo assembly of the goldfish (Carassius auratus) genome and the evolution of genes after whole genome duplication

For over a thousand years throughout Asia, the common goldfish (Carassius auratus) was raised for both food and as an ornamental pet. Selective breeding over more than 500 years has created a wide array of body and pigmentation variation particularly valued by ornamental fish enthusiasts. As a very close relative of the common carp (Cyprinus carpio), goldfish shares the recent genome duplication that occurred approximately 14-16 million years ago (mya) in their common ancestor. The combination of centuries of breeding and a wide array of interesting body morphologies is an exciting opportunity to link genotype to phenotype as well as understanding the dynamics of genome evolution and speciation. Here we generated a high-quality draft sequence of a “Wakin” goldfish using 71X PacBio long-reads. We identified 70,324 coding genes and more than 11,000 non-coding transcripts. We found that the two sub-genomes in goldfish retained extensive synteny and collinearity between goldfish and zebrafish. However, “ohnologous” genes were lost quickly after the carp whole-genome duplication, and the expression of 30% of the retained duplicated gene diverged significantly across seven tissues sampled. Loss of sequence identity and/or exons determined the divergence of the expression across all tissues, while loss of conserved, non-coding elements determined expression variance between different tissues. This draft assembly also provides an important resource for comparative genomics with the very commonly used zebrafish model (Danio rerio), and for understanding the underlying genetic causes of goldfish variants.

Abstract 2261: DLGAP5, MAT1A, SKA3, and ZMYM5 are novel susceptibility genes for aggressive prostate cancer

Prostate cancer is a common disease with approximately 233,000 men estimated to be diagnosed in the United States alone in 2014. Yet, it is usually an indolent disease with only 13% of patients succumbing to prostate cancer, and the molecular determinants of aggressive prostate cancer remain unclear. Previously, we reported that germline variation influences disease aggressiveness in the C57BL/6-Tg(TRAMP)8247Ng/J (TRAMP) mouse model. These mice develop neuroendocrine prostate tumors similar to a subset of human prostate tumors associated with poor outcomes. Here, we used a multifaceted approach to identify candidate genes for susceptibility to aggressive prostate tumorigenesis and metastasis using the TRAMP mouse model. Candidate prostate cancer metastasis susceptibility genes were identified through quantitative trait locus (QTL) mapping in 201 (TRAMP x PWK/PhJ) F2 males. Two aggressive disease QTLs were identified; one for lymph node metastasis burden on chromosome 12 (LOD = 5.86) and one for distant metastasis-free survival on chromosome 14 (LOD = 4.41). Correlation analysis using microarray data derived from 27 (TRAMP x PWK/PhJ) F2 prostate tumors identified 35 metastasis-associated transcripts within the two loci. The role of these genes in susceptibility to aggressive human prostate cancer was analyzed in two different datasets. First, logistic regression and survival analyses in human prostate cancer gene expression datasets demonstrated that the expression levels of 5 of the 35 candidate genes was associated with both an increased risk of aggressive disease and a poorer disease-free survival. Second, four of these genes - DLGAP5, MAT1A, SKA3, and ZMYM5 - harbored SNPs associated with aggressive tumorigenesis in the PLCO/CGEMS GWAS cohort of 1,172 prostate cancer patients. This approach, novel to the prostate cancer field, demonstrates how mouse models can be used to identify aggressive disease susceptibility genes, and gives new insight into the molecular mechanisms of aggressive disease. Citation Format: Minnkyong Lee, Kendra A. Williams, Ying Hu, Jonathan Andreas, Shashankkumar J. Patel, Suiyuan Zhang, Nigel PS Crawford. DLGAP5, MAT1A, SKA3, and ZMYM5 are novel susceptibility genes for aggressive prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2261. doi:10.1158/1538-7445.AM2015-2261