Publications by authors named "Yuezheng Zhang"

8 Publications

  • Page 1 of 1

PolyG-DS: An ultrasensitive polyguanine tract-profiling method to detect clonal expansions and trace cell lineage.

Proc Natl Acad Sci U S A 2021 Aug;118(31)

Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195;

Polyguanine tracts (PolyGs) are short guanine homopolymer repeats that are prone to accumulating mutations when cells divide. This feature makes them especially suitable for cell lineage tracing, which has been exploited to detect and characterize precancerous and cancerous somatic evolution. PolyG genotyping, however, is challenging because of the inherent biochemical difficulties in amplifying and sequencing repetitive regions. To overcome this limitation, we developed PolyG-DS, a next-generation sequencing (NGS) method that combines the error-correction capabilities of duplex sequencing (DS) with enrichment of PolyG loci using CRISPR-Cas9-targeted genomic fragmentation. PolyG-DS markedly reduces technical artifacts by comparing the sequences derived from the complementary strands of each original DNA molecule. We demonstrate that PolyG-DS genotyping is accurate, reproducible, and highly sensitive, enabling the detection of low-frequency alleles (<0.01) in spike-in samples using a panel of only 19 PolyG markers. PolyG-DS replicated prior results based on PolyG fragment length analysis by capillary electrophoresis, and exhibited higher sensitivity for identifying clonal expansions in the nondysplastic colon of patients with ulcerative colitis. We illustrate the utility of this method for resolving the phylogenetic relationship among precancerous lesions in ulcerative colitis and for tracing the metastatic dissemination of ovarian cancer. PolyG-DS enables the study of tumor evolution without prior knowledge of tumor driver mutations and provides a tool to perform cost-effective and easily scalable ultra-accurate NGS-based PolyG genotyping for multiple applications in biology, genetics, and cancer research.
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http://dx.doi.org/10.1073/pnas.2023373118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8346827PMC
August 2021

Characterization of TP53 mutations in Pap test DNA of women with and without serous ovarian carcinoma.

Gynecol Oncol 2020 02 12;156(2):407-414. Epub 2019 Dec 12.

Department of Pathology, University of Washington, Seattle, WA 98195, USA. Electronic address:

Objective: Pap tests hold promise as a molecular diagnostic for serous ovarian cancer, but previous studies reported limited sensitivity. Furthermore, the presence of somatic mutations in normal tissue is increasingly recognized as a challenge to the specificity of mutation-based cancer diagnostics. We applied an ultra-deep sequencing method with the goal of improving sensitivity and characterizing the landscape of low-frequency somatic TP53 mutations in Pap tests.

Methods: We used CRISPR-DS to deeply sequence (mean Duplex depth ~3000×) the TP53 gene in 30 Pap tests from 21 women without cancer and 9 women with serous ovarian carcinoma with known TP53 driver mutations. Mutations were annotated and compared to those in the TP53 cancer database.

Results: The tumor-derived mutation was identified in 3 of 8 Pap tests from women with ovarian cancer and intact tubes. In addition, 221 low-frequency (≲0.001) exonic TP53 mutations were identified in Pap tests from women with ovarian cancer (94 mutations) and without ovarian cancer (127 mutations). Many of these mutations resembled TP53 mutations found in cancer: they impaired protein activity, were predicted to be pathogenic, and clustered in exons 5 to 8 and hotspot codons. Cancer-like mutations were identified in all women but at higher frequency in women with ovarian cancer.

Conclusions: Pap tests have low sensitivity for ovarian cancer detection and carry abundant low-frequency TP53 mutations. These mutations are more frequently pathogenic in women with ovarian cancer. Determining whether low-frequency TP53 mutations in normal gynecologic tissues are associated with an increased cancer risk warrants further study.
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http://dx.doi.org/10.1016/j.ygyno.2019.11.124DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7018621PMC
February 2020

Cancer-Associated Mutations but No Cancer: Insights into the Early Steps of Carcinogenesis and Implications for Early Cancer Detection.

Trends Cancer 2019 09 22;5(9):531-540. Epub 2019 Aug 22.

Department of Pathology, University of Washington, Seattle, WA, USA. Electronic address:

Cancer is a disease of aging fueled by the accumulation of somatic mutations. While mutations in tumors are well characterized, little is known about the early mutational processes that initiate tumorigenesis. Recent advances in next-generation sequencing (NGS) have enabled the detection of mutations in normal tissue, revealing an unanticipated high level of age-related somatic mutations affecting most individuals and tissues. Surprisingly, many of these mutations are similar to mutations commonly found in tumors, suggesting an ongoing process of positive selection and clonal expansion akin to what occurs in cancer, but within normal tissue. Here we discuss some of the most important biological and clinical implications of these novel findings, with a special focus on their impact for cancer detection and prediction.
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http://dx.doi.org/10.1016/j.trecan.2019.07.007DOI Listing
September 2019

Aging-like Spontaneous Epigenetic Silencing Facilitates Wnt Activation, Stemness, and Braf-Induced Tumorigenesis.

Cancer Cell 2019 02;35(2):315-328.e6

CRB1, Department of Oncology and The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University School of Medicine, Room 530, Baltimore, MD 21287, USA. Electronic address:

We addressed the precursor role of aging-like spontaneous promoter DNA hypermethylation in initiating tumorigenesis. Using mouse colon-derived organoids, we show that promoter hypermethylation spontaneously arises in cells mimicking the human aging-like phenotype. The silenced genes activate the Wnt pathway, causing a stem-like state and differentiation defects. These changes render aged organoids profoundly more sensitive than young ones to transformation by Braf, producing the typical human proximal BRAF-driven colon adenocarcinomas characterized by extensive, abnormal gene-promoter CpG-island methylation, or the methylator phenotype (CIMP). Conversely, CRISPR-mediated simultaneous inactivation of a panel of the silenced genes markedly sensitizes to Braf-induced transformation. Our studies tightly link aging-like epigenetic abnormalities to intestinal cell fate changes and predisposition to oncogene-driven colon tumorigenesis.
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http://dx.doi.org/10.1016/j.ccell.2019.01.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6636642PMC
February 2019

Genetic Load and Potential Mutational Meltdown in Cancer Cell Populations.

Mol Biol Evol 2019 03;36(3):541-552

Key Laboratory of Genomics and Precision Medicine, Beijing Institute of Genomics, Beijing, China.

Large genomes with elevated mutation rates are prone to accumulating deleterious mutations more rapidly than natural selection can purge (Muller's ratchet). As a consequence, it may lead to the extinction of small populations. Relative to most unicellular organisms, cancer cells, with large and nonrecombining genome and high mutation rate, could be particularly susceptible to such "mutational meltdown." However, the most common type of mutation in organismal evolution, namely, deleterious mutation, has received relatively little attention in the cancer biology literature. Here, by monitoring single-cell clones from HeLa cell lines, we characterize deleterious mutations that retard the rate of cell proliferation. The main mutation events are copy number variations (CNVs), which, estimated from fitness data, happen at a rate of 0.29 event per cell division on average. The mean fitness reduction, estimated reaching 18% per mutation, is very high. HeLa cell populations therefore have very substantial genetic load and, at this level, natural population would likely face mutational meltdown. We suspect that HeLa cell populations may avoid extinction only after the population size becomes large enough. Because CNVs are common in most cell lines and tumor tissues, the observations hint at cancer cells' vulnerability, which could be exploited by therapeutic strategies.
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http://dx.doi.org/10.1093/molbev/msy231DOI Listing
March 2019

Targeted genome fragmentation with CRISPR/Cas9 enables fast and efficient enrichment of small genomic regions and ultra-accurate sequencing with low DNA input (CRISPR-DS).

Genome Res 2018 10 19;28(10):1589-1599. Epub 2018 Sep 19.

Department of Pathology, University of Washington, Seattle, Washington 98195, USA.

Next-generation sequencing methods suffer from low recovery, uneven coverage, and false mutations. DNA fragmentation by sonication is a major contributor to these problems because it produces randomly sized fragments, PCR amplification bias, and end artifacts. In addition, oligonucleotide-based hybridization capture, a common target enrichment method, has limited efficiency for small genomic regions, contributing to low recovery. This becomes a critical problem in clinical applications, which value cost-effective approaches focused on the sequencing of small gene panels. To address these issues, we developed a targeted genome fragmentation approach based on CRISPR/Cas9 digestion that produces DNA fragments of similar length. These fragments can be enriched by a simple size selection, resulting in targeted enrichment of up to approximately 49,000-fold. Additionally, homogenous length fragments significantly reduce PCR amplification bias and maximize read usability. We combined this novel target enrichment approach with Duplex Sequencing, which uses double-strand molecular tagging to correct for sequencing errors. The approach, termed CRISPR-DS, enables efficient target enrichment of small genomic regions, even coverage, ultra-accurate sequencing, and reduced DNA input. As proof of principle, we applied CRISPR-DS to the sequencing of the exonic regions of and performed side-by-side comparisons with standard Duplex Sequencing. CRISPR-DS detected previously reported pathogenic mutations present as low as 0.1% in peritoneal fluid of women with ovarian cancer, while using 10- to 100-fold less DNA than standard Duplex Sequencing. Whether used as standalone enrichment or coupled with high-accuracy sequencing methods, CRISPR-based fragmentation offers a simple solution for fast and efficient small target enrichment.
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http://dx.doi.org/10.1101/gr.235291.118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6169890PMC
October 2018

Free-living human cells reconfigure their chromosomes in the evolution back to uni-cellularity.

Elife 2017 12 18;6. Epub 2017 Dec 18.

Key Laboratory of Genomic and Precision Medicine, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China.

Cells of multi-cellular organisms evolve toward uni-cellularity in the form of cancer and, if humans intervene, continue to evolve in cell culture. During this process, gene dosage relationships may evolve in novel ways to cope with the new environment and may regress back to the ancestral uni-cellular state. In this context, the evolution of sex chromosomes vis-a-vis autosomes is of particular interest. Here, we report the chromosomal evolution in ~ 600 cancer cell lines. Many of them jettisoned either Y or the inactive X; thus, free-living male and female cells converge by becoming 'de-sexualized'. Surprisingly, the active X often doubled, accompanied by the addition of one haploid complement of autosomes, leading to an X:A ratio of 2:3 from the extant ratio of 1:2. Theoretical modeling of the frequency distribution of X:A karyotypes suggests that the 2:3 ratio confers a higher fitness and may reflect aspects of sex chromosome evolution.
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http://dx.doi.org/10.7554/eLife.28070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5734875PMC
December 2017

An unusual haplotype structure on human chromosome 8p23 derived from the inversion polymorphism.

Hum Mutat 2008 Oct;29(10):1209-16

Beijing Institute of Genomics, Chinese Academy of Sciences, P.R. China.

Chromosomal inversion is an important type of genomic variations involved in both evolution and disease pathogenesis. Here, we describe the refined genetic structure of a 3.8-Mb inversion polymorphism at chromosome 8p23. Using HapMap data of 1,073 SNPs generated from 209 unrelated samples from CEPH-Utah residents with ancestry from northern and western Europe (CEU); Yoruba in Ibadan, Nigeria (YRI); and Asian (ASN) samples, which were comprised of Han Chinese from Beijing, China (CHB) and Japanese from Tokyo, Japan (JPT)-we successfully deduced the inversion orientations of all their 418 haplotypes. In particular, distinct haplotype subgroups were identified based on principal component analysis (PCA). Such genetic substructures were consistent with clustering patterns based on neighbor-joining tree reconstruction, which revealed a total of four haplotype clades across all samples. Metaphase fluorescence in situ hybridization (FISH) in a subset of 10 HapMap samples verified their inversion orientations predicted by PCA or phylogenetic tree reconstruction. Positioning of the outgroup haplotype within one of YRI clades suggested that Human NCBI Build 36-inverted order is most likely the ancestral orientation. Furthermore, the population differentiation test and the relative extended haplotype homozygosity (REHH) analysis in this region discovered multiple selection signals, also in a population-specific manner. A positive selection signal was detected at XKR6 in the ASN population. These results revealed the correlation of inversion polymorphisms to population-specific genetic structures, and various selection patterns as possible mechanisms for the maintenance of a large chromosomal rearrangement at 8p23 region during evolution. In addition, our study also showed that haplotype-based clustering methods, such as PCA, can be applied in scanning for cryptic inversion polymorphisms at a genome-wide scale.
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http://dx.doi.org/10.1002/humu.20775DOI Listing
October 2008
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