Genomic profiling of subcutaneous patient-derived xenografts reveals immune constraints on tumor evolution in childhood solid cancer.

Subcutaneous patient-derived xenografts (PDXs) are an important tool for childhood cancer research. Here, we describe a resource of 68 early passage PDXs established from 65 pediatric solid tumor patients. Through genomic profiling of paired PDXs and patient tumors (PTs), we observe low mutational similarity in about 30% of the PT/PDX pairs. Clonal analysis in these pairs show an aggressive PT minor subclone seeds the major clone in the PDX. We show evidence that this subclone is more immunogenic and is likely suppressed by immune responses in the PT. These results suggest interplay between intratumoral heterogeneity and antitumor immunity may underlie the genetic disparity between PTs and PDXs. We further show that PDXs generally recapitulate PTs in copy number and transcriptomic profiles. Finally, we report a gene fusion LRPAP1-PDGFRA. In summary, we report a childhood cancer PDX resource and our study highlights the role of immune constraints on tumor evolution.

Spatial Multiplexed Protein Profiling of Cardiac Ischemia-Reperfusion Injury.

BACKGROUND: Reperfusion therapy is critical to myocardial salvage in the event of a myocardial infarction but is complicated by ischemia-reperfusion injury (IRI). Limited understanding of the spatial organization of cardiac cells, which governs cellular interaction and function, has hindered the search for targeted interventions minimizing the deleterious effects of IRI. METHODS: We used imaging mass cytometry to characterize the spatial distribution and dynamics of cell phenotypes and communities in the mouse left ventricle following IRI. Heart sections were collected from 12 cardiac segments (basal, mid-cavity, apical, and apex of the anterior, lateral, and inferior wall) and 8 time points (before ischemia [I-0H], and postreperfusion [R-0H, R-2H, R-6H, R-12H, R-1D, R-3D, R-7D]), and stained with 29 metal-isotope-tagged antibodies. Cell community analysis was performed on reconstructed images, and the most disease-relevant cell type and target protein were selected for intervention of IRI. RESULTS: We obtained a total of 251 multiplexed images, and identified 197 063 single cells, which were grouped into 23 distinct cell communities based on the structure of cellular neighborhoods. The cellular architecture was heterogeneous throughout the ventricular wall and exhibited swift changes following IRI. Analysis of proteins with posttranslational modifications in single cells unveiled 13 posttranslational modification intensity clusters and highlighted increased H3K9me3 (tri-methylated lysine 9 of histone H3) as a key regulatory response in endothelial cells during the middle stage of IRI. Erasing H3K9 methylation, by silencing its methyltransferase Suv39h1 or overexpressing its demethylase Kdm4d in isolated endothelial cells, attenuated cardiac dysfunction and pathological remodeling following IRI. in vitro, H3K9me3 binding significantly increased at endothelial cell function-related genes upon hypoxia, suppressing tube formation, which was rescued by inhibiting H3K9me3. CONCLUSIONS: We mapped the spatiotemporal heterogeneity of cellular phenotypes in the adult heart upon IRI, and uncovered H3K9me3 in endothelial cells as a potential therapeutic target for alleviating pathological remodeling of the heart following myocardial IRI.

Draft Genome of White-blotched River Stingray Provides Novel Clues for Niche Adaptation and Skeleton Formation.

The white-blotched river stingray (Potamotrygon leopoldi) is a cartilaginous fish native to the Xingu River, a tributary of the Amazon River system. As a rare freshwater-dwelling cartilaginous fish in the Potamotrygonidae family in which no member has the genome sequencing information, P. leopoldi provides the evolutionary details in fish phylogeny, niche adaptation, and skeleton formation. In this study, we present its draft genome of 4.11 Gb comprised of 16,227 contigs and 13,238 scaffolds, with contig N50 of 3937 kb and scaffold N50 of 5675 kb in size. Our analysis shows that P. leopoldi is a slow-evolving fish that diverged from elephant sharks about 96 million years ago. Moreover, two gene families related to the immune system, immunoglobulin heavy constant delta genes and T-cell receptor alpha/delta variable genes, exhibit expantion in P. leopoldi only. We also identified the Hox gene clusters in P. leopoldi and discovered that seven Hox genes shared by five representative fish species are missing in P. leopoldi. The RNA sequencing data from P. leopoldi and other three fish species demonstrate that fishes have a more diversified tissue expression spectrum as compared with the corresponding mammalian data. Our functional studies suggest that the lack of the GC gene encoding vitamin D-binding protein in cartilaginous fishes (both P. leopoldi and Callorhinchus milii) could partly explain the absence of hard bone in their endoskeleton. Overall, this genome resource provides new insights into the niche adaptation, body plan, and skeleton formation of P. leopoldi as well as the genome evolution in cartilaginous fishes.

Comprehensive analysis reveals distinct mutational signature and its mechanistic insights of alcohol consumption in human cancers.

Alcohol consumption is a critical risk factor for multiple types of cancer. A genome can be attacked and acquire numerous somatic mutations in the environment of alcohol exposure. Mutational signature has the capacity illustrating the complex somatic mutation patterns in cancer genome. Recent studies have discovered distinct mutational signatures associating with alcohol consumption in liver and esophageal cancers. However, their prevalence among diverse cancers, impact of genetic background and origin of alcohol-induced mutational signatures remain unclear. By a comprehensive bioinformatics analysis on somatic mutations from patients of four cancer types with drinking information, we identified nine mutational signatures (signatures B-J), among which signature J (similar to COSMIC signature 16) was distinctive to alcohol drinking. Signature J was associated with HNSC, ESCA and LIHC but not PAAD. Interestingly, patients with mutated allele rs1229984 in ADH1B had lower level of signature J while mutated allele rs671 in ALDH2 exhibited higher signature J abundance, suggesting acetaldehyde is one cause of signature J. Intriguingly, somatic mutations of three potential cancer driver genes (TP53, CUL3 and NSD1) were found the critical contributors for increased mutational load of signature J in alcohol consumption patients. Furthermore, signature J was enriched with early accumulated clonal mutations compared to mutations derived from late tumor growth. This study systematically characterized alcohol-related mutational signature and indicated mechanistic insights into the prevalence, origin and gene-environment interaction regarding the risk oncogenic mutations associated with alcohol intake.

The phylogenetic relationship within SARS-CoV-2s: An expanding basal clade.

The COVID-19 pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) whose origin is still shed in mystery. In this study, we developed a method to search the basal SARS-CoV-2 clade among collected SARS-CoV-2 genome sequences. We first identified the mutation sites in the SARS-CoV-2 whole genome sequence alignment. Then by the pairwise comparison of the numbers of mutation sites among all SARS-CoV-2s, the least mutated clade was identified, which is the basal clade under parsimony principle. In our first analysis, we used 168 SARS-CoV-2 sequences (GISAID dataset till 2020/03/04) to identify the basal clade which contains 33 identical viral sequences from seven countries. To our surprise, in our second analysis with 367 SARS-CoV-2 sequences (GISAID dataset till 2020/03/17), the basal clade has 51 viral sequences, 18 more sequences added. The much larger NCBI dataset shows that this clade has expanded with 85 unique sequences by 2020/04/04. The expanding basal clade tells a chilling fact that the least mutated SARS-CoV-2 sequence was replicating and spreading for at least four months. It is known that coronaviruses have the RNA proofreading capability to ensure their genome replication fidelity. Interestingly, we found that the SARS-CoV-2 without its nonstructural proteins 13 to 16 (Nsp13-Nsp16) exhibits an unusually high mutation rate. Our result suggests that SARS-CoV-2 has an unprecedented RNA proofreading capability which can intactly preserve its genome even after a long period of transmission. Our selection analyses also indicate that the positive selection event enabling SARS-CoV-2 to cross species and adapt to human hosts might have been achieved before its outbreak.

Global Analysis of Gene Expression Profiles Provides Novel Insights into the Development and Evolution of the Large Crustacean Eriocheir sinensis.

Chinese mitten crab (Eriocheir sinensis) is an important aquaculture species in Crustacea. Functional analysis, although essential, has been hindered due to the lack of sufficient genomic or transcriptomic resources. In this study, transcriptome sequencing was conducted on 59 samples representing diverse developmental stages (fertilized eggs, zoea, megalopa, three sub-stages of larvae, juvenile crabs, and adult crabs) and different tissues (eyestalk, hepatopancreas, and muscle from juvenile crabs, and eyestalk, hepatopancreas, muscle, heart, stomach, gill, thoracic ganglia, intestine, ovary, and testis from adult crabs) of E. sinensis. A comprehensive reference transcriptome was assembled, including 19,023 protein-coding genes. Hierarchical clustering based on 128 differentially expressed cuticle-related genes revealed two distinct expression patterns during the early larval developmental stages, demonstrating the distinct roles of these genes in "crab-like" cuticle formation during metamorphosis and cuticle calcification after molting. Phylogenetic analysis of 1406 one-to-one orthologous gene families identified from seven arthropod species and Caenorhabditis elegans strongly supported the hypothesis that Malacostraca and Branchiopoda do not form a monophyletic group. Furthermore, Branchiopoda is more phylogenetically closely related to Hexapoda, and the clade of Hexapoda and Branchiopoda and the clade of Malacostraca belong to the Pancrustacea. This study offers a high-quality transcriptome resource for E. sinensis and demonstrates the evolutionary relationships of major arthropod groups. The differentially expressed genes identified in this study facilitate further investigation of the cuticle-related gene expression networks which are likely associated with "crab-like" cuticle formation during metamorphosis and cuticle calcification after molting.

The Impact of DNA Methylation Dynamics on the Mutation Rate During Human Germline Development.

DNA methylation is a dynamic epigenetic modification found in most eukaryotic genomes. It is known to lead to a high CpG to TpG mutation rate. However, the relationship between the methylation dynamics in germline development and the germline mutation rate remains unexplored. In this study, we used whole genome bisulfite sequencing (WGBS) data of cells at 13 stages of human germline development and rare variants from the 1000 Genome Project as proxies for germline mutations to investigate the correlation between dynamic methylation levels and germline mutation rates at different scales. At the single-site level, we found a significant correlation between methylation and the germline point mutation rate at CpG sites during germline developmental stages. Then we explored the mutability of methylation dynamics in all stages. Our results also showed a broad correlation between the regional methylation level and the rate of C > T mutation at CpG sites in all genomic regions, especially in intronic regions; a similar link was also seen at all chromosomal levels. Our findings indicate that the dynamic DNA methylome during human germline development has a broader mutational impact than is commonly assumed.

Convergent degeneration of olfactory receptor gene repertoires in marine mammals.

BACKGROUND: Olfactory receptors (ORs) can bind odor molecules and play a crucial role in odor sensation. Due to the frequent gains and losses of genes during evolution, the number of OR members varies greatly among different species. However, whether the extent of gene gains/losses varies between marine mammals and related terrestrial mammals has not been clarified, and the factors that might underlie these variations are unknown. RESULTS: To address these questions, we identified more than 10,000 members of the OR family in 23 mammals and classified them into 830 orthologous gene groups (OGGs) and 281 singletons. Significant differences occurred in the number of OR repertoires and OGGs among different species. We found that all marine mammals had fewer OR genes than their related terrestrial lineages, with the fewest OR genes found in cetaceans, which may be closely related to olfactory degradation. ORs with more gene duplications or loss events tended to be under weaker purifying selection. The average gain and loss rates of OR genes in terrestrial mammals were higher than those of mammalian gene families, while the average gain and loss rates of OR genes in marine mammals were significantly lower and much higher than those of mammalian gene families, respectively. Additionally, we failed to detect any one-to-one orthologous genes in the focal species, suggesting that OR genes are not well conserved among marine mammals. CONCLUSIONS: Marine mammals have experienced large numbers of OR gene losses compared with their related terrestrial lineages, which may result from the frequent birth-and-death evolution under varied functional constrains. Due to their independent degeneration, OR genes present in each lineage are not well conserved among marine mammals. Our study provides a basis for future research on the olfactory receptor function in mammals from the perspective of evolutionary trajectories.

Comparative Transcriptome Analyses Reveal the Role of Conserved Function in Electric Organ Convergence Across Electric Fishes.

The independent origins of multiple electric organs (EOs) of fish are fascinating examples of convergent evolution. However, comparative transcriptomics of different electric fish lineages are scarce. In this study, we found that the gene expression of EOs and skeletal muscles from three lineages (Mormyroidea, Siluriformes, and Gymnotiformes) tended to cluster together based on the species of origin, irrespective of the organ from which they are derived. A pairwise comparison of differentially expressed genes (DEGs) revealed that no less than half of shared DEGs exhibited parallel expression differentiation, indicating conserved directionality of differential expression either in or between lineages, but only a few shared DEGs were identified across all focal species. Nevertheless, the functional enrichment analysis of DEGs indicated that there were more parallel gene expression changes at the level of pathways and biological functions. Therefore, we may conclude that there is no parallel evolution of the entire transcriptomes of EOs among different lineages. Further, our results support the hypothesis that it is not different genes but conserved biological functions that play a crucial role in the convergence of complex phenotypes. This study provides insight into the genetic basis underlying the EO convergent evolution; however, more studies in different cases will be needed to demonstrate whether this pattern can be extended to other cases to derive a general rule for convergent evolution.

Integrative Analysis of Somatic Mutations in Non-coding Regions Altering RNA Secondary Structures in Cancer Genomes.

RNA secondary structure may influence many cellular processes, including RNA processing, stability, localization, and translation. Single-nucleotide variations (SNVs) that alter RNA secondary structure, referred to as riboSNitches, are potentially causative of human diseases, especially in untranslated regions (UTRs) and noncoding RNAs (ncRNAs). The functions of somatic mutations that act as riboSNitches in cancer development remain poorly understood. In this study, we developed a computational pipeline called SNIPER (riboSNitch-enriched or depleted elements in cancer genomes), which employs MeanDiff and EucDiff to detect riboSNitches and then identifies riboSNitch-enriched or riboSNitch-depleted non-coding elements across tumors. SNIPER is available at github: https://github.com/suzhixi/SNIPER/ . We found that riboSNitches were more likely to be pathogenic. Moreover, we predicted several UTRs and lncRNAs (long non-coding RNA) that significantly enriched or depleted riboSNitches in cancer genomes, indicative of potential cancer driver or essential noncoding elements. Our study highlights the possibly neglected importance of RNA secondary structure in cancer genomes and provides a new strategy to identify new cancer-associated genes.

Identification and characterization of tyrosine kinases in anole lizard indicate the conserved tyrosine kinase repertoire in vertebrates.

The tyrosine kinases (TKs) play principal roles in regulation of multicellular aspects of the organism and are implicated in many cancer types and congenital disorders. The anole lizard has recently been introduced as a model organism for laboratory-based studies of organismal function and field studies of ecology and evolution. However, the TK family of anole lizard has not been systematically identified and characterized yet. In this study, we identified 82 TK-encoding genes in the anole lizard genome and classified them into 28 subfamilies through phylogenetic analysis, with no member from ROS and STYK1 subfamilies identified. Although TK domain sequences and domain organization in each subfamily were conserved, the total number of TKs in different species was much variable. In addition, extensive evolutionary analysis in metazoans indicated that TK repertoire in vertebrates tends to be remarkably stable. Phylogenetic analysis of Eph subfamily indicated that the divergence of EphA and EphB occurred prior to the whole genome duplication (WGD) but after the split of Urochordates and vertebrates. Moreover, the expression pattern analysis of lizard TK genes among 9 different tissues showed that 14 TK genes exhibited tissue-specific expression and 6 TK genes were widely expressed. Comparative analysis of TK expression suggested that the tissue specifically expressed genes showed different expression pattern but the widely expressed genes showed similar pattern between anole lizard and human. These results may provide insights into the evolutionary diversification of animal TK genes and would aid future studies on TK protein regulation of key growth and developmental processes.

NF90 regulates PARP1 mRNA stability in hepatocellular carcinoma.

Poly (ADP-ribose) polymerase 1 (PARP1) is an ADP- ribosylation enzyme and plays important roles in a variety of cellular processes, including DNA damage response and tumor development. However, the post-transcriptional regulation of PARP1 remains largely unknown. In this study, we identified that the mRNA of PARP1 is associated with nuclear factor 90 (NF90) by RNA immunoprecipitation plus sequencing (RIP-seq) assay. The mRNA and protein levels of PARP1 are dramatically decreased in NF90-depleted cells, and NF90 stabilizes PARP1's mRNA through its 3'UTR. Moreover, the expression levels of PARP1 and NF90 are positively correlated in hepatocellular carcinoma (HCC). Finally, we demonstrated that NF90-depleted cells are sensitive to PARP inhibitor Olaparib (AZD2281) and DNA damage agents. Taken together, these results suggest that NF90 regulates PARP1 mRNA stability in hepatocellular carcinoma cells, and NF90 is a potential target to inhibit PARP1 activity.

Complete Mitochondrial Genome of a Tongue Worm Armillifer agkistrodontis.

Armillifer agkistrodontis (Ichthyostraca: Pantastomida) is a parasitic pathogen, only reported in China, which can cause a zoonotic disease, pentastomiasis. A complete mitochondrial (mt) genome was 16,521 bp comprising 13 protein-coding genes (PCGs), 22 tRNA genes, 2 rRNA genes, and 1 non-coding region (NCR). A phylogenetic tree drawn with the concatenated amino acid sequences of the 6 conserved PCGs (atp6, cox1-3, and nad2) showed that A. agkistrodontis and Armillifer armillatus constituted a clade Pentastomida which was a sister group of the Branchiura. The complete mt genome sequence of A. agkistrodontis provides important genetic markers for both phylogenetic and epidemiological studies of pentastomids.