Structural assessment of HLA-A2-restricted SARS-CoV-2 spike epitopes recognized by public and private T-cell receptors

T cells play a vital role in combatting SARS-CoV-2 and forming long-term memory responses. Whereas extensive structural information is available on neutralizing antibodies against SARS-CoV-2, such information on SARS-CoV-2-specific T-cell receptors (TCRs) bound to their peptide–MHC targets is lacking. Here we determine the structures of a public and a private TCR from COVID-19 convalescent patients in complex with HLA-A2 and two SARS-CoV-2 spike protein epitopes (YLQ and RLQ). The structures reveal the basis for selection of particular TRAV and TRBV germline genes by the public but not the private TCR, and for the ability of the TCRs to recognize natural variants of RLQ but not YLQ. Neither TCR recognizes homologous epitopes from human seasonal coronaviruses. By elucidating the mechanism for TCR recognition of an immunodominant yet variable epitope (YLQ) and a conserved but less commonly targeted epitope (RLQ), this study can inform prospective efforts to design vaccines to elicit pan-coronavirus immunity.

Molecular Pathogenesis in Myeloid Neoplasms with Germline Predisposition

Myeloid neoplasms with germline predisposition have recently been added as distinct provisional entities in the 2017 revision of the World Health Organization’s classification of tumors of hematopoietic and lymphatic tissue. Individuals with germline predisposition have increased risk of developing myeloid neoplasms—mainly acute myeloid leukemia and myelodysplastic syndrome. Although the incidence of myeloid neoplasms with germline predisposition remains poorly defined, these cases provide unique and important insights into the biology and molecular mechanisms of myeloid neoplasms. Knowledge of the regulation of the germline genes and their interactions with other genes, proteins, and the environment, the penetrance and clinical presentation of inherited mutations, and the longitudinal dynamics during the process of disease progression offer models and tools that can further our understanding of myeloid neoplasms. This knowledge will eventually translate to improved disease sub-classification, risk assessment, and development of more effective therapy. In this review, we will use examples of these disorders to illustrate the key molecular pathways of myeloid neoplasms.

The zinc-finger transcription factor LSL-1 is a major regulator of the germline transcriptional program in C. elegans

Specific gene transcriptional programs are required to ensure proper proliferation and differentiation processes underlying the production of specialized cells during development. Gene activity is mainly regulated by the concerted action of transcription factors and chromatin proteins. In the nematode C. elegans, mechanisms that silence improper transcriptional programs in germline and somatic cells have been well studied, however, how are tissue specific sets of genes turned on is less known. LSL-1 is herein defined as a novel crucial transcriptional regulator of germline genes in C. elegans. LSL-1 is first detected in the P4 blastomere and remains present at all stages of germline development, from primordial germ cell proliferation to the end of meiotic prophase. lsl-1 loss-of-function mutants exhibit many defects including meiotic prophase progression delay, a high level of germline apoptosis, and production of almost no functional gametes. Transcriptomic analysis and ChIP-seq data show that LSL-1 binds to promoters and acts as a transcriptional activator of germline genes involved in various processes, including homologous chromosome pairing, recombination, and genome stability. Furthermore, we show that LSL-1 functions by antagonizing the action of the heterochromatin proteins HPL-2/HP1 and LET-418/Mi2 known to be involved in the repression of germline genes in somatic cells. Based on our results, we propose LSL-1 to be a major regulator of the germline transcriptional program during development.

Repression of germline genes by PRC1.6 and SETDB1 in the early embryo precedes DNA methylation-mediated silencing

Silencing of a subset of germline genes is dependent upon DNA methylation (DNAme) post-implantation. However, these genes are generally hypomethylated in the blastocyst, implicating alternative repressive pathways before implantation. Indeed, in embryonic stem cells (ESCs), an overlapping set of genes, including germline “genome-defence” (GGD) genes, are upregulated following deletion of the H3K9 methyltransferase SETDB1 or subunits of the non-canonical PRC1 complex PRC1.6. Here, we show that in pre-implantation embryos and naïve ESCs (nESCs), hypomethylated promoters of germline genes bound by the PRC1.6 DNA-binding subunits MGA/MAX/E2F6 are enriched for RING1B-dependent H2AK119ub1 and H3K9me3. Accordingly, repression of these genes in nESCs shows a greater dependence on PRC1.6 than DNAme. In contrast, GGD genes are hypermethylated in epiblast-like cells (EpiLCs) and their silencing is dependent upon SETDB1, PRC1.6/RING1B and DNAme, with H3K9me3 and DNAme establishment dependent upon MGA binding. Thus, GGD genes are initially repressed by PRC1.6, with DNAme subsequently engaged in post-implantation embryos.

Single Molecule Real-Time Sequencing of the M Protein (SMaRT M-Seq): Toward Personalized Medicine Approaches in Monoclonal Gammopathies

Introduction In patients affected by monoclonal gammopathies, tumoral B cells or plasma cells secrete a monoclonal antibody (termed M protein), which can be used to track the presence of the tumor itself. Moreover, the M protein can directly cause potentially life-threatening organ damage, which is dictated by the specific, patient's unique clonal light and/or heavy chain, as in patients affected by immunoglobulin light chain (AL) amyloidosis. Yet, the current paradigm in the diagnosis and management of these conditions treats the M protein as a simple tumor biomarker to be identified/quantified. Patients' specific M protein sequences remain mostly undefined and molecular mechanisms underlying M-protein related clinical manifestations are largely obscure. Methods By combining the unbiased amplification of expressed immunoglobulin genes with long-read, single molecule real-time DNA sequencing and bioinformatics analyses, we have established a method to identify the full-length sequence of the variable region of expressed immunoglobulin genes and to rank the obtained sequences based on their relative abundance, thus enabling the identification of the full-length variable sequence of M protein genes from a high number of patients analysed in parallel. Results The assay, which we termed Single Molecule Real-Time Sequencing of the M protein (SMaRT M-Seq), has undergone an extensive technical validation. Sequencing of contrived bone marrow samples generated through serial dilutions of plasma cell lines into control bone marrow, as well as sequencing of bona fide bone marrow samples from AL patients and comparison with gold-standard techniques of immunoglobulin gene sequencing showed: 100% sequence-accuracy at the individual base-pair level; High repeatability (CV<0.8% for sequencing of pentaplicates) in defining the molecular clonal size (i.e. the fraction of total immunoglobulin sequences coinciding with the clonal sequence); A high sensitivity in identifying clonal immunoglobulin sequences (10 -3 when employing low-coverage sequencing on multiple, pooled samples). Noteworthy, SMaRT M Seq was applied to a cohort of 86 consecutive patients with AL amyloidosis (17 κ and 69 λ; median BMPC infiltration 9%, IQR 6-13%; median dFLC 176 mg/L, IQR 75-370 mg/L), including cases with small clonal burden and M protein which was undetectable with conventional M protein studies. A full-length sequence of the variable region of the clonal light chain was obtained in all patients (median molecular clonal size of 88.3%, IQR: 70.7 - 93%). The most common κ germline genes were IGKV1-33 and IGKV4-01 (24% each of the 17 κ AL patients), and the most common λ germline genes were IGLV6-57 (26% of the 69 λ AL patients), IGLV2-14 (17%), IGLV3-01 (17%) and IGLV1-44 (10%). The most frequent λ and κ germline genes together (IGLV6-57, IGLV2-14, IGLV3-01, IGLV1-44, IGKV1-33 and IGKV4-01) accounted for 66% of all the clones. Germline gene usage correlated with selected clinical features. Sequence information was then exploited to improve mass spectrometry-based amyloid typing on fat pad aspirates and to enable the sensitive detection of clonotypic sequences using short-read DNA sequencing of the involved light chain isotype (up to 10 -7 dilution). Conclusions We have established SMaRT M-Seq as a novel valuable assay to reliably identify the full-length variable sequence of M proteins. SMaRT M-Seq has undergone extensive technical validation, showing high accuracy, repeatability and sensitivity. The latter is determined by the number of reads analyzed per sample. This is in turn dictated by the sequencing output of the employed sequencing platform, and by the number of pooled samples analyzed in a given sequencing round, thus proving to be scalable. Even when analyzing multiple samples on a sequencing platform with low sequencing output, the achieved sensitivity of SMaRT M-Seq significantly exceeds the requirements for the identification of clonal B cells/plasma cells in patients with AL amyloidosis. Sequencing disease-associated M proteins from large cohorts of patients has the potential to uncover molecular mechanisms of M protein-related clinical manifestations which have remained largely unexplored so far, and could enable approaches of personalized medicine for the sensitive detection of patients' specific M proteins at diagnosis and after anti-clonal therapy. Disclosures Milani: Celgene: Other: Travel support; Janssen-Cilag: Honoraria. Fazio: Janseen: Honoraria. Petrucci: GSK: Honoraria, Other: Advisory Board; Amgen: Honoraria, Other: Advisory Board; Takeda: Honoraria, Other: Advisory Board; BMS: Honoraria, Other: Advisory Board; Janssen-Cilag: Honoraria, Other: Advisory Board; Celgene: Honoraria, Other: Advisory Board; Karyopharm: Honoraria, Other: Advisory Board. Palladini: Pfizer: Honoraria; Siemens: Honoraria; Janssen Global Services: Honoraria, Other: advisory board fees. Nuvolone: Janssen-Cilag: Honoraria; Oncopeptides, Inc.: Research Funding.

Cancer/Testis genes are predictive of breast tumor subtypes

Breast cancer is the most prevalent type of cancer in women worldwide. Within breast tumors, the basal-like subtype has the worst prognosis and no dedicated therapy, therefore new tools to understand, detect, and treat these tumors are needed. Certain germline genes are re-expressed in tumors, and constitute the Cancer/Testis genes; their misexpression has diagnostic and therapeutic applications. Here, we designed a new approach to examine Cancer/Testis gene misexpression in breast tumors. We identify several new markers in Luminal and HER-2 positive tumors, some of which predict response to chemotherapy. We then use machine learning to identify the 2 Cancer/Testis genes most associated with basal-like breast tumors: HORMAD1 and CT83. We show that these genes are expressed by tumor cells but not the microenvironment, and that they are not expressed by normal breast progenitors, in other words their activation occurs de novo. We find these genes are epigenetically repressed by DNA methylation, and that their activation upon DNA demethylation is irreversible, providing a memory of past epigenetic disturbances. Basal-like tumors expressing both genes have a poorer outcome than tumors expressing either gene alone or neither gene. Therefore, these findings suggest a potential synergistic effect between Cancer/Testis genes in basal breast tumors; these findings have consequences for the understanding, diagnosis, and therapy of the breast tumors with the worse outcomes.

Novel Allele Detection Tool Benchmark and Application With Antibody Repertoire Sequencing Dataset

Detailed knowledge of the diverse immunoglobulin germline genes is critical for the study of humoral immunity. Hundreds of alleles have been discovered by analyzing antibody repertoire sequencing (Rep-seq or Ig-seq) data via multiple novel allele detection tools (NADTs). However, the performance of these NADTs through antibody sequences with intrinsic somatic hypermutations (SHMs) is unclear. Here, we developed a tool to simulate repertoires by integrating the full spectrum features of an antibody repertoire such as germline gene usage, junctional modification, position-specific SHM and clonal expansion based on 2152 high-quality datasets. We then systematically evaluated these NADTs using both simulated and genuine Ig-seq datasets. Finally, we applied these NADTs to 687 Ig-seq datasets and identified 43 novel allele candidates (NACs) using defined criteria. Twenty-five alleles were validated through findings of other sources. In addition to the NACs detected, our simulation tool, the results of our comparison, and the streamline of this process may benefit further humoral immunity studies via Ig-seq.

Development of a novel embryonic germline gene-related prognostic model of lung adenocarcinoma

Background Emerging evidence implicates the correlation of embryonic germline genes with the tumor progress and patient’s outcome. However, the prognostic value of these genes in lung adenocarcinoma (LUAD) has not been fully studied. Here we systematically evaluated this issue, and constructed a novel signature and a nomogram associated with embryonic germline genes for predicting the outcomes of lung adenocarcinoma. Methods The LUAD cohorts retrieved from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database were used as training set and testing set, respectively. The embryonic germline genes were downloaded from the website https://venn.lodder.dev. Then, the differentially expressed embryonic germline genes (DEGGs) between the tumor and normal samples were identified by limma package. The functional enrichment and pathway analyses were also performed by clusterProfiler package. The prognostic model was constructed by the least absolute shrinkage and selection operator (LASSO)-Cox regression method. Survival and Receiver Operating Characteristic (ROC) analyses were performed to validate the model using training set and four testing GEO datasets. Finally, a prognostic nomogram based on the signature genes was constructed using multivariate regression method. Results Among the identified 269 DEGGs, 249 were up-regulated and 20 were down-regulated. GO and KEGG analyses revealed that these DEGGs were mainly enriched in the process of cell proliferation and DNA damage repair. Then, 103 DEGGs with prognostic value were identified by univariate Cox regression and further filtered by LASSO method. The resulting sixteen DEGGs were included in step multivariate Cox regression and an eleven embryonic germline gene related signature (EGRS) was constructed. The model could robustly stratify the LUAD patients into high-risk and low-risk groups in both training and testing sets, and low-risk patients had much better outcomes. The multi-ROC analysis also showed that the EGRS model had the best predictive efficacy compared with other common clinicopathological factors. The EGRS model also showed robust predictive ability in four independent external datasets, and the area under curve (AUC) was 0.726 (GSE30219), 0.764 (GSE50081), 0.657 (GSE37745) and 0.668 (GSE72094). More importantly, the expression level of some genes in EGRS has a significant correlation with the progression of LUAD clinicopathology, suggesting these genes might play an important role in the progression of LUAD. Finally, based on EGRS genes, we built and calibrated a nomogram for conveniently evaluating patients’ outcomes.

Enhancer-associated H3K4 methylation safeguards in vitro germline competence

Germline specification in mammals occurs through an inductive process whereby competent cells in the post-implantation epiblast differentiate into primordial germ cells (PGC). The intrinsic factors that endow epiblast cells with the competence to respond to germline inductive signals remain unknown. Single-cell RNA sequencing across multiple stages of an in vitro PGC-like cells (PGCLC) differentiation system shows that PGCLC genes initially expressed in the naïve pluripotent stage become homogeneously dismantled in germline competent epiblast like-cells (EpiLC). In contrast, the decommissioning of enhancers associated with these germline genes is incomplete. Namely, a subset of these enhancers partly retain H3K4me1, accumulate less heterochromatic marks and remain accessible and responsive to transcriptional activators. Subsequently, as in vitro germline competence is lost, these enhancers get further decommissioned and lose their responsiveness to transcriptional activators. Importantly, using H3K4me1-deficient cells, we show that the loss of this histone modification reduces the germline competence of EpiLC and decreases PGCLC differentiation efficiency. Our work suggests that, although H3K4me1 might not be essential for enhancer function, it can facilitate the (re)activation of enhancers and the establishment of gene expression programs during specific developmental transitions.

TR Locus Annotation and Characteristics of Rhinolophus ferrumequinum

T-cell antigen receptors (TRs) in vertebrates can be divided into αβ or γδ, encoded by TRA/D, TRG, or TRB loci. TRs play a central role in mammal cellular immunity, which occurs by rearrangement of V, D, J, and C genes in the loci. The bat is the only mammal with flying ability and is considered the main host of zoonotic viruses, an important public health concern. However, at present, little is known about the composition of bat TR genes. Based on the whole genome sequence of the greater horseshoe bat (Rhinolophus ferrumequinum) and referring to the TR/IG annotation rules formulated by the international ImMunoGeneTics information system (IMGT), we present a complete annotation of TRA/D, TRG, and TRB loci of R. ferrumequinum. A total of 128 V segments, three D segments, 85 J segments, and 6 C segments were annotated and compared with other known mammalian data. The characteristics of the TR locus and germline genes of R. ferrumequinum are analyzed.