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• Development of a diagnostic gene panel for Gorlin syndrome and its application to liquid biopsy

  Gorlin syndrome is an autosomal dominant, rare disease caused by mutations in PTCH1, PTCH2, and SUFU with various symptoms in multiple organs making early diagnosis challenging. In this study, we generated a Gorlin syndrome gene panel that could help to overcome the difficulties in diagnosing Gorlin syndrome using a single test. This gene panel is time- and cost-efficient and highly reliable with a high-quality score of 30, on-target ratio, and coverage depth, and could detect more mutations than whole-exome sequencing of the same patient. Although the current in silico prediction tools have a limited genetic database of gene mutations in rare hereditary diseases, five prediction tools were used to identify pathological mutations. Pathogenic gene mutations were detected not only in PTCH1 but also in PTCH2 in five out of 12 patients with Gorlin syndrome diagnosed based on clinical symptoms. Using this gene panel, we showed the same gene mutation in the patients and their asymptomatic relatives; hence, it has enabled a highly reliable genetic diagnosis of Gorlin syndrome at a low cost requiring only blood sample.

  Study JGAS000308

• RNA sequencing and Illumina 2.5M SNP array data collected from 675 commonly used human cancer cell lines.

  Tumor-derived cell lines have served as vital models to advance our understanding of oncogene function and therapeutic response1. Although substantial effort has been directed to defining the genomic constitution of cancer cell line panels2–4, the transcriptome – which represents the active program of a cell – remains understudied. Here, we describe RNA sequencing and SNP array analysis of 675 commonly used human cancer cell lines. We explore numerous transcriptome features including coding and non-coding gene expression, transcribed mutations, gene fusion and expression of non-human sequences. Aside from many known aberrations we find new surprising characteristics, including more than 2200 unique fusion gene pairs representing a vast, testable repertoire of oncogenic fusions, many of which have analogs found in primary human tumors. We show that a combination of multiple genome and transcriptome features in a novel pathway-based approach enhances prediction of response to various targeted therapeutics. Our results provide valuable new insights into these critical pre-clinical models and provide added context for interpreting the numerous studies that employ these widely used cell lines.

  Study EGAS00001000610

• Androgen deprivation therapy promotes an inflammatory and obesity-like microenvironment in periprostatic fat

  Prostate cancer is a leading cause of cancer-related death and morbidity worldwide. Androgen deprivation therapy (ADT) is the cornerstone of management for advanced disease. The use of androgen deprivation therapies is associated with multiple side effects, including metabolic syndrome and truncal obesity. At the same time, obesity has been associated with both prostate cancer development and disease progression, linked to its effects on chronic inflammation at a tissue level. The connection between androgen deprivation therapy, obesity, inflammation, and prostate cancer progression is well-established in clinical settings; however, an understanding of the changes in adipose tissue at the molecular level induced by castrating therapies is missing. Here we investigated the transcriptional changes in periprostatic fat tissue induced by profound androgen deprivation therapy in a group of patients with high-risk tumours compared to a matching untreated cohort. We find that androgen deprivation therapy is associated with a pro-inflammatory and obesity-like adipose tissue microenvironment. This study suggests that the beneficial effect of androgen deprivation therapy may be partially counteracted by metabolic and inflammatory side effects in the adipose tissue surrounding the prostate.

  Study EGAS00001003286

• B cell receptor repertoire kinetics after SARS-CoV-2 infection and vaccination

  B cells play a central role in the immune response to both SARS-CoV-2 infection and vaccination, but the development of the B cell receptor (BCR) repertoire in both contexts has not been defined nor compared. We analysed serial samples from 171 SARS-CoV-2-infected individuals with a range of disease severities together with 63 vaccine recipients, and found marked differences in the global BCR repertoire after natural infection compared to vaccination. Following infection, the proportion of BCRs bearing IgG1/3 and IgA1 isotypes increased, somatic hypermutation (SHM) was markedly decreased and, in patients with severe disease, expansion of IgM and IgA clones was observed. In contrast, after vaccination the proportion of BCRs bearing IgD/M isotypes increased, SHM was unchanged and expansion of IgG clones was prominent. Infection generated a broad distribution of SARS-CoV-2-specific clones predicted to target the spike protein whilst vaccination produced a more focused response mainly targeting the spike’s receptor-binding domain. These findings offer insights into how different immune exposure to SARS-CoV-2 impacts upon BCR repertoire development, potentially informing vaccine strategies.

  Study EGAS00001005816

• Discovery of immunotherapy targets for pediatric solid and brain tumors by exon-level expression

  Immunotherapy with chimeric antigen receptor T cells for pediatric solid and brain tumors is constrained by available targetable antigens. Cancer-specific exons present a promising reservoir of targets; however, these have not been explored and validated systematically in a pan-cancer fashion. To identify cancer specific exon targets, we analyze 1,532 RNA-seq datasets from 16 types of pediatric solid and brain tumors for comparison with normal tissues using a newly developed workflow. We find 2,933 exons in 157 genes encoding proteins of the surfaceome or matrisome with high cancer specificity either at the gene (n=148) or the alternatively spliced isoform (n=9) level. Expression of selected alternatively spliced targets, including the EDB domain of fibronectin 1, and gene targets, such as COL11A1, are validated in pediatric patient derived xenograft tumors. We generate T cells expressing chimeric antigen receptors specific for the EDB domain or COL11A1 and demonstrate that these have antitumor activity. The full target list, explorable via an interactive web portal (https://cseminer.stjude.org/), provides a rich resource for developing immunotherapy of pediatric solid and brain tumors using gene or AS targets with high expression specificity in cancer.

  Study EGAS00001007766

• Whole genome sequencing of retinoblastoma reveals the diversity of rearrangements disrupting RB1 and uncovers a treatment related mutational signature

  Background: The development of retinoblastoma is thought to require pathological genetic changes in both alleles of the RB1 gene. However, cases exist where RB1 mutations are undetectable suggesting alternative pathways to malignancy. Methods: We applied comprehensive whole genome sequencing (WGS) and transcriptomics to sporadic retinoblastomas derived from twenty patients attending our clinic, contrasting these results to that obtained through customary clinical testing. We sought RB1 and other driver mutations, investigated mutation burden, mutational signatures and phylogenetic relatedness in one case of bilateral retinoblastoma. Results: At least one RB1 mutation was identified in all retinoblastomas. We confirmed RB1 mutations previously identified by clinical screening, identified three new RB1 mutations and provided clarity to the mechanism behind a further six mutations. Eight tumours carried structural rearrangements involving RB1 ranging from relatively simple to extremely complex rearrangement patterns, including a chromothripsis-like pattern in one tumour. Potential driver mutations included mutations in BCOR (5/20) and amplification of MYCN (2/20) and MDM4 (1/20). We show that RB1 mutations are not mutually exclusive of MYCN amplifications, and further reveal that all tumours demonstrate increased MYCN expression suggesting a universal role in retinoblastoma tumorigenesis.  Bilateral tumours obtained from one patient harboured conserved germline but divergent somatic RB1 mutations, indicating independent evolution. In-keeping with previous WGS of paediatric cancers, the mutation burden in retinoblastomas was extremely low. Mutational signature analysis showed a predominance of signatures associated with cell division and an absence of ultraviolet-related DNA damage. In a tumour exposed to chemotherapy prior to enucleation, a profound platinum-related mutational signature was observed. Conclusions: WGS provides a complete picture of the genomic landscape of retinoblastomas, allowing the discovery of mutations otherwise undetected by conventional clinical screening approaches. The presence of at least one RB1 mutation in all retinoblastomas and the relative paucity of driver mutations in other genes suggests mutations beyond RB1, MYCN and BCOR are rare. Whilst most RB1 mutations are identifiable by clinical screening, the increased resolution and ability to detect otherwise elusive rearrangements of RB1 by WGS, confirming whether they are somatic or germline, has important repercussions on clinical management and advice on recurrence risks.

  Dataset EGAD00001006431

• Whole Exome Sequencing of Pancreatic Neuroendocrine Tumors at The Human Genome Sequencing Center, Baylor College of Medicine (HGSC-BCM)

  Pancreatic neuroendocrine tumors (PNETs), often referred to as "islet cell tumors", are neuroendocrine neoplasms that arise from cells of the endocrine and nervous system within the pancreas. These rare tumors which originate from the pancreatic islet are divided into many categories and are often classified by the hormone most strongly secreted. With the collaboration of the Elkins Pancreatic Center, the Human Genome Sequencing Center (HGSC) at Baylor College of Medicine had access to approximately 30 untreated tumor specimens and matched normal blood samples. Since the onset and progression of cancer is driven by extensive mutation of the genome, we are combining enrichment of exonic DNA with next generation sequencing to detect and characterize the somatic mutation profile of patients with pancreatic neuroendocrine cancer. This work was done at the Human Genome Sequencing Center (HGSC) in collaboration with the Elkins Pancreatic Center at Baylor College of Medicine in Houston, TX and was supported by grant number 5U54HG003273 from National Human Genome Research Institute (NHGRI).

  Study phs000871

• Genomic Analysis of Fibrolamellar Hepatocellular Carcinoma

  Fibrolamellar hepatocellular carcinoma (FL-HCC) is a very rare and distinct subtype of hepatocellular carcinoma that occurs in the previously healthy livers of adolescents and young adults. The low incidence rate has kept FL-HCC an understudied cancer, thus the list of FL-HCC markers is limited and the genetic alterations driving its growth have remained unknown. In order to gain a better understanding of the molecular mechanisms underlying FL-HCC initiation and progression, we performed an in-depth genomic analyses of one tumor followed by immunohistochemistry validation on seven other tumors. We showed the expression of neuroendocrine markers in FL-HCC. In addition, DNA/RNA sequencing revealed that common cancer pathways are not visibly altered in FL-HCC but identified two novel structural variants, both resulting in fusion transcripts. Through in vitro studies, we demonstrated the oncogenic properties of these fusion transcripts. These experiments further highlight the tumorigenic role of gene fusions in the etiology of pediatric solid tumors and identify both candidate biomarkers and possible therapeutic targets for this lethal pediatric disease.

  Study phs000828

• Whole-Genome Sequencing Analysis of Extrachromosomal DNA with Amplicon Architect

  The study is related to our manuscript entitled "Single-cell genetic heterogeneity linked to immune infiltration in glioblastoma". Using multiplexed FISH analysis of 3-4 tumor cores from 17 glioblastoma formalin-fixed paraffin-embedded (FFPE) tumors, we identified two classes of tumors based on single cell co-occurrence of EGFR and CDK4 amplification. Tumors with a low odds ratio for finding EGFR and CDK4 amplified in the same cell (ORlow tumors) had higher EGFR copy number and higher diversity of copy number in cells harboring EGFR amplification. This suggested that in ORlow tumors EGFR is likely present on extrachromosomal DNA. To test this hypothesis, we performed whole genome sequencing on DNA extracted from FFPE slides from 3 ORlow samples and 3 ORhigh samples and used AmpliconArchitect to investigate the structure of the EGFR amplicon. We found multiple breakpoints and high complexity structure in the 3 tested ORlow samples, but not in the ORhigh samples, supporting the possibility of an extrachromosomal nature of EGFR amplification in the first group.

  Study phs003100

• Juvenile Sjogren's Syndrome (JSS) Transcriptome Study

  Sjögren's disease (SjD) is a systemic autoimmune disorder with major clinical manifestations of dryness in the eyes and mouth, fatigue, and joint pain. Our interdisciplinary experts in SjD at the University of Florida newly discovered and established a cohort of SjD in children. Many of these patients with childhood SjD (cSjD) demonstrated a prominent feature of recurrent parotitis (RP). To understand the immunopathogenesis of childhood SjD (cSjD) for the first time in the field, we profiled the transcriptome of five groups of four PBMC samples by unbiased, high-throughput single-cell RNA sequencing (scRNA-seq): cSjD (n=4), non-cSjD (n=4), biopsy-positive non-cSjD (BP, n=4), biopsy-positive non-cSjD with RP (BPRP, n=4), and healthy controls (HC, n=4). In this study, RNA sequencing data, as well as all barcodes.tsv.gz, features.tsv.gz, and matrix.mtx.gz that may be used to create a Seurat object in R, will be availableTo protect the confidentiality of subjects, certain data were not assessed or collected in the subject phenotype dataset, such as race, age, height, weight, and education.

  Study phs003048

• The Landscape of Antisense Gene Expression in Human Cancers

  High throughput RNA Sequencing has revealed that the human genome is widely transcribed. However, the extent of natural antisense transcription, the molecular mechanisms by which natural antisense transcripts (NATs) might affect their cognate sense genes, and the role of NATs in cancer are less well understood. Here, we use strand-specific paired-end RNA sequencing (ssRNASeq) on a cohort of 376 cancer patients covering 9 tissue types to comprehensively characterize the landscape of antisense expression. Our results reveal that greater than 60% of annotated transcripts have measureable antisense expression and the expression of sense and antisense transcript pairs is in general positively correlated. Furthermore, by studying the expression of sense/antisense pairs across tissues we identify lineage-specific, ubiquitous and cancer-specific antisense loci. Our results raise the possibility that NATs participate in the regulation of well-known tumor suppressors and oncogenes. Finally, this study provides a catalogue of cancer related genes with significant antisense transcription (oncoNAT). This resource will allow researchers to investigate the molecular mechanisms of sense/antisense regulation and further advance our understanding of their role in cancer.

  Study phs000937

• Functionally Active Copy Number Variants Associated with Prostate Cancer Risk

  Prostate cancer is a leading cause of cancer death in males throughout the world and has the largest estimated effect of heritability among the most common tumor types. Copy Number Variants (CNVs) are a recently recognized class of human germline polymorphisms (Iafrate AJ, et al. (2004) Nat Genet 36, 949-951; Sebat J, et al. (2004) Science 305, 525-528.) and are associated with a variety of human diseases, including cancer. This study characterized 1,903 individuals from the Tyrol Early Prostate Cancer Detection Program (Bartsch G, et al. (2008) BJU Int 101, 809-816) using a computational framework (Banerjee S, et al. (2011) PLoS One 29;6(3)). The study results establish non-coding and coding germline CNVs as significant risk factors for prostate cancer susceptibility and implicate their role in disease development and progression. The study "Identification of functionally active, low frequency copy number variants at 15q21.3 and 12q21.31 associated with prostate cancer risk," Demichelis F, Setlur SR, Proc Natl Acad Sci U S A. 2012 Apr 24;109(17):6686-91.

  Study phs000487

• Evolutionary trajectories of IDH-mutant astrocytoma identify molecular grading markers related to cell cycling

  To study the evolutionary processes that drive malignant transformation in IDH-mutant astrocytomas, we performed multi-omics on a large cohort of matched initial and recurrent tumor samples. We find that genome-wide DNA-methylation levels decreased over time, mainly in patients with high-grade recurrences. DNA-demethylation was lifted from specific loci associated with DNA replication, and was associated with upregulation of cell cycling associated genes. Upregulation of cell cycling genes occurred predominantly in proliferating tumor cells, and was associated with tumor grade. Temporal DNA-demethylation and upregulation of cell cycling were hardly affected by chemo- and/or radiotherapy, indicating treatment does not affect the course of disease. Further, we defined a DNA-methylation based signature associated with tumor grade and poor prognostic genetic events, with a prognostic power stronger than CDKN2A/B deletion. We validated its prognostic power on primary tumor samples of patients included in the CATNON randomized phase 3 clinical trial. Therefore this model can serve as a molecular grading marker for IDH-mutant astrocytomas.

  Study EGAS00001007527

• Blood-based monitoring of relapsed/refractory cHL patients predict responses to PD-1 blockade treatment

  Hodgkin lymphoma (cHL) patients are uniquely susceptible to treatment with programmed cell death-1 (PD-1) treatment. However, monitoring with FDG-PET/CT, the current response detection standard, is challenging. Here, we address the potential applicability of tissue biomarkers and blood-based biomarkers in PD-1 treated cHL patients. We evaluated 9p24.1/PD-L1/PD-L2 alterations, and expression of PD-L1 and antigen presentation molecules (HLA class I/II) in 9 tissue biopsies of 4 patients. In addition, we assessed circulating tumor DNA (ctDNA), extracellular vesicle associated miRNAs (EV-miRNAs), soluble PD-L1 and serum TARC (sTARC) in 26 longitudinal blood samples of these patients during PD-1 treatment. We found that the predictive power of tissue biomarkers is dependent on the timing of the biopsy . The dynamics of blood-based biomarkers: sTARC, EV-miRNAs and ctDNA corresponded well immunotherapy treatment response. Therefore, blood-based biomarkers are promising monitoring strategies in PD-1 treated cHL patients and should be further explored in clinical trials or observational studies.

  Study EGAS00001005894

• Proteogenomic Analysis of CALGB40601 (ALLIANCE) a Neoadjuvant Phase III HER2-Positive Breast Cancer Trial

  80 frozen core needle biopsies from 54 HER2+ breast cancer patients from the CALGB 40601 trial (NCT00770809) were processed for proteogenomic analysis to identify genes, proteins, and phosphosites associated with pathological complete response to neodjuvant anti-HER2 therapies. The final set included 22 patients treated with trastuzumab plus lapatinib in combination with pacletaxel (THL arm), 24 patients treated with trastuzumab in combination with pacletaxel (TH arm), and 8 patients treated lapatinib in combination with pacletaxel (TL arm). Principal findings of this study included identifying negative cases misdiagnosed as HER2+ that did not respond to targeted therapy and observing higher levels of two biomarker candidates in non-pCR tumors. Mass spec-based proteomics and phosphoproteomics data generated from 75 biopsies (all 54 patients) will be made available via the Proteomic Data Commons. Whole exome- (67 biopsies from 49 patients) and RNA-sequencing (52 biopsies from 39 patients) data for the subset profiled with proteogenomics will be made available through dbGaP, but genomic and transcriptomic profiling data for the whole cohort has previously been deposited (phs001570).

  Study phs003576

• Whole Genome Sequencing Consortium on Frontotemporal Dementia With Underlying TDP-43 Pathology

  Frontotemporal lobar degeneration (FTLD) is one of the leading causes of dementia in individuals younger than 65 years. The FTLD symptoms of most patients are not yet explained by mutations in the known FTLD genes (C9orf72, GRN, MAPT). Identifying genetic risk associated with the disease is key for developing disease models and new therapeutic avenues. We performed short-read whole-genome sequencing (WGS) on 19 neuropathologically normal individuals and 560 patients with FTLD, including 171 pathologically confirmed FTLD patients, 352 clinically diagnosed FTLD patients, and 37 autosomal dominant FTLD patients. Pathologically confirmed FTLD patients include FTLD with TDP43 inclusions (FTLD-TDP) and FTLD with FUS inclusions (FTLD-FUS), autosomal dominant FTLD patients include GRN (FTLD-TDP GRN) and C9ORF72 (FTLD-TDP C9ORF72) mutation carriers, clinically diagnosed patients include behavioral variant of frontotemporal dementia (bvFTD), frontotemporal dementia with amyotrophic lateral sclerosis (FTD-ALS), frontotemporal dementia with corticobasal syndrome (FTD-CBS), semantic variant of primary progressive aphasia (svPPA), and non-fluent variant of primary progressive aphasia (nfvPPA).

  Study phs003309

• Development of a fully human glioblastoma-in-brain-spheroid model for accelerated translational research

  In glioblastoma (GBM) the intricate interplay between tumor cells and the surrounding microenvironment plays a crucial role in tumor progression, invasion, and therapeutic resistance. So far, studying these interactions in a controlled and representative model system has been challenging. Here, we report the development of hGliCS, a human glioma-cortical spheroid model that allows the elucidation of the biology of GBM cells and their interactions with a human-specific brain-like microenvironment and neurons. GBM cells efficiently invade the cortical spheroids, forming a well-connected network of communicating cells. The heterogeneous cellular states of the GBM cells within this model closely resembled findings previously observed in glioblastoma patients and in mouse xenografts. We observed a transition from predominantly mesenchymal-like cells to heterotopic states with a high diversity. In contrast to the substantial changes observed in the tumor cell population, the impact of the GBM cells on the neurons was minimal. We further demonstrate the suitability of hGliCS to test compounds targeting tumor-specific neurobiological features.

  Study EGAS50000000757

• 10x Multiome from Human Fetal Heart

  We hope to uncover the genetic basis of congenital heart disease by examining how genetic variants, especially those in non-coding regions, influence heart development. To achieve this goal, our research team created a single-cell atlas of human fetal heart development. The study population consists of 41 structurally normal fetal hearts spanning 6 to 22 weeks post-conception. We profiled close to 750,000 using single-cell RNA sequencing and ATAC sequencing technologies via the 10x Genomics Multiome platform.The molecular technologies employed allowed for simultaneous analysis of gene expression and chromatin accessibility at the single-cell level. This approach identified numerous distinct cell types and states within the developing heart, offering detailed insights into gene activity and enhancer usage during critical stages of heart development.Principal findings include the characterization of diverse cell populations and the identification of specific gene expression patterns and regulatory elements active during heart formation. This high-resolution atlas provides valuable insights into how genetic variants may disrupt normal heart development, particularly those in non-coding regions that affect gene regulation.

  Study phs003778

• DHODH is a synthetic-lethal vulnerability in BCOR-deficient acute myeloid leukemia

  Acute Myeloid Leukemia (AML) remains challenging to treat, especially in cases with mutations in the BCL-6 co- repressor (BCOR), which are associated with poor prognosis and chemo-resistance. In this study, we reveal a synthetic lethal interaction between BCOR and dihydroorotate dehydrogenase (DHODH). We demonstrate that BCOR-deficient cells have a heightened sensitivity to DHODH inhibitors such as brequinar and leflunomide, that are already in clinical use. We confirm that DHODH inhibition selectively induces cell death in BCOR-mutant cells in multiple cellular models, in malignant and non-malignant cells, through chemical and genetic manipulation. Interestingly, we find that the dependency on DHODH does not stem from its role in de novo pyrimidine biosynthesis disruption. Rather, DHODH’s role in the electron transport chain, essential for mitigating reactive oxygen species, may be the physiological vulnerability that pushes BCOR-mutant cells toward cell death when DHODH is inhibited. DHODH inhibitors could be repurposed as targeted therapies for BCOR-mutant tumors, offering a promising strategy for precision medicine in AML and other cancers.

  Study EGAS50000001108

• DHODH is a synthetic-lethal vulnerability in BCOR-deficient acute myeloid leukemia

  Acute Myeloid Leukemia (AML) remains challenging to treat, especially in cases with mutations in the BCL-6 co- repressor (BCOR), which are associated with poor prognosis and chemo-resistance. In this study, we reveal a synthetic lethal interaction between BCOR and dihydroorotate dehydrogenase (DHODH). We demonstrate that BCOR-deficient cells have a heightened sensitivity to DHODH inhibitors such as brequinar and leflunomide, that are already in clinical use. We confirm that DHODH inhibition selectively induces cell death in BCOR-mutant cells in multiple cellular models, in malignant and non-malignant cells, through chemical and genetic manipulation. Interestingly, we find that the dependency on DHODH does not stem from its role in de novo pyrimidine biosynthesis disruption. Rather, DHODH’s role in the electron transport chain, essential for mitigating reactive oxygen species, may be the physiological vulnerability that pushes BCOR-mutant cells toward cell death when DHODH is inhibited. DHODH inhibitors could be repurposed as targeted therapies for BCOR-mutant tumors, offering a promising strategy for precision medicine in AML and other cancers.

  Study EGAS50000001060

• Chromatin accessibility in stem cells unveils progressive transcriptional reprogramming in myelodysplastic syndrome

  Myelodysplastic syndromes (MDS) originate from hematopoietic stem cell (HSC) clones with acquired gene mutations/deletions. However, our knowledge on the epigenetic properties of MDS stem cells are limited. Here, we examined chromatin accessibility of MDS stem cells. Chromatin accessibility profiles of MDS stem cells represented the disease status better than progenitor cells and unveiled the process of stem cell reprograming during disease progression. Characterization of differentially accessible regions (DARs) revealed that MDS stem cells acquire progenitor-like chromatin accessibility with disease progression, resulting in imprecise stem-progenitor hierarchy. Profiling of transcriptional factor binding motifs at DARs revealed precocious inactivation and activation of HSC and myeloid transcriptional networks, respectively, in MDS stem cells. Increased chromatin accessibility at CEBP target sites well represented the myeloid reprograming of MDS stem cells and stratified MDS into distinct subgroups. Newly developed "Progenitor scores" based on chromatin accessibility well stratified the disease status and correlated with prognosis. These results highlight that the chromatin properties of MDS stem cells define the cell-autonomous behavior of MDS and disease progression.

  Study JGAS000718

• TGF-β signaling mediates microglial resilience to spatiotemporally restricted myelin degeneration

  Microglia survey and regulate central nervous system myelination during embryonic development and adult homeostasis. However, whether microglia-myelin interactions are spatiotemporally regulated remains unexplored. By examining spinal cord white matter tracts, we found that myelin degeneration was particularly prominent in the dorsal column (DC) during normal aging. This was accompanied by molecular and functional changes in DC microglia as well as an upregulation of TGF-β signaling. Disrupting TGF-β signaling in microglia led to unchecked microglial responses and myelin loss in the DC, accompanied by neurological deficits exacerbated with aging. snRNA-seq revealed the emergence of a TGF-β signaling-sensitive microglial subset and a disease-associated oligodendrocyte subset, both spatially restricted to the DC. We further discovered that microglia rely on a TGFβ autocrine mechanism to prevent damage of myelin in the DC. These findings demonstrate that TGF-β signaling is indispensable for maintaining microglial resilience to myelin degeneration in the DC during the aging process. This highlights a previously unresolved checkpoint mechanism of TGF-β signaling with regional specificity and spatially restricted microglia-oligodendrocyte interactions.

  Study EGAS50000001413

• Inferring tumor genomes from peripheral blood i.e. CTCs and plasma-DNA using deep sequencing and targeted enrichment

  In this study we tested whether complex tumor genomes can be inferred from the peripheral blood (plasma DNA /CTCs) of 32 patients with stage IV colorectal carcinoma (CRC). To establish the percentage of mutated plasma DNA fragments we used 8 patient samples with different plasma DNA size distributions and KRAS mutations in their corresponding primary tumors and employed ultra-deep pyrosequencing with 3 different sequencing reaction sizes (i.e., 119 bp, 168 bp, and 323 bp). Furthermore, we used massive parallel sequencing of a panel of 68 CRC-associated genes to establish the mutation spectrum of cancer driver genes in the primary tumors, metastases, and CTCs of two colorectal cancer patients. To investigate, whether mutations found in only one CTC (“private CTC mutations”) are true mutations occurring with allele frequencies below the resolution limits of current detection methods, or whether they are amplification or sequencing artifacts, we performed ultra-deep sequencing of the primary tumors, metastases, plasma DNAs and normal tissues.

  Study EGAS00001000337

• Passive and active DNA methylation and the interplay with genetic variation in gene regulation

  DNA methylation is an essential1 epigenetic mark whose role in gene regulation and its dependency on genomic sequence and environment are not yet fully understood2,3. In this study we provide novel insights into the mechanistic relationships between genetic variation, DNA methylation and transcriptome sequencing data in three different cell-types of the GenCord human population cohort4. We find that the association between DNA methylation and gene expression variation among individuals are likely due to different mechanisms from those establishing methylation-expression patterns during differentiation. Furthermore, cell-type differential DNA methylation may delineate a platform in which more local inter-individual changes may respond to or act in gene regulation. We show that unlike genetic regulatory variation, DNA methylation alone does not significantly drive allele specific expression.. Finally, inferred mechanistic relationships using genetic variation as well as correlations with TF abundance reveal both a passive and active role of DNA methylation to regulatory interactions influencing gene expression.

  Study EGAS00001000446

• Somatic pathogenic variants in the normal mammary gland of sporadic breast cancer patients.

  The mammary gland undergoes hormonally stimulated cycles of proliferation, lactation and involution. We hypothesized that these factors increase the mutational burden in glandular tissue and may explain high cancer incidence rate in the general population and recurrent disease. Hence, we investigated the DNA sequence variants in the normal mammary gland, tumor and peripheral blood from 52 reportedly sporadic breast cancer patients, including breast-conserving surgery cases. Targeted resequencing of 542 cancer associated genes revealed mosaic somatic pathogenic variants of: PIK3CA, TP53, AKT1, MAP3K1, CDH1, RB1, NCOR1, MED12, CBFB, TBX3 and TSHR in the normal mammary gland, at considerable allelic frequencies (9x10-2 to 5.2x10-1) indicating clonal expansion. Further evaluation of the frequently damaged PIK3CA and TP53 genes by ultra-sensitive duplex sequencing demonstrated a diversified picture of multiple low level-mosaic (in 10-2 to 10-4 alleles) hotspot pathogenic variants. Our results raise a question about the oncogenic potential in non-tumor mammary gland tissue of breast-conserving surgery patients.

  Study EGAS00001005698