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At least 19 recordsLinked to original sources

Analysis of rat repetitive DNA sequences.

Parameters of repetitive sequence organization have been measured in the rat genome. Experiments using melting, hydroxylapatite binding, and single strand specific nuclease digestion have been used to measure the number, length, and arrangement of repeated DNA sequences. Renaturation and melting or S1 nuclease digestion of 1.0 kbp DNA fragment show about 20% of rat DNA sequences are 3000-fold repeated. Renatured duplexes from 4.0 kbp DNA fragments display two repetitive size fractions after nuclease digestion. About 60% of the repeated sequences are 0.2-0.4 kbp long while the remainder are longer than 1.5 kbp. The arrangement of the repeated sequences has been measured by hydroxylapatite fractionation of DNA fragments of varying lengths bearing a repeated sequence. Repeated DNA sequences are interspersed among 2.5 kbp long nonrepeated sequences throughout more than 70% of the rat genome. There are approximately 350 different 3000-fold short repeated sequences in the rat interspersed among 600,000 nonrepeated DNA sequences.

Animals

Passage of phenotypes of chemically transformed cells via transfection of DNA and chromatin.

DNA was prepared from 15 different mouse and rat cell lines transformed by chemical carcinogens in vitro and in vivo. These DNAs were applied to NIH3T3 mouse fibroblast cultures by using the calcium phosphate transfection technique. DNAs of five donor lines were able to induce foci on the recipient monolayers. Ten other donor DNAs yielded few or no foci. DNAs from control, nontransformed parental cell lines induced few or no foci. Chromosomes were transfected from one donor whose naked DNA was unable to induce foci, and morphologic transformation of recipients was observed. These experiments prove that in five of these cell lines the chemically induced phenotype is encoded in DNA, and the sequences specifying the transformed phenotype behave as a dominant allele in the NIH3T3 recipient cells. The sequences encoding the transformation are likely found on a single fragment of DNA.

Alleles

Single-cell multimodal profiling of pan-cancer cell lines uncovers gene regulatory principles underlying intrinsic cell states and environmental features.

Cancer arises from genetic and epigenetic alterations that reshape chromatin, transcriptional regulation, and malignant cell states. To chart cancer-intrinsic regulatory programs, we build a pan-cancer single-cell atlas of 60 cancer cell lines spanning 16 tissue origins and 20 cancer types, comprising 240,957 snRNA-seq and 223,347 snATAC-seq profiles. Integrative analyses reveal cell-state heterogeneity, core gene-regulatory networks, and a conserved EMT axis transcending tissue of origin; copy-number analysis identifies transcription factor amplification and hyperactivation as drivers of state reprogramming. Comparing cutaneous melanoma with acral melanoma, a rare subtype underrepresented in previous studies, uncovers a universal inflammation-suppressive program in acral and an inflamed landscape in cutaneous melanoma, with JAK-STAT activity as the central discriminator. Integrating data across models and patient cohorts links tumor-intrinsic regulation to microenvironmental composition and therapeutic response. By profiling rare alongside common subtypes, this atlas offers a resource for mapping pan-cancer and subtype-specific regulatory programs shaping cell-state plasticity.

Humans

The offonome reveals on and off states of gene expression near the detection limit of RNA-seq.

RNA-seq, widely used for gene expression profiling, provides nucleotide level genome coverage and summary gene expression values. Generally, low-expressed genes are ignored due to their unfavorable signal-to-noise ratio, however, these genes may offer crucial information, such as detecting rare cells in bulk tissues. In this study, we applied an approach that transforms the expression levels of low-expressed genes into a robust dichotomized on/off state by leveraging similarities in transcript coverage shape. Applied to three human cancer cohorts from the Cancer Genome Atlas (TCGA), chosen based on tissue morphology and anatomic site, we identified genes, the "offonome" near the detection limit, consistently or occasionally off across samples. Genes in the offonome spectrum proved useful for supervised and unsupervised applications, including characterizing oncogenic pathways, and identifying rare populations of cells in bulk tissue. Interrogating the offonome is relevant to bulk tumor analyses like TCGA, potentially expediting gene investigation in low-input situations like single cell RNA-seq.

Humans

1-Mb resolution array-based comparative genomic hybridization using a BAC clone set optimized for cancer gene analysis.

Array-based comparative genomic hybridization (aCGH) is a recently developed tool for genome-wide determination of DNA copy number alterations. This technology has tremendous potential for disease-gene discovery in cancer and developmental disorders as well as numerous other applications. However, widespread utilization of a CGH has been limited by the lack of well characterized, high-resolution clone sets optimized for consistent performance in aCGH assays and specifically designed analytic software. We have assembled a set of approximately 4100 publicly available human bacterial artificial chromosome (BAC) clones evenly spaced at approximately 1-Mb resolution across the genome, which includes direct coverage of approximately 400 known cancer genes. This aCGH-optimized clone set was compiled from five existing sets, experimentally refined, and supplemented for higher resolution and enhancing mapping capabilities. This clone set is associated with a public online resource containing detailed clone mapping data, protocols for the construction and use of arrays, and a suite of analytical software tools designed specifically for aCGH analysis. These resources should greatly facilitate the use of aCGH in gene discovery.

Cell Line, Tumor

Clinical and genetic features of Ph-negative myeloproliferative neoplasms with dual-driver gene positivity.

OBJECTIVES: To investigate the clinical laboratory characteristics and gene mutation features of dual-driver gene positivity in patients with Philadelphia chromosome-negative myeloproliferative neoplasm (Ph-negative MPN). METHODS: We conducted a retrospective analysis of clinical data and genetic test results from 203 newly diagnosed patients with Ph-negative MPN. Of these, 194 had single-driver gene positivity and 9 had dual-driver gene positivity. High-throughput sequencing was used to detect mutations in JAK2, CALR, and MPL. Clinical characteristics and gene mutation profiles were compared between the two patient groups. RESULTS: The incidence of dual-driver gene positivity was 4.4% (9/203), with the most common combinations being JAK2 with CALR (4 patients) and JAK2 with MPL (4 patients). Compared with the single-driver group, the dual-driver group had a significantly higher risk of bleeding [4.1% (8/194) vs. 33.3% (3/9), P = 0.008] and a higher proportion of uncommon mutations [3.6% (7/194) vs. 33.3% (3/9), P = 0.006]. No statistically significant differences were observed between the two groups regarding age, thrombosis incidence, splenomegaly, or routine blood test indicators. During follow-up, 1 patient in the dual-driver group died from cerebrovascular disease. No leukaemia transformation or disease-related deaths occurred among the remaining patients. DISCUSSION: The increased bleeding risk in dual-driver patients may be related to a higher proportion of CALR mutations, elevated platelet counts, and higher variant allele frequencies, though these findings require validation in larger cohorts due to the small sample size. The higher prevalence of uncommon mutations suggests a more complex mutational landscape in this subgroup. CONCLUSION: Patients with Ph-negative MPN and dual-driver gene positivity may have a higher risk of bleeding and a more complex gene mutation profile.

Humans

Fecal immunochemical tests from population-based colorectal cancer screening programs support prospective microbiome cohorts.

BACKGROUND: Large, prospective cohorts are needed to research the gut microbiome's role in colorectal cancer (CRC) risk. We evaluated the gut microbiome leveraging residual fecal immunochemical tests (FIT) from a CRC screening program in Turin, Italy, and conducted one of the largest population-based case-control studies across the adenoma-carcinoma sequence to date. METHODS: We extracted DNA from residual FIT stool, used whole-genome shotgun sequencing, and included those with CRC (N = 44), advanced adenomas (N = 269), early adenomas (N = 134), and FIT-negative controls (N = 478). Alpha diversity, beta diversity, and species, gene, and pathway relative abundances were estimated. Multivariable logistic regression models were used to estimate associations of these metrics with colorectal neoplasms. RESULTS: Alpha diversity was mostly inversely associated with colorectal neoplasms, particularly early adenomas (OR: 0.45, 95% CI: 0.25-0.80; P = 0.01). Presence of oral pathogens, including Parvimonas micra, was associated with higher odds of CRC. Furthermore, Escherichia coli and Bacteroides fragilis were strongly associated with higher odds of all colorectal neoplasms. Several genes and pathways were associated with colorectal neoplasms. CONCLUSIONS: Our findings align with smaller studies of the gut microbiome and colorectal neoplasms, supporting that CRC screening programs provide opportunities to prospectively study the gut microbiome's association with cancer risk in large populations.

Humans

Rat hepatoma cells nucleolar DNA. II. A possible model of nucleolar DNA organisation.

A model of nucleolar DNA organization has been established. Three clearly defined main components are found in ascites hepatoma cell nucleolar DNA by CsCl gradient analysis. A linear arrangement for nucleolar DNA and a model of DNA organization in the neighbourhood of a set of ribosomal genes, which may play a fundamental role in the elaboration of nucleolar chromatin tertiary structure, are presented.

Animals

Genetics of retinoblastoma.

Retinoblastoma may be due to (1) a somatic mutation, which is not hereditary, (2) a germinal mutation, which is dominantly inherited, and (3) a deletion of the long arm of chromosome 13. In unilateral cases of retinoblastoma, the risk for the offspring is 5-6%, as 10-15% of these cases are due to a germinal mutation. In all the bilateral cases and in the unilateral hereditary cases, the risk for the offspring or the sibs is 40-50% depending on the penetrance of the gene.

Chromosome Deletion

Colorectal carcinoma as a genetic phenomenon.

Carcinogenesis in human large intestine is a result of multiple, heterogeneous and random genetic changes. Deletion of tumor suppressor genes and activation of oncogenes appear to be important molecular events. These compromise the loss of chromosomes 5, 17, 18 or functional inactivation of FAP, p53 and DCC genes. Activation of Ki-ras and c-myc oncogenes seems to be crucial for both cell immortalization and morphology modification. Identification of genes involved in this process enables both a screening and a new classification. Also it is an important step towards a gene therapy.

Animals

A very large repeating unit of mouse DNA containing the 18S, 28S and 5.8S rRNA genes.

The organization of the 18S, 28S and 5.8S rRNA genes in the mouse has been elucidated by mapping with restriction endonucleases Eco RI, Hind III and Bam HI. Ribosomal DNA fragments were detected in electrophoretically fractionated digests of total nuclear DNA by in situ hybridization with radioiodinated rRNAs or with complementary RNA synthesized directly on rRNA templates. A map of the rDNA which includes 13 restriction sites was constructed from the sizes of rDNA fragments and their labeling by different probes The map indicates that the rRNA genes lie within remarkably large units of reiterated DNA, at least 44,000 base pairs long. At least two, and possibly four, classes of repeating unit can be distinguished, the heterogeneity probably residing in the very large nontranscribed spacer region. The 5.8S rRNA gene lies in the transcribed region between the 18S and 28S genes.

Animals