The Child Surgical Patient in the Early Twentieth Century.

In the second half of the nineteenth century, scientific and technological developments in surgery permitted safer procedures to be carried out. Theoretically, therefore, children whose lives would otherwise have been blighted by disease could be saved by timely operative interference. The reality was more complicated, however, as this article shows. Through an exploration of British and American surgical textbooks and an in-depth analysis of the child surgical patient base at one London general hospital, the tensions between the possibilities and the actualities of surgery on children can be examined for the first time. Hearing the child's voice through case notes allows both a restoration of these complex patients to the history of medicine and a questioning of the wider application of science and technology to working-class bodies, situations, and environments which resist such treatment.

Histone chaperone HIRA deposits histone H3.3 onto foreign viral DNA and contributes to anti-viral intrinsic immunity.

The HIRA histone chaperone complex deposits histone H3.3 into nucleosomes in a DNA replication- and sequence-independent manner. As herpesvirus genomes enter the nucleus as naked DNA, we asked whether the HIRA chaperone complex affects herpesvirus infection. After infection of primary cells with HSV or CMV, or transient transfection with naked plasmid DNA, HIRA re-localizes to PML bodies, sites of cellular anti-viral activity. HIRA co-localizes with viral genomes, binds to incoming viral and plasmid DNAs and deposits histone H3.3 onto these. Anti-viral interferons (IFN) specifically induce HIRA/PML co-localization at PML nuclear bodies and HIRA recruitment to IFN target genes, although HIRA is not required for IFN-inducible expression of these genes. HIRA is, however, required for suppression of viral gene expression, virus replication and lytic infection and restricts murine CMV replication in vivo. We propose that the HIRA chaperone complex represses incoming naked viral DNAs through chromatinization as part of intrinsic cellular immunity.

DNA damage marker phosphorylated histone H2AX is a potential predictive marker for progression of epithelial dysplasia of the oral cavity.

AIMS: To evaluate the relationships between immunohistochemical markers related to cellular senescence, cell proliferation and histological grade of epithelial dysplasia (OD) of the oral cavity. In addition, the predictive value of these markers for progression of OD was assessed. METHODS AND RESULTS: Retrospective immunohistochemical analyses were performed on 86 formalin-fixed paraffin-embedded specimens of OD and oral squamous cell carcinoma (OSCC) for Ki67, phosphorylated histone H2AX (γH2AX), p53, p16, trimethyl-histone H3 (Lys9) (H3K9me3) and cyclin D1 (CycD1). Three separate areas representing the highest severity of OD on each slide were annotated digitally by two independent pathologists. Mean automated histoscores of the selected markers were generated and compared to that of age-matched healthy controls (n = 24). Follow-up data of OD were retrieved and anonymized by a clinical team member and linked using unique participant identifiers. The median follow-up was 10.9 years (interquartile range: 10.1-11.5). Ki67 (P < 0.0001), γH2AX (P = 0.03) and p53 (P = 0.04) were increased significantly with higher histological grade of OD. γH2AX (P = 0.03), but not histological grade of OD (P = 0.73), was associated prospectively with disease progression. Using the median histoscore for γH2AX (median histoscore = 17) as a cut-off, histoscore ≥17 was associated with an increased risk of disease progression [hazard ratio (HR) = 3.15, 95% confidence interval (CI): 1.41-7.39, P = 0.0064]. CONCLUSIONS: Although proliferation marker Ki67, DNA damage/checkpoint markers γH2AX and p53 were increased in higher grade of OD, only γH2AX was predictive of disease progression. These observations may reflect the role of DNA replicative stress in the transformation from OD to OSCC. Larger studies should evaluate whether γH2AX can be used as a predictive marker of OD.

Diverse interventions that extend mouse lifespan suppress shared age-associated epigenetic changes at critical gene regulatory regions.

BACKGROUND: Age-associated epigenetic changes are implicated in aging. Notably, age-associated DNA methylation changes comprise a so-called aging "clock", a robust biomarker of aging. However, while genetic, dietary and drug interventions can extend lifespan, their impact on the epigenome is uncharacterised. To fill this knowledge gap, we defined age-associated DNA methylation changes at the whole-genome, single-nucleotide level in mouse liver and tested the impact of longevity-promoting interventions, specifically the Ames dwarf Prop1 df/df mutation, calorie restriction and rapamycin. RESULTS: In wild-type mice fed an unsupplemented ad libitum diet, age-associated hypomethylation was enriched at super-enhancers in highly expressed genes critical for liver function. Genes harbouring hypomethylated enhancers were enriched for genes that change expression with age. Hypermethylation was enriched at CpG islands marked with bivalent activating and repressing histone modifications and resembled hypermethylation in liver cancer. Age-associated methylation changes are suppressed in Ames dwarf and calorie restricted mice and more selectively and less specifically in rapamycin treated mice. CONCLUSIONS: Age-associated hypo- and hypermethylation events occur at distinct regulatory features of the genome. Distinct longevity-promoting interventions, specifically genetic, dietary and drug interventions, suppress some age-associated methylation changes, consistent with the idea that these interventions exert their beneficial effects, in part, by modulation of the epigenome. This study is a foundation to understand the epigenetic contribution to healthy aging and longevity and the molecular basis of the DNA methylation clock.

Mitotic Stress Is an Integral Part of the Oncogene-Induced Senescence Program that Promotes Multinucleation and Cell Cycle Arrest.

Oncogene-induced senescence (OIS) is a tumor suppression mechanism that blocks cell proliferation in response to oncogenic signaling. OIS is frequently accompanied by multinucleation; however, the origin of this is unknown. Here, we show that multinucleate OIS cells originate mostly from failed mitosis. Prior to senescence, mutant H-RasV12 activation in primary human fibroblasts compromised mitosis, concordant with abnormal expression of mitotic genes functionally linked to the observed mitotic spindle and chromatin defects. Simultaneously, H-RasV12 activation enhanced survival of cells with damaged mitoses, culminating in extended mitotic arrest and aberrant exit from mitosis via mitotic slippage. ERK-dependent transcriptional upregulation of Mcl1 was, at least in part, responsible for enhanced survival and slippage of cells with mitotic defects. Importantly, mitotic slippage and oncogene signaling cooperatively induced senescence and key senescence effectors p21 and p16. In summary, activated Ras coordinately triggers mitotic disruption and enhanced cell survival to promote formation of multinucleate senescent cells.

Acute Inhibition of MEK Suppresses Congenital Melanocytic Nevus Syndrome in a Murine Model Driven by Activated NRAS and Wnt Signaling.

Congenital melanocytic nevus (CMN) syndrome is the association of pigmented melanocytic nevi with extra-cutaneous features, classically melanotic cells within the central nervous system, most frequently caused by a mutation of NRAS codon 61. This condition is currently untreatable and carries a significant risk of melanoma within the skin, brain, or leptomeninges. We have previously proposed a key role for Wnt signaling in the formation of melanocytic nevi, suggesting that activated Wnt signaling may be synergistic with activated NRAS in the pathogenesis of CMN syndrome. Some familial pre-disposition suggests a germ-line contribution to CMN syndrome, as does variability of neurological phenotypes in individuals with similar cutaneous phenotypes. Accordingly, we performed exome sequencing of germ-line DNA from patients with CMN to reveal rare or undescribed Wnt-signaling alterations. A murine model harboring activated NRAS(Q61K) and Wnt signaling in melanocytes exhibited striking features of CMN syndrome, in particular neurological involvement. In the first model of treatment for this condition, these congenital, and previously assumed permanent, features were profoundly suppressed by acute post-natal treatment with a MEK inhibitor. These data suggest that activated NRAS and aberrant Wnt signaling conspire to drive CMN syndrome. Post-natal MEK inhibition is a potential candidate therapy for patients with this debilitating condition.

HIRA orchestrates a dynamic chromatin landscape in senescence and is required for suppression of neoplasia.

Cellular senescence is a stable proliferation arrest that suppresses tumorigenesis. Cellular senescence and associated tumor suppression depend on control of chromatin. Histone chaperone HIRA deposits variant histone H3.3 and histone H4 into chromatin in a DNA replication-independent manner. Appropriately for a DNA replication-independent chaperone, HIRA is involved in control of chromatin in nonproliferating senescent cells, although its role is poorly defined. Here, we show that nonproliferating senescent cells express and incorporate histone H3.3 and other canonical core histones into a dynamic chromatin landscape. Expression of canonical histones is linked to alternative mRNA splicing to eliminate signals that confer mRNA instability in nonproliferating cells. Deposition of newly synthesized histones H3.3 and H4 into chromatin of senescent cells depends on HIRA. HIRA and newly deposited H3.3 colocalize at promoters of expressed genes, partially redistributing between proliferating and senescent cells to parallel changes in expression. In senescent cells, but not proliferating cells, promoters of active genes are exceptionally enriched in H4K16ac, and HIRA is required for retention of H4K16ac. HIRA is also required for retention of H4K16ac in vivo and suppression of oncogene-induced neoplasia. These results show that HIRA controls a specialized, dynamic H4K16ac-decorated chromatin landscape in senescent cells and enforces tumor suppression.

Senescent cells harbour features of the cancer epigenome.

Altered DNA methylation and associated destabilization of genome integrity and function is a hallmark of cancer. Replicative senescence is a tumour suppressor process that imposes a limit on the proliferative potential of normal cells that all cancer cells must bypass. Here we show by whole-genome single-nucleotide bisulfite sequencing that replicative senescent human cells exhibit widespread DNA hypomethylation and focal hypermethylation. Hypomethylation occurs preferentially at gene-poor, late-replicating, lamin-associated domains and is linked to mislocalization of the maintenance DNA methyltransferase (DNMT1) in cells approaching senescence. Low-level gains of methylation are enriched in CpG islands, including at genes whose methylation and silencing is thought to promote cancer. Gains and losses of methylation in replicative senescence are thus qualitatively similar to those in cancer, and this 'reprogrammed' methylation landscape is largely retained when cells bypass senescence. Consequently, the DNA methylome of senescent cells might promote malignancy, if these cells escape the proliferative barrier.