Defective Nuclear Lamina in Aneuploidy and Carcinogenesis

Aneuploidy, loss or gain of whole chromosomes, is a prominent feature of carcinomas, and is generally considered to play an important role in the initiation and progression of cancer. In high-grade serous ovarian cancer, the only common gene aberration is the p53 point mutation, though extensive genomic perturbation is common due to severe aneuploidy, which presents as a deviant karyotype. Several mechanisms for the development of aneuploidy in cancer cells have been recognized, including chromosomal non-disjunction during mitosis, centrosome amplification, and more recently, nuclear envelope rupture at interphase. Many cancer types including ovarian cancer have lost or reduced expression of Lamin A/C, a structural component of the lamina matrix that underlies the nuclear envelope in differentiated cells. Several recent studies suggest that a nuclear lamina defect caused by the loss or reduction of Lamin A/C leads to failure in cytokinesis and formation of tetraploid cells, transient nuclear envelope rupture, and formation of nuclear protrusions and micronuclei during the cell cycle gap phase. Thus, loss and reduction of Lamin A/C underlies the two common features of cancer—aberrations in nuclear morphology and aneuploidy. We discuss here and emphasize the newly recognized mechanism of chromosomal instability due to the rupture of a defective nuclear lamina, which may account for the rapid genomic changes in carcinogenesis

Perception of differentiation cues by GATA factors in primitive endoderm lineage determination of mouse embryonic stem cells

AbstractThe formation of the primitive endoderm covering the inner cell mass of early mouse embryos can be simulated in vitro by the differentiation of mouse embryonic stem (ES) cells in culture following either aggregation of suspended cells or stimulation of cell monolayers with retinoic acid. The developmentally regulated transcription factors GATA-4 and GATA-6 have determining role in mouse extraembryonic endoderm development. We analyzed the in vitro differentiation of mouse embryonic stem cells deficient of GATA factors and conclude that GATA-4 is required for ES cells to perceive a cell positioning (cell aggregation) signal and GATA-6 is required to sense morphogenic (retinoic acid) signal. The collaboration between GATA-6 and GATA-4, or GATA-6 and GATA-5 which can substitute for GATA-4, is involved in the perception of differentiation cues by embryonic stem cells in their determination of endoderm lineage. This study indicates that the lineage differentiation of ES cells can be manipulated by the expression of GATA factors

Alteration of Differentiation Potentials by Modulating GATA Transcription Factors in Murine Embryonic Stem Cells

Background. Mouse embryonic stem (ES) cells can be differentiated in vitro by aggregation and/or retinoic acid (RA) treatment. The principal differentiation lineage in vitro is extraembryonic primitive endoderm. Dab2, Laminin, GATA4, GATA5, and GATA6 are expressed in embryonic primitive endoderm and play critical roles in its lineage commitment. Results. We found that in the absence of GATA4 or GATA5, RA-induced primitive endoderm differentiation of ES cells was reduced. GATA4 (−/−) ES cells express higher level of GATA5, GATA6, and hepatocyte nuclear factor 4 alpha marker of visceral endoderm lineage. GATA5 (−/−) ES cells express higher level of alpha fetoprotein marker of early liver development. GATA6 (−/−) ES cells express higher level of GATA5 as well as mesoderm and cardiomyocyte markers which are collagen III alpha-1 and tropomyosin1 alpha. Thus, deletion of GATA6 precluded endoderm differentiation but promoted mesoderm lineages. Conclusions. GATA4, GATA5, and GATA6 each convey a unique gene expression pattern and influences ES cell differentiation. We showed that ES cells can be directed to avoid differentiating into primitive endoderm and to adopt unique lineages in vitro by modulating GATA factors. The finding offers a potential approach to produce desirable cell types from ES cells, useful for regenerative cell therapy

Genome-wide association analysis provides insights into the genetic basis of photosynthetic responses to low-temperature stress in spring barley

Low-temperature stress (LTS) is among the major abiotic stresses affecting the geographical distribution and productivity of the most important crops. Understanding the genetic basis of photosynthetic variation under cold stress is necessary for developing more climate-resilient barley cultivars. To that end, we investigated the ability of chlorophyll fluorescence parameters (FVFM, and FVF0) to respond to changes in the maximum quantum yield of Photosystem II photochemistry as an indicator of photosynthetic energy. A panel of 96 barley spring cultivars from different breeding zones of Canada was evaluated for chlorophyll fluorescence-related traits under cold acclimation and freeze shock stresses at different times. Genome-wide association studies (GWAS) were performed using a mixed linear model (MLM). We identified three major and putative genomic regions harboring 52 significant quantitative trait nucleotides (QTNs) on chromosomes 1H, 3H, and 6H for low-temperature tolerance. Functional annotation indicated several QTNs were either within the known or close to genes that play important roles in the photosynthetic metabolites such as abscisic acid (ABA) signaling, hydrolase activity, protein kinase, and transduction of environmental signal transduction at the posttranslational modification levels. These outcomes revealed that barley plants modified their gene expression profile in response to decreasing temperatures resulting in physiological and biochemical modifications. Cold tolerance could influence a long-term adaption of barley in many parts of the world. Since the degree and frequency of LTS vary considerably among production sites. Hence, these results could shed light on potential approaches for improving barley productivity under low-temperature stress

Biallelic disruption of DDX41 activity is associated with distinct genomic and immunophenotypic hallmarks in acute leukemia

IntroductionInherited DDX41 mutations cause familial predisposition to hematologic malignancies including acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), with the majority of DDX41 mutated MDS/AMLs described to date harboring germline DDX41 and co-occurring somatic DDX41 variants. DDX41-AMLs were shown to share distinguishing clinical features such as a late AML onset and an indolent disease associated with a favorable outcome. However, genotype-phenotype correlation in DDX41-MDS/AMLs remain poorly understood.MethodsHere, we studied the genetic profile, bone marrow morphology and immunophenotype of 51 patients with DDX41 mutations. We further assessed the functional impact of ten previously uncharacterized DDX41 variants of uncertain significance.ResultsOur results demonstrate that MDS/AML cases harboring two DDX41 variants share specific clinicopathologic hallmarks that are not seen in other patients with monoallelic DDX41 related hematologic malignancies. We further showed that the features seen in these individuals with two DDX41 variants were concordant with biallelic DDX41 disruption.DiscussionHere, we expand on previous clinicopathologic findings on DDX41 mutated hematologic malignancies. Functional analyses conducted in this study unraveled previously uncharacterized DDX41 alleles and further illustrate the implication of biallelic disruption in the pathophysiology of this distinct AML entity

Nuclear envelope structural defects cause chromosomal numerical instability and aneuploidy in ovarian cancer

<p>Abstract</p> <p>Background</p> <p>Despite our substantial understanding of molecular mechanisms and gene mutations involved in cancer, the technical approaches for diagnosis and prognosis of cancer are limited. In routine clinical diagnosis of cancer, the procedure is very basic: nuclear morphology is used as a common assessment of the degree of malignancy, and hence acts as a prognostic and predictive indicator of the disease. Furthermore, though the atypical nuclear morphology of cancer cells is believed to be a consequence of oncogenic signaling, the molecular basis remains unclear. Another common characteristic of human cancer is aneuploidy, but the causes and its role in carcinogenesis are not well established.</p> <p>Methods</p> <p>We investigated the expression of the nuclear envelope proteins lamin A/C in ovarian cancer by immunohistochemistry and studied the consequence of lamin A/C suppression using siRNA in primary human ovarian surface epithelial cells in culture. We used immunofluorescence microscopy to analyze nuclear morphology, flow cytometry to analyze cellular DNA content, and fluorescence <it>in situ </it>hybridization to examine cell ploidy of the lamin A/C-suppressed cells.</p> <p>Results</p> <p>We found that nuclear lamina proteins lamin A/C are often absent (47%) in ovarian cancer cells and tissues. Even in lamin A/C-positive ovarian cancer, the expression is heterogeneous within the population of tumor cells. In most cancer cell lines, a significant fraction of the lamin A/C-negative population was observed to intermix with the lamin A/C-positive cells. Down regulation of lamin A/C in non-cancerous primary ovarian surface epithelial cells led to morphological deformation and development of aneuploidy. The aneuploid cells became growth retarded due to a p53-dependent induction of the cell cycle inhibitor p21.</p> <p>Conclusions</p> <p>We conclude that the loss of nuclear envelope structural proteins, such as lamin A/C, may underlie two of the hallmarks of cancer - aberrations in nuclear morphology and aneuploidy.</p

Point-of-Care Ultrasound for Tuberculosis Management in Sub-Saharan Africa-A Balanced SWOT Analysis.

Point-of-care ultrasound (POCUS) is an increasingly accessible skill, allowing for the decentralization of its use to non-specialist healthcare workers to guide routine clinical decision making. The advent of ultrasound-on-a-chip has transformed the technology into a portable mobile health device. Due to its high sensitivity to detect small consolidations, pleural effusions and sub pleural nodules, POCUS has recently been proposed as a sputum-free likely triage tool for tuberculosis (TB). To make an objective assessment of the potential and limitations of POCUS in routine TB management, we present a Strengths, Weaknesses, Opportunities & Threats (SWOT) analysis based on a review of the relevant literature and focusing on Sub-Saharan Africa (SSA). We idenitified numerous strengths and opportunities of POCUS for TB management e.g.; accessible, affordable, easy to use & maintain, expedited diagnosis, extra-pulmonary TB detection, safer pleural/pericardial puncture, use in children/pregnant women/PLHIV, targeted screening of TB contacts, monitoring TB sequelae, and creating AI decision support. Weaknesses and external threats such as operator dependency, lack of visualization of central lung pathology, poor specificity, lack of impact assessments and data from Sub-Saharan Africa must be taken into consideration to ensure that the potential of the technology can be fully realized in research as in practice

Compound heterozygous variants in NBAS as a cause of atypical osteogenesis imperfecta

Background Osteogenesis imperfecta (OI), the commonest inherited bone fragility disorder, affects 1 in 15,000 live births resulting in frequent fractures and reduced mobility, with significant impact on quality of life. Early diagnosis is important, as therapeutic advances can lead to improved clinical outcome and patient benefit. Report Whole exome sequencing in patients with OI identified, in two patients with a multi-system phenotype, compound heterozygous variants in NBAS (neuroblastoma amplified sequence). Patient 1: NBAS c.5741G > A p.(Arg1914His); c.3010C > T p.(Arg1004*) in a 10-year old boy with significant short stature, bone fragility requiring treatment with bisphosphonates, developmental delay and immunodeficiency. Patient 2: NBAS c.5741G > A p.(Arg1914His); c.2032C > T p.(Gln678*) in a 5-year old boy with similar presenting features, bone fragility, mild developmental delay, abnormal liver function tests and immunodeficiency. Discussion Homozygous missense NBAS variants cause SOPH syndrome (short stature; optic atrophy; Pelger-Huet anomaly), the same missense variant was found in our patients on one allele and a nonsense variant in the other allele. Recent literature suggests a multi-system phenotype. In this study, patient fibroblasts have shown reduced collagen expression, compared to control cells and RNAseq studies, in bone cells show that NBAS is expressed in osteoblasts and osteocytes of rodents and primates. These findings provide proof-of-concept that NBAS mutations have mechanistic effects in bone, and that NBAS variants are a novel cause of bone fragility, which is distinguishable from ‘Classical’ OI. Conclusions Here we report on variants in NBAS, as a cause of bone fragility in humans, and expand the phenotypic spectrum associated with NBAS. We explore the mechanism underlying NBAS and the striking skeletal phenotype in our patients

Ablation of Dido3 compromises lineage commitment of stem cells in vitro and during early embryonic development

The death inducer obliterator (Dido) locus encodes three protein isoforms, of which Dido3 is the largest and most broadly expressed. Dido3 is a nuclear protein that forms part of the spindle assembly checkpoint (SAC) and is necessary for correct chromosome segregation in somatic and germ cells. Here we report that specific ablation of Dido3 function in mice causes lethal developmental defects at the onset of gastrulation. Although these defects are associated with centrosome amplification, spindle malformation and a DNA damage response, we provide evidence that embryonic lethality of the Dido3 mutation cannot be explained by its impact on chromosome segregation alone. We show that loss of Dido3 expression compromises differentiation of embryonic stem cells in vitro and of epiblast cells in vivo, resulting in early embryonic death at around day 8.5 of gestation. Close analysis of Dido3 mutant embryoid bodies indicates that ablation of Dido3, rather than producing a generalized differentiation blockade, delays the onset of lineage commitment at the primitive endoderm specification stage. The dual role of Dido3 in chromosome segregation and stem cell differentiation supports the implication of SAC components in stem cell fate decisions

Cathepsins B, L and cystatin C in cyst fluid of ovarian tumors

Contains fulltext : 88032.pdf (publisher's version ) (Closed access)INTRODUCTION: In cancer, an extracellular and membrane bound localization of cathepsins contribute to the invasion of tumor cells at the basement membrane. METHODS: This is the first study that explored levels of cathepsins B (CatB), L (CatL) and their inhibitor cystatin C (CysC) in the cystic fluid (CF) of ovarian tumors (n = 110). RESULTS: CF contained considerable amounts of CatB, CatL and CysC. Remarkable differences in CatB and CatL and CysC CF levels were found between different histopathological tumor subtypes. Levels of CatB and CysC were significantly higher in CF of malignant serous tumors compared to those found in benign serous tumors (p = 0.010 and p = 0.001 respectively), whereas levels of CatL were significantly higher in CF of malignant mucinous tumors compared to those found in benign mucinous tumors (p = 0.035). CatB and CysC showed a strong correlation in the group of patients with malignant serous tumors (p < 0.001; R = 0.921) suggesting that the increase in CatB might be balanced by a corresponding increase in CysC. CONCLUSION: Further studies are warranted to investigate cathepsins as possible prognostic biomarkers for the aggressiveness of ovarian cancer.1 mei 201