What goes on when tertiary students are engaged in an online academic writing course?

The learning process is a complex one with many intertwining variables. The learners’ characteristics could be a defining factor and so is prior learning experiences and knowledge, which are the manifests of metacognitive, socio-affective and cognitive systems. A learning task engagement calls for an exertion of personal control and the fulfillment of efficiency expectations. In learning, the learner activates a number of processes such as those that concern attentional, retrieval, metacognitive and rehearsal strategies. McCombs (1988) sums up these complexities in his multimodal model of learning with certain underlying assumptions. Among them is that learning success can be manipulated. In promoting learning, the teacher can promote strategy learning such as self-directed learning. Learners if trained can select and be their own judge as to the efficacy of strategy use for the learning task. Lessard-Closton (1997) identified several basic characteristics to describe language learning strategies: they are learner-generated, they enhance language learning and competence, they may be visible or unseen and they involve the processing of information and the use of memory

Identification of dynamic undifferentiated cell states within the male germline

The role of stem cells in tissue maintenance is appreciated and hierarchical models of stem cell self-renewal and differentiation often proposed. Stem cell activity in the male germline is restricted to undifferentiated A-type spermatogonia (A(undiff)); however, only a fraction of this population act as stem cells in undisturbed testis and A(undiff) hierarchy remains contentious. Through newly developed compound reporter mice, here we define molecular signatures of self-renewing and differentiation-primed adult Aundiff fractions and dissect A(undiff) heterogeneity by single-cell analysis. We uncover an unappreciated population within the self-renewing Aundiff fraction marked by expression of embryonic patterning genes and homeodomain transcription factor PDX1. Importantly, we find that PDX1 marks a population with potent stem cell capacity unique to mature, homeostatic testis and demonstrate dynamic interconversion between PDX1+ and PDX1-(Aundiff) states upon transplant and culture. We conclude that Aundiff exist in a series of dynamic cell states with distinct function and provide evidence that stability of such states is dictated by niche-derived cues

Measures of frailty in population-based studies: An overview

Although research productivity in the field of frailty has risen exponentially in recent years, there remains a lack of consensus regarding the measurement of this syndrome. This overview offers three services: first, we provide a comprehensive catalogue of current frailty measures; second, we evaluate their reliability and validity; third, we report on their popularity of use

Regulation of E6AP and involvement of the E6AP/PML axis in human cancer

© 2013 Dr. Ai-Leen ChanThe ubiquitin-proteasome system (UPS) plays a major role in the regulation of many cellular processes. However, aberrations in the regulation of the UPS can lead to a variety of pathological conditions. A firm link has been established between UPS and the development of cancer. Velcade, a proteasome inhibitor, is in clinical use for the treatment of diseases such as multiple myeloma. This thesis is based on our recent findings of a new regulatory pathway of tumour suppression. We discovered that the HECT E3 ligase, E6-associated protein (E6AP), is a key regulator of the tumour suppressor promeylocytic protein (PML). My thesis describes 3 studies: the regulation of E6AP by c-Abl (Chapter 3); the involvement of the E6AP-PML axis in colorectal cancer (Chapter 4) and also in prostate cancer (Chapter 5). Regulation of E6AP by c-Abl: In human papillomavirus (HPV) - infected cells, p53 is degraded by the HPV-E6/E6AP complex. Our laboratory previously demonstrated that the c-Abl tyrosine kinase protects p53 from ubiquitination and degradation by the HPV-E6/E6AP complex under stress conditions. Chapter 3 explores the underlying mechanism of this protection. We demonstrated an interaction between c-Abl and E6AP in vivo and in vitro. Activation of c-Abl by DNA damage leads to phosphorylation of E6AP. Mass spectrometric analysis revealed that tyrosine (Y) 636 within the HECT catalytic domain of E6AP is phosphorylated by c-Abl. Further computational analysis of E6AP trimerisation revealed an interaction between Y636 and glutamate (E) 544 in a neighbouring E6AP molecule. Using substitution mutants we examined the effect of Y636 phosphorylation, and its interaction with E544, on the E3 ligase activity of E6AP. We demonstrated that Y636 and E544 regulate the E3 ligase activity of E6AP, in a substrate-specific manner. Our findings suggest that in response to stress, c-Abl phosphorylates E6AP on Y636, thereby reducing the interaction with E544 leading to inhibition of E6AP E3 ligase activity. This is the first description of a post-translational modification of E6AP regulating its activity. This also provides a molecular explanation for the protection of p53 in HPV-infected cells under stress. Involvement of the E6AP-PML axis in cancer: PML protein expression have been shown to be down-regulated in multiple cancer types. Since we discovered E6AP as the E3 ligase of PML, we hypothesized that E6AP may be responsible for the loss of PML expression in colon and prostate cancers. Using a panel of colorectal cancer cell lines we did not find a significant elevation of E6AP correlating with low PML, nor were we able to restore PML expression by down-regulating E6AP (Chapter 4). On the other hand, we found an inverse correlation between E6AP and PML in a panel of prostate cancer cell lines. Down-regulation of E6AP was also associated with a reduction in cell numbers and an increased sensitization of prostate cancer cells to stress-induced death. This study supports a role for the E6AP-PML axis in prostate cancer. This is consistent with our analysis of prostate cancer samples demonstrating the poorest survival for patients with high E6AP and low PML expression (Chapter 5)

Germline Stem Cell Activity Is Sustained by SALL4-Dependent Silencing of Distinct Tumor Suppressor Genes

Sustained spermatogenesis in adult males and fertility recovery following germ cell depletion are dependent on undifferentiated spermatogonia. We previously demonstrated a key role for the transcription factor SALL4 in spermatogonial differentiation. However, whether SALL4 has broader roles within spermatogonia remains unclear despite its ability to co-regulate genes with PLZF, a transcription factor required for undifferentiated cell maintenance. Through development of inducible knockout models, we show that short-term integrity of differentiating but not undifferentiated populations requires SALL4. However, SALL4 loss was associated with long-term functional decline of undifferentiated spermatogonia and disrupted stem cell-driven regeneration. Mechanistically, SALL4 associated with the NuRD co-repressor and repressed expression of the tumor suppressor genes Foxl1 and Dusp4. Aberrant Foxl1 activation inhibited undifferentiated cell growth and survival, while DUSP4 suppressed self-renewal pathways. We therefore uncover an essential role for SALL4 in maintenance of undifferentiated spermatogonial activity and identify regulatory pathways critical for germline stem cell function

Cep55 overexpression causes male-specific sterility in mice by suppressing Foxo1 nuclear retention through sustained activation of PI3K/Akt signaling

Spermatogenesis is a dynamic process involving self-renewal and differentiation of spermatogonial stem cells, meiosis, and ultimately, the differentiation of haploid spermatids into sperm. Centrosomal protein 55 kDa (CEP55) is necessary for somatic cell abscission during cytokinesis. It facilitates equal segregation of cytoplasmic contents between daughter cells by recruiting endosomal sorting complex required for transport machinery (ESCRT) at the midbody. In germ cells, CEP55, in partnership with testes expressed-14 (TEX14) protein, has also been shown to be an integral component of intercellular bridge before meiosis. Various in vitro studies have demonstrated a role for CEP55 in multiple cancers and other diseases. However, its oncogenic potential in vivo remains elusive. To investigate, we generated ubiquitously overexpressing Cep55 transgenic ( Cep55Tg/Tg) mice aiming to characterize its oncogenic role in cancer. Unexpectedly, we found that Cep55Tg/Tg male mice were sterile and had severe and progressive defects in spermatogenesis related to spermatogenic arrest and lack of spermatids in the testes. In this study, we characterized this male-specific phenotype and showed that excessively high levels of Cep55 results in hyperactivation of PI3K/protein kinase B (Akt) signaling in testis. In line with this finding, we observed increased phosphorylation of forkhead box protein O1 (FoxO1), and suppression of its nuclear retention, along with the relative enrichment of promyelocytic leukemia zinc finger (PLZF) -positive cells. Independently, we observed that Cep55 amplification favored upregulation of ret ( Ret) proto-oncogene and glial-derived neurotrophic factor family receptor α-1 ( Gfra1). Consistent with these data, we observed selective down-regulation of genes associated with germ cell differentiation in Cep55-overexpressing testes at postnatal day 10, including early growth response-4 ( Egr4) and spermatogenesis and oogenesis specific basic helix-loop-helix-1 ( Sohlh1). Thus, Cep55 amplification leads to a shift toward the initial maintenance of undifferentiated spermatogonia and ultimately results in progressive germ cell loss. Collectively, our findings demonstrate that Cep55 overexpression causes change in germ cell proportions and manifests as a Sertoli cell only tubule phenotype, similar to that seen in many azoospermic men

A novel method for detection of phosphorylation in single cells by surface enhanced Raman scattering (SERS) using composite organic-inorganic nanoparticles (COINs).

BACKGROUND:Detection of single cell epitopes has been a mainstay of immunophenotyping for over three decades, primarily using fluorescence techniques for quantitation. Fluorescence has broad overlapping spectra, limiting multiplexing abilities. METHODOLOGY/PRINCIPAL FINDINGS:To expand upon current detection systems, we developed a novel method for multi-color immuno-detection in single cells using "Composite Organic-Inorganic Nanoparticles" (COINs) Raman nanoparticles. COINs are Surface-Enhanced Raman Scattering (SERS) nanoparticles, with unique Raman spectra. To measure Raman spectra in single cells, we constructed an automated, compact, low noise and sensitive Raman microscopy device (Integrated Raman BioAnalyzer). Using this technology, we detected proteins expressed on the surface in single cells that distinguish T-cells among human blood cells. Finally, we measured intracellular phosphorylation of Stat1 (Y701) and Stat6 (Y641), with results comparable to flow cytometry. CONCLUSIONS/SIGNIFICANCE:Thus, we have demonstrated the practicality of applying COIN nanoparticles for measuring intracellular phosphorylation, offering new possibilities to expand on the current fluorescent technology used for immunoassays in single cells

Cep55 overexpression causes male-specific sterility in mice by suppressing Foxo1 nuclear retention through sustained activation of PI3K/Akt signaling

Spermatogenesis is a dynamic process involving self-renewal and differentiation of spermatogonial stem cells, meiosis, and ultimately, the differentiation of haploid spermatids into sperm. Centrosomal protein (CEP)-55 is necessary for somatic cell abscission during cytokinesis. It facilitates equal segregation of cytoplasmic contents between daughter cells by recruiting endosomal sorting complex required for transport machinery (ESCRT) at the midbody. In germ cells, CEP55, in partnership with testes expressed-14 protein (TEX14), has also been shown to be an integral component of intercellular bridge before meiosis. Various in vitro studies have demonstrated a role for CEP55 in multiple cancers and other diseases. However, its oncogenic potential in vivo remains elusive. To investigate, we generated ubiquitously overexpressing Cep55 transgenic mice ( Cep55) aiming to characterize its oncogenic role in cancer. Unexpectedly, we found that Cep55 male mice were sterile and had severe and progressive defects in spermatogenesis related to spermatogenic arrest and lack of spermatids in the testes. In this study, we characterized this male-specific phenotype and showed that excessively high levels of Cep55 results in hyperactivation of PI3K/protein kinase B (Akt) signaling in testis. In line with this finding, we observed increased phosphorylation of forkhead box protein O1 (FoxO1), and suppression of its nuclear retention, along with the relative enrichment of promyelocytic leukemia zinc finger (PLZF) -positive cells. Independently, we observed that Cep55 amplification favored upregulation of ret ( Ret) proto-oncogene and glial-derived neurotrophic factor family receptor α-1 ( Gfra1). Consistent with these data, we observed selective down-regulation of genes associated with germ cell differentiation in Cep55-overexpressing testes at postnatal day 10, including early growth response-4 ( Egr4) and spermatogenesis and oogenesis specific basic helix-loop-helix-1 ( Sohlh1). Thus, Cep55 amplification leads to a shift toward the initial maintenance of undifferentiated spermatogonia and ultimately results in progressive germ cell loss. Collectively, our findings demonstrate that Cep55 overexpression causes change in germ cell proportions and manifests as a Sertoli cell only tubule phenotype, similar to that seen in many azoospermic men.-Sinha, D., Kalimutho, M., Bowles, J., Chan, A.-L., Merriner, D. J., Bain, A. L., Simmons, J. L., Freire, R., Lopez, J. A., Hobbs, R. M., O'Bryan, M. K., Khanna, K. K. Cep55 overexpression causes male-specific sterility in mice by suppressing Foxo1 nuclear retention through sustained activation of PI3K/Akt signaling