P53-dependent Tumorigenesis And Gene Expression In Mammalian Brain

Astrocytic gliomas are the most common brain cancers of adults. The goal of this research was to examine the molecular genetic determinants of gliomas, with particular emphasis on the tumor suppressor gene P53. First, I studied the frequency, nature and timing of P53 mutations in human gliomas. I observed that glioma-prone families do not have inherited mutations of P53, nor of the Nf1-GRD, Nf2, MTS1, MTS2, or CDK4 genes. However, a high frequency of loss of heterozygosity at chromosome 9p was noted in gliomas that cluster in families. In a second study of low-grade gliomas that progressed to higher grade malignancies, I observed that those with P53 mutations progressed slowly to anaplastic pathology whereas those without mutation progressed directly to glioblastoma omitting the anaplastic stage. Next, I studied the biological consequences of P53 disruption on tumorigenesis and brain development in mice. I introduced a disrupted P53 gene into astrocytoma-susceptible inbred mice to augment astrocytoma formation and generate an experimental model. These P53-null mice did not exhibit enhanced incidence of astrocytic glioma but did develop high grade lymphomas at a significantly younger age than control P53-null mice. Lastly, I examined gene expression in the brains of wild-type and P53-null mouse embryos. Expression of the WAF1/p21 and IGF-BP3 genes in the developing head responded to loss of p53 in a gender-specific manner, suggesting that female-restricted defects of neural tube closure in P53-null mice may be explained by insufficient compensatory gene expression. I also noted that P53-deficiency causes lethal developmental defects other than exencephaly in females. Loss of one copy of P53 caused a moderate decrease in the number of female embryos relative to males early in gestation, while loss of both copies resulted in additional perinatal attrition of females. Together, the experiments described in this thesis contribute to our knowledge of the role of P53 in glioma predisposition and progression in humans, and to tumorigenesis and nervous system development in mice

Identification of genes influencing dendrite morphogenesis in developing peripheral sensory and central motor neurons.

BACKGROUND: Developing neurons form dendritic trees with cell type-specific patterns of growth, branching and targeting. Dendrites of Drosophila peripheral sensory neurons have emerged as a premier genetic model, though the molecular mechanisms that underlie and regulate their morphogenesis remain incompletely understood. Still less is known about this process in central neurons and the extent to which central and peripheral dendrites share common organisational principles and molecular features. To address these issues, we have carried out two comparable gain-of-function screens for genes that influence dendrite morphologies in peripheral dendritic arborisation (da) neurons and central RP2 motor neurons. RESULTS: We found 35 unique loci that influenced da neuron dendrites, including five previously shown as required for da dendrite patterning. Several phenotypes were class-specific and many resembled those of known mutants, suggesting that genes identified in this study may converge with and extend known molecular pathways for dendrite development in da neurons. The second screen used a novel technique for cell-autonomous gene misexpression in RP2 motor neurons. We found 51 unique loci affecting RP2 dendrite morphology, 84% expressed in the central nervous system. The phenotypic classes from both screens demonstrate that gene misexpression can affect specific aspects of dendritic development, such as growth, branching and targeting. We demonstrate that these processes are genetically separable. Targeting phenotypes were specific to the RP2 screen, and we propose that dendrites in the central nervous system are targeted to territories defined by Cartesian co-ordinates along the antero-posterior and the medio-lateral axes of the central neuropile. Comparisons between the screens suggest that the dendrites of peripheral da and central RP2 neurons are shaped by regulatory programs that only partially overlap. We focused on one common candidate pathway controlled by the ecdysone receptor, and found that it promotes branching and growth of developing da neuron dendrites, but a role in RP2 dendrite development during embryonic and early larval stages was not apparent. CONCLUSION: We identified commonalities (for example, growth and branching) and distinctions (for example, targeting and ecdysone response) in the molecular and organizational framework that underlies dendrite development of peripheral and central neurons.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Rab-mediated vesicular transport is required for neuronal positioning in the developing Drosophila visual system

<p>Abstract</p> <p>Background</p> <p>The establishment of tissue architecture in the nervous system requires the proper migration and positioning of newly born neurons during embryonic development. Defects in nuclear translocation, a key process in neuronal positioning, are associated with brain diseases such as lissencephaly in humans. Accumulated evidence suggests that the molecular mechanisms controlling neuronal movement are conserved throughout evolution. While the initial events of neuronal migration have been extensively studied, less is known about the molecular details underlying the establishment of neuronal architecture after initial migration.</p> <p>Results</p> <p>In a search for novel players in the control of photoreceptor (R cell) positioning in the developing fly visual system, we found that misexpression of the RabGAP RN-Tre disrupted the apical localization of R-cell nuclei. RN-Tre interacts with Rab5 and Rab11 in the fly eye. Genetic analysis shows that Rab5, Shi and Rab11 are required for maintaining apical localization of R-cell nuclei.</p> <p>Conclusions</p> <p>We propose that Rab5, Shi and Rab11 function together in a vesicular transport pathway for regulating R-cell positioning in the developing eye.</p

Ihog and Boi are essential for Hedgehog signaling in Drosophila

<p>Abstract</p> <p>Background</p> <p>The Hedgehog (Hh) signaling pathway is important for the development of a variety of tissues in both vertebrates and invertebrates. For example, in developing nervous systems Hh signaling is required for the normal differentiation of neural progenitors into mature neurons. The molecular signaling mechanism underlying the function of Hh is not fully understood. In <it>Drosophila</it>, Ihog (Interference hedgehog) and Boi (Brother of Ihog) are related transmembrane proteins of the immunoglobulin superfamily (IgSF) with orthologs in vertebrates. Members of this IgSF subfamily have been shown to bind Hh and promote pathway activation but their exact role in the Hh signaling pathway has remained elusive. To better understand this role <it>in vivo</it>, we generated loss-of-function mutations of the <it>ihog </it>and <it>boi </it>genes, and investigated their effects in developing eye and wing imaginal discs.</p> <p>Results</p> <p>While mutation of either <it>ihog </it>or <it>boi </it>alone had no discernible effect on imaginal tissues, cells in the developing eye disc that were mutant for both <it>ihog </it>and <it>boi </it>failed to activate the Hh pathway, causing severe disruption of photoreceptor differentiation in the retina. In the anterior compartment of the developing wing disc, where different concentrations of the Hh morphogen elicit distinct cellular responses, cells mutant for both <it>ihog </it>and <it>boi </it>failed to activate responses at either high or low thresholds of Hh signaling. They also lost their affinity for neighboring cells and aberrantly sorted out from the anterior compartment of the wing disc into posterior territory. We found that <it>ihog </it>and <it>boi </it>are required for the accumulation of the essential Hh signaling mediator Smoothened (Smo) in Hh-responsive cells, providing evidence that Ihog and Boi act upstream of Smo in the Hh signaling pathway.</p> <p>Conclusions</p> <p>The consequences of <it>boi;ihog </it>mutations for eye development, neural differentiation and wing patterning phenocopy those of <it>smo </it>mutations and uncover an essential role for Ihog and Boi in the Hh signaling pathway.</p

Assessing trauma in a transcultural context: Challenges in mental health care with immigrants and refugees

The growing numbers of refugees and immigrants from conflict-prone areas settling throughout the world bring several challenges for those working in the mental health care system. Immigrants and refugees of all ages arrive with complex and nuanced mental health histories of war, torture, and strenuous migration journeys. Many of the challenges of addressing the health care needs for this growing population of immigrants and refugees are often unfamiliar, and thus practices to address these challenges are not yet routine for care providers and health care organizations. In particular, complex trauma can make mental health assessments difficult for health care organizations or care providers with limited experience and training in transcultural or trauma-informed care. Using a transcultural approach can improve assessment and screening processes, leading to more effective and high-quality care for immigrant and refugee families experiencing mental health disorders. This paper presents findings from an assessment of current mental health services focusing on current practices and experiences with immigrant and refugee patients and families. The difficulties in developing shared understandings about mental health can hinder the therapeutic process; therefore, it is imperative to ensure an effective assessment right from the beginning, yet there is limited use of existing cultural formulation tools from the DSM-IV or DSM-5. The paper outlines current practices, approaches, challenges, and recommendations shared by mental health care providers and program leaders in addressing the mental health care needs of immigrants and refugees. The results from this study demonstrate that there are many challenges and inconsistencies in providing transcultural, trauma-informed care. Respondents emphasized the need for a thorough yet flexible and adaptive approach that allows for an exploration of differences in cultural interpretations of mental health. Our study concluded that ensuring a mindful, reflexive, transcultural, and trauma-informed health care workforce, and a learning environment to support staff with education, resources, and tools will improve the health care experiences of immigrants and refugees in the mental health care system

The position of combined medical treatment in acromegaly

Advances in combination medical treatment have offer new perspectives for acromegaly patients with persistent disease activity despite receiving the available medical monotherapies. The outcomes of combination medical treatment may reflect both additive and synergistic effects. This review focuses on combination medical treatment and its current position in acromegaly, based on clinical studies evaluating the efficacy and safety of combined medical treatment(s) and our own experiences with combination therapy. Arch Endocrinol Metab. 2019;63(6):646-52

Excellent response to pasireotide therapy in an aggressive and dopamine-resistant prolactinoma.

peer reviewedProlactinomas are the most commonly encountered pituitary adenomas in the clinical setting. While most can be controlled by dopamine agonists, a subset of prolactinomas are dopamine-resistant and very aggressive. In such tumors, the treatment of choice is neurosurgery and radiotherapy, with or without temozolomide. Here, we report a patient with an highly aggressive, dopamine-resistant prolactinoma, who only achieved biochemical and tumor control during pasireotide long-acting release (PAS-LAR) therapy , a second-generation somatostatin receptor ligand (SRL). Interestingly, cystic degeneration, tumor cell necrosis, or both was observed after PAS-LAR administration suggesting an antitumor effect. This case shows that PAS-LAR therapy holds clinical potential in selective aggressive, dopamine-resistant prolactinomas that express somatostatin (SST) receptor subtype 5 and appears to be a potential new treatment option before starting temozolomide. In addition, PAS-LAR therapy may induce cystic degeneration, tumor cell necrosis, or both in prolactinomas

SSDP cofactors regulate neural patterning and differentiation of specific axonal projections

The developmental activity of LIM homeodomain transcription factors (LIM-HDs) is critically controlled by LIM domain-interacting cofactors of LIM-HDs (CLIM, also known as NLI or LDB). CLIM cofactors associate with single-stranded DNA binding proteins (SSDPs, also known as SSBPs) thereby recruiting SSDP1 and/or SSDP2 to LIM-HD/CLIM complexes. Although evidence has been presented that SSDPs are important for the activity of specific LIM-HD/CLIM complexes, the developmental roles of SSDPs are unclear. We show that SSDP1a and SSDP1b mRNAs are widely expressed early during zebrafish development with conspicuous expression of SSDP1b in sensory trigeminal and Rohon-Beard neurons. SSDP1 and CLIM immunoreactivity co-localize in these neuronal cell types and in other structures. Over-expression of the N-terminal portion of SSDP1 (N-SSDP1), which contains the CLIM-interaction domain, increases endogenous CLIM protein levels in vivo and impairs the formation of eyes and midbrain-hindbrain boundary. In addition, manipulation of SSDP1 via N-SSDP1 over-expression or SSDP1b knock down impairs trigeminal and Rohon-Beard sensory axon growth. We show that N-SSDP1 is able to partially rescue the inhibition of axon growth induced by a dominant-negative form of CLIM (DN-CLIM). These results reveal specific functions of SSDP in neural patterning and sensory axon growth, in part due to the stabilization of LIM-HD/CLIM complexes