Medulloblastoma is a highly malignant cerebellar childhood tumor. As in many other brain tumors, expression of platelet-derived growth factor (PDGF) and its receptors has been shown in medulloblastoma. To reveal the importance of this growth factor in cerebellar development and tumorigenesis, analyses were performed on human medulloblastoma cell lines and on tissue from normal mouse brain at different stages of development. The in vivo effect of a forced expression of PDGF-B in the cerebellar primordium was examined in transgenic mice. In the normal mouse embryo, we found PDGF receptor-α-positive cells in the early neuroepithelium and on neuronal precursors. In the postnatal cerebellum, cells in the external germinal layer and Purkinje cells expressed the receptor. In the medulloblastoma cells, expression of all the three PDGF isoforms and PDGF receptors was seen and correlated to neuronal differentiation. Endogenously activated, i.e. tyrosine phosphorylated, PDGF receptors were identified. To reveal the role of PDGF in normal cerebellar development, we established transgenic mice where a PDGF-B cDNA was introduced via homologous recombination into the engrailed-1 gene. Engrailed-1 is specifically expressed at the mid-/hindbrain boundary of the early neural tube, i.e. in an area from which the cerebellar primordium develops. The ectopic expression of PDGF-B caused a disturbance of cerebellar development. Midline fusion of the cerebellar primordium did not occur properly, which resulted in cerebellar dysplasia in the adult mouse. In a parallel study, the expression pattern of a glial fibrillary acidic protein (GFAP)-lacZ transgene was followed in the embryonic mouse central nervous system. It was shown that the human GFAP promoter was already active by embryonic day 9.5 and as development proceeded, expression occured in different, independent cell populations. Among these cell populations were the radial glial cells in the neocortex.

Altered afferent input resulting from neck joint dysfunction has become a growing area of study. Cervical spine manipulation, specifically in individuals with subclinical neck pain (SNCP); induces neurological changes, suggesting it has a positive neuromodulatory effect on brain processing. The effects of manipulation on motor learning in individuals with SCNP have not been investigated until now. Studies in this thesis sought to develop and investigate a novel motor training task to be coupled with cervical spine manipulation to investigate its effects on individual’s ability to process new task information. The studies revealed significant changes in neural activity specific to the cerebellum and sensorimotor integration following a complex motor training task as compared to a simple repetitive task, suggesting that those specific regions are involved in processing of more complex motor skill learning tasks. This novel task was then coupled with manipulation which revealed significant activation increases in cortical and decreases in subcortical brain regions following manipulation. Regions specific to sensorimotor integration (SMI) showed increased activation in both the manipulation and passive head movement control groups, corroborating with the results from the first study. The use of a complex motor training task is a useful tool for determining intervention effects on neural processing in individuals with SCNP. / UOIT

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 89-100).

Delay classical eyeblink conditioning is an important model of associative, cerebellar dependent learning. Norepinephrine (NE) plays a significant modulatory role in the acquisition of learning; other neurotransmitter systems are also at play. The goal of this dissertation was to determine whether NE, GABA and glutamate (Glu) release is observed in cerebellar cortex during delay eye blink conditioning, and whether such release was selectively associated with training and not due only to stimulatory sensory input. The data support the hypothesis of noradrenergic and GABAergic system involvement in motor learning with NE as a modulator of early responding and GABA as a mediator of the learned response. In addition to neurotransmitter levels, we found that the local administration into the cerebellum of Rp-cAMP and propranolol impair the consolidation of learning when administered post training on the eyeblink conditioning task indicating that the B-adrenergic receptor and the cAMP downstream signaling cascade are essential for memory consolidation. These results support the hypothesis of NE acting as a neuromodulator in the cerebellum for the acquisition of motor learning. A similar experimental design was applied to aged animals and the neurochemical pattern of release was haracterized by a delay in the response to eyeblink conditioning and smaller amounts of the neurotransmitter evoked by the paired US-CS. It is hypothesized that the impairment in aging could be due to excitotoxicity caused by chronic inflammation. The present study also approached this issue by targeting the pro-inflammatory cytokine TNF-a and we found that suppression of TNF-a in aged animals improved learning.

Μελετήθηκαν αλληλεπιδράσεις μεταξύ της παρεγκεφαλίδας και των βασικών γαγγλίων στον εγκέφαλο ενήλικων μυών. Για τη μελέτη της επίδρασης της παρεγκεφαλίδας στα βασικά γάγγλια εξετάστηκαν οι επιπτώσεις της εκφύλισης του παρεγκεφαλιδικού φλοιού στη νευροχημεία των βασικών γαγγλίων. Χρησιμοποιήθηκαν δύο μοντέλα εκφύλισης: το μεταλλαγμένο στέλεχος μυός PCD που εμφανίζει πλήρη εκφύλιση των κυττάρων Purkinje και μύες με μερική δεξιά εκφύλιση του παρεγκεφαλιδικού φλοιού μετά από ένεση καϊνικού οξέος στην περιοχή του παρασκώληκα. Ιn vitro ποσοτική αυτοραδιογραφία έδειξε αναβάθμιση των υποδοχέων ντοπαμίνης D1 στα βασικά γάγγλια και των δύο μοντέλων εκφύλισης. Για τη μελέτη της επίδρασης των βασικών γαγγλίων στην παρεγκεφαλίδα μελετήθηκε ο μεταφορέας της ντοπαμίνης στον παρεγκεφαλιδικό ιστό μυών με μεθόδους ποσοτικής αυτοραδιογραφίας, μεμβρανικής δέσμευσης και ανοσοϊστοχημείας. Τα αποτελέσματα έδειξαν την ύπαρξη, την ανατομική κατανομή και τις ιδιότητες του μεταφορέα της νοτπαμίνης στην παρεγκεφαλίδα. / The study of the interactions between the cerebellum and the basal ganglia was the aim of this thesis. To study cerebellar influences on the basal ganglia I investigated the effects of cerebellar cortical degeneration on basal ganglia neurochemistry. Two models of cerebellar degeneration were used: the mutant mouse strain \\\"Purkinje cell degenaration\\\" that completely lacks Purkinje cells, and mice with partial Purkije cell lesion after kainic acid injections in the right paravermis. In vitro quantitative receptor autoradiography showed an up-regulation of D1 dopamine receptors in the basal ganglia of both cerebellar degeneration models. This may reflect a compensatory adaptation. To study basal ganglia influences on the cerebellum I characterized the dopamine transporter of the mouse cerebellum by using receptor binding and determined its anatomical distribution by using receptor autoradiography and immunoistochemistry.

<p>During development, the precise regulation of the processes of proliferation, migration, and differentiation is required to establish proper organ structure and function and to prevent the deregulation that can lead to disease, such as cancer. Improved understanding of the signals that regulate these processes is therefore necessary to both gain insight into the mechanisms by which organ development proceeds and to identify strategies for treating the consequences of deregulation of these processes. In the cerebellum, some of the factors that regulate these processes have been identified but remain incompletely understood. Our studies have focused on the signals that regulate the migration of cerebellar granule neuron progenitors (GNPs) and the contribution of the SDF-1/CXCR4 signaling axis to postnatal cerebellar development. Using conditional knockout mice to delete CXCR4 specifically in GNPs, we show that loss of CXCR4 results in premature migration of a subset of GNPs throughout postnatal development that are capable of proliferation and survival outside of their normal mitogenic niche. Loss of CXCR4 also causes a reduction in the activity of the Sonic hedgehog (SHH) pathway (the primary mitogen for GNPs) but does not affect GNP proliferation, differentiation, or capacity for tumor formation. Our data suggest that while other factors likely contribute, SDF-1/CXCR4 signaling is necessary for proper migration of GNPs throughout cerebellar development. </p><p>In addition to understanding the signals that regulate normal development, the identification of vulnerabilities of established tumors is also necessary to improve cancer treatment. One strategy to improve treatment involves targeting the cells that are critical for maintaining tumor growth, known as tumor-propagating cells (TPCs). In the context of the cerebellar tumor medulloblastoma (MB), we have previously identified a population of TPCs in tumors from patched mutant mice that express the cell surface carbohydrate antigen CD15/SSEA-1. Here, we employed multiple approaches in an effort to target these cells, including a biochemical approach to identify molecules that carry the CD15 carbohydrate epitope as well as an immunotoxin approach to specifically target CD15-expressing cells. Unfortunately, these strategies were ultimately unsuccessful, but an alternative approach that recognized a vulnerability of CD15+ cells was identified. We show that CD15+ cells express elevated levels of genes associated with the G2/M phases of the cell cycle, progress more rapidly through the cell cycle than CD15- cells, and contain an increased proportion of cells in G2/M. Exposure of tumor cells to inhibitors of Aurora and Polo-like kinases, key regulators of G2/M, induces cell cycle arrest, apoptosis and enhanced sensitivity to conventional chemotherapy, and treatment of tumor-bearing mice with these agents significantly inhibits tumor progression. Importantly, cells from human patient-derived MB xenografts are also sensitive to Aurora and Polo-like kinase inhibitors. Our findings suggest that targeting G2/M regulators may represent a novel approach for the treatment of human MB.</p> / Dissertation

Research suggests that the cerebellum is involved in cognition, but its exact role is unclear. The efficiency theory posits that the cerebellum supports processing speed. Other researchers argue that the cerebellum is functionally heterogeneous, and damage to lobes of the cerebellum causes selective loss of cognitive functions. This study sought to determine whether selective impairment in motor, verbal fluency, or processing speed occurred depending on the lobe of the cerebellum that was lesioned. Lesion mapping was used to measure lesion size and volumetric methods were used to measure atrophy in 25 adult survivors of cerebellar tumors. Participants had too a high degree of heterogeneous cerebellar lesions and accompanying atrophy to explore specialization. However, total cerebellar atrophy negatively impacted written and oral processing speed to a greater degree than total cerebellar lesion size. Younger ages at diagnosis and radiation therapy were associated with greater cerebellar atrophy.

Access to abstract permanently restricted to Ball State community only / Access to thesis permanently restricted to Ball State community only / Department of Educational Psychology

Running title: Climbing fibers in myosin Va mutants

Brain tumours comprise about 25% of all cancers in children. Medulloblastoma – which arise in the cerebellum – are the most common and severe malignant pediatric brain tumour and the leading cause of cancer-related deaths in children under the age of 9. Treatment of medulloblastoma remains conventional, with surgery followed by chemotherapy and radiation. These measures are successful in about 60-80% of cases but treatment results in severe side effects due to its toxicity to the central nervous system. Therefore it is of utmost importance to define the signalling pathways and genetic changes involved in the formation of medulloblastoma in order to allow for better diagnosis and treatments with higher efficiency and decreased toxicity. The cell of origin for medulloblastoma is thought to be the granule neuron progenitor, a cell type arising from cerebellar stem cells of the ventricular zone. After birth granule neuron progenitors differentiate into mature granule neurons which populate the majority of the cerebellum and are crucial for its cognitive functions and motor coordination. The Hedgehog signalling pathway plays an important role in medulloblastoma generation and murine models with activated Hedgehog signalling develop medulloblastoma at high frequencies. In addition, the Notch pathway has been implicated in the generation of medulloblastoma, and interaction between the two pathways has been suggested. Inhibitors of both Hedgehog and Notch are currently in clinical trials however knowledge of possible interactions between them could lead to more effective treatment strategies. The aim of this project was to investigate the interaction of Hedgehog and Notch signalling in normal brain development and medulloblastoma. Two mouse models allowed activation of Hedgehog and inactivation of Notch signalling in granule neuron progenitors and cerebellar ventricular zone stem cells. In granule neuron progenitors canonical Notch signalling is not required and the layering and cell types of RBP-Jlox/lox;Math1-Cre cerebella appear identical to control brains. In contrast, Notch inactivation in ventricular zone stem cells with GFAP-Cre resulted in increased differentiation of stem cells into progenitor cells accompanied by an overall developmental delay in neuronal differentiation. Medulloblastoma generated by Hedgehog activation (through inactivation of the negative Hedgehog regulator Ptc1) in both cell types cannot be blocked by Notch inactivation. Furthermore, medulloblastoma of Ptc1lox/lox;RBP-Jlox/lox;GFAP-Cre and those of Ptc1lox/lox;RBP-Jlox/lox;Math1-Cre mice are identical in incidence as well as histology to the tumours in which only Hedgehog signalling is activated. This implies that even though Notch signalling plays an important role in cerebellar stem cells it is not required for the initiation and development of Hedgehog induced medulloblastoma. Therefore it may be crucial to consider the Hedgehog status of patients in order to interpret clinical data of Notch pathway inhibitors and even more importantly these results suggest that determining the Hedgehog status might be crucial before treatment of medulloblastoma patients with Notch pathway inhibitors.