Intracranial Nimodipine Implant: Feasibility and Implications for the Treatment of Subarachnoid Hemorrhage – A Pre-Clinical Study

Intracranial aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening condition requiring immediate neurocritical care. A ruptured aneurysm must be isolated from arterial circulation to prevent rebleeding. Open surgical clipping of the neck of the aneurysm or intra-arterial filling of the aneurysm sack with platinum coils are major treatment strategies in an acute phase. About 40% of the patients suffering from aSAH die within a year of the bleeding despite the intensive treatment. After aSAH, the patient may develop a serious complication called vasospasm. Major risk for the vasospasm takes place at days 5–14 after the primary bleeding. In vasospasm, cerebral arteries contract uncontrollably causing brain ischemia that may lead to death. Nimodipine (NDP) is used to treat of vasospasm and it is administrated intravenously or orally every four hours for 21 days. NDP treatment has been scientifically proven to improve patients’ clinical outcome. The therapeutic effect of L-type calcium channel blocker NDP is due to the ability to dilate cerebral arteries. In addition to vasodilatation, recent research has shown the pleiotropic effect of NDP such as inhibition of neuronal apoptosis and inhibition of microthrombi formation. Indeed, NDP inhibits cortical spreading ischemia. Knowledge of the pathophysiology of the vasospasm has evolved in recent years to a complex entity of early brain injury, secondary injuries and cortical spreading ischemia, instead of being pure intracranial vessel spasm. High NDP levels are beneficial since they protect neurons and inhibit the cortical spreading ischemia. One of the drawbacks of the intravenous or oral administration of NPD is systemic hypotension, which is harmful particularly when the brain is injured. Maximizing the beneficial effects and avoiding systemic hypotension of NDP, we developed a sustained release biodegradable NDP implant that was surgically positioned in the basal cistern of animal models (dog and pig). Higher concentrations were achieved locally and lower concentrations systemically. Using this treatment approach in humans, it may be possible to reduce incidence of harmful hypotension and potentiate beneficial effects of NDP on neurons. Intracellular calcium regulation has a pivotal role in brain plasticity. NDP blocks L-type calcium channels in neurons, substantially decreasing intracellular calcium levels. Thus, we were interested in how NDP affects brain plasticity and tested the hypothesis in a mouse model. We found that NDP activates Brain-derived neurotrophic factor (BDNF) receptor TrkB and its downstream signaling in a reminiscent of antidepressant drugs. In contrast to antidepressant drugs, NDP activates Akt, a major survival-promoting factor. Our group’s previous findings demonstrate that long-term antidepressant treatment reactivates developmental-type of plasticity mechanisms in the adult brain, which allows the remodeling of neuronal networks if combined with appropriate rehabilitation. It seems that NDP has antidepressant-like properties and it is able to induce neuronal plasticity. In general, drug induced neuronal plasticity has a huge potential in neurorehabilitation and more studies are warranted.

Negative Regulation of Receptor Tyrosine Kinases by T-cell Protein Tyrosine Phosphatase

Protein tyrosine phosphorylation controls a wide array of cellular responses such as growth, migration, proliferation, differentiation, metabolism and cytoskeletal organisation. Tyrosine phosphorylation is a dynamic process involving the competing activities of protein tyrosine kinases and protein tyrosine phosphatases. The protein tyrosine kinases are further divided into non-receptor- and receptor tyrosine kinases. The latter are transmembrane glycoproteins activated by the binding of specific ligands, mostly growth factors, to their extracellular domain, transmitting different signals to the cell. Growth factor receptors such as the epidermal growth factor receptor, vascular endothelial growth factor receptor 2 and platelet-derived growth factor receptor β, belong to the receptor tyrosine kinases, the signalling of which is often disturbed in various diseases, including cancer. This has led to the development of receptor tyrosine kinase antagonists for use as anti-cancer drugs. As the receptor tyrosine kinases, also the protein tyrosine phosphatases can be divided into receptor- and non-receptor types. The protein tyrosine phosphatases have attained much less attention than the receptor tyrosine kinases partly because they were identified later. However, accumulating evidence shows that the protein tyrosine phosphatases have important roles as specific and active regulators of tyrosine phosphorylation in cells and of physiological processes. Consequently, the protein tyrosine phosphatases are receiving arising interest as novel drug targets. The aim of this work was to elucidate the negative regulation of receptor tyrosine kinases by one non-receptor protein tyrosine phosphatase, T-cell protein tyrosine phosphatase TCPTP. The results show that TCPTP activated by cell adhesion receptor integrin α1 functions as a negative regulator of the epidermal growth factor receptor. It was also found that TCPTP affects vascular endothelial growth factor receptor 2 signalling and angiogenesis. Lastly, a High-throughput screen with 64,280 compounds was performed to identify novel TCPTP activators, resulting in identification of one small molecule compound capable of exerting similar effects on TCPTP signalling as integrin α1. This compound is shown to downregulate signalling of epidermal growth factor receptor and platelet-derived growth factor receptor β, as well as to inhibit cell proliferation and angiogenesis. Our results suggest that a suitable small-molecule TCPTP activator could be utilized in the development of novel anti-cancer drugs.

Therapeutic Properties of Superoxide Dismutase 3 and Mesenchymal Stromal Cells in Peripheral Ischemia

The aim of this study was to characterize the cellular mechanisms leading to the beneficial effect of anti-oxidative gene therapy and pro-angiogenic stem cell therapy in acute peripheral ischemia. Post-ischemic events aim to re-establish tissue blood perfusion, to clear cellular debris, and to regenerate lost tissue by differentiation of satellite cells into myoblasts. Although leukocytes have an essential role in clearing cellular debris and promoting angiogenesis, they also contribute to tissue injury through excessive ROS production. First, we investigated the therapeutic properties of extracellular superoxide dismutase (SOD3) gene transfer. SOD3 was shown to reduce oxidative stress, to normalize glucose metabolism, and to enhance cell proliferation in the ischemic muscle. Analysis of the mitogenic Ras-Erk1/2 pathway showed SOD3 mediated induction offering a plausible explanation for enhanced cell proliferation. In addition, SOD3 reduced NF-κB activity by enhancing IκBα expression thus leading to reduced expression of inflammatory cytokines and adhesion molecules with consequent reduction in macrophage infiltration. Secondly, we sought to determine the fate and the effect of locally transplanted mesenchymal stem/stromal cells (MSCs) in acute ischemia. We showed that a vast majority of the transplanted cells are cleared from the injury site within 24 hours after local transplantation. Despite rapid clearance, transplantation was able to temporarily promote angiogenesis and cell proliferation in the muscle. Lack of graft-derived growth factor expression suggests other than secretory function to mediate this observed effect. In conclusion, both SOD3 and MSCs could be utilized to alleviate peripheral ischemia induced tissue injury. We have described a previously unidentified growth regulatory role for SOD3, and suggest a novel mechanism whereby transplanted MSCs enhance the reparative potential of the recipient tissue through physical contacts.

Antenatal inflammation and brain pathology in preterm infants

Chorioamnionitis is known to be an important risk factor underlying preterm delivery, and it has also been suggested to associate with brain lesions and deviant neurological development in both preterm and term infants. Cytokines are believed to be the link causing the deleterious effects of inflammation to the nervous system. Their genetic regulation has also been suggested to play a role, as interleukin (IL)-6 -174 and -572 genotypes, which partly regulate IL-6 synthesis responses, have been connected with deviant neurological development in preterm infants. We evaluated the association of histological chorioamnionitis with brain lesions, regional brain volumes, and the functioning of the auditory pathway in very low birth weight/very low gestational age (VLBW/VLGA) infants. In addition, we investigated the association between IL-6 -174 and -572 genotypes and histological chorioamnionitis, neonatal infections, and brain lesions and regional brain volumes in VLBW/VLGA infants. This study is a part of a larger multidisciplinary project PIPARI (Development and Functioning of Very Low Birth Weight Infants from Infancy to School Age), in which the survivors of a 6-year cohort of VLBW/VLGA infants (n=274) are being followed until school age in Turku University Central Hospital, Finland. Placental samples were collected in the delivery room, and were analyzed for histological inflammatory findings. Blood samples from the infants were collected and DNA was genotyped for IL-6-174 and -572 polymorphisms (GG/GC/CC). Brain ultrasound examinations were performed repeatedly in the neonatal intensive care unit and at term age, and were analysed for structural brain lesions. Brain magnetic resonance imaging was performed at term age, and was analysed for regional brain volumes. In addition, diffusion tensor imaging was performed at term, and was used to analyse fractional anisotrophy and the apparent diffusion coefficient of inferior colliculus. The brainstem auditory evoked potential recordings were carried out according to the routine clinical procedure at median age of 30 days after term age. In our study, we found that histological chorioamnionitis was not an independent risk factor for brain lesions, reduced regional brain volumes or abnormal functioning of the auditory pathway in VLBW/VLGA infants. In addition, we found that IL-6 -174 GG and -572 GC genotypes were associated with a higher incidence of histological chorioamnionitis, and that -174 CC genotype associated with higher incidence of septicaemia. The analysed IL-6 genotypes were not associated with other brain lesions, but a reduced volume of basal ganglia and thalami was associated with IL-6 -174 CC and -572 GG genotypes. In conclusion, our findings suggest that histological chorioamnionitis is not an independent risk factor for the brain development of VLBW/VLGA infants, or that the risk caused by inflammation does not exceed the risks attributed to other underlying pathologies behind preterm deliveries. In addition, our findings give reason to propose that IL-6 promoter genotypes have a role in the defence against serious infections and in the brain development of VLBW/VLGA infants.

Brain Dopamine and Serotonin Receptors in the Perception of Pain. Positron Emission Tomography Studies in Healthy Subjects

The role of dopamine and serotonin in spinal pain regulation is well established. However, little is known concerning the role of brain dopamine and serotonin in the perception of pain in humans. The aim of this study was to assess the potential role of brain dopamine and serotonin in determining experimental pain sensitivity in humans using positron emission tomography (PET) and psychophysical methods. A total of 39 healthy subjects participated in the study, and PET imaging was performed to assess brain dopamine D2/D3 and serotonin 5-HT_1A receptor availability. In a separate session, sensitivity to pain and touch was assessed with traditional psychophysical methods, allowing the evaluation of potential associations between D2/D3 and 5-HT_1A binding and psychophysical responses. The subjects’ responses were also analyzed according to Signal Detection Theory, which enables separate assessment of the subject’s discriminative capacity (sensory factor) and response criterion (non-sensory factor). The study found that the D2/D3 receptor binding in the right putamen was inversely correlated with pain threshold and response criterion. 5-HT_1A binding in cingulate cortex, inferior temporal gyrus and medial prefrontal cortex was inversely correlated with discriminative capacity for touch. Additionally, the response criterion for pain and intensity rating of suprathreshold pain were inversely correlated with 5-HT_1A binding in multiple brain areas. The results suggest that brain D2/D3 receptors and 5-HT_1A receptors modulate sensitivity to pain and that the pain modulatory effects may, at least partly, be attributed to influences on the response criterion. 5-HT_1A receptors are also involved in the regulation of touch by having an effect on discriminative capacity.

The Vulnerable Brain and Very Preterm Infants - Findings from the PIPARI-Study

Preterm birth is a risk for normal brain development. Brain maturation that normally happens in the uterus is in very preterm infants a developmental challenge during their stay in a neonatal intensive care unit (NICU). Typical brain injuries of preterm infants include ischemic injuries, brain haemorrhages, ventricular dilatation (VD), and reduced brain volumes. Brain injury is a serious complication of prematurity leading to possible long term consequences for the neurodevelopment of the very low birth weight (VLBW) infant, such as cerebral palsy (CP), hearing impairments, vision problems, and delay in cognitive development.There is a need for further studies to ascertain the potential risk factors and their causal relationships to brain vulnerability, growth and development in the increasing number of surviving VLBW infants. This thesis consists of four studies evaluating the definitions, causes and consequences of brain lesions in VLBW(<1500g) or very low gestationalage (VLGA) (gestational age <32 gestational weeks) infants. We showed that the redistribution of fetal blood flow is a risk factor for smaller brain volumes at term. In addition,we showed that brain lesions related to prematurity are not associated with increased spontaneous crying behaviour or circadian rhythm development in infancy. However, the preterm infants began to fuss more often and were held more than term infants at five months of age. Furthermore, we showed that VD is associated with brain lesions and smaller brain volumes. Therefore, brain magneticresonance imaging can be recommended for infants with VD. VD together with other brain pathology is a risk factor for the onset of developmental impairments in VLBW/VLGA infants at two years of age.

JNK, a versatile regulator of kinesin-1 transport and cytoskeleton dynamics

C-Jun N-terminal kinase (JNK) is traditionally recognized as a crucial factor in stress response and inducer of apoptosis upon various stimulations. Three isoforms build the JNK subfamily of MAPK; generally expressed JNK1 and JNK2 and brain specific JNK3. Degenerative potency placed JNK in the spotlight as potential pharmacological option for intervention. Unfortunately, adverse effects of potential drugs and observation that expression of only JNK2 and JNK3 are induced upon stress, restrained initial enthusiasm. Notably, JNK1 demonstrated atypical high constitutive activity in neurons that is not responsive to cellular stresses and indicated existence of physiological activity. This thesis aimed at revealing the physiological functions of JNK1 in actin homeostasis through novel effector MARCKS-Like 1 (MARCKSL1) protein, neuronal trafficking mediated by major kinesin-1 motor protein and microtubule (MT) dynamics via STMN2/SCG10. The screen for novel physiological JNK substrates revealed specific phosphorylation of C-terminal end of MARCKSL1 at S120, T148 and T183 both ex vivo and in vitro. By utilizing site-specific mutagenesis, various actin dynamics and migrations assays we were able to demonstrate that JNK1 phosphorylation specifically facilitates F-actin bundling and thus filament stabilisation. Consecutively, this molecular mechanism was proved to enhance formation of filopodia; cell surface projections that allow cell sensing surrounding environment and migrate efficiently. Our results visualize JNK dependent and MARCKSL1 executed induction of filopodia in neurons and fibroblast indicating general mechanism. Subsequently, inactivation of JNK action on MARCKSL1 shifts cellular actin machinery into lamellipodial dynamic arrangement. Tuning of actin cytoskeleton inevitably melds with cell migration. We observed that both active JNK and JNK pseudo-phosphorylated form of MARCKSL1 reduce actin turnover in intact cells leading to overall diminished cell motility. We demonstrate that tumour transformed cells from breast, prostate, lung and muscle-derived cancers upregulate MARCKSL1. We showed on the example of prostate cancer PC-3 cell line that JNK phosphorylation negatively controls MARCKSL1 ability to induce migration, which precedes cancer cell metastasis. The second round of identification of JNK physiological substrates resulted in detection of predominant motor protein kinesin-1 (Kif5). Mass spectrometry detailed analysis showed evident endogenous phosphorylation of kinesin-1 on S176 within motor domain that interacts with MT. In vitro phosphorylation of bacterially expressed kinesin heavy chain by JNK isoforms displayed higher specificity of JNK1 when compared to JNK3. Since, JNK1 is constitutively active in neurons it signified physiological aspect of kinesin-1 regulation. Subsequent biochemical examination revealed that kinesin-1, when not phosphorylated on JNK site, exhibits much higher affinity toward MTs. Expression of the JNK non-phosphorable kinesin-1 mutant in intact cells as well as in vitro single molecule imaging using total internal reflection fluorescence microscopy indicated that the mutant loses normal speed and is not able to move processively into proper cellular compartments. We identify novel kinesin-1 cargo protein STMN2/SCG10, which along with known kinesin-1 cargo BDNF is showing impaired trafficking when JNK activity is inhibited. Our data postulates that constitutive JNK activity in neurons is crucial for unperturbed physiologically relevant transport of kinesin-1 dependant cargo. Additionally, my work helps to validate another novel physiological JNK1 effector STMN2/SCG10 as determinant of axodendritic neurites dynamics in the developing brain through regulation of MT turnover. We show successively that this increased MT dynamics is crucial during developmental radial migration when brain layering occurs. Successively, we are able to show that introduction of JNK phosphorylation mimicking STMN2/SCG10 S62/73D mutant rescues completely JNK1 genetic deletion migration phenotype. We prove that STMN2/SCG10 is predominant JNK effector responsible for MT depolymerising activity and neurite length during brain development. Summarizing, this work describes identification of three novel JNK substrates MARCKSL1, kinesin-1 and STMN2/SCG10 and investigation of their roles in cytoskeleton dynamics and cargo transport. This data is of high importance to understand physiological meaning of JNK activity, which might have an adverse effect during pharmaceutical intervention aiming at blocking pathological JNK action.

Fetal alcohol spectrum disorders in Finnish children and adolescents : diagnosis, cognition, behavior, adaptation and brain metabolic alterations

Alcohol consumption during pregnancy can potentially affect the developing fetus in devastating ways, leading to a range of physical, neurological, and behavioral alterations most accurately termed Fetal Alcohol Spectrum Disorders (FASD). Despite the fact that it is a preventable disorder, prenatal alcohol exposure today constitutes a leading cause of intellectual disability in the Western world. In Western countries where prevalence studies have been performed the rates of FASD exceed, for example, autism spectrum disorders, Down’s syndrome and cerebral palsy. In addition to the direct effects of alcohol, children and adolescents with FASD are often exposed to a double burden in life, as their neurological sequelae are accompanied by adverse living surroundings exposing them to further environmental risk. However, children with FASD today remain remarkably underdiagnosed by the health care system. This thesis forms part of a larger multinational research project, The Collaborative Initiative on Fetal Alcohol Spectrum Disorders (the CIFASD), initiated by the National Institute of Alcohol Abuse and Alcoholism (NIAAA) in the U.S.A. The general aim of the present thesis was to examine a cohort of children and adolescents growing up with fetal alcohol-related damage in Finland. The thesis consists of five studies with a broad focus on diagnosis, cognition, behavior, adaptation and brain metabolic alterations in children and adolescents with FASD. The participants consisted of four different groups: one group with histories of prenatal exposure to alcohol, the FASD group; one IQ matched contrast group mostly consisting of children with specific learning disorder (SLD); and two typically-developing control groups (CON1 and CON2). Participants were identified through medical records, random sampling from the Finnish national population registry and email alerts to students. Importantly, the participants in the present studies comprise a group of very carefully clinically characterized children with FASD as the studies were performed in close collaboration with leading experts in the field (Prof. Edward Riley and Prof. Sarah Mattson, Center for Behavioral Teratology, San Diego State University, U.S.A; Prof. Eugene Hoyme, Sanford School of Medicine, University of South Dakota, U.S.A.). In the present thesis, the revised Institute of Medicine diagnostic criteria for FASD were tested on a Finnish population and found to be a reliable tool for differentiating among the subgroups of FASD. A weighted dysmorphology scoring system proved to be a valuable additional adjunct in quantification of growth deficits and dysmorphic features in children with FASD (Study 1). The purpose of Study 2 was to clarify the relationship between alcohol-related dysmorphic features and general cognitive capacity. Results showed a significant correlation between dysmorphic features and cognitive capacity, suggesting that children with more severe growth deficiency and dysmorphic features have more cognitive limitations. This association was, however, only moderate, indicating that physical markers and cognitive capacity not always go hand in hand in individuals with FASD. Behavioral problems in the FASD group proved substantial compared to the typically developing control group. In Study 3 risk and protective factors associated with behavioral problems in the FASD group were explored further focusing on diagnostic and environmental factors. Two groups with elevated risks for behavioral problems emerged: length of time spent in residential care and a low dysmorphology score proved to be the most pervasive risk factor for behavioral problems. The results underscore the clinical importance of appropriate services and care for less visibly alcohol affected children and highlight the need to attend to children with FASD being raised in institutions. With their background of early biological and psychological impairment compounded with less opportunity for a close and continuous caregiver relationship, such children seem to run an especially great risk of adverse life outcomes. Study 4 focused on adaptive abilities such as communication, daily living skills and social skills, in other words skills that are important for gradually enabling an independent life, maintain social relationships and allow the individual to become integrated into society. The results showed that adaptive abilities of children and adolescents growing up with FASD were significantly compromised compared to both typically-developing peers and IQ-matched children with SLD. Clearly different adaptive profiles were revealed where the FASD group performed worse than the SLD group, who in turn performed worse than the CON1 group. Importantly, the SLD group outperformed the FASD group on adaptive behavior in spite of comparable cognitive levels. This is the first study to compare adaptive abilities in a group of children and adolescents with FASD relative to both a contrast group of IQ-matched children with SLD and to a group of typically-developing peers. Finally, in Study 5, through magnetic resonance spectroscopic imaging (MRS) evidence of longstanding neurochemical alterations were observed in adolescents and young adults with FASD related to alcohol exposure in utero 14-20 years earlier. Neurochemical alterations were seen in several brain areas: in frontal and parietal cortices, corpus callosum, thalamus and frontal white matter areas as well as in the cerebellar dentate nucleus. The findings are compatible with neuropsychological findings in FASD. Glial cells seemed to be more affected than neurons. In conclusion, more societal efforts and resources should be focused on recognizing and diagnosing FASD, and supporting subgroups with elevated risk of poor outcome. Without adequate intervention children and adolescents with FASD run a great risk of marginalization and social maladjustment, costly not only to society but also to the lives of the many young people with FASD.

Smoking during pregnancy and fetal brain development

Background: Although the knowledge of adverse effects of smoking during pregnancy has increased in recent years, more research is needed to gain a better understanding of the effects of smoking during pregnancy. Smoking exposure is the most common preventable factor that causes adverse pregnancy outcomes. Aims and Methods: First, data on smoking habits during pregnancy from the Nordic Medical Birth Registers was used to study the national differences in trends of smoking during pregnancy. Second, the effects of prenatal smoking exposure on fetal brain development, assessed by brain MRI at term age, were studied by using data from the multidisciplinary PIPARI Study consisting of a 6-year cohort of VLBW/VLGA infants (n = 232, of which 18.1% were exposed to prenatal smoking) born in Turku University Hospital, Finland. Third, the effects of prenatal smoking exposure on psychiatric morbidity and use of psychotropic medication were studied in a cohort of children born from 1987–1989 in Finland (n = 175,869, of which 15.3% were exposed). The data used were obtained from population-based longitudinal registers from the National Institute of Health and Welfare, the Statistics Finland, and the Finnish Social Insurance Institution. Results: Smoking rates during pregnancy differed considerably between the countries. Smoking rates were highest among teenagers and women with lower socioeconomic positions. The smoking prevalence was found to be increasing among teenagers in both Finland and Norway. Prenatal smoking exposure was associated with smaller frontal lobe and cerebellar volumes in preterm infants. A clear association was found between prenatal smoking exposure and psychiatric morbidity treated with specialized hospital care and the use of various psychotropic medications. Conclusions: Prenatal smoking exposure had adverse effects on fetal brain development. These effects might explain part of the association found between smoking exposure and psychiatric problems in later life. Our study suggests that prenatal smoking exposure is linked with both mild and severe psychiatric problems. This study emphasizes the importance of efforts to reduce smoking during pregnancy.

Herpes simplex virus type 1 (HSV-1) pathogenesis and HSV gene therapy of experimental autoimmune encephalomyelitis

The aim of this thesis was to develop new herpes simplex virus (HSV) vectors for gene therapy of experimental autoimmune encephalomyelitis (EAE), the principal model of multiple sclerosis (MS), and to study the pathogenesis of wild-type HSV-1 and HSV-1 vectors in vivo. By introducing potential immunomodulatory factors into mice with EAE we strived to develop therapies and possibly find molecules improving recovery from EAE. We aimed at altering the immune response by inducing favorable Th2-type cytokines, thus shifting the immune response from a Th1- or a Th17-response. Our HSV vector expressing interleukin (IL)-5 modulated the cytokine responses, decreased inflammation and alleviated EAE. The use of a novel method, bacterial artificial chromosome (BAC), for engineering recombinant HSV facilitated the construction of a new vector expressing leukemia inhibitory factor (LIF). LIF is a neurotropic cytokine with broad functions in the central nervous system (CNS). LIF promotes oligodendrocyte maturation and decreases demyelination and oligodendrocyte loss. The BAC-derived HSV-LIF vector alleviated the clinical symptoms, induced a higher number of oligodendrocytes and modulated T cell responses. By administering HSV via different infection routes, e.g. peripherally via the nose or eye, or intracranially to the brain, the effect of the immune response on HSV spread at different points of the natural infection route was studied. The intranasal infection was an effective delivery route of HSV to the trigeminal ganglion and CNS, whereas corneal infection displayed limited spread. The corneal and intranasal infections induced different peripheral immune responses, which might explain the observed differences in viral spread.

The interplay of JNK and SCG10 during cortical development and in excitotoxic responses in brain

Initially identified as stress activated protein kinases (SAPKs), the c-Jun Nterminal kinases (JNKs) are currently accepted as potent regulators of various physiologically important cellular events. Named after their competence to phosphorylate transcription factor c-Jun in response to UVtreatment, JNKs play a key role in cell proliferation, cell death or cell migration. Interestingly, these functions are crucial for proper brain formation. The family consists of three JNK isoforms, JNK1, JNK2 and JNK3. Unlike brain specific JNK3 isoform, JNK1 and JNK2 are ubiquitously expressed. It is estimated that ten splice variants exist. However, the detailed cellular functions of these remain undetermined. In addition, physiological conditions keep the activities of JNK2 and JNK3 low in comparison with JNK1, whereas cellular stress raises the activity of these isoforms dramatically. Importantly, JNK1 activity is constitutively high in neurons, yet it does not stimulate cell death. This suggests a valuable role for JNK1 in brain development, but also as an important mediator of cell wellbeing. The aim of this thesis was to characterize the functional relationship between JNK1 and SCG10. We found that SCG10 is a bona fide target for JNK. By employing differential centrifugation we showed that SCG10 co-localized with active JNK, MKK7 and JIP1 in a fraction containing endosomes and Golgi vesicles. Investigation of JNK knockout tissues using phosphospecific antibodies recognizing JNK-specific phosphorylation sites on SCG10 (Ser 62/Ser 73) showed that phosphorylation of endogenous SCG10 was dramatically decreased in Jnk1-/- brains. Moreover, we found that JNK and SCG10 co-express during early embryonic days in brain regions that undergo extensive neuronal migration. Our study revealed that selective inhibition of JNK in the cytoplasm significantly increased both the frequency of exit from the multipolar stage and radial migration rate. However, as a consequence, it led to ill-defined cellular organization. Furthermore, we found that multipolar exit and radial migration in Jnk1 deficient mice can be connected to changes in phosphorylation state of SCG10. Also, the expression of a pseudo-phosphorylated mutant form of SCG10, mimicking the JNK1- phopshorylated form, brings migration rate back to normal in Jnk1 knockout mouse embryos. Furthermore, we investigated the role of SCG10 and JNK in regulation of Golgi apparatus (GA) biogenesis and whether pathological JNK action could be discernible by its deregulation. We found that SCG10 maintains GA integrity as with the absence of SCG10 neurons present more compact fragmented GA structure, as shown by the knockdown approach. Interestingly, neurons isolated from Jnk1-/- mice show similar characteristics. Block of ER to GA is believed to be involved in development of Parkinson's disease. Hence, by using a pharmacological approach (Brefeldin A treatment), we showed that GA recovery is delayed upon removal of the drug in Jnk1-/- neurons to an extent similar to the shRNA SCG10-treated cells. Finally, we investigated the role of the JNK1-SCG10 duo in the maintenance of GA biogenesis following excitotoxic insult. Although the GA underwent fragmentation in response to NMDA treatment, we observed a substantial delay in GA disintegration in neurons lacking either JNK1 or SCG10.