Hippocampal NPY gene transfer attenuates seizures without affecting epilepsy-induced impairment of LTP

Recent advancements in stem cell and gene therapies for neurological disorders and intractable epilepsy

The potential applications of stem cell therapies for treating neurological disorders are enormous. Many laboratories are focusing on stem cell treatments for CNS diseases, including spinal cord injury, Amyotrophic lateral sclerosis, Parkinson's disease, Huntington's disease, multiple sclerosis, stroke, traumatic brain injury, and epilepsy. Among the many stem cell types under testing for neurological treatments, the most common are fetal and adult brain stem cells, embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells. An expanding toolbox of molecular probes is now available to allow analyses of neural stem cell fates prior to and after transplantation. Concomitantly, protocols are being developed to direct the fates of stem cell-derived neural progenitors, and also to screen stem cells for tumorigenicity and aneuploidy. The rapid progress in the field suggests that novel stem cell and gene therapies for neurological disorders are in the pipeline.

Impaired neurogenesis, learning and memory and low seizure threshold associated with loss of neural precursor cell survivin

BACKGROUND

Survivin is a unique member of the inhibitor of apoptosis protein (IAP) family in that it exhibits antiapoptotic properties and also promotes the cell cycle and mediates mitosis as a chromosome passenger protein. Survivin is highly expressed in neural precursor cells in the brain, yet its function there has not been elucidated.

RESULTS

To examine the role of neural precursor cell survivin, we first showed that survivin is normally expressed in periventricular neurogenic regions in the embryo, becoming restricted postnatally to proliferating and migrating NPCs in the key neurogenic sites, the subventricular zone (SVZ) and the subgranular zone (SGZ). We then used a conditional gene inactivation strategy to delete the survivin gene prenatally in those neurogenic regions. Lack of embryonic NPC survivin results in viable, fertile mice (SurvivinCamcre) with reduced numbers of SVZ NPCs, absent rostral migratory stream, and olfactory bulb hypoplasia. The phenotype can be partially rescued, as intracerebroventricular gene delivery of survivin during embryonic development increases olfactory bulb neurogenesis, detected postnatally. SurvivinCamcre brains have fewer cortical inhibitory interneurons, contributing to enhanced sensitivity to seizures, and profound deficits in memory and learning.

CONCLUSIONS

The findings highlight the critical role that survivin plays during neural development, deficiencies of which dramatically impact on postnatal neural function.

Fear of harm, a possible phenotype of pediatric bipolar disorder: a dimensional approach to diagnosis for genotyping psychiatric syndromes

BACKGROUND

In a prior concordance study of affected sibling pairs with a community diagnosis of pediatric bipolar disorder (PBD) a behavioral phenotype termed Fear of Harm (FOH) was found to have one of the strongest concordance coefficients (rho) between probands and siblings, and the widest contrasts between the rho-estimates for the proband/sibling vs. proband/comparison pairs [Papolos, D., Hennen, J., Cockerham, M.S, Lachman, H., 2007]. A strategy for identifying phenotypic subtypes: concordance of symptom dimensions between sibling pairs who met screening criteria for a genetic linkage study of childhood-onset bipolar disorder using the Child Bipolar Questionnaire (CBQ) was employed. J. Affect. Disord. 99, 27-36.]. We used the Child Bipolar Questionnaire (OUT) (CBQ) to further elucidate this behavioral phenotype of PBD. We hypothesized that selective factors including parent reported symptoms of mania and depression, would be distinguishing features of impairment between groups defined by 1) the magnitude of their score on a continuous measure of FOH, and 2) the high FOH group would have significantly greater levels of severity on course of illness variables. These measures included earlier age of onset of first psychiatric symptoms, first hospitalization, and frequency of psychiatric hospitalizations, as well as, degree of social impairment as determined by exposure to the juvenile justice system and school performance problems.

METHODS

The sample was comprised of children with community diagnoses of bipolar disorder or at risk for the illness based on enriched family history with multiple first degree relatives diagnosed with BPD (N=5335). Included were all subjects who had >40 positively endorsed CBQ symptom items at frequencies of very often, almost always, and always. This group was divided randomly into two groups, the exploratory group (N=2668) and the hypothesis testing (study) group (N=2666). The exploratory group was used for the development of hypotheses and the study group was used to test these hypotheses on a new set of data. All results reported here derive from the latter group. In subsequent analyses, we classified each child as having a high degree of FOH, low FOH, or no FOH. We examined a subset of the sample for differences in age of onset of first psychiatric symptoms, course of illness and measures of symptom severity. These groups were compared using the chi-square procedure for categorical data and the Analysis of Variance (ANOVA) with Scheffe pair wise tests for continuous variables. The Child Bipolar Questionnaire V.2.0, the Yale-Brown Obsessive Compulsive Scale (YBOCS) and the Overt Aggression Scale (OAS) were the principal instruments used to obtain diagnostic information for this study.

RESULTS

We found that children representative of the FOH phenotype when compared to children with PBD who lack this trait had higher indices of severity of mania and depression, as well as other indices that reflect severity and course of illness. Trait factors were derived from a factor analysis of CBQ in a large population of children diagnosed with or at risk for PBD, and used to further elucidate trait features of children with FOH. Children with the FOH traits were also more likely to be defined by six CBQ factors; Sleep/Arousal, Harm to Self and Others, Territorial Aggression, Anxiety, Self-esteem, Psychosis/Parasomnias/Sweet Cravings/Obsessions (PPSO).

LIMITATIONS

This data is derived from samples enriched with bipolar disorder cases. Further validation is needed with samples in which childhood-onset BD is rarer and diagnoses more diverse. Clinician diagnosis was not validated via research interview.

CONCLUSIONS

The FOH phenotype, as defined by a metric derived from combining items from the YBOCS/OAS, is a clinically homogeneous behavioral phenotype of PBD with early age of onset, severe manic and depressive symptoms, and significant social impairment that is strongly associated with 6 CBQ factors and can be easily identified using the CBQ. Through the examination of dimensional features of PBD in an enriched sample of large size, we were able to further refine a phenotype and identify clinical dimensions potentially linked to endophenotypic markers that may prove fruitful in differential diagnosis, treatment and etiological studies of PBD. The nature of the sets of specific symptoms that comprise the FOH factors enabled us to propose a biological model for the phenotype (OUT) that involves a complex orexigenic circuit which links hypothalamic, limbic, and other brain nuclei primarily responsible for the regulation of behavioral and proposed physiological features of the FOH phenotype.

Neuropeptide Y overexpression using recombinant adeno-associated viral vectors

Gene therapy may represent a promising alternative treatment of epileptic patients who are resistant to conventional anti-epileptic drugs. Among the various approaches for the application of gene therapy in the treatment of CNS disorders, recombinant adeno-associated viral (AAV) vectors have been most widely used. Preclinical studies using a selection of "therapeutic" genes injected into the rodent brain to correct the compromised balance between inhibitory and excitatory transmission in epilepsy, showed significant reduction of seizures and inhibition of epileptogenesis. In particular, transduction of neuropeptide genes, such as galanin and neuropeptide Y (NPY) in specific brain areas in experimental models of seizures resulted in significant anticonvulsant effects. Recent findings showed a long-lasting NPY over-expression in the rat hippocampus by local application of recombinant AAV vectors associated with reduced generalization of seizures, delayed kindling epileptogenesis, and strong reduction of chronic spontaneous seizures. These results establish a proof-of-principle evidence of the efficacy of gene therapy as anticonvulsant treatment. Additional investigations are required to address safety concerns and possible side effects in more detail.