Janice R. Naegele

Long-term behavioral recovery in Parkinsonian rats by an HSV vector expressing tyrosine hydroxylase

One therapeutic approach to treating Parkinsons disease is to convert endogenous striatal cells into levo-3,4-dihydroxyphenylalanine (L-dopa)-producing cells. A defective herpes simplex virus type 1 vector expressing human tyrosine hydroxylase was delivered into the partially denervated striatum of 6-hydroxydopamine-lesioned rats, used as a model of Parkinsons disease. Efficient behavioral and biochemical recovery was maintained for 1 year after gene transfer. Biochemical recovery included increases in both striatal tyrosine hydroxylase enzyme activity and in extracellular dopamine concentrations. Persistence of human tyrosine hydroxylase was revealed by expression of RNA and immunoreactivity.

The postnatal development of monocular optokinetic nystagmus in infants.

Monocular optokinetic nystagmus (OKN) was studied in 24 human infants aged 3-35 weeks using electro-oculography and moving vertical gratings. At a constant velocity of 25 deg/sec, infants display direction dependent slow phase asymmetries until approximately 5 months after birth. A comparison was made of the cumulative eye displacement during the slow phases of OKN for nasal and temporal movement.

IGF-1 receptor-mediated ERK/MAPK signaling couples status epilepticus to progenitor cell proliferation in the subgranular layer of the dentate gyrus

Adult progenitor cell proliferation in the subgranular zone (SGZ) of the dentate gyrus is a dynamic process that is modulated by an array of physiological process, including locomotor activity and novel environmental stimuli. In addition, pathophysiological events, such as ischemia and status epilepticus (SE), have been shown to stimulate neurogenesis. Currently, limited information is available regarding the extracellular stimuli, receptors, and downstream intracellular effectors that couple excitotoxic stimulation to progenitor cell proliferation. Here we show that pilocarpine‐induced SE triggers a set of signaling events that impinge upon the p42/44 mitogen‐activated protein kinase (MAPK) pathway to drive progenitor cell proliferation in the SGZ at 2‐days post‐SE. Increased proliferation was dependent on insulin‐like growth factor‐1 (IGF‐1), which was localized to activated microglia near the SGZ. Using a combination of techniques, we show that IGF‐1 is a CREB‐regulated gene and that SE triggered CRE‐dependent transcription in microglia at 2‐days post‐SE. Together, these data identify a potential signaling program that couples SE to progenitor cell proliferation. SE triggers CREB‐dependent transcription in reactive microglia. As a CREB‐target gene, IGF‐1 expression is upregulated, and by 2‐days post‐SE, IGF‐1 triggers MAPK pathway activation in progenitor cells and, in turn, an increase in progenitor cell proliferation.

Molecular determinants of GABAergic local-circuit neurons in the visual cortex.

Golgi impregnation, intracellular marking techniques and immunocytochemistry have led to the identification of several distinct GABAergic cell types. Co-localization of neuropeptides or calcium-binding proteins has provided additional markers for GABAergic cells. Recently, immunological or lectin probes have helped to identify additional subsets of GABAergic neurons. In combination with other immunocytochemical and anatomical approaches, these probes are now being used to link molecular composition to cellular architecture in the visual cortex.

Genetic manipulation of STEP reverses behavioral abnormalities in a fragile X syndrome mouse model

Fragile X syndrome (FXS), the most common inherited form of intellectual disability and prevailing known genetic basis of autism, is caused by an expansion in the Fmr1 gene that prevents transcription and translation of fragile X mental retardation protein (FMRP). FMRP binds to and controls translation of mRNAs downstream of metabotropic glutamate receptor (mGluR) activation. Recent work shows that FMRP interacts with the transcript encoding striatal‐enriched protein tyrosine phosphatase (STEP; Ptpn5). STEP opposes synaptic strengthening and promotes synaptic weakening by dephosphorylating its substrates, including ERK1/2, p38, Fyn and Pyk2, and subunits of N‐methyl‐d‐aspartate (NMDA) and AMPA receptors. Here, we show that basal levels of STEP are elevated and mGluR‐dependent STEP synthesis is absent in Fmr1KO mice. We hypothesized that the weakened synaptic strength and behavioral abnormalities reported in FXS may be linked to excess levels of STEP. To test this hypothesis, we reduced or eliminated STEP genetically in Fmr1KO mice and assessed mice in a battery of behavioral tests. In addition to attenuating audiogenic seizures and seizure‐induced c‐Fos activation in the periaqueductal gray, genetically reducing STEP in Fmr1KO mice reversed characteristic social abnormalities, including approach, investigation and anxiety. Loss of STEP also corrected select nonsocial anxiety‐related behaviors in Fmr1KO mice, such as light‐side exploration in the light/dark box. Our findings indicate that genetically reducing STEP significantly diminishes seizures and restores select social and nonsocial anxiety‐related behaviors in Fmr1KO mice, suggesting that strategies to inhibit STEP activity may be effective for treating patients with FXS.

Status Epilepticus-Induced Somatostatinergic Hilar Interneuron Degeneration Is Regulated by Striatal Enriched Protein Tyrosine Phosphatase

Excitotoxic cell death is one of the precipitating events in the development of temporal lobe epilepsy. Of particular prominence is the loss of GABAergic hilar neurons. Although the molecular mechanisms responsible for the selective vulnerability of these cells are not well understood, activation of the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway has been implicated in neuroprotective responses to excitotoxicity in other neuronal populations. Here, we report that high levels of the striatal-enriched protein tyrosine phosphatase (STEP), a key regulator of ERK/MAPK signaling, are found in vulnerable somatostatin-immunoreactive hilar interneurons. Under both control conditions and after pilocarpine-induced status epilepticus (SE), ERK/MAPK activation was repressed in STEP-immunoreactive hilar neurons. This contrasts with robust SE-induced ERK/MAPK activation in the granule cell layer of the dentate gyrus, a cell region that does not express STEP. During pilocarpine-induced SE, in vivo disruption of STEP activity allowed activation of the MAPK pathway, leading to immediate-early gene expression and significant rescue from cell death. Thus, STEP increases the sensitivity of neurons to SE-induced excitotoxicity by specifically blocking a latent neuroprotective response initiated by the MAPK pathway. These findings identify a key set of signaling events that render somatostatinergic hilar interneurons vulnerable to SE-induced cell death.

Visual acuity and its meridional variations in children aged 7–60 months

A new operant procedure was used to assess grating acuity in children aged 7-60 months. The procedure was successful for 95% of the children sampled and had high test-retest reliability. Visual acuity for main axis (horizontal and vertical) gratings improved from 6/15 at 12 months to 6/6 at 60 months. For the 7-16 month age group, preferential-looking estimates of acuity agreed well with operant estimates. Acuity for oblique gratings was approximately 1/4 octave lower than main axis acuity throughout the age range. The results suggest that the human visual system continues to develop throughout the first 5 years of life.

Neuronal subsets express multiple high-molecular-weight cell-surface glycoconjugates defined by monoclonal antibodies Cat-301 and VC1.1.

Cat-301 and VC1.1 are monoclonal antibodies that recognize surface- associated molecules on subsets of mammalian CNS neurons. Earlier work demonstrated that Cat-301 recognizes a 680-kDa chondroitin sulfate proteoglycan (PG). VC1.1 has been shown to recognize 3 polypeptide bands on Western blot analysis; a major band at 95-105 kDa and additional bands at 145 kDa and 170 kDa. In the present report, we show that VC1.1 also reacts with a high-molecular-weight glycoconjugate. Immunoprecipitation experiments and biochemical characterizations indicate that Cat-301 and VC1.1 define at least 3 distinct high- molecular-weight antigens. The VC1.1 antigens react with antikeratan sulfate antibodies, while the Cat-301 antigens do not. By immunodepletion, we show that some VC1.1 antigens are Cat-301 positive, while others are Cat-301 negative. In addition, Cat-301-reactive proteoglycans are heterogeneous with respect to the presence or absence of VC1.1 epitopes. Double-label immunofluorescence studies with these 2 antibodies are consistent with the biochemical results and show that there are 3 classes of immunoreactive neurons in the cat CNS:Cat- 301+/VC1.1+, Cat-301-/VC1.1+, and Cat-301+/VC1.1-. These results indicate that structural microheterogeneity exists among Cat-301 and VC1.1 high-molecular-weight glycoconjugates. This heterogeneity may be a reflection of the diverse neuronal phenotypes that are recognized by Cat-301 and VC1.1 in the mammalian CNS.

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, Parkinsons disease, Huntingtons 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.

Differentiation and Functional Incorporation of Embryonic Stem Cell-Derived GABAergic Interneurons in the Dentate Gyrus of Mice with Temporal Lobe Epilepsy

Cell therapies for neurological disorders require an extensive knowledge of disease-associated neuropathology and procedures for generating neurons for transplantation. In many patients with severe acquired temporal lobe epilepsy (TLE), the dentate gyrus exhibits sclerosis and GABAergic interneuron degeneration. Mounting evidence suggests that therapeutic benefits can be obtained by transplanting fetal GABAergic progenitors into the dentate gyrus in rodents with TLE, but the scarcity of human fetal cells limits applicability in patient populations. In contrast, virtually limitless quantities of neural progenitors can be obtained from embryonic stem (ES) cells. ES cell-based therapies for neurological repair in TLE require evidence that the transplanted neurons integrate functionally and replace cell types that degenerate. To address these issues, we transplanted mouse ES cell-derived neural progenitors (ESNPs) with ventral forebrain identities into the hilus of the dentate gyrus of mice with TLE and evaluated graft differentiation, mossy fiber sprouting, cellular morphology, and electrophysiological properties of the transplanted neurons. In addition, we compared electrophysiological properties of the transplanted neurons with endogenous hilar interneurons in mice without TLE. The majority of transplanted ESNPs differentiated into GABAergic interneuron subtypes expressing calcium-binding proteins parvalbumin, calbindin, or calretinin. Global suppression of mossy fiber sprouting was not observed; however, ESNP-derived neurons formed dense axonal arborizations in the inner molecular layer and throughout the hilus. Whole-cell hippocampal slice electrophysiological recordings and morphological analyses of the transplanted neurons identified five basic types; most with strong after-hyperpolarizations and smooth or sparsely spiny dendritic morphologies resembling endogenous hippocampal interneurons. Moreover, intracellular recordings of spontaneous EPSCs indicated that the new cells functionally integrate into epileptic hippocampal circuitry.