Stem cell-derived neurons from autistic individuals with SHANK3 mutation show morphogenetic abnormalities during early development.

Shank3 is a structural protein found predominantly at the postsynaptic density. Mutations in the SHANK3 gene have been associated with risk for autism spectrum disorder (ASD). We generated induced pluripotent stem cells (iPSCs) from control individuals and from human donors with ASD carrying microdeletions of SHANK3. In addition, we used Zinc finger nucleases to generate isogenic SHANK3 knockout human embryonic stem (ES) cell lines. We differentiated pluripotent cells into either cortical or olfactory placodal neurons. We show that patient-derived placodal neurons make fewer synapses than control cells. Moreover, patient-derived cells display a developmental phenotype: young postmitotic neurons have smaller cell bodies, more extensively branched neurites, and reduced motility compared with controls. These phenotypes were mimicked by SHANK3-edited ES cells and rescued by transduction with a Shank3 expression construct. This developmental phenotype is not observed in the same iPSC lines differentiated into cortical neurons. Therefore, we suggest that SHANK3 has a critical role in neuronal morphogenesis in placodal neurons and that early defects are associated with ASD-associated mutations.

Glypican-2 levels in cerebrospinal fluid predict the status of adult hippocampal neurogenesis.

Adult hippocampal neurogenesis is a remarkable form of brain plasticity through which new neurons are generated throughout life. Despite its important roles in cognition and emotion and its modulation in various preclinical disease models, the functional importance of adult hippocampal neurogenesis in human health has not been revealed because of a lack of tools for monitoring adult neurogenesis in vivo. Therefore, we performed an unbiased proteomics screen to identify novel proteins expressed during neuronal differentiation using a human neural stem cell model, and we identified the proteoglycan Glypican-2 (Gpc2) as a putative secreted marker of immature neurons. Exogenous Gpc2 binds to FGF2 and inhibits FGF2-induced neural progenitor cell proliferation. Gpc2 is enriched in neurogenic regions of the adult brain. Its expression is increased by physiological stimuli that increase hippocampal neurogenesis and decreased in transgenic models in which neurogenesis is selectively ablated. Changes in neurogenesis also result in changes in Gpc2 protein level in cerebrospinal fluid (CSF). Gpc2 is detectable in adult human CSF, and first pilot experiments with a longitudinal cohort indicate a decrease over time. Thus, Gpc2 may serve as a potential marker to monitor adult neurogenesis in both animal and human physiology and disease, warranting future studies.

CREB signalling regulates early survival, neuronal gene expression and morphological development in adult subventricular zone neurogenesis.

Neural stem cells in the subventricular zone (SVZ) of the lateral ventricles give rise to new interneurons of the olfactory bulb (OB) throughout life. SVZ/OB neurogenesis is influenced by olfactory network activity, which modulates the survival of new neurons during their integration into the OB network. Previous work suggested that such activity-dependent survival is regulated via the CREB signalling pathway. Curiously, CREB signalling is already active during the early developmental stages of adult SVZ/OB neurogenesis. To investigate the role of cell autonomous CREB signalling during early stages of adult SVZ/OB neurogenesis, we ablated CREB-pathway activity in the SVZ/OB neurogenic lineage using a retroviral strategy. Surprisingly, loss of CREB signalling resulted in increased cell death and loss of expression of the neurogenic transcription factor Pax 6, and of a subset of neuronal proteins in migrating neurons of the RMS. Moreover, post-migratory neurons in the OB displayed impaired dendritic development. These results demonstrate an essential role for CREB signalling in maturation of newborn neurons in the OB and uncover a novel role for CREB signalling in the survival and maintenance of neuronal gene expression during the early stages of SVZ/OB neurogenesis.

Optimum dose of histamine for maximal acid output in underweight subjects.

The effects of increasing doses of histamine acid phosphate on the gastric secretion of acid has been studied in a randomized fashion in five normal control and 15 duodenal ulcer subjects. The dose of histamine acid phosphate used in each individual was 40, 70, 76 and 80 mug/kg. and 3.2 mg. of histamine. In 12 of 20 subjects the highest mean +/- S.D. acid output was observed after a dose of 76 mug./kg. body weight. When the acid output was expressed as the percentage of the highest response with different doses of HAP, the response was maximum with 76 mug. kg. dose. Further statistical analysis by rank totals and X2r by Friedman's two-way analysis by ranks also revealed highest acid output after a 76 mug./kg. dose of HAP. These findings suggest that 76 mug./kg. is the optimum dose for maximal acid output in underweight subjects. Only one patient showed highest acid output after a 3.2 mg. dose of histamine. The mean +/- S.D. acid output after 76 mug./kg. was higher than that after a 3.2 mg. dose of histamine. Hence, for estimating maximal acid output, a weight related dose and not a fixed dose is recommended. Further, it was shown that there was significant correlation between PAO and MAO after various doses of histamine in both the groups. Hence, for clinical purposes, estimation of one hourly poststimulatory maximal acid output after a dose of 76 mug./kg. body weight of histamine acid phosphate is recommended for underweight subjects.