Kaichi Yoshizaki

Chronic cerebral hypoperfusion induced by right unilateral common carotid artery occlusion causes delayed white matter lesions and cognitive impairment in adult mice

Some lines of evidence have suggested that subcortical ischemic vascular dementia (SIVD) is a common form of vascular dementia (VaD), and that its pathological changes are the development of ischemic white matter (WM) lesions under chronic hypoperfusion and lacunes. Here, we have developed a novel mouse model of VaD with WM lesions, which was induced by right unilateral common carotid artery occlusion (rUCCAO). The mice subjected to rUCCAO exhibited chronic cerebral hypoperfusion in the cerebral hemisphere ipsilateral to rUCCAO monitored using a laser-Doppler flow meter (p<0.01), and significant WM damage in the corpus callosum (p<0.05) and deficits in object recognition test correlated with the damage of frontal-subcortical circuits (p<0.01). However, no differences in spontaneous alternation or spontaneous motor activity were observed. Furthermore, the levels of pro-inflammatory cytokines, such as interleukin-1beta (IL-1beta) and interleukin-6 (IL-6), significantly increased (p<0.01), and those of anti-inflammatory cytokines, such as interleukin-4 (IL-4) and interleukin-10 (IL-10), significantly decreased in the ischemic brain (p<0.05). These results suggest that this model is a useful tool for investigating the associations among inflammatory reactions, cognitive impairment, and WM damage, which may help elucidating the pathomechanism of VaD, particularly SIVD.

Impaired hippocampal neurogenesis and vascular formation in ephrin-A5-deficient mice.

Neurogenesis occurs throughout the life in the mammalian brain. The hippocampal dentate gyrus (DG) is one of the major regions of the adult neurogenesis, where neural stem/progenitor cells continuously generate new granule neurons, although molecular mechanisms underlying generation and maintenance of newly born neurons are still elusive. Here we show that ephrin‐A5, a ligand for Eph receptor tyrosine kinases, plays multiple roles in both neurogenesis and vascular formation in the adult hippocampus. In mice lacking ephrin‐A5 function, cell proliferation and survival of newborn neurons were severely reduced in the hippocampus DG. Furthermore, ephrin‐A5‐deficient mice exhibited altered distribution of EphA4 receptor in the vascular endothelial cells and increased narrower capillaries in the hippocampus DG. EphA/ephrin‐A signaling thus plays crucial roles in the establishment and/or maintenance of the brain vascular system, as an essential constituent of the adult neurogenic niche. STEM CELLS 2010;28:974–983

A Sensitive Period for GABAergic Interneurons in the Dentate Gyrus in Modulating Sensorimotor Gating

Developmental perturbations during adolescence have been hypothesized to be a risk factor for the onset of several neuropsychiatric diseases. However the physiological alterations that result from such insults are incompletely understood. We investigated whether a defined perturbation during adolescence affected hippocampus-dependent sensorimotor gating functions, a proposed endophenotype in several psychiatric diseases, most notably schizophrenia. The developmental perturbation was induced during adolescence in mice using an antimitotic agent, methylazoxymethanol acetate (MAM), during postnatal weeks (PW) 4–6. MAM-treated mice showed a decrease in hippocampal neurogenesis immediately after treatment, which was restored by PW10 in adulthood. However, the mice treated with MAM during adolescent stages exhibited a persistent sensorimotor gating deficiency and a reduction in prepulse inhibition-related activation of hippocampal and prefrontal neurons in adulthood. Cellular analyses found a reduction of GABAergic inhibitory neurons and abnormal dendritic morphology of immature neurons in the dentate gyrus (DG). Interestingly, bilateral infusion of muscimol, a GABAA receptor agonist, into the DG region reversed the prepulse inhibition abnormality in MAM-treated mice. Furthermore, the behavioral deficits together with the decrease in the number of GABAergic neurons in this MAM model were rescued by exposure to an enriched environment during a defined critical adolescent period. These observations suggest a possible role for GABAergic interneurons in the DG during adolescence. This role may be related to the establishment of neural circuitry required for sensorimotor gating. It is plausible that changes in neurogenesis during this window may affect the survival of GABAergic interneurons, although this link needs to be causally addressed.

Maternal dietary imbalance between omega-6 and omega-3 polyunsaturated fatty acids impairs neocortical development via epoxy metabolites

Omega‐6 (n‐6) and omega‐3 (n‐3) polyunsaturated fatty acids (PUFAs) are essential nutrients. Although several studies have suggested that a balanced dietary n‐6:n‐3 ratio is essential for brain development, the underlying cellular and molecular mechanism is poorly understood. Here, we found that feeding pregnant mice an n‐6 excess/n‐3 deficient diet, which reflects modern human diets, impairsed neocortical neurogenesis in the offspring. This impaired neurodevelopment occurs through a precocious fate transition of neural stem cells from the neurogenic to gliogenic lineage. A comprehensive mediator lipidomics screen revealed key mediators, epoxy metabolites, which were confirmed functionally using a neurosphere assay. Importantly, although the offspring were raised on a well‐balanced n‐6:n‐3 diet, they exhibited increased anxiety‐related behavior in adulthood. These findings provide compelling evidence that excess maternal consumption of n‐6 PUFAs combined with insufficient intake of n‐3 PUFAs causes abnormal brain development that can have long‐lasting effects on the offsprings mental state. Stem Cells 2016;34:470–482

Maternal Nutritional Imbalance between Linoleic Acid and Alpha-Linolenic Acid Increases Offspring’s Anxious Behavior with a Sex-Dependent Manner in Mice

Omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFAs) are essential nutrients for normal brain development. The principal dietary n-6 and n-3 PUFAs are linoleic acid (LA) and α-linolenic acid (ALA), respectively, We have previously shown that maternal dietary imbalance between these PUFAs, i.e., rich in LA and poor in ALA, affected brain development and increased anxiety-related behavior in the mouse offspring. Here we further addressed sex difference in anxiety-related behavior in the offspring exposed to maternal LA:ALA imbalance. We fed pregnant mice a LA excess/ALA deficient (LA(ex)/ALA(def)) diet, and raised their offspring on a well-balanced LA:ALA diet from an early lactation period. When the offspring were grown to adulthood, they were subjected to behavioral and biochemical analyses. We found that both male and female offspring exposed to the LA(ex)/ALA(def) diet showed increased anxiety-related behavior compared to those exposed to the control diet, which was differently observed between the sexes. The female offspring also exhibited hyperactivity by maternal intake of the LA(ex)/ALA(def) diet. On the other hand, abnormal depressive behavior was undetected in both sexes. We also found that the ratio of n-6 to n-3 PUFAs in the brain was unaffected regardless of maternal diet or offsprings sex. Since the n-6/n-3 ratio is known to influence emotional behavior, it is reasonable to assume that LA:ALA imbalance exposed during brain development is the key for causing enhanced anxiety in adulthood. The present study indicates that maternal dietary imbalance between LA and ALA increases offsprings anxiety-related behavior with a sex-dependent manner.

Paternal Aging Affects Behavior in Pax6 Mutant Mice: A Gene/Environment Interaction in Understanding Neurodevelopmental Disorders.

Neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention deficit and hyperactivity disorder (ADHD) have increased over the last few decades. These neurodevelopmental disorders are characterized by a complex etiology, which involves multiple genes and gene-environmental interactions. Various genes that control specific properties of neural development exert pivotal roles in the occurrence and severity of phenotypes associated with neurodevelopmental disorders. Moreover, paternal aging has been reported as one of the factors that contribute to the risk of ASD and ADHD. Here we report, for the first time, that paternal aging has profound effects on the onset of behavioral abnormalities in mice carrying a mutation of Pax6, a gene with neurodevelopmental regulatory functions. We adopted an in vitro fertilization approach to restrict the influence of additional factors. Comprehensive behavioral analyses were performed in Sey/+ mice (i.e., Pax6 mutant heterozygotes) born from in vitro fertilization of sperm taken from young or aged Sey/+ fathers. No body weight changes were found in the four groups, i.e., Sey/+ and wild type (WT) mice born to young or aged father. However, we found important differences in maternal separation-induced ultrasonic vocalizations of Sey/+ mice born from young father and in the level of hyperactivity of Sey/+ mice born from aged fathers in the open-field test, respectively, compared to WT littermates. Phenotypes of anxiety were observed in both genotypes born from aged fathers compared with those born from young fathers. No significant difference was found in social behavior and sensorimotor gating among the four groups. These results indicate that mice with a single genetic risk factor can develop different phenotypes depending on the paternal age. Our study advocates for serious considerations on the role of paternal aging in breeding strategies for animal studies.

Dynamic expression patterns of Pax6 during spermatogenesis in the mouse.

Spermatogenesis is a series of complex processes to generate mature sperm, and various molecules play crucial roles in regulating these processes. Previous studies imply a possibility that a transcriptional factor Pax6, a key player of brain and sensory organ development, could be involved in spermatogenesis, but neither expression nor function of Pax6 in the adult testis has been examined yet. In the present study, we described for the first time Pax6 expression dynamics in the adult mouse testis. Using cell‐type‐specific markers, the expression of Pax6 was detected in 67.0% of promyelocytic leukemia zinc finger (Plzf)‐positive type A spermatogonia. The expression of Pax6 was also observed in p63‐positive spermatocytes and round spermatids. We did not detect any expression of Pax6 in Sox9‐positive Sertoli cells or in elongated spermatids and mature sperm. High‐resolution analyses revealed that Pax6 formed a single dot‐like structure during mid‐phase of the pachytene spermatocyte. This dot‐like structure co‐localized with γH2A.X demarcating XY body, a domain in which X and Y chromosomes are silenced and compartmentalized. These results may suggest a novel role of Pax6 in spermatogenesis.

Risk of Neurodevelopmental Disease by Paternal Aging: A Possible Influence of Epigenetic Alteration in Sperm

Sincethe theory of DOHaD has been thrown in the spotlight, most attention has focused on environmental effects of the uterus on developing embryos/fetuses. However, the ontogenesis traces back to gametogenesis. Compared to oogenesis, spermatogenesis goes through far more cell divisions and is therefore more prone to genetic variation and epigenetic alterations. This article will mainly discuss recent findings about the effects of the advanced paternal age on the next generation, in relation to the onset of psychiatric disorders such as autism spectrum disorder. We would like to advocate for further exploration on the DOHaD theory in a wider view.

Fabp7, a brain specific fatty acid binding protein, regulates proliferation of oligodendrocyte precursor cells

reduced by administration of the intracellular Ca2+ store depletor, thapsigargin or IP3 receptor antagonist, 2-APB. Therefore, these Ca2+ rhythms were not induced by action potential, and mainly due to Ca2+ release from an intracellular Ca2+ store (i.e. endoplasmic reticulum) via IP3 receptor.Activation of some kind of metabotropic receptors induces the Ca2+ release from an intracellular Ca2+ store. It was reported that metabotropic glutamate receptor type 5 (mGluR5) was one of therapeutic targets for Parkinson’s disease. Thus, we investigated effects of mGluR5 on the spontaneous Ca2+ rhythms. Antagonist of mGluR5, MPEP, suppressed the spontaneous Ca2+ rhythms. Thus, mGluR5PLC-IP3 signal cascade might be concerned with the Ca2+ rhythms. This result suggested that mGluR5 might contribute to the information processing in striatum by means of regulating intracellular Ca2+ concentration. Research fund: JST, CREST.

Influence of chronic subcortical ischemia on depressive phenotypes

P3-t05 Pattern separation related activity in dentate gyrus is associated with subjective mood: A functional MRI study Takeshi Fujii 1 , Daisuke N. Saito 1,2, Hisakazu T. Yanaka 1,2, Hirotaka Kosaka 3, Hiroshi Oikawa 1, Hidehiko Okazawa 1 1 Biomedical Imaging Research Center, University of Fukui, Japan 2 Research and Education Program for Life Science, University of Fukui, Fukui, Japan 3 Department of Neuropsychiatry, Faculty of Medical Sciences, University of Fukui, Fukui, Japan