Expression of proliferating cell nuclear antigen (PCNA) in the adult and developing mouse nervous system

11β-Hydroxysteroid dehydrogenase type 2 may mediate the stress-specific effects of cortisol on brain cell proliferation in adult zebrafish (Danio rerio)

Stress-induced increases in cortisol can stimulate or inhibit brain cell proliferation, but the mechanisms behind these opposing effects are unknown. We tested the hypothesis that 11β-hydroxysteroid dehydrogenase type 2 (Hsd11b2), a glucocorticoid-inactivating enzyme expressed in neurogenic regions of the adult zebrafish brain, mitigates cortisol-induced changes to brain cell proliferation, using one of three stress regimes: a single 1 min air exposure (acute stress), two air exposures spaced 24 h apart (repeat acute stress) or social subordination (chronic stress). Plasma cortisol was significantly elevated 15 min after air exposure and recovered within 24 h after acute and repeat acute stress, whereas subordinate fish exhibited significant and sustained elevations relative to dominant fish for 24 h. Following acute stress, brain hsd11b2 transcript abundance was elevated up to 6 h after a single air exposure but was unchanged by repeat acute stress or social subordination. A sustained increase in brain Hsd11b2 protein levels occurred after acute stress, but not after repeat or chronic stress. Following acute and repeat acute stress, brain pcna transcript abundance (a marker of cell proliferation) exhibited a prolonged elevation, but was unaffected by social subordination. Interestingly, the number of telencephalic BrdU+ cells increased in fish after a single air exposure but was unchanged by repeat acute stress. Following acute and repeat acute stress, fish expressed lower brain glucocorticoid and mineralocorticoid receptor (gr and mr) transcript abundance while subordinate fish exhibited no changes. Taken together, these results demonstrate stressor-specific regulation of Hsd11b2 in the zebrafish brain that could modulate rates of cortisol catabolism contributing to observed differences in brain cell proliferation.

Therapeutic validation of MMR-associated genetic modifiers in a human ex vivo model of Huntington disease

The pathological huntingtin (HTT) trinucleotide repeat underlying Huntington disease (HD) continues to expand throughout life. Repeat length correlates both with earlier age at onset (AaO) and faster progression, making slowing its expansion an attractive therapeutic approach. Genome-wide association studies have identified candidate variants associated with altered AaO and progression, with many found in DNA mismatch repair (MMR)-associated genes. We examine whether lowering expression of these genes affects the rate of repeat expansion in human ex vivo models using HD iPSCs and HD iPSC-derived striatal medium spiny neuron-enriched cultures. We have generated a stable CRISPR interference HD iPSC line in which we can specifically and efficiently lower gene expression from a donor carrying over 125 CAG repeats. Lowering expression of each member of the MMR complexes MutS (MSH2, MSH3, and MSH6), MutL (MLH1, PMS1, PMS2, and MLH3), and LIG1 resulted in characteristic MMR deficiencies. Reduced MSH2, MSH3, and MLH1 slowed repeat expansion to the largest degree, while lowering either PMS1, PMS2, or MLH3 slowed it to a lesser degree. These effects were recapitulated in iPSC-derived striatal cultures where MutL factor expression was lowered. CRISPRi-mediated lowering of key MMR factor expression to levels feasibly achievable by current therapeutic approaches was able to effectively slow the expansion of the HTT CAG tract. We highlight members of the MutL family as potential targets to slow pathogenic repeat expansion with the aim to delay onset and progression of HD and potentially other repeat expansion disorders exhibiting somatic instability.

Impaired oligodendrogenesis in the white matter of aged mice following diffuse traumatic brain injury

Senescence is a negative prognostic factor for outcome and recovery following traumatic brain injury (TBI). TBI-induced white matter injury may be partially due to oligodendrocyte demise. We hypothesized that the regenerative capacity of oligodendrocyte precursor cells (OPCs) declines with age. To test this hypothesis, the regenerative capability of OPCs in young [(10 weeks ±2 (SD)] and aged [(62 weeks ±10 (SD)] mice was studied in mice subjected to central fluid percussion injury (cFPI), a TBI model causing widespread white matter injury. Proliferating OPCs were assessed by immunohistochemistry for the proliferating cell nuclear antigen (PCNA) marker and labeled by 5-ethynyl-2'-deoxyuridine (EdU) administered daily through intraperitoneal injections (50 mg/kg) from day 2 to day 6 after cFPI. Proliferating OPCs were quantified in the corpus callosum and external capsule on day 2 and 7 post-injury (dpi). The number of PCNA/Olig2-positive and EdU/Olig2-positive cells were increased at 2dpi (p < .01) and 7dpi (p < .01), respectively, in young mice subjected to cFPI, changes not observed in aged mice. Proliferating Olig2+/Nestin+ cells were less common (p < .05) in the white matter of brain-injured aged mice, without difference in proliferating Olig2+/PDGFRα+ cells, indicating a diminished proliferation of progenitors with different spatial origin. Following TBI, co-staining for EdU/CC1/Olig2 revealed a reduced number of newly generated mature oligodendrocytes in the white matter of aged mice when compared to the young, brain-injured mice (p < .05). We observed an age-related decline of oligodendrogenesis following experimental TBI that may contribute to the worse outcome of elderly patients following TBI.

Calcium imaging of adult olfactory epithelium reveals amines as important odor class in fish

The odor space of aquatic organisms is by necessity quite different from that of air-breathing animals. The recognized odor classes in teleost fish include amino acids, bile acids, reproductive hormones, nucleotides, and a limited number of polyamines. Conversely, a significant portion of the fish olfactory receptor repertoire is composed of trace amine-associated receptors, generally assumed to be responsible for detecting amines. Zebrafish possess over one hundred of these receptors, but the responses of olfactory sensory neurons to amines have not been known so far. Here we examined odor responses of zebrafish olfactory epithelial explants at the cellular level, employing calcium imaging. We report that amines elicit strong responses in olfactory sensory neurons, with a time course characteristically different from that of ATP-responsive (basal) cells. A quantitative analysis of the laminar height distribution shows amine-responsive cells undistinguishable from ciliated neurons positive for olfactory marker protein. This distribution is significantly different from those measured for microvillous neurons positive for transient receptor potential channel 2 and basal cells positive for proliferating cell nuclear antigen. Our results suggest amines as an important odor class for teleost fish.

Bifenthrin induces cell death in bovine mammary epithelial cells via ROS generation, calcium ion homeostasis disruption, and MAPK signaling cascade alteration

Bifenthrin is one of the widely used synthetic pyrethroid insecticides, employed for various purposes worldwide. As lipophilic pyrethroids can easily bind to soil particles, which is why their residues are detected in various environments. Consequently, the toxicity of bifenthrin to non-target organisms can be regarded as an environmental concern. The toxic effects of bifenthrin have been studied in various animal models and cell lines; however, its toxic effects on cattle remain unclear. In particular, gaining insights into the toxic effects of bifenthrin on the mammary lactation system is crucial for the dairy industry. Therefore, we proceeded to investigate the toxic effects of bifenthrin on the bovine mammary epithelial cells (MAC-T cells). We established that bifenthrin inhibited cell proliferation and triggered apoptosis in MAC-T cells. Additionally, bifenthrin induced mitochondrial dysfunction and altered inflammatory gene expression by disrupting mitochondrial membrane potential (MMP) and generating excessive reactive oxygen species (ROS). We also demonstrated that bifenthrin disrupted both cytosolic and mitochondrial calcium ion homeostasis. Furthermore, bifenthrin altered mitogen-activated protein kinase (MAPK) signaling cascades and downregulated casein-related genes. Collectively, we confirmed the multiple toxic effects of bifenthrin on MAC-T cells, which could potentially reduce milk yield and quality.

Vildagliptin restores cognitive function and mitigates hippocampal neuronal apoptosis in cisplatin-induced chemo-brain: Imperative roles of AMPK/Akt/CREB/ BDNF signaling cascades

Cisplatin (CP) is a broad-spectrum antineoplastic agent used to treat many human cancers. Nonetheless, most patients receiving CP suffer from cognitive deficits, a phenomenon termed "chemo-brain". Recently, vildagliptin (Vilda), a DPP-4 inhibitor, has demonstrated promising neuroprotective properties against various neurological diseases. Therefore, the present study aims to investigate the potential neuroprotective properties of Vilda against CP-induced neurotoxicity and elucidate the underlying molecular mechanisms. Chemo-brain was induced in Sprague-Dawley rats by i.p injection of CP at a dose of 5 mg/kg once weekly for four weeks. Vilda was administered daily at a dose (10 mg/kg; P.O) for four weeks. The results revealed that Vilda restored the cognitive function impaired by CP, as assessed by the Morris water maze, Y-maze, and passive avoidance tests. Moreover, Vilda alleviated the CP-induced neurodegeneration, as shown by toluidine blue staining, besides markedly reduced amyloid plaque deposition, as evidenced by Congo red staining. Notably, Vilda boosted cholinergic neurotransmission through the downregulation of the acetylcholinesterase enzyme. In addition, the neuroprotective mechanisms of Vilda include diminishing oxidative stress by reducing MDA levels while raising GSH levels and SOD activity, repressing neuronal apoptosis as shown by elevated Bcl-2 levels together with diminished Bax and caspase-3 expressions, inhibiting neuroinflammation as shown by decreased GFAP expression, and finally boosting hippocampal neurogenesis and survival by upregulating expressions of BDNF and PCNA. These effects were mainly mediated by activating AMPK/Akt/CREB signaling cascades. In summary, Vilda can be considered a promising candidate for guarding against CP-induced chemo-brain and neurodegeneration, thus improving the quality of life of cancer patients.

Pendimethalin exposure induces bovine mammary epithelial cell death through excessive ROS production and alterations in the PI3K and MAPK signaling pathways

Herbicides are chemicals that have been established to have adverse impacts. However, they are still widely used in agriculture. Pendimethalin (PDM) is an herbicide that is widely used in many countries to control annual grasses. The possibility of livestock being exposed to PDM is relatively high, considering the half-life of PDM and its residues in water, soil and crops. However, the toxicity of PDM in cattle, especially in the mammary glands, has not been reported. Therefore, we investigated whether PDM has toxic effects in the mammary epithelial cells (MAC-T) of cattle. MAC-T cells were treated with various doses (0, 2.5, 5 and 10 μM) of PDM. We found that PDM affected cell viability and cell proliferation and causes cell cycle arrest. Furthermore, PDM triggered cell apoptosis, induced excessive ROS production and mitochondrial membrane potential (MMP) loss, and disrupted calcium homeostasis. In addition, PDM altered the activation of proteins associated with the endoplasmic reticulum (ER) stress response and modified PI3K and MAPK signaling cascades. In conclusion, our current study unveiled the mechanism of PDM in MAC-T cells and we suggest that PDM might be harmful to the mammary gland system of cattle, possibly affecting milk production.

Glyphosate, AMPA and glyphosate-based herbicide exposure leads to GFAP, PCNA and caspase-3 increased immunoreactive area on male offspring rat hypothalamus

Glyphosate, aminomethylphosphonic acid (AMPA), and glyphosate-based herbicides altered the neuroendocrine axis, the content of brain neurotransmitters, and behavior in experimental animal models. Glyphosate alone, AMPA or Roundup® Active were administered to postpartum female rats, from P0 to P10, and their water consumption was measured daily. The immunoreactivity for glial fibrillary acidic protein (GFAP), proliferating cell nuclear antigen (PCNA) and caspase-3 was measured in the anterior, medial preoptic, periventricular, supraoptic and lateroanterior hypothalamic nuclei of P0-P10 male pups after exposure, via lactation, to these xenobiotics. Puppies exposed to glyphosate had a moderate level of GFAP with no overlapping astrocyte processes, but this overlapping was observed after Roundup® Active or AMPA exposure. After being exposed to Roundup® Active or AMPA, PCNA-positive cells with strong immunoreactivity were found in some hypothalamic nuclei. Cells containing caspase-3 were found in all hypothalamic nuclei studied, but the labeling was stronger after Roundup® Active or AMPA exposure. Xenobiotics significantly increased the immunoreactivity area for all of the markers studied in the majority of cases (p<0.05). AMPA or Roundup® Active treated animals had a greater area of PCNA immunoreactivity than control or glyphosate alone treated animals (p<0.05). The effects observed after xenobiotic exposure were not due to increased water intake. The increased immunoreactivity areas observed for the markers studied suggest that xenobiotics induced a neuro-inflammatory response, implying increased cell proliferation, glial activation, and induction of apoptotic pathways. The findings also show that glyphosate metabolites/adjuvants and/or surfactants present in glyphosate commercial formulations had a greater effect than glyphosate alone. In summary, glyphosate, AMPA, and glyphosate-based herbicides altered GFAP, caspase-3, and PCNA expression in the rat hypothalamus, altering the neuroendocrine axis.

Spatiotemporal mapping of gene expression landscapes and developmental trajectories during zebrafish embryogenesis

A major challenge in understanding vertebrate embryogenesis is the lack of topographical transcriptomic information that can help correlate microenvironmental cues within the hierarchy of cell-fate decisions. Here, we employed Stereo-seq to profile 91 zebrafish embryo sections covering six critical time points during the first 24 h of development, obtaining a total of 152,977 spots at a resolution of 10 × 10 × 15 μm³ (close to cellular size) with spatial coordinates. Meanwhile, we identified spatial modules and co-varying genes for specific tissue organizations. By performing the integrated analysis of the Stereo-seq and scRNA-seq data from each time point, we reconstructed the spatially resolved developmental trajectories of cell-fate transitions and molecular changes during zebrafish embryogenesis. We further investigated the spatial distribution of ligand-receptor pairs and identified potentially important interactions during zebrafish embryo development. Our study constitutes a fundamental reference for further studies aiming to understand vertebrate development.

Therapeutic role of adipose tissue-derived stem cells versus microvesicles in a rat model of cerebellar injury

Monosodium glutamate (MSG) is a controversial food additive reported to cause negative effects on public health. Adipose stem cells (ASCs) and their derived vesicles (MVs) represent a promising cure for human diseases. This work was planned to compare the therapeutic effects of adipose stem cells and microvesicles in MSG-induced cerebellar damage. Forty adult healthy male Wister rats were equally divided into four groups: Group I (control group), group II (MSG-treated), group III (MSG/ASCs-treated), and group IV (MSG/MVs-treated). Motor behaviour of rats was assessed. Characterization of ASCs and MVs was done by flow cytometry. The cerebellum was processed for light and electron microscopic studies, and immunohistochemical localization of PCNA and GFAP. Morphometry was done for the number of Purkinje cells in H&E-stained sections, area per cent of GFAP immune reactivity and number of positive PCNA cells. Our results showed MSG-induced deterioration in the motor part. Moreover, MSG increases oxidant and apoptotic with decreases of antioxidant biomarkers. Structural changes in the cerebellar cortex as degeneration of nerve cells and gliosis were detected. There were also a decrease in the number of Purkinje cells, an increase in the area per cent of GFAP immune reactivity and a decrease in the number of positive PCNA cells, as compared to the control. Rats treated with ASCs showed marked functional and structural improvement in comparison with MV-treated rats. Thus, both ASCs and MVs had therapeutic potential for MSG-induced cerebellar damage with better results in case of ASCs.

Reviving through human hippocampal newborn neurons

Recent contradictory data has renewed discussion regarding the existence of adult hippocampal neurogenesis (AHN) in humans, i.e., the continued production of new neurons in the brain after birth. The present review revisits the debate of AHN in humans from a historical point of view in the face of contradictory evidence, analyzing the methods employed to investigate this phenomenon. Thus, to date, of the 57 studies performed in humans that we reviewed, 84% (48) concluded in favor of the presence of newborn neurons in the human adult hippocampus. Besides quality of the tissue (such as postmortem intervals below 26hours as well as tissue conservation and fixation), considerations for assessing and quantify AHN in the human brain require the use of stereology and toxicological analyses of clinical data of the patient.

An Ancient Adenosine Receptor Gains Olfactory Function in Bony Vertebrates

Nucleotides are an important class of odorants for aquatic vertebrates such as frogs and fishes, but also have manifold signaling roles in other cellular processes. Recently, an adenosine receptor believed to belong to the adora2 clade has been identified as an olfactory receptor in zebrafish. Here, we set out to elucidate the evolutionary history of both this gene and its olfactory function. We have performed a thorough phylogenetic study in vertebrates, chordates and their sister group, ambulacraria, and show that the origin of the zebrafish olfactory receptor gene can be traced back to the most recent common ancestor of all three groups as a segregate sister clade (adorb) to the adora gene family. Eel, carp, and clawed frog all express adorb in a sparse and distributed pattern within their olfactory epithelium very similar to the pattern observed for zebrafish that is, consistent with a function as olfactory receptor. In sharp contrast, lamprey adorb-expressing cells are absent from the sensory region of the lamprey nose, but form a contiguous domain directly adjacent to the sensory region. Double-labeling experiments confirmed the expression of lamprey adorb in nonneuronal cells and are consistent with an expression in neuronal progenitor cells. Thus, adorb may have undergone a switch of function in the jawed lineage of vertebrates towards a role as olfactory receptor.

Effect of prenatal exposure of green tea extract on the developing central nervous system of rat fetuses; histological, immune-histochemical and ultrastructural studies

Although, several health benefits were associated with green tea, these effects may be beneficial up to a certain dose. Higher doses of green tea may cause several adverse effects. So, there is a need to test the potential negative effects of green tea during pregnancy. This study was designated to evaluate the effect of prenatal exposure of green tea extract on the development of the central nervous system of 20-day old rat fetuses. The pregnant rats were divided into 4 groups; the control group (received distal water) and the other 3 groups received green tea extract at different doses (200, 600 & 1000 mg/kg/day, respectively) from the 6th to 15th day of gestation i.e., during the organogenesis phase of development. Cerebral cortex, cerebellum and spinal cord specimens were subjected to histological, immunohistochemical and ultrastructure investigations. The body weight of both mothers and fetuses was significantly decreased in the groups that received 600 and 1000 mg green tea extract. Also, the neuronal tissues displayed various signs of degeneration which were evident with the 600 and 1000 mg doses. Green tea extract also increases the glial fibrillary acidic protein (GFAP) and decreases the proliferating cell nuclear antigen (PCNA) which were directly proportional with increasing the dose. Administration of green tea extract during rat organogenesis period induced various histological, immunohistochemical and ultrastructural degenerative changes in the cerebral cortex, cerebellum and spinal cord of 20-day old rat fetuses. These deleterious changes were directly proportional to increasing the green tea extract dose. Thus, it should be stressed that the effect of green tea is dose-dependent and therefore it can be either beneficial or adverse.

Contribution of Human Trophoblast Progenitor Cells to Neurogenesis in Rat Focal Cerebral Ischemia Model

OBJECTIVE

: A decrease in the blood flow below a current level in the brain results in ischemia. Studies demonstrated that human trophoblast progenitor cells (hTPCs) contribute to the treatment of many diseases. Therefore, hTPCs might be a promising source to repair ischemia in cerebral ischemia models. For this purpose, we evaluated the expression of many neurogenesis markers by performing hTPC transplantation after focal cerebral ischemia in rats.

METHODS

: hTPCs, isolated from the term placentae, were characterized by immunofluorescent staining and differentiated into neuron-like cells. Differentiation was confirmed with immunostaining of GFAP and NeuN proteins. Cerebral ischemia models were generated in rats via middle cerebral artery occlusion and, after 24 hours, hTPCs were injected via the tail vein. Animals were sacrificed on day 3 or day 11. Immunohistochemical analysis was performed with proteins associated with neurogenesis and neuronal development, such as DLX2, DLX5, LHX6, NGN1, and NGN2, Olig1, Olig2, and PDGFRα.

RESULTS

: According to our results, hTPCs may alleviate ischemic damage in the brain and contribute to the neurogenesis after ischemia.

CONCLUSIONS

: Based on our findings, this topic should be further investigated as the hTPC-based therapies may be a reliable source that can be used in the treatment of stroke and ischemia.

Ablation of Vti1a/1b Triggers Neural Progenitor Pool Depletion and Cortical Layer 5 Malformation in Late-embryonic Mouse Cortex

Cortical morphogenesis entails several neurobiological events, including proliferation and differentiation of progenitors, migration of neuroblasts, and neuronal maturation leading to functional neural circuitry. These neurodevelopmental processes are delicately regulated by many factors. Endosomal SNAREs have emerged as formidable modulators of neuronal growth, aside their well-known function in membrane/vesicular trafficking. However, our understanding of their influence on cortex formation is limited. Here, we report that the SNAREs Vti1a and Vti1b (Vti1a/1b) are critical for proper cortical development. Following null mutation of Vti1a/1b in mouse, the late-embryonic mutant cortex appeared dysgenic, and the cortical progenitors therein were depleted beyond normal. Notably, cortical layer 5 (L5) is distinctively disorganized in the absence of Vti1a/1b. The latter defect, coupled with an overt apoptosis of Ctip2-expressing L5 neurons, likely contributed to the substantial loss of corticospinal and callosal projections in the Vti1a/1b-deficient mouse brain. These findings suggest that Vti1a/1b serve key neurodevelopmental functions during cortical histogenesis, which when mechanistically elucidated, can lend clarity to how endosomal SNAREs regulate brain development, or how their dysfunction may have implications for neurological disorders.

Early life stress decreases cell proliferation and the number of putative adult neural stem cells in the adult hypothalamus

Stress is a potent environmental factor that can confer potent and enduring effects on brain structure and function. Exposure to stress during early life (ELS) has been linked to a wide range of consequences later in life. In particular, ELS exerts lasting effects on neurogenesis in the adult hippocampus, suggesting that ELS is a significant regulator of adult neural stem cell numbers and function. Here, we investigated the effect of ELS on cell proliferation and the numbers of neural stem/precursor cells in another neurogenic region: the hypothalamus of adult mice. We show that ELS has long-term suppressive effects on cell proliferation in the hypothalamic parenchyma and reduces the numbers of putative hypothalamic neural stem/precursor cells at 4 months of age. Specifically, ELS reduced the number of PCNA + cells present in hypothalamic areas surrounding the 3rd ventricle with a specific reduction in the proliferation of Sox2+/Nestin-GFP + putative stem cells present in the median eminence at the base of the 3rd ventricle. Furthermore, ELS reduced the total numbers of β-tanycytes lining the ventral 3rd ventricle, without affecting α-tanycyte numbers in more dorsal areas. These results are the first to indicate that ELS significantly reduces proliferation and β-tanycyte numbers in the adult hypothalamus, and may have (patho)physiological consequences for metabolic regulation or other hypothalamic functions in which β-tanycytes are involved.

Lengthening Neurogenic Period during Neocortical Development Causes a Hallmark of Neocortex Expansion

A hallmark of the evolutionary expansion of the neocortex is a specific increase in the number of neurons generated for the upper neocortical layers during development. The cause underlying this increase is unknown. Here, we show that lengthening the neurogenic period during neocortical development is sufficient to specifically increase upper-layer neuron generation. Thus, embryos of mouse strains with longer gestation exhibited a longer neurogenic period and generated more upper-layer, but not more deep-layer, neurons than embryos with shorter gestation. Accordingly, long-gestation embryos showed a greater abundance of neurogenic progenitors in the subventricular zone than short-gestation embryos at late stages of cortical neurogenesis. Analysis of a mouse-rat chimeric embryo, developing inside a rat mother, pointed to factors in the rat environment that influenced the upper-layer neuron generation by the mouse progenitors. Exploring a potential maternal source of such factors, short-gestation strain mouse embryos transferred to long-gestation strain mothers exhibited an increase in the length of the neurogenic period and upper-layer neuron generation. The opposite was the case for long-gestation strain mouse embryos transferred to short-gestation strain mothers, indicating a dominant maternal influence on the length of the neurogenic period and hence upper-layer neuron generation. In summary, our study uncovers a hitherto unknown link between embryonic cortical neurogenesis and the maternal gestational environment and provides experimental evidence that lengthening the neurogenic period during neocortical development underlies a key aspect of neocortical expansion.

Mitotic activity, modulation of DNA processing, and purinergic signalling in the adult rat auditory brainstem following sensory deafferentation

A complex scenario of cellular network reorganization is caused by unilateral sensory deafferentation (USD) in the adult rat central auditory system. We asked whether this plasticity response involves mitosis. Immunohistochemistry was applied to brainstem sections for the detection and localization of mitotic markers Ki67 and PCNA, the growth-associated protein Gap43 and purine receptor P2X4. Fluorescent double staining was done for Ki67:PCNA and for both of them with HuC/HuD (neurons), S100 (astrocytes), Iba1 (microglia) and P2X4. Inquiring 1-7 days after USD, we found Ki67 expression to be changed in cellular profiles of cochlear nucleus (CN) with a significant increase in number by 1-3 days, followed by reset to control level within 1 week. USD-induced mitosis exclusively occurred in microglia and was absent elsewhere in the auditory brainstem. PCNA staining of small cellular profiles increased similarly but remained elevated. PCNA staining intensity also changed in CN, superior olive and inferior colliculus in neuronal nuclei, suggesting shifts in DNA processing. No apoptotic cell death was detected in any region of the adult auditory brainstem after USD. A comparison of anterograde and retrograde effects of nerve damage revealed proliferating microglia expressing P2X4 receptors in CN upon USD, but not in the facial nucleus after facial nerve transection. In conclusion, the deafferentation model studied here permits insight into the capacity of the adult mammalian brain to invoke mitosis among glia cells, adjustment of gene processing in neurons and purinergic signalling between them, jointly accounting for a multilayered neuro- and glioplastic response.

Resistance-exercise training ameliorates LPS-induced cognitive impairment concurrent with molecular signaling changes in the rat dentate gyrus

Effective treatments preventing brain neuroinflammatory diseases are lacking. Resistance-exercise training (RT) ameliorates mild cognitive impairment (MCI), a forerunner to neuroinflammatory diseases. However, few studies have addressed the molecular basis by which RT abates MCI. Thus experiments were performed to identify some molecular changes occurring in response to RT in young, female Wistar rats. To induce MCI, intraventricular lipopolysaccharide (LPS) injections were used to increase dentate gyrus inflammation, reflected by significantly increased TNF-α (~400%) and IL-1β (~1,500%) mRNA (P < 0.0001) after 6 wk. Five days after LPS injections, half of LPS-injected rats performed RT by ladder climbing for 6 wk, 3 days/wk, whereas half remained without ladders. RT for 6 wk increased lean body mass percentage (P < 0.05), individual muscle masses (gastrocnemius and tibialis anterior) (P < 0.05), and maximum lifting capacity (P < 0.001). The RT group, compared with sedentary controls, had 1) ameliorated spatial learning deficits (P < 0.05), 2) increased dentate gyrus phosphorylation of IGF-1R, protein kinase B, and GSK-3β proteins (P < 0.05), components of downstream IGF-1 signaling, and 3) increased dentate gyrus synaptic plasticity marker synapsin protein (P < 0.05). Two follow-up experiments (without LPS) characterized dentate gyrus signaling during short-term RT. Twenty-four hours following the third workout in a 1-wk training duration, phosphorylation of ERK1/2 and GSK-3β proteins, as well as proliferation marker protein, PCNA, were significantly increased (P < 0.05). Similar changes did not occur in a separate group of rats following a single RT workout. Taken together, these data indicate that RT ameliorates LPS-induced MCI after RT, possibly mediated by increased IGF-1 signaling pathway components within the dentate gyrus. NEW & NOTEWORTHY The data suggest that resistance-exercise training restores cognitive deficits induced by lipopolysaccharides and can activate associated IGF-1 signaling in the dentate gyrus. Our data show, for the first time, that as few as three resistance-exercise workouts (spread over 1 wk) can activate IGF-1 downstream signaling and increase proliferation marker PCNA in the dentate gyrus.

Antidepressant and pro-neurogenic effects of agmatine in a mouse model of stress induced by chronic exposure to corticosterone

Agmatine is an endogenous neuromodulator that has been shown to have beneficial effects in the central nervous system, including antidepressant-like effects in animals. In this study, we investigated the ability of agmatine (0.1mg/kg, p.o.) and the conventional antidepressant fluoxetine (10mg/kg, p.o.) to reverse the behavioral effects and morphological alterations in the hippocampus of mice exposed to chronic corticosterone (20mg/kg, p.o.) treatment for a period of 21days as a model of stress and depressive-like behaviors. Chronic corticosterone treatment increased the immobility time in the tail suspension test (TST), but did not cause anhedonic-like and anxiety-related behaviors, as assessed with the splash test and the open field test (OFT), respectively. Of note, the depressive-like behaviors induced by corticosterone were accompanied by a decrease in hippocampal cell proliferation, although no changes in hippocampal neuronal differentiation were observed. Our findings provide evidence that, similarly to fluoxetine, agmatine was able to reverse the corticosterone-induced depressive-like behaviors in the TST as well as the deficits in hippocampal cell proliferation. Additionally, fluoxetine but not agmatine, increased hippocampal differentiation. Agmatine, similar to fluoxetine, was capable of increasing both dendritic arborization and length in the entire dentate hippocampus, an effect more evident in the ventral portion of the hippocampus, as assessed with the modified Sholl analysis. Altogether, our results suggest that the increase in hippocampal proliferation induced by agmatine may contribute, at least in part, to the antidepressant-like response of this compound in this mouse model of stress induced by chronic exposure to corticosterone.

Proliferating cell nuclear antigen in neutrophil fate

The life span of a neutrophil is a tightly regulated process as extended survival is beneficial for pathogen elimination and cell death necessary to prevent cytotoxic content release from activated neutrophils at the inflammatory site. Therefore, the control between survival and death must be a dynamic process. We have previously described that proliferating cell nuclear antigen (PCNA) which is known as a nuclear protein pivotal in DNA synthesis, is a key element in controlling neutrophil survival through its association with procaspases. Contrary to the dogma which asserted that PCNA has a strictly nuclear function, in mature neutrophils, PCNA is present exclusively within the cytosol due to its nuclear export at the end of the granulocytic differentiation. More recent studies are consistent with the notion that the cytosolic scaffold of PCNA is aimed at modulating neutrophil fate rather than simply preventing death. Ultimately, targeting neutrophil survival might have important applications not just in the field of immunology and inflammation, but also in hematology and transfusion. The neutrophil emerges as a unique and powerful cellular model to unravel the basic mechanisms governing the cell cycle-independent functions of PCNA and should be considered as a leader of the pack.

Human adult neurogenesis across the ages: An immunohistochemical study

AIMS

Neurogenesis in the postnatal human brain occurs in two neurogenic niches; the subventricular zone (SVZ) in the wall of the lateral ventricles and the subgranular zone (SGZ) of the hippocampus. The extent to which this physiological process continues into adulthood is an area of ongoing research. This study aimed to characterize markers of cell proliferation and assess the efficacy of antibodies used to identify neurogenesis in both neurogenic niches of the human brain.

METHODS

Cell proliferation and neurogenesis were simultaneously examined in the SVZ and SGZ of 23 individuals aged 0.2-59 years, using immunohistochemistry and immunofluorescence in combination with unbiased stereology.

RESULTS

There was a marked decline in proliferating cells in both neurogenic niches in early infancy with levels reaching those seen in the adjacent parenchyma by 4 and 1 year of age, in the SVZ and SGZ, respectively. Furthermore, the phenotype of these proliferating cells in both niches changed with age. In infants, proliferating cells co-expressed neural progenitor (epidermal growth factor receptor), immature neuronal (doublecortin and beta III tubulin) and oligodendrocytic (Olig2) markers. However, after 3 years of age, microglia were the only proliferating cells found in either niche or in the adjacent parenchyma.

CONCLUSIONS

This study demonstrates a marked decline in neurogenesis in both neurogenic niches in early childhood, and that the sparse proliferating cells in the adult brain are largely microglia.

Different dose-dependent effects of ebselen in sciatic nerve ischemia-reperfusion injury in rats

Ebselen is an organoselenium compound which has strong antioxidant and anti-inflammatory effects. We investigated the neuroprotective role of ebselen pretreatment in rats with experimental sciatic nerve ischemia-reperfusion (I/R) injury. Adult male Sprague Dawley rats were divided into four groups (N = 7 in each group). Before sciatic nerve I/R was induced, ebselen was injected intraperitoneally at doses of 15 and 30 mg/kg. After a 2 h ischemia and a 3 h reperfusion period, sciatic nerve tissues were excised. Tissue levels of malondialdehyde (MDA) and nitric oxide (NO), and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were measured. Sciatic nerve tissues were also examined histopathologically. The 15 mg/kg dose of ebselen reduced sciatic nerve damage and apoptosis (p<0.01), levels of MDA, NO, and inducible nitric oxide synthase (iNOS) positive cells (p<0.01, p<0.05, respectively), and increased SOD, GPx, and CAT activities (p<0.001, p<0.01, p<0.05, respectively) compared with the I/R group that did not receive ebselen. Conversely, the 30 mg/kg dose of ebselen increased sciatic nerve damage, apoptosis, iNOS positive cells (p<0.01, p<0.05, p<0.001) and MDA and NO levels (p<0.05, p<0.01) and decreased SOD, GPx, and CAT activities (p<0.05) compared with the sham group. The results of this study suggest that ebselen may cause different effects depending on the dose employed. Ebselen may be protective against sciatic nerve I/R injury via antioxidant and antiapoptotic activities at a 15 mg/kg dose, conversely higher doses may cause detrimental effects.

Localization of diacylglycerol lipase alpha and monoacylglycerol lipase during postnatal development of the rat retina

In recent decades, there has been increased interest in the physiological roles of the endocannabinoid (eCB) system and its receptors, the cannabinoid receptor types 1 (CB1R) and 2 (CB2R). Exposure to cannabinoids during development results in neurofunctional alterations, which implies that the eCB system is involved in the developmental processes of the brain. Because of their lipophilic nature, eCBs are synthesized on demand and are not stored in vesicles. Consequently, the enzymes responsible for their synthesis and degradation are key regulators of their physiological actions. Therefore, knowing the localization of these enzymes during development is crucial for a better understanding of the role played by eCBs during the formation of the central nervous system. In this study, we investigated the developmental protein localization of the synthesizing and catabolic enzymes of the principal eCB, 2-arachidonoylglycerol (2-AG) in the retinas of young and adult rats. The distribution of the enzymes responsible for the synthesis (DAGLα) and the degradation (MAGL) of 2-AG was determined for every retinal cell type from birth to adulthood. Our results indicate that DAGLα is present early in postnatal development. It is highly expressed in photoreceptor, horizontal, amacrine, and ganglion cells. MAGL appears later during the development of the retina and its presence is limited to amacrine and Müller cells. Overall, these results suggest that 2-AG is strongly present in early retinal development and might be involved in the regulation of the structural and functional maturation of the retina.

Deletion of the NMDA receptor GluN2A subunit significantly decreases dendritic growth in maturing dentate granule neurons

It is known that NMDA receptors can modulate adult hippocampal neurogenesis, but the contribution of specific regulatory GluN2 subunits has been difficult to determine. Here we demonstrate that mice lacking GluN2A (formerly NR2A) do not show altered cell proliferation or neuronal differentiation, but present significant changes in neuronal morphology in dentate granule cells. Specifically, GluN2A deletion significantly decreased total dendritic length and dendritic complexity in DG neurons located in the inner granular zone. Furthermore, the absence of GluN2A also resulted in a localized increase in spine density in the middle molecular layer, a region innervated by the medial perforant path. Interestingly, alterations in dendritic morphology and spine density were never seen in dentate granule cells located in the outer granular zone, a region that has been hypothesized to contain older, more mature, neurons. These results indicate that although the GluN2A subunit is not critical for the cell proliferation and differentiation stages of the neurogenic process, it does appear to play a role in establishing synaptic and dendritic morphology in maturing dentate granule cells localized in the inner granular zone.

Development of barcode and proteome profiling of glioblastoma

High grade glioma (glioblastoma) is the most common brain tumor. Its malignancy makes it the fourth biggest cause of cancer death. In our experiments we used several glioblastoma cell lines generated in our laboratory to obtain proteomics information specific for this disease. This study starts our developing the complete 2DE map of glioblastoma proteins. 2DE separation with following imaging, immunochemistry, spot picking, and mass-spectrometry allowed us detecting and identifying more than 100 proteins. Several of them have prominent differences in their level between norm and cancer. Among them are alpha-enolase (ENOA_HUMAN), pyruvate kinase isozymes M1/M2 (KPYM_HUMAN), cofilin 1 (COF1_HUMAN), translationally-controlled tumor protein TCTP_HUMAN, annexin 1 (ANXA1_HUMAN), PCNA (PCNA_HUMAN), p53 (TP53_HUMAN) and others. Most interesting results were obtained with protein p53. In all glioblastoma cell lines, its level was dramatically up regulated and enriched by multiple additional isoforms. This distribution is well correlated with presence of these proteins inside of cells themselves. At this initial step we suggest the panel of specific brain tumor markers (signature) to help creating noninvasive techniques to diagnose disease. These preliminary data point to these proteins as promising markers of glioblastoma.

A single-day treatment with mifepristone is sufficient to normalize chronic glucocorticoid induced suppression of hippocampal cell proliferation

Background

Chronic stress or prolonged administration of glucocorticoids suppresses proliferation and/or survival of newborn cells in adult rat dentate gyrus. Earlier we showed that administration of the glucocorticoid receptor antagonist mifepristone during the final 4 days of a 21 days period of corticosterone treatment fully normalized the number of newborn cells. Here we aimed to better understand how mifepristone achieves this effect and questioned whether an even shorter (single day) mifepristone treatment (instead of 4 days) also suffices to normalize neurogenesis.

Methods

We investigated various steps of the neurogenic process, using the immunohistochemical markers BrdU, doublecortin, proliferating cell nuclear antigen as well as glial fibrillary acidic protein, after 17 or 21 days of corticosterone (versus vehicle) treatment.

Results

Corticosterone primarily attenuates the proliferation of cells which subsequently develop into neurons; this is fully reversed by mifepristone. Surprisingly, the corticosteroid effects on neurogenesis can even be fully re-set by a single-day treatment with mifepristone (on day 18), despite the continued corticosterone exposure on subsequent days.

Conclusions

Our results emphasize that studies into the therapeutical efficacy of new antidepressants, especially those targeting HPA-activity or the glucocorticoid receptor, should explore the possibility to reduce treatment duration.

Fluoxetine rescues impaired hippocampal neurogenesis in a transgenic A53T synuclein mouse model

The accumulation of alpha-synuclein in Lewy bodies and Lewy neurites of different neuronal populations is one of the neuropathological hallmarks in Parkinson disease (PD). Overexpression of human wildtype or mutant alpha-synuclein affects the generation of new neurons in the adult dentate gyrus (DG) of the hippocampus in models of PD. Hippocampal dysfunction with reduced neurogenesis plays an important role in the pathogenesis of depression, an important non-motor symptom in PD. Moreover, effective antidepressant treatment is still an unmet need in PD. The present study explored if impaired hippocampal neurogenesis in the A53T transgenic animal model of PD may be restored by chronic oral application of the selective serotonin reuptake inhibitor (SSRI) fluoxetine. First, we determined the expression pattern of transgenic mutant A53T synuclein in developing DG neurons and showed early expression of the transgene linked to a severely impaired neurogenesis. After chronic fluoxetine treatment we observed an increased adult neurogenesis in the hippocampus of more than threefold in treated A53T mice compared with controls. The pro-neurogenic effect of chronic fluoxetine application is predominantly related to an increased proliferation of neural precursor cells in the DG, and to a lesser extent by induction of differentiation into mature neurons. Analysis of the underlying mechanisms revealed an induction of brain-derived and glial cell-derived neurotrophic factor levels as a result of fluoxetine treatment. This study underlines the large potential of SSRI-dependent mechanisms to stimulate adult hippocampal neurogenesis in alpha-synuclein models and may lead to novel means to improve neuropsychiatric symptoms in PD.

Absence of the calcium-binding protein calretinin, not of calbindin D-28k, causes a permanent impairment of murine adult hippocampal neurogenesis

Calretinin (CR) and calbindin D-28k (CB) are cytosolic EF-hand Ca(2+)-binding proteins and function as Ca(2+) buffers affecting the spatiotemporal aspects of Ca(2+) transients and possibly also as Ca(2+) sensors modulating signaling cascades. In the adult hippocampal circuitry, CR and CB are expressed in specific principal neurons and subsets of interneurons. In addition, CR is transiently expressed within the neurogenic dentate gyrus (DG) niche. CR and CB expression during adult neurogenesis mark critical transition stages, onset of differentiation for CR, and the switch to adult-like connectivity for CB. Absence of either protein during these stages in null-mutant mice may have functional consequences and contribute to some aspects of the identified phenotypes. We report the impact of CR- and CB-deficiency on the proliferation and differentiation of progenitor cells within the subgranular zone (SGZ) neurogenic niche of the DG. Effects were evaluated (1) two and four weeks postnatally, during the transition period of the proliferative matrix to the adult state, and (2) in adult animals (3 months) to trace possible permanent changes in adult neurogenesis. The absence of CB from differentiated DG granule cells has no retrograde effect on the proliferative activity of progenitor cells, nor affects survival or migration/differentiation of newborn neurons in the adult DG including the SGZ. On the contrary, lack of CR from immature early postmitotic granule cells causes an early loss in proliferative capacity of the SGZ that is maintained into adult age, when it has a further impact on the migration/survival of newborn granule cells. The transient CR expression at the onset of adult neurogenesis differentiation may thus have two functions: (1) to serve as a self-maintenance signal for the pool of cells at the same stage of neurogenesis contributing to their survival/differentiation, and (2) it may contribute to retrograde signaling required for maintenance of the progenitor pool.

Fatty acid amide hydrolase expression during retinal postnatal development in rats

The endocannabinoid (eCB) system is thought to participate in developmental processes in the CNS. The rodent retina represents a valuable model to study CNS development because it contains well-identified cell types with established developmental timelines. The distribution of cannabinoid receptor type 1 (CB1R) was recently revealed in the developing retina; however, the expression patterns of other elements of this system remain unknown. In this study, we investigated the expression pattern of the degradative enzyme fatty acid amide hydrolase (FAAH), a key regulator of the eCB system, in the rat retina during postnatal development. To identify the cells expressing the enzyme, co-stainings were carried out for FAAH and retinal cell type markers. FAAH was expressed at postnatal day (P) 1 in ganglion and cholinergic amacrine cells. In the course of development, it appeared in cones, horizontal, and bipolar cells. For most cell types (horizontal, cholinergic amacrine cells, and cone bipolar cells), FAAH was transiently expressed, suggesting an important redistribution of the enzyme during postnatal development and thus a potential role of the eCB system in developmental processes. Our results also indicated that, in the adult retina, FAAH is expressed in cones, rod bipolar cells, and some retinal ganglion cells. The presence of FAAH in adult animals supports the hypothesis that the eCB system is involved in retinal functions. Overall these results indicate that, as shown in other structures of the brain, the eCB system could play an instrumental role in the development and function of the retina.

New ependymal cells are born postnatally in two discrete regions of the mouse brain and support ventricular enlargement in hydrocephalus

A heterogeneous population of ependymal cells lines the brain ventricles. The evidence about the origin and birth dates of these cell populations is scarce. Furthermore, the possibility that mature ependymal cells are born (ependymogenesis) or self-renewed (ependymal proliferation) postnatally is controversial. The present study was designed to investigate both phenomena in wild-type (wt) and hydrocephalic α-SNAP mutant (hyh) mice at different postnatal stages. In wt mice, proliferating cells in the ventricular zone (VZ) were only found in two distinct regions: the dorsal walls of the third ventricle and Sylvian aqueduct (SA). Most proliferating cells were monociliated and nestin+, likely corresponding to radial glial cells. Postnatal cumulative BrdU-labeling showed that most daughter cells remained in the VZ of both regions and they lost nestin-immunoreactivity. Furthermore, some labeled cells became multiciliated and GLUT-1+, indicating they were ependymal cells born postnatally. Postnatal pulse BrdU-labeling and Ki-67 immunostaining further demonstrated the presence of cycling multiciliated ependymal cells. In hydrocephalic mutants, the dorsal walls of the third ventricle and SA expanded enormously and showed neither ependymal disruption nor ventriculostomies. This phenomenon was sustained by an increased ependymogenesis. Consequently, in addition to the physical and geometrical mechanisms traditionally explaining ventricular enlargement in fetal-onset hydrocephalus, we propose that postnatal ependymogenesis could also play a role. Furthermore, as generation of new ependymal cells during postnatal stages was observed in distinct regions of the ventricular walls, such as the roof of the third ventricle, it may be a key mechanism involved in the development of human type 1 interhemispheric cysts.

Neural stem and progenitor cells shorten S-phase on commitment to neuron production

During mammalian cerebral cortex development, the G1-phase of the cell cycle is known to lengthen, but it has been unclear which neural stem and progenitor cells are affected. In this paper, we develop a novel approach to determine cell-cycle parameters in specific classes of neural stem and progenitor cells, identified by molecular markers rather than location. We found that G1 lengthening was associated with the transition from stem cell-like apical progenitors to fate-restricted basal (intermediate) progenitors. Unexpectedly, expanding apical and basal progenitors exhibit a substantially longer S-phase than apical and basal progenitors committed to neuron production. Comparative genome-wide gene expression analysis of expanding versus committed progenitor cells revealed changes in key factors of cell-cycle regulation, DNA replication and repair and chromatin remodelling. Our findings suggest that expanding neural stem and progenitor cells invest more time during S-phase into quality control of replicated DNA than those committed to neuron production.

During neurogenesis, neural stem and progenitor cells can either proliferate or produce neurons. Here, the authors show that proliferating neural stem and progenitor cells have a longer S-phase portion of the cell cycle than cells committed to neuron production, suggesting that this may enable faithful DNA replication.

Cell proliferation and apoptosis in the olfactory epithelium of the shark Scyliorhinus canicula

To date, no study has been published on cell renewal in the olfactory epithelium of Chondrichthyes. Our work aimed at detecting proliferating cells (by Proliferating Cell Nuclear Antigen - PCNA immunohistochemistry) and apoptotic cells (by terminal uridine deoxynucleotidyl transferase nick end labeling method) in the olfactory epithelium of the shark Scyliorhinus canicula. PCNA immunoreactivity and mitotic figures were localized almost exclusively at the basal and apical thirds of the epithelial thickness. Double immunofluorescence for PCNA and OMP (a marker of mature olfactory neurons) showed that PCNA immunoreactivity is lacking in mature olfactory neurons, with the exception of crypt neurons. Crypt neurons, a cell type peculiar to fish, often showed PCNA immunoreactivity in the nucleus and may be involved in repair processes. The role of PCNA in mature crypt neurons requires further investigation to be clarified. Apoptosis was observed in sensory neurons and in basal cells. Our data highlight the presence of cell proliferation at different levels within the epithelium and the occurrence of apoptosis in both mature and proliferating cells.

Immunohistochemical evaluation of Ki-67, PCNA and MCM2 proteins proliferation index (PI) in advanced gastric cancer

The current study objective was to assess the proliferation indices (PI) of Ki-67, PCNA and MCM2 proteins in advanced gastric cancer and in metastatic lymph node in correlation with certain clinicopathological features and with postoperative survival of patients. The study was conducted in a group of 100 patients with advanced gastric cancers. Involvement of local lymph nodes was present in 36 cases. Immunohistochemical investigations were carried out using monoclonal antibodies against Ki-67 (DAKO), PCNA (DAKO) and polyclonal antibody to MCM2 (Santa Cruz Biotechnology). Visualization of the antigen/antibody complex was performed using LSAB technique (biotin-streptavidin-peroxidase) followed by application of chromogene DAB (DAKO). Statistical analysis revealed no correlations of Ki-67, PCNA and MCM2 PI in tumour tissue or metastatic lymph node with patients' age and gender, tumour location, histological grade, macroscopic type according to Bormann's classification and histological grading by Lauren's and Goseki's classifications. Moreover, no correlation was observed of Ki-67 and MCM2 PI in tumour tissue with histological grading. No correlation was also noted between the proliferation indices of all the three proteins in the affected lymph node and grade of histological differentiation. Such clinicopathological parameters as patients' age and gender, histological grading by Lauren's and Goseki's classifications and lymph node involvement did not correlate with survival time of patients. Furthermore, no statistically significant correlation was shown of postoperative survival time with Ki-67 and MCM2 PI in tumour tissue and metastatic lymph nodes and with PCNA PI in the affected lymph nodes. However, a statistically significant correlation was found of Ki-67, PCNA and MCM2 PI in tumour tissue and metastatic lymph nodes with depth of wall invasion and local lymph node involvement. A statistically significant correlation was also noted between PCNA PI in the main mass of tumour and histological grading. The postoperative survival time of patients exhibited a statistically significant correlation with tumour location and macroscopic type according to Bormann's classification. Correlations on statistical borderline were noted between survival time and depth of gastric wall invasion and PCNA PI in the main mass of tumour.

Molecular networks involved in mouse cerebral corticogenesis and spatio-temporal regulation of Sox4 and Sox11 novel antisense transcripts revealed by transcriptome profiling

BACKGROUND

Development of the cerebral cortex requires highly specific spatio-temporal regulation of gene expression. It is proposed that transcriptome profiling of the cerebral cortex at various developmental time points or regions will reveal candidate genes and associated molecular pathways involved in cerebral corticogenesis.

RESULTS

Serial analysis of gene expression (SAGE) libraries were constructed from C57BL/6 mouse cerebral cortices of age embryonic day (E) 15.5, E17.5, postnatal day (P) 1.5 and 4 to 6 months. Hierarchical clustering analysis of 561 differentially expressed transcripts showed regionalized, stage-specific and co-regulated expression profiles. SAGE expression profiles of 70 differentially expressed transcripts were validated using quantitative RT-PCR assays. Ingenuity pathway analyses of validated differentially expressed transcripts demonstrated that these transcripts possess distinctive functional properties related to various stages of cerebral corticogenesis and human neurological disorders. Genomic clustering analysis of the differentially expressed transcripts identified two highly transcribed genomic loci, Sox4 and Sox11, during embryonic cerebral corticogenesis. These loci feature unusual overlapping sense and antisense transcripts with alternative polyadenylation sites and differential expression. The Sox4 and Sox11 antisense transcripts were highly expressed in the brain compared to other mouse organs and are differentially expressed in both the proliferating and differentiating neural stem/progenitor cells and P19 (embryonal carcinoma) cells.

CONCLUSIONS

We report validated gene expression profiles that have implications for understanding the associations between differentially expressed transcripts, novel targets and related disorders pertaining to cerebral corticogenesis. The study reports, for the first time, spatio-temporally regulated Sox4 and Sox11 antisense transcripts in the brain, neural stem/progenitor cells and P19 cells, suggesting they have an important role in cerebral corticogenesis and neuronal/glial cell differentiation.

DNA polymerase beta-catalyzed-PCNA independent long patch base excision repair synthesis: a mechanism for repair of oxidatively damaged DNA ends in post-mitotic brain

Oxidative DNA damage incidental to normal respiratory metabolism poses a particular threat to genomes of highly metabolic-long lived cells. We show that post-mitotic brain has capacity to repair oxidatively damaged DNA ends, which are targets of the long patch (LP) base excision repair (BER) subpathway. LP-BER relies, in part, on proteins associated with DNA replication, including proliferating cell nuclear antigen and is inherent to proliferating cells. Nonetheless, repair products are generated with brain extracts, albeit at slow rates, in the case of 5'-DNA ends modeled with tetrahydrofuran (THF). THF at this position is refractory to DNA polymerase beta 5'-deoxyribose 5-phosphate lyase activity and drives repair into the LP-BER subpathway. Comparison of repair of 5'-THF-blocked termini in the post-mitotic rat brain and proliferative intestinal mucosa, revealed that in mucosa, resolution of damaged 5'-termini is accompanied by formation of larger repair products. In contrast, adducts targeted by the single nucleotide BER are proficiently repaired with both extracts. Our findings reveal mechanistic differences in BER processes selective for the brain versus proliferative tissues. The differences highlight the physiological relevance of the recently proposed 'Hit and Run' mechanism of alternating cleavage/synthesis steps, in the proliferating cell nuclear antigen-independent LP-BER process.

Protocols for studying adult neurogenesis: insights and recent developments

The first evidence that neurogenesis occurs in the adult brain was reported in rodents in the early 1960s, using [(3)H]-thymidine autoradiography. In the 1980s and 90s, the advent of new techniques and protocols for studying cell proliferation in situ, and particularly bromodeoxyuridine labeling, helped to confirm that neurogenesis occurs in the adult brain and neural stem cells reside in the adult CNS, including in humans. Bromodeoxyuridine labeling is currently the method most commonly used for studying neurogenesis in the adult brain. However, this procedure is not without limitations, and controversies. In this article, I will review recent protocols for studying adult neurogenesis, particularly new protocols for studying cell kinetics and cell proliferative history, using halopyrimidines. I will review these techniques, and discuss their implications for the field of adult neurogenesis.

Absence of LPA1 signaling results in defective cortical development

Lysophosphatidic acid (LPA) is a simple phospholipid with extracellular signaling properties mediated by specific G protein-coupled receptors. At least 2 LPA receptors, LPA(1) and LPA(2), are expressed in the developing brain, the former enriched in the neurogenic ventricular zone (VZ), suggesting a normal role in neurogenesis. Despite numerous studies reporting the effects of exogenous LPA using in vitro neural models, the first LPA(1) loss-of-function mutants reported did not show gross cerebral cortical defects in the 50% that survived perinatal demise. Here, we report a role for LPA(1) in cortical neural precursors resulting from analysis of a variant of a previously characterized LPA(1)-null mutant that arose spontaneously during colony expansion. These LPA(1)-null mice, termed maLPA(1), exhibit almost complete perinatal viability and show a reduced VZ, altered neuronal markers, and increased cortical cell death that results in a loss of cortical layer cellularity in adults. These data support LPA(1) function in normal cortical development and suggest that the presence of genetic modifiers of LPA(1) influences cerebral cortical development.

Proliferative activity in the frog brain: a PCNA-immunohistochemistry analysis

By means proliferating cell nuclear antigen (PCNA) immunohistochemistry, we have provided a detailed neuroanatomical mapping of proliferative activity during development and adulthood in the frog (Rana esculenta) brain. Western blot analysis confirmed the presence of this protein in brain extracts from adults and tadpoles. Proliferative activity was observed in the ventricular and subventricular zones throughout the brain. The present study provides details as to which of the morphologically distinguishable brain region(s) has a long-lasting proliferative activity and in which region this activity undergoes a progressive decrease during development. In the subventricular zones of the third ventricle, PCNA-labeled cells were particularly abundant in the magnocellular preoptic nucleus and the ventromedial thalamic nucleus. It was observed that proliferation zones are present practically in all major subdivisions of the forebrain, midbrain and hindbrain, including the cerebellum in which PCNA-labeled cells were located in the outer granular layer and the inner molecular layer. The habenulae, epiphysis and isthmic nuclei never showed the presence of PCNA-immunoreactive nuclei. The widespread proliferative activity implies that the frog brain has a great potential for neurogenesis/gliogenesis not only during larval development but also in the adulthood.

Proliferation and migration of granule cells in the developing rat cerebellum: cisplatin effects

We evaluated the relationship among proliferation, death and migration of granule cells in lobules VI-VIII of vermis, in comparison with lobule III, during cerebellar development. To this aim, a single injection of cisplatin, i.e., a cytostatic agent that is known to induce death of proliferating granule cells, was given to 10-day-old rats. Histochemical markers of proliferating (PCNA immunoreaction) and apoptotic (TUNEL staining) cells were used; the variations of the external granular layer (EGL) thickness were evaluated in parallel. After PCNA and TUNEL reactions, evident changes of the whole EGL were found on PD11 (1 day after treatment), when a reduction of the thickness of this layer was found in treated rats, mainly in consequence of the high number of apoptotic cells in all the cerebellar lobules. On PD17 (7 days after treatment), a thick layer of proliferating cells was observed in lobules VI-VIII of treated rats, while the peculiar pattern of the normal development showed a thin EGL. At the same time, in treated rats, the number of apoptotic cells in EGL was low. In all developmental stages of treated rats, after GFAP immunoreaction, glial fibers appeared twisted, thickened, and with an irregular course; intensely labeled end-feet were present. The damage of radial glia suggests an alteration of migratory processes of granule cells, which is also evidenced by the decreased thickness of the premigratory zone of the EGL. Injured radial glia fibers were restricted to lobules VI-VIII and they persisted at PD30, leading to the presence of ectopic granule cells in the molecular layer, as we previously described.

Expression of discoidin domain receptor 1 during mouse brain development follows the progress of myelination

Discoidin domain receptor 1 is a tyrosine kinase receptor expressed in a variety of tissues including the brain. This study describes mRNA and protein expression of discoidin domain receptor 1 in mouse brain during development and provides new insights into its role during gliogenesis and neurogenesis. We performed in situ hybridization for discoidin domain receptor 1 in mouse brains at embryonic day 18, postnatal days 5, 9, 15, 21 and adulthood and observed a diffuse pattern in the proliferative areas during embryogenesis. From postnatal day 5 onwards, a defined cellular expression pattern of discoidin domain receptor 1 was observed, mainly located in white matter tracts and following a spatio-temporal pattern that overlapped the progress of myelination. Next, we performed double-labeling reactions (in situ hybridization followed by immunohistochemistry) that confirmed that discoidin domain receptor 1 was expressed by mature oligodendrocytes. We observed that cells positive for discoidin domain receptor 1 also expressed carnosine and anti-adenomatous polyposis coli, two mature oligodendrocyte markers. Based on the localization of discoidin domain receptor 1 specifically in the white matter fiber tracts during postnatal development, we suggest that discoidin domain receptor 1 participates in the development and maintenance of the myelin sheath.

The cell cycle-apoptosis connection revisited in the adult brain

Adult neurogenesis is studied in vivo using thymidine analogues such as bromodeoxyuridine (BrdU) to label DNA synthesis during the S phase of the cell cycle. However, BrdU may also label DNA synthesis events not directly related to cell proliferation, such as DNA repair and/or abortive reentry into the cell cycle, which can occur as part of an apoptotic process in postmitotic neurons. In this study, we used three well-characterized models of injury-induced neuronal apoptosis and the combined visualization of cell birth (BrdU labeling) and death (Tdt-mediated dUTP-biotin nick end labeling) to investigate the specificity of BrdU incorporation in the adult mouse brain in vivo. We present evidence that BrdU is not significantly incorporated during DNA repair and that labeling is not detected in vulnerable or dying postmitotic neurons, even when a high dose of BrdU is directly infused into the brain. These findings have important implications for a controversy surrounding adult neurogenesis: the connection between cell cycle reactivation and apoptosis of terminally differentiated neurons.

Proliferation markers in the adult rodent brain: bromodeoxyuridine and proliferating cell nuclear antigen

The rostral migratory stream is one of the few regions of the adult mammalian central nervous system in which cellular migration and proliferation have been described. Most rostral migratory stream cells divide rapidly and hence different proliferation markers have been employed to identify them. Nitrogen base substitutes, such as tritiated thymidine or 5-bromo-2'-deoxyuridine (BrdU), together with endogenous molecules, such as Proliferating Cell Nuclear Antigen (PCNA), are the cell cycle markers most widely employed. Protocols for BrdU and PCNA localization are both plentiful and diverse, but to date no optimized protocol for obtaining trustworthy double staining of both markers has been described. In this work, we propose optimized protocols for achieving both single staining and the joint detection of BrdU and PCNA in the rodent brain using double-immunofluorescence procedures. The double labeling described allows the discrimination of different cell cycle stages in migratory cells from the mouse brain.

Immunohistochemical Studies Concerning the Neuronal Cell Cycle of the Cat using PCNA, Ki-67 and p53 Markers

Recent studies about parvovirus replication in mature neurones of cats indicate that even feline neurones do not seem to be terminally differentiated. For further determination of the proliferative capability of feline neurones, an immunohistochemical study investigating the neuronal expression of the cell cycle-related proteins, proliferating cell nuclear antigen (PCNA), Ki-67 and p53 was initiated. Brains of 50 cats of different age and gender, dying of various diseases, were examined. Strong PCNA clone PC10 expression could be observed in neurones of the cerebellar cortex and the vestibular nuclei, whereas entorhinal cortex, lateral geniculate nucleus and cerebral cortex revealed only weak immunolabelling. The PCNA clone 19F4 labelled numerous neurones in vestibular nuclei and some Purkinje cells of the cerebellum. Nuclear expression of Ki-67 was sporadic in the vestibular nuclei, but p53 expression could not be detected anywhere in the feline brain. However, the presence of nuclear PCNA and Ki-67 expression indicates that certain feline neurones are capable of re-entering the cell cycle.

Up-regulation of a growth arrest and DNA damage protein (GADD34) in the ischaemic human brain: implications for protein synthesis regulation and DNA repair

GADD34 is a growth arrest and DNA damage inducible gene up-regulated in response to DNA damage, cell cycle arrest and apoptosis. It is thought that GADD34 may play a crucial role in cell survival in ischaemia. GADD34 expression was assessed immunohistochemically in post-mortem human hippocampal tissue obtained from patients surviving for defined periods (0-24 h; 24 h-7 days) after a cardiac arrest and in age-matched control subjects. In control brain, cytoplasm staining in GADD34 immunopositive cells was faint but present throughout the hippocampus and cortex. There was minimal change in GADD34 expression in the group surviving 0-24 h after cardiac arrest. However GADD34 immunostaining was markedly increased in selectively vulnerable regions in the 24 h-7 day survival group. Increased GADD34 staining was present in ischaemic neurones and in some morphologically normal neurones after cardiac arrest. Extensive ischaemic damage was found to correlate with elevated GADD34 immunostaining in the CA1 layer of the hippocampus (**P < 0.0016). In addition, GADD34 was found to colocalize with proliferating cell nuclear antigen in some neurones. The up-regulation of GADD34 in response to global ischaemia in the human brain plus its influence on protein synthesis and DNA repair suggests that this protein may have the potential to influence cell survival.