FABP4 Research Articles

Dopamine D1 receptor activation regulates the expression of the estrogen synthesis gene aromatase B in radial glial cells.

Radial glial cells (RGCs) are abundant stem-like non-neuronal progenitors that are important for adult neurogenesis and brain repair, yet little is known about their regulation by neurotransmitters. Here we provide evidence for neuronal-glial interactions via a novel role for dopamine to stimulate RGC function. Goldfish were chosen as the model organism due to the abundance of RGCs and regenerative abilities of the adult central nervous system. A close anatomical relationship was observed between tyrosine hydroxylase-positive catecholaminergic cell bodies and axons and dopamine-D1 receptor expressing RGCs along the ventricular surface of telencephalon, a site of active neurogenesis. A primary cell culture model was established and immunofluorescence analysis indicates that in vitro RGCs from female goldfish retain their major characteristics in vivo, including expression of glial fibrillary acidic protein and brain lipid binding protein. The estrogen synthesis enzyme aromatase B is exclusively found in RGCs, but this is lost as cells differentiate to neurons and other glial types in adult teleost brain. Pharmacological experiments using the cultured RGCs established that specific activation of dopamine D1 receptors up-regulates aromatase B mRNA through a cyclic adenosine monophosphate-dependent molecular mechanism. These data indicate that dopamine enhances the steroidogenic function of this neuronal progenitor cell.

Association of adipocyte fatty acid-binding protein with cholesterol metabolism

Adipocyte fatty acid-binding protein(FABP4)is abundantly expressed in adipocytes and macrophages, and the physiologic function of this lipid chaperone is involved in the intracellular trafficking and targeting of fatty acids inside cell. Studies have shown that FABP4 plays a significant role in cholesterol metabolism. FABP4 can affect some key gene expression for cholesterol metabolism, thus regulate the metabolism, storage, and trafficking of cholesterol. As the development of FABP4 inhibitors, drugs targeting FABP4 are possible and can lead to a novel therapeutic strategy to prevent and treat obesity, type 2 diabetes, hypercholesterolemia, and atherosclerosis. Key words: Adipocyte fatty-acid binding protein; Cholesterol metabolism; Atherosclerosis; Inflammatory response

Maternal exposure to hexachlorophene targets intermediate-stage progenitor cells in the hippocampal neurogenesis involving myelin vacuolation of cholinergic and glutamatergic inputs in mice.

Hexachlorophene (HCP) has been shown to induce myelin vacuolation due to intramyelinic edema of the nerve fibers in animal neural tissue. We investigated the maternal exposure effect of HCP on hippocampal neurogenesis in the offspring of pregnant mice supplemented with 0 (control), 33 or 100 ppm HCP in diet from gestational day 6 to day 21 after delivery. On postnatal day (PND) 21, offspring as examined in males exhibited decreased granule cell lineage populations expressing paired box 6, sex-determining region Y-box 2 and eomesodermin in the hippocampal subgranular zone (SGZ) accompanied by myelin vacuolation involving white matter tracts of the hippocampal fimbria at ≥ 33 ppm. However, SGZ cellular populations expressing brain lipid binding protein and doublecortin were unchanged at any dose. Transcript expression of cholinergic receptor genes, Chrna4 and Chrnb2, and glutamate receptor genes, Grm1 and Grin2d, examined at 100 ppm, decreased in the dentate gyrus. HCP exposure did not alter the number of proliferating or apoptotic cells in the SGZ, or reelin- or calcium-binding protein-expressing γ-aminobutyric acid (GABA)ergic interneurons in the dentate hilus, on PND 21 and PND 77. All neurogenesis-related changes observed in HCP-exposed offspring on PND 21 disappeared on PND 77, suggesting that maternal HCP exposure at ≥ 33 ppm reversibly decreased type 2 intermediate-stage progenitor cells in the hippocampal neurogenesis. Myelin vacuolation might be responsible for changes in neurogenesis possibly by reducing nerve conduction velocity of cholinergic inputs from the septal-hippocampal pathway to granule cell lineages and/or GABAergic interneurons, and of glutamatergic inputs to granule cell lineages.

Chronic intestinal inflammation alters hippocampal neurogenesis.

BackgroundAdult neurogenesis in the subgranular zone of the hippocampus is involved in learning, memory, and mood control. Decreased hippocampal neurogenesis elicits significant behavioral changes, including cognitive impairment and depression. Inflammatory bowel disease (IBD) is a group of chronic inflammatory conditions of the intestinal tract, and cognitive dysfunction and depression frequently occur in patients suffering from this disorder. We therefore tested the effects of chronic intestinal inflammation on hippocampal neurogenesis.MethodsThe dextran sodium sulfate (DSS) mouse model of IBD was used. Mice were treated with multiple-cycle administration of 3% wt/vol DSS in drinking water on days 1 to 5, 8 to 12, 15 to 19, and 22 to 26. Mice were sacrificed on day 7 (acute phase of inflammation) or day 29 (chronic phase of inflammation) after the beginning of the treatment.ResultsDuring the acute phase of inflammation, we found increased plasma levels of IL-6 and TNF-α and increased expression of Iba1, a marker of activated microglia, accompanied by induced IL-6 and IL-1β, and the cyclin-dependent kinase inhibitor p21Cip1 (p21) in hippocampus. During the chronic phase of inflammation, plasma levels of IL-6 were elevated. In the hippocampus, p21 protein levels were continued to be induced. Furthermore, markers of stem/early progenitor cells, including nestin and brain lipid binding protein (BLBP), and neuronal marker doublecortin (DCX) were all down-regulated, whereas glial fibrillary acidic protein (GFAP), a marker for astroglia, was induced. In addition, the number of proliferating precursors of neuronal lineage assessed by double Ki67 and DCX staining was significantly diminished in the hippocampus of DSS-treated animals, indicating decreased production of new neurons.ConclusionsWe show for the first time that chronic intestinal inflammation alters hippocampal neurogenesis. As p21 arrests early neuronal progenitor proliferation, it is likely that p21 induction during acute phase of inflammation resulted in the reduction of hippocampal neurogenesis observed later, on day 29, after the beginning of DSS treatment. The reduction in hippocampal neurogenesis might underlie the behavioral manifestations that occur in patients with IBD.

Evolution of Transcriptional Regulation of Duplicated Fatty Acid‐Binding Protein Genes by PPARs in Zebrafish: a Pharmacological Approach

Duplication of genes is thought to facilitate increasing organismal complexity. Duplicated genes may be retained in the genome if one of the duplicates acquires a novel function, or the functions of the ancestral gene are subdivided between the duplicates. A likely process for the retention of duplicates is the loss or gain of regulatory elements in the promoters of duplicated genes.The objective of this study was to explore the evolution of gene promoters using the multigene family of fatty acid‐binding proteins (fabp) in zebrafish. Previous studies had implicated the peroxisome proliferator‐activated receptors (PPARs) in the regulation of some fabp genes. The promoters of the zebrafish fabp1a, fabp1b.1 and fabp1b.2 genes, duplicated by a whole genome duplication (fabp1a and ancestral fabp1b) followed by a tandem gene duplication (fabp1b.1 and fabp1b.2), were cloned into firefly luciferase reporter plasmids, transfected into HEK cells, and tested in the presence of PPARα‐ and PPARγ‐selective agonists. Expression of these genes was further analyzed by qRT‐PCR in explant cultures of zebrafish liver and intestine treated with PPAR agonists.fabp1a expression was selectively increased by PPARα‐agonism in HEK cells and intestine. fabp1b.1 expression was selectively increased by PPARγ‐agonism in HEK cells and liver. fabp1b.2 promoter activity was not induced by PPAR modulation. The differential PPAR regulation of the duplicated fabp1 genes provide evidence of divergence of regulatory elements in these gene promoters, which may account for the retention of the duplicated fabp1 genes in the zebrafish genome.Funding from NSERC, CIHR, and Dalhousie University.

HDAC1 regulates the proliferation of radial glial cells in the developing Xenopus tectum.

In the developing central nervous system (CNS), progenitor cells differentiate into progeny to form functional neural circuits. Radial glial cells (RGs) are a transient progenitor cell type that is present during neurogenesis. It is thought that a combination of neural trophic factors, neurotransmitters and electrical activity regulates the proliferation and differentiation of RGs. However, it is less clear how epigenetic modulation changes RG proliferation. We sought to explore the effect of histone deacetylase (HDAC) activity on the proliferation of RGs in the visual optic tectum of Xenopus laevis. We found that the number of BrdU-labeled precursor cells along the ventricular layer of the tectum decrease developmentally from stage 46 to stage 49. The co-labeling of BrdU-positive cells with brain lipid-binding protein (BLBP), a radial glia marker, showed that the majority of BrdU-labeled cells along the tectal midline are RGs. BLBP-positive cells are also developmentally decreased with the maturation of the brain. Furthermore, HDAC1 expression is developmentally down-regulated in tectal cells, especially in the ventricular layer of the tectum. Pharmacological blockade of HDACs using Trichostatin A (TSA) or Valproic acid (VPA) decreased the number of BrdU-positive, BLBP-positive and co-labeling cells. Specific knockdown of HDAC1 by a morpholino (HDAC1-MO) decreased the number of BrdU- and BLBP-labeled cells and increased the acetylation level of histone H4 at lysine 12 (H4K12). The visual deprivation-induced increase in BrdU- and BLBP-positive cells was blocked by HDAC1 knockdown at stage 49 tadpoles. These data demonstrate that HDAC1 regulates radial glia cell proliferation in the developing optical tectum of Xenopus laevis.

Delivery and tracking of quantum dot peptide bioconjugates in an intact developing avian brain.

Luminescent semiconductor ∼9.5 nm nanoparticles (quantum dots: QDs) have intrinsic physiochemical and optical properties which enable us to begin to understand the mechanisms of nanoparticle mediated chemical/drug delivery. Here, we demonstrate the ability of CdSe/ZnS core/shell QDs surface functionalized with a zwitterionic compact ligand to deliver a cell-penetrating lipopeptide to the developing chick embryo brain without any apparent toxicity. Functionalized QDs were conjugated to the palmitoylated peptide WGDap(Palmitoyl)VKIKKP9GGH6, previously shown to uniquely facilitate endosomal escape, and microinjected into the embryonic chick spinal cord canal at embryo day 4 (E4). We were subsequently able to follow the labeling of spinal cord extension into the ventricles, migratory neuroblasts, maturing brain cells, and complex structures such as the choroid plexus. QD intensity extended throughout the brain, and peaked between E8 and E11 when fluorescence was concentrated in the choroid plexus before declining to hatching (E21/P0). We observed no abnormalities in embryonic patterning or embryo survival, and mRNA in situ hybridization confirmed that, at key developmental stages, the expression pattern of genes associated with different brain cell types (brain lipid binding protein, Sox-2, proteolipid protein and Class III-β-Tubulin) all showed a normal labeling pattern and intensity. Our findings suggest that we can use chemically modified QDs to identify and track neural stem cells as they migrate, that the choroid plexus clears these injected QDs/nanoparticles from the brain after E15, and that they can deliver drugs and peptides to the developing brain.

Expression of a novel serine/threonine kinase gene, Ulk4, in neural progenitors during Xenopus laevis forebrain development

We have analyzed the expression pattern of a novel serine/threonine kinase gene Ulk4 during forebrain development in Xenopus laevis. To this aim, we firstly cloned a Ulk4 cDNA fragment from X.laevis and generated a RNA probe that was used for its detection by in situ hybridization. Throughout development xUlk4 expression was detected along the ventricular (vz) and subventricular zones (svz) of all forebrain regions, with the exception of the vz of the striatum. In the adult, xUlk4 was also mainly located in the vz, with some xUlk4 expressing cells reaching the svz/mantle zone (mz). This xUlk4 expression was especially remarkable in forebrain regions involving the homeostatic control of the brain such as the preoptic region, the hypothalamic territory and some neurosecretory circumventricular organs (CVOs). We further combined in situ hybridization for xUlk4 with immunohistochemistry for the neural progenitor cell marker SOX3, the radial glial marker brain lipid-binding protein (BLBP), neuronal markers MAP2 and doublecortin (DCX) and the specific neuronal marker tyrosine hydroxylase (TH). xUlk4 was co-expressed with the neural stem/progenitor cell marker SOX3 in the vz of all the forebrain regions throughout development and in the adult, and this co-expression was also especially evident in the svz of the hypothalamic region. xUlk4 was also expressed in the radial glia along the whole brain. We have also found minor expression of xUlk4 in some DCX- or MAP2-positive cells but not in TH-positive neurons. These findings suggest that Ulk4 may play roles in neural stem/progenitor cells during neurogenesis both in development and in the adulthood, in migrating cells as well as in cells committed to neuronal fate in Xenopus. Moreover, the results obtained in this study argue for an involvement of Ulk4 in the control of the neuroendocrine homeostatic functions in the brain.

Stability of Reference Genes during Tri-Lineage Differentiation of Human Adipose-Derived Stromal Cells.

Quantitative real-time PCR can detect variations in gene expression. The identification of the stable reference genes (RGs) is necessary to evaluate the expression of specific genes of interest under various conditions in many cell types, including human adipose-derived stromal cells (hASCs). In this study, we used the algorithms BestKeeper, NormFinder, geNorm, and RefFinder to investigate the stability of 15 potential RGs (B2M, eEF1A1, GAPDH, H2AFZ, HMBS, HPRT1, PGK1, PPIA, RPL5, SDHA, TBP, TKT, TRFC, TUBB, and UBC) in hASCs during control, adipo-, chondro-, and osteogenic differentiation for 28 days. RPL5, GAPDH, H2AFZ, and HPRT1 were the most stable RGs, while B2M and UBC were the least stable RGs for the majority of group analyses (tri-lineage differentiation and control analyzed combined or individually; each lineage combined with the control). These RGs were used to normalize adipo- (FABP4, LPL, and PPARG), chondro- (COMP and SOX9), and osteogenic gene expression markers (BMP4, COL1A1, and RUNX2). Each marker showed a similar expression when normalized by H2AFZ, HPRT1, or RPL5, confirming that these RGs exhibit stable expression. However, GAPDH, B2M, and UBC exhibited high standard deviation (SD), down-regulated and/or up-regulated differentiation gene expression markers when compared with stable RGs, demonstrating that these RGs are unstable.

Permissive Schwann Cell Graft/Spinal Cord Interfaces for Axon Regeneration

The transplantation of autologous Schwann cells (SCs) to repair the injured spinal cord is currently being evaluated in a clinical trial. In support, this study determined properties of spinal cord/SC bridge interfaces that enabled regenerated brainstem axons to cross them, possibly leading to improvement in rat hindlimb movement. Fluid bridges of SCs and Matrigel were placed in complete spinal cord transections. Compared to pregelled bridges of SCs and Matrigel, they improved regeneration of brainstem axons across the rostral interface. The regenerating brainstem axons formed synaptophysin(+) bouton-like terminals and contacted MAP2A(+) dendrites at the caudal interface. Brainstem axon regeneration was directly associated with glial fibrillary acidic protein (GFAP(+)) astrocyte processes that elongated into the SC bridge. Electron microscopy revealed that axons, SCs, and astrocytes were enclosed together within tunnels bounded by a continuous basal lamina. Neuroglycan (NG2) expression was associated with these tunnels. One week after injury, the GFAP(+) processes coexpressed nestin and brain lipid-binding protein, and the tips of GFAP(+)/NG2(+) processes extended into the bridges together with the regenerating brainstem axons. Both brainstem axon regeneration and number of GFAP(+) processes in the bridges correlated with improvement in hindlimb locomotion. Following SCI, astrocytes may enter a reactive state that prohibits axon regeneration. Elongation of astrocyte processes into SC bridges, however, and formation of NG2(+) tunnels enable brainstem axon regeneration and improvement in function. It is important for spinal cord repair to define conditions that favor elongation of astrocytes into lesions/transplants.

Selective Calcium Sensitivity in Immature Glioma Cancer Stem Cells

Tumor-initiating cells are a subpopulation in aggressive cancers that exhibit traits shared with stem cells, including the ability to self-renew and differentiate, commonly referred to as stemness. In addition, such cells are resistant to chemo- and radiation therapy posing a therapeutic challenge. To uncover stemness-associated functions in glioma-initiating cells (GICs), transcriptome profiles were compared to neural stem cells (NSCs) and gene ontology analysis identified an enrichment of Ca2+ signaling genes in NSCs and the more stem-like (NSC-proximal) GICs. Functional analysis in a set of different GIC lines regarding sensitivity to disturbed homeostasis using A23187 and Thapsigargin, revealed that NSC-proximal GICs were more sensitive, corroborating the transcriptome data. Furthermore, Ca2+ drug sensitivity was reduced in GICs after differentiation, with most potent effect in the NSC-proximal GIC, supporting a stemness-associated Ca2+ sensitivity. NSCs and the NSC-proximal GIC line expressed a larger number of ion channels permeable to potassium, sodium and Ca2+. Conversely, a higher number of and higher expression levels of Ca2+ binding genes that may buffer Ca2+, were expressed in NSC-distal GICs. In particular, expression of the AMPA glutamate receptor subunit GRIA1, was found to associate with Ca2+ sensitive NSC-proximal GICs, and decreased as GICs differentiated along with reduced Ca2+ drug sensitivity. The correlation between high expression of Ca2+ channels (such as GRIA1) and sensitivity to Ca2+ drugs was confirmed in an additional nine novel GIC lines. Calcium drug sensitivity also correlated with expression of the NSC markers nestin (NES) and FABP7 (BLBP, brain lipid-binding protein) in this extended analysis. In summary, NSC-associated NES+/FABP7+/GRIA1+ GICs were selectively sensitive to disturbances in Ca2+ homeostasis, providing a potential target mechanism for eradication of an immature population of malignant cells.

Molecular characterization and different expression patterns of the FABP gene family during goat skeletal muscle development.

The FABP (adipocyte fatty acid-binding protein) genes play an important role in intracellular fatty acid transport and considered to be candidate genes for fatness traits in domestic animal. In this study, we cloned the cDNA sequences of goat FABP family genes and their expression patterns were detected by semi-quantitative RT-PCR and quantitative real time RT-PCR. Expression analysis showed that goat FABP1 gene was predominantly expressed in liver, kidney and large intestine. While FABP4 was widely expressed in many tissues with a high expression level was observed in the fat, skeletal muscle, stomach and lung. Notably, FABP2 gene was expressed specifically in small intestine. Moreover, goat FABP3 was expressed at 60 day with the highest level, then significantly (p < 0.01) decreased at the 90 day. No significant expression differences were observed in longissimus dorsi muscles among 3 day, 30 day and 60 day. Goat FABP4 was expressed at 3 day with the lowest level, then significantly (p < 0.01) increased to a peak at the 60 day. In addition, a significant relationship between FABP3 mRNA expression levels and intramuscular fat (IMF) content was observed. These results suggest that the FABP3 and FABP4 may be important genes for meat quality and provides useful information for further studies on their roles in skeletal muscle IMF deposit.

Expression profiles analysis of differential genes in rat visual cortex depending upon postnatal days by microarray

Background Visual adaptive mechanism of mammalian is close responsible for the development of visual cortex.The various genes with different biological functions in different developing stages of visual cortex participate in regulation of visual development.To investigate the differential expression profiles of various genes in different ages of rat cortex can offer basis and evidence for the study of visual development.Objective Present study aimed to investigate the genes that changed continuously in the postnatal developmental process of rat visual cortex by microarray analysis of visual cortex RNA.Methods Sixty clean SD rats were grouped numbered and randomized into the postnatal day 0 group (P0,n =20),before eye opening group (postnatal day 10,P10,n =15),before the critical period of visual cortex growth group (postnatal day 20,P20,n =15) and the end of development of visual cortex group(postnatal day 45,P45,n=15).The rats were sacrificed at corresponding time point respectively,and the fresh visual cortex were obtained for the extraction of total RNA and microarray analysis.Genes exhibiting changes in expression by≥2.0 folds were further confirmed using real-time PCR(RT-PCR).In order to evaluate the association of differential gene expression with growth,the postnatal stages were paired as 36 groups with the 3 pairs for each target gene (P45/P0,P20/P0,P10/P0).Results Microarray analysis showed that the gene with differential ratio ≥ 2.0 folds in rat visual cortex included Akap7,Asam,Casp3,Cxcr4,Egr1,Ennp2,Fabp7,Gpr88,Inpp5d,Rpsa,Stk32c and Vamp1.Real-time PCR verified that 24 genes form 26 probe sets had the same-phase regulating tendency,including 20 up-regulating probe sets and 6 down-regulating probe sets.The homodromous expressing tendency was seen in Akap7,Asam,Casp3,Cxcr4,Egr1,Ennp2,Fabp7,Inpp5d,Rpsa and Vamp1 genes between microarray analysis and RT-PCR.However,reverse expressions were found in the P45/P0 of Gpr88 and Stk32c genes,showing the up-regulation in the microarray analysis and down-regulation in RT-PCR.The concordant rate of gene expression between microarray analysis and RT-PCR was 94.44％.The expressing genes mainly functioned nervous system development,(metal) ion binding/transport,metabolism,regulation of neuronal synaptic plasticity.Conclusions New relevant candidate genes of age-associated rat visual cortex can be identified by microarray analysis,which provide a clue for the research of visual plasticity. Key words: Gene expression profiling; Rat, Sprague-Dawley; Visual cortex/growth and development; Oligonucleotide array sequence analysis; Neuronal plasticity; Polymerase chain reaction

Cyp19a1 (Aromatase) Expression in the Xenopus Brain at Different Developmental Stages

Cytochrome P450 aromatase (P450arom; aromatase) is a microsomal enzyme involved in the production of endogeneous sex steroids by converting testosterone into oestradiol. Aromatase is the product of the cyp19a1 gene and plays a crucial role in the sexual differentiation of the brain and in the regulation of reproductive functions. In the brain of mammals and birds, expression of cyp19a1 has been demonstrated in neuronal populations of the telencephalon and diencephalon. By contrast, a wealth of evidence established that, in teleost fishes, aromatase expression in the brain is restricted to radial glial cells. The present study investigated the precise neuroanatomical distribution of cyp19a1 mRNA during brain development in Xenopus laevis (late embryonic to juvenile stages). For this purpose, we used in situ hybridisation alone or combined with the detection of a proliferative (proliferating cell nuclear antigen), glial (brain lipid binding protein, Vimentin) or neuronal (acetylated tubulin; HuC/D; NeuroβTubulin) markers. We provide evidence that cyp19a1 expression in the brain is initiated from the very early larval stage and remains strongly detected until the juvenile and adult stages. At all stages analysed, we found the highest expression of cyp19a1 in the preoptic area and the hypothalamus compared to the rest of the brain. In these two brain regions, cyp19a1-positive cells were never detected in the ventricular layers. Indeed, no co-labelling could be observed with radial glial (brain lipid binding protein, Vimentin) or dividing progenitors (proliferating cell nuclear antigen) markers. By contrast, cyp19a1-positive cells perfectly matched with the distribution of post-mitotic neurones as shown by the use of specific markers (HuC/D, acetylated tubulin and NeuroβTubulin). These data suggest that, similar to that found in other tetrapods, aromatase in the brain of amphibians is found in post-mitotic neurones and not in radial glia as reported in teleosts.

Cyp19a1 (Aromatase) Expression in the Xenopus Brain at Different Developmental Stages

Cytochrome P450 aromatase (P450arom; aromatase) is a microsomal enzyme involved in the production of endogeneous sex steroids by converting testosterone into oestradiol. Aromatase is the product of the cyp19a1 gene and plays a crucial role in the sexual differentiation of the brain and in the regulation of reproductive functions. In the brain of mammals and birds, expression of cyp19a1 has been demonstrated in neuronal populations of the telencephalon and diencephalon. By contrast, a wealth of evidence established that, in teleost fishes, aromatase expression in the brain is restricted to radial glial cells. The present study investigated the precise neuroanatomical distribution of cyp19a1 mRNA during brain development in Xenopus laevis (late embryonic to juvenile stages). For this purpose, we used in situ hybridisation alone or combined with the detection of a proliferative (proliferating cell nuclear antigen), glial (brain lipid binding protein, Vimentin) or neuronal (acetylated tubulin; HuC/D; NeuroβTubulin) markers. We provide evidence that cyp19a1 expression in the brain is initiated from the very early larval stage and remains strongly detected until the juvenile and adult stages. At all stages analysed, we found the highest expression of cyp19a1 in the preoptic area and the hypothalamus compared to the rest of the brain. In these two brain regions, cyp19a1-positive cells were never detected in the ventricular layers. Indeed, no co-labelling could be observed with radial glial (brain lipid binding protein, Vimentin) or dividing progenitors (proliferating cell nuclear antigen) markers. By contrast, cyp19a1-positive cells perfectly matched with the distribution of post-mitotic neurones as shown by the use of specific markers (HuC/D, acetylated tubulin and NeuroβTubulin). These data suggest that, similar to that found in other tetrapods, aromatase in the brain of amphibians is found in post-mitotic neurones and not in radial glia as reported in teleosts.

Liver X receptor β delays transformation of radial glial cells into astrocytes during mouse cerebral cortical development

Radial glial (RG) cells serve as stem cells to produce new born neurons and scaffolds for neuronal migration during corticogenesis. After neurogenesis and migration are completed, most RG cells transform into astrocytes. However, the mechanisms that determine how RG cells are transformed into astrocytes are not well understood. Using nestin as a specific marker for both RG cells and astrocytes, we found that loss of LXRβ caused a reduction in the level of RG fibers and increase in the astrocytes. At the same time, we showed that the level of brain lipid–binding protein (BLBP), a RG-specific protein, was lower in the LXRβ knockout (LXRβ−/−) mice than in the wild type (WT) littermates from E18.5 to P14, a time period when most of RG cells are transformed into astrocytes. However, loss of LXRβ induced significant increase in the number of GFAP labeled astrocytes in the cerebral cortex. An increase of the transformation of RG cells into astrocytes in LXRβ−/− mice was further confirmed by the increased percentage of BLBP and GFAP double stained cells in the total BLBP positive cells of the Layer I and Layers V–VI. TGF-β1 and Smad4 are thought to be involved in the transformation of RG cells into astrocytes. The expression levels of TGF-β1mRNA and Smad4 mRNA were significantly higher in the cerebral cortex of LXRβ−/− mice than that in the WT littermates at P2 and P7, but by P10 and P14, mRNA levels had normalized and no differences were observed between WT and LXRβ−/− mice. Taken together, our findings suggest that loss of LXRβ accelerates the transformation of RG cells into astrocytes and that this acceleration may be correlated to higher levels TGF-β1 and Smad4 in the cerebral cortex between P2 and P7.

Molecular Diversity Subdivides the Adult Forebrain Neural Stem Cell Population

Neural stem cells (NSCs) in the ventricular domain of the subventricular zone (V-SVZ) of rodents produce neurons throughout life while those in humans become largely inactive or may be lost during infancy. Most adult NSCs are quiescent, express glial markers, and depend on Notch signaling for their self-renewal and the generation of neurons. Using genetic markers and lineage tracing, we identified subpopulations of adult V-SVZ NSCs (type 1, 2, and 3) indicating a striking heterogeneity including activated, brain lipid binding protein (BLBP, FABP7) expressing stem cells. BLBP(+) NSCs are mitotically active components of pinwheel structures in the lateral ventricle walls and persistently generate neurons in adulthood. BLBP(+) NSCs express epidermal growth factor (EGF) receptor, proliferate in response to EGF, and are a major clonogenic population in the SVZ. We also find BLBP expressed by proliferative ventricular and subventricular progenitors in the fetal and postnatal human brain. Loss of BLBP(+) stem/progenitor cells correlates with reduced neurogenesis in aging rodents and postnatal humans. These findings of molecular heterogeneity and proliferative differences subdivide the NSC population and have implications for neurogenesis in the forebrain of mammals during aging.

Comparative analysis and molecular characterization of genomic sequences and proteins of FABP4 and FABP5 from the giant panda (Ailuropoda melanoleuca)

Fatty acid binding proteins (FABPs) are a family of small, highly conserved cytoplasmic proteins that bind long-chain fatty acids and other hydrophobic ligands. In this study, cDNA and genomic sequences of FABP4 and FABP5 were cloned successfully from the giant panda (Ailuropoda melanoleuca) using reverse transcription polymerase chain reaction (RT-PCR) technology and touchdown-PCR. The cDNAs of FABP4 and FABP5 cloned from the giant panda were 400 and 413 bp in length, containing an open reading frame of 399 and 408 bp, encoding 132 and 135 amino acids, respectively. The genomic sequences of FABP4 and FABP5 were 3976 and 3962 bp, respectively, which each contained four exons and three introns. Sequence alignment indicated a high degree of homology with reported FABP sequences of other mammals at both the amino acid and DNA levels. Topology prediction revealed seven protein kinase C phosphorylation sites, two casein kinase II phosphorylation sites, two N-myristoylation sites, and one cytosolic fatty acid-binding protein signature in the FABP4 protein, and three N-glycosylation sites, three protein kinase C phosphorylation sites, one casein kinase II phosphorylation site, one N-myristoylation site, one amidation site, and one cytosolic fatty acid-binding protein signature in the FABP5 protein. The FABP4 and FABP5 genes were overexpressed in Escherichia coli BL21 and they produced the expected 16.8- and 17.0-kDa polypeptides. The results obtained in this study provide information for further in-depth research of this system, which has great value of both theoretical and practical significance.

Glial Modulation of Vibrissal Sensory Processing in Rats

Interactions between neurons and glial cells in the brain have important roles in brain functions such as development and plasticity of neural circuits or functions. Glial cells are much more actively involved in brain functions than previously thought. Here, we used vibrissal stimuli to induce sensoryevoked responses and multiunit spikes in the contralateral barrel cortex in a rat model. Local application of the gliotoxin DL-alpha-aminoadipate (AA) revealed that glial cells were involved in the sensoryevoked responses. The increases in the amplitude of somatosensory-evoked potential (SEP) and multiunit sensory-evoked spike rates in barrel cortex after AA injection were dramatic. Immunohistochemical staining of brain lipid binding protein (BLBP) and NeuN showed AA decreased cell number of astrocytes but not neurons in the barrel cortex. In conclusion, our results suggested an important role for astrocyte metabolism in normal synaptic activities.

The inner lining of the reptilian brain: A heterogeneous cellular mosaic

The ependymal layer is a preserved structure across vertebrates but its functional significance remains poorly understood. Modern studies emphasize the role played by radial glia (RG) as neurogenic progenitors. We speculated that the cells lining the prosencephalon ventricles of freshwater turtles may have retained key features of RG. To test this idea, we applied an approach that combined cellular, molecular, fine structural, and electrophysiological techniques. In the prosencephalon of juvenile turtles, we found cells with typical radial morphology that expressed four RG proteins: glial fibrillary acidic protein (GFAP), vimentin, S100/S100β and brain lipid-binding protein (BLBP). Most of these cells expressed the transcription factor Sox2 but few co-expressed Pax6. One type of RG had their somata close to the ventricle lumen and bear multiple cilia. A second class with cell bodies far from the lumen was usually uniciliated. RGs had low input resistances, passive properties and were coupled via Cx43 at the level of the cell bodies and radial processes. A third kind of cell was uncoupled, expressed neuronal proteins (HuC/D and NeuN) and fired spikes. The differential expression of HuC/D and NeuN together with their electrophysiological properties suggested various maturational stages. The occurrence of ependymal patches with a high density of 5-bromo-2-deoxyuridine (BrdU) labeled cells provides evidence of the proliferative capability of ependymal RG. Our data support the view that RG have retained key properties of neuroepithelial cells. The maintenance of proliferating RG could be also related with the outstanding endogenous ability of lower vertebrates for self-repair after injury.