Repopulated microglia are solely derived from the proliferation of residual microglia after acute depletion.

In adult mice the cytochrome P450 Cyp1a1 gene is not constitutively expressed but is highly inducible by foreign compounds acting through the aryl hydrocarbon (Ah) receptor. However, the expression profile of the Cyp1a1 gene in the developing embryo is not well under-stood. Using established transgenic mouse lines where 8.5 kb of the rat CYP1A1 promoter is cloned upstream of the lacZ reporter gene (1), we describe the expression of the CYP1A1-driven reporter gene in all tissues through-out stages E7-E14 of embryonic development. In contrast to the absence of constitutive Cyp1a1 and lacZ transgene expression in tissues of the adult mouse, a constitutive cell-specific and time-dependent pattern of CYP1A1 promoter activity was observed in the embryo. This expression pattern was confirmed as reflecting the endogenous gene by measuring Cyp1a1 mRNA levels and protein expression by immunohistochemistry. The number of cells displaying endogenous CYP1A1 activity could be increased in the embryo upon xenobiotic challenge, but only within areas where the CYP1A1 promotor was already active. When reporter mice were bred onto a genetic background expressing a lower affinity form of the Ah receptor (DBA allele), transgene and murine Cyp1a1 protein expression were both attenuated in the adult mouse liver upon xenobiotic challenge. By comparison, constitutive CYP1A1 promoter activity in the embryo was identical in the presence of either the high or low affinity Ah receptor. These novel data suggest that the Cyp1a1 protein may play a role in murine development and that regulation of the Cyp1a1 gene during this period is either through the action of a high affinity Ah receptor ligand or by an alternative regulatory pathway.

Robust In Vivo Transduction of Nervous System and Neural Stem Cells by Early Gestational Intra Amniotic Gene Transfer Using Lentiviral Vector

Age‐related decline in neurogenesis: Old cells or old environment?

In Vivo Clonal Analysis Reveals Self-Renewing and Multipotent Adult Neural Stem Cell Characteristics

Genetic analysis of Ntn1 in adult mouse midbrain neurons reveals its function in maintaining excitatory synapses, loss of Ntn1 function in inhibitory neurons is significantly detrimental to mesolimbic system function.

Erythropoietin (Epo) and its receptor (EpoR), critical for erythropoiesis, are expressed in the nervous system. Prior to death in utero because of severe anemia EpoR-null mice have fewer neural progenitor cells, and differentiated neurons are markedly sensitive to hypoxia, suggesting that during development Epo stimulates neural cell proliferation and prevents neuron apoptosis by promoting oxygen delivery to brain or by direct interaction with neural cells. Here we present evidence that neural progenitor cells express EpoR at higher levels compared with mature neurons; that Epo stimulates proliferation of embryonic neural progenitor cells; and that endogenous Epo contributes to neural progenitor cell proliferation and maintenance. EpoR-null mice were rescued with selective EpoR expression driven by the endogenous EpoR promoter in hematopoietic tissue but not in brain. Although these mice exhibited normal hematopoiesis and erythrocyte production and survived to adulthood, neural cell proliferation and viability were affected. Embryonic brain exhibited increased neural cell apoptosis, and neural cell proliferation was reduced in the adult hippocampus and subventricular zone. Neural cells from these animals were more sensitive to hypoxia/glutamate neurotoxicity than normal neurons in culture and in vivo. These observations demonstrate that endogenous Epo/EpoR signaling promotes cell survival in embryonic brain and contributes to neural cell proliferation in adult brain in regions associated with neurogenesis. Therefore, Epo exerts extra-hematopoietic function and contributes directly to brain development, maintenance, and repair by promoting cell survival and proliferation independent of insult, injury, or ischemia.

Habenula “Cholinergic” Neurons Corelease Glutamate and Acetylcholine and Activate Postsynaptic Neurons via Distinct Transmission Modes

Hematopoietic stem cell-specific GFP-expressing transgenic mice generated by genetic excision of a pan-hematopoietic reporter gene.

Absence of Both Thyroid Hormone Transporters MCT8 and OATP1C1 Impairs Neural Stem Cell Fate in the Adult Mouse Subventricular Zone.

The discovery, in 1998, that the adult human brain contains at least two populations of progenitor cells and that progenitor cells are upregulated in response to a range of degenerative brain diseases has raised hopes for their use in replacing dying brain cells. Since these early findings, the race has been on to understand the biology of progenitor cells in the human brain, and they have now been isolated and studied in many major neurodegenerative diseases. Before these cells can be exploited for cell replacement purposes, it is important to understand how to (1) locate them, (2) label them, (3) determine what receptors they express, (4) isolate them, and (5) examine their electrophysiological properties when differentiated. In this chapter we have described the methods we use for studying progenitor cells in the adult human brain and in particular the tissue processing, immunohistochemistry, autoradiography, progenitor cell culture, and electrophysiology on brain cells. The Neurological Foundation of New Zealand Human Brain Bank has been receiving human tissue for approximately 25years during which time we have developed a number of unique ways to examine and isolate progenitor cells from resected surgical specimens as well as from postmortem brain tissue. There are ethical and technical considerations that are unique to working with human brain tissue, and these, as well as the processing of this tissue and the culturing of it for the purpose of studying progenitor cells, are the topic of this chapter.

The discovery, in 1998, that the adult human brain contains at least two populations of progenitor cells and that progenitor cells are upregulated in response to a range of degenerative brain diseases has raised hopes for their use in replacing dying brain cells. Since these early findings the race has been on to understand the biology of progenitor cells in the human brain and they have now been isolated and studied in many major neurodegenerative diseases. Before these cells can be exploited for cell replacement purposes it is important to understand how to: (1) find them, (2) label them, (3) determine what receptors they express, (4) isolate them, and (5) examine their electrophysiological properties when differentiated. In this chapter we have described the methods we use for studying progenitor cells in the adult human brain and in particular the tissue processing, immunohistochemistry, autoradiography, progenitor cell culture, and electrophysiology on brain cells. The Neurological Foundation of New Zealand Human Brain Bank has been receiving human tissue for approximately 20 years during which time we have developed a number of unique ways to examine and isolate progenitor cells from resected surgical specimens as well as from postmortem brain tissue. There are ethical and technical considerations that are unique to working with human brain tissue and these, as well as the processing of this tissue and the culturing of it for the purpose of studying progenitor cells, are the topic of this chapter.

Secreted Frizzled-Related Protein 3 Regulates Activity-Dependent Adult Hippocampal Neurogenesis

Chronically Increased Transforming Growth Factor-β1 Strongly Inhibits Hippocampal Neurogenesis in Aged Mice

NEX (neuronal helix-loop-helix protein) is an atonal-related basic helix-loop-helix (bHLH) transcription factor that belongs to the subfamily of neuronal differentiation factors, which also includes NeuroD and NDRF. NEX is expressed in postmitotic pyramidal neurons throughout CNS development and in the adult brain. In rodents, expression starts around embryonic day 11 in postmitotic pyramidal neurons of the cortical plate. In the adult mouse brain expression is maintained in hippocampus proper, amygdala, entorhinal cortex and subiculum. Recent in vitro studies have suggested that NEX promotes neurite outgrowth and regeneration and facilitates neuronal survival. Since inactivation of the Nex gene per se does not have an obvious impact on forebrain formation in the mouse, it is likely that the closely related proteins NeuroD and NDRF can compensate for the loss of NEX protein. However, sustained NEX expression in adult pyramidal neurons of several brain areas, which are implicated in memory formation and retrieval, suggests a function of NEX in neuronal plasticity and higher cognitive functions. The goal of this study was to investigate the function of NEX during murine telencephalon development and in experience-dependent plasticity of the adult brain. To study the role of NEX in the adult brain, a microarray analysis of the hippocampal CA3 region of NEX null mutants versus wildtype animals was performed. In order to test the effect of the NEX null mutation on experience-induced plasticity, an enriched environment paradigm was applied prior to transcriptome analysis. The comparison of gene expression profiles of null mutant and control animals revealed a differential regulation of metabolic pathways and several genes involved in learning and memory. In line with increased metabolic activity of hippocampal neurons, NEX null mutants exhibited hyperactivity in the open field, light-dark preference and plus maze test. Further behavioural studies demonstrated a learning delay in spatial learning tasks and impaired contextual memory formation in NEX null mutants. The spatiotemporal expression pattern of NEX during development and altered expression of cell cycle genes in null mutants suggested a role for NEX in cell cycle exit control and neuronal differentiation. To study the role of NEX during early cortical development a transgenic mouse line was generated, in which NEX expression can be induced by Cre-recombinase. NEX overexpression in neuronal progenitors, but not in postmitotic neurons, resulted in the reduction of cerebral hemisphere size and abnormal cortical layer formation. Massive apoptosis of ventricular zone progenitors and ectopic expression of neuronal differentiation markers indicated premature cell cycle exit and impaired migration. Additionally, a transgenic mouse line allowing doxycycline-regulated control of gene expression in postmitotic pyramidal neurons was created during this study. The NEX-htTA transgenic line is currently being used to study mechanisms of cortical lamination.

Contributions of Mouse and Human Hematopoietic Cells to Remodeling of the Adult Auditory Nerve After Neuron Loss.