Heterogeneity of neural progenitor cells revealed by enhancers in the nestin gene

Identification of a Chondrocyte-Specific Enhancer in the Hoxc8 Gene

Hox genes encode transcription factors whose roles in patterning animal body plans during embryonic development are well-documented. Multiple studies demonstrate that Hox genes continue to act in adult cells, in normal differentiation, in regenerative processes, and, with abnormal expression, in diverse types of cancers. However, surprisingly little is known about the regulatory mechanisms that govern Hox gene expression in specific cell types, as they differentiate during late embryonic development, and in the adult organism. The murine Hoxc8 gene determines the identity of multiple skeletal elements in the lower thoracic and lumbar region and continues to play a role in the proliferation and differentiation of cells in cartilage as the skeleton matures. This study was undertaken to identify regulatory elements in the Hoxc8 gene that control transcriptional activity, specifically in cartilage-producing chondrocytes. We report that an enhancer comprising two 416 and 224 bps long interacting DNA elements produces reporter gene activity when assayed on a heterologous transcriptional promoter in transgenic mice. This enhancer is distinct in spatial, temporal, and molecular regulation from previously identified regulatory sequences in the Hoxc8 gene that control its expression in early development. The identification of a tissue-specific Hox gene regulatory element now allows mechanistic investigations into Hox transcription factor expression and function in differentiating cell types and adult tissues and to specifically target these cells during repair processes and regeneration.

Use of Brain-Derived Stem/Progenitor Cells and Derived Extracellular Vesicles to Repair Damaged Neural Tissues: Lessons Learned from Connective Tissue Repair Regarding Variables Limiting Progress and Approaches to Overcome Limitations

Pluripotent neural stem or progenitor cells (NSC/NPC) have been reported in the brains of adult preclinical models for decades, as have mesenchymal stem/stromal cells (MSC) been reported in a variety of tissues from adults. Based on their in vitro capabilities, these cell types have been used extensively in attempts to repair/regenerate brain and connective tissues, respectively. In addition, MSC have also been used in attempts to repair compromised brain centres. However, success in treating chronic neural degenerative conditions such as Alzheimer's disease, Parkinson's disease, and others with NSC/NPC has been limited, as have the use of MSC in the treatment of chronic osteoarthritis, a condition affecting millions of individuals. However, connective tissues are likely less complex than neural tissues regarding cell organization and regulatory integration, but some insights have been gleaned from the studies regarding connective tissue healing with MSC that may inform studies attempting to initiate repair and regeneration of neural tissues compromised acutely or chronically by trauma or disease. This review will discuss the similarities and differences in the applications of NSC/NPC and MSC, where some lessons have been learned, and potential approaches that could be used going forward to enhance progress in the application of cellular therapy to facilitate repair and regeneration of complex structures in the brain. In particular, variables that may need to be controlled to enhance success are discussed, as are different approaches such as the use of extracellular vesicles from stem/progenitor cells that could be used to stimulate endogenous cells to repair the tissues rather than consider cell replacement as the primary option. Caveats to all these efforts relate to whether cellular repair initiatives will have long-term success if the initiators for neural diseases are not controlled, and whether such cellular initiatives will have long-term success in a subset of patients if the neural diseases are heterogeneous and have multiple etiologies.

Circulating Nestin-GFP+ Cells Participate in the Pathogenesis of Paracoccidioides brasiliensis in the Lungs

Multiple infectious diseases lead to impaired lung function. Revealing the cellular mechanisms involved in this impairment is crucial for the understanding of how the lungs shift from a physiologic to a pathologic state in each specific condition. In this context, we explored the pathogenesis of Paracoccidioidomycosis, which affects pulmonary functioning. The presence of cells expressing Nestin-GFP has been reported in different tissues, and their roles as tissue-specific progenitors have been stablished in particular organs. Here, we explored how Nestin-GFP⁺ cells are affected after lung infection by Paracoccidioides brasiliensis, a model of lung granulomatous inflammation with fibrotic outcome. We used Nestin-GFP transgenic mice, parabiosis surgery, confocal microscopy and flow cytometry to investigate the participation of Nestin-GFP⁺ cells in Paracoccidioides brasiliensis pathogenesis. We revealed that these cells increase in the lungs post-Paracoccidioides brasiliensis infection, accumulating around granulomas. This increase was due mainly to Nestin-GPF⁺ cells derived from the blood circulation, not associated to blood vessels, that co-express markers suggestive of hematopoietic cells (Sca-1, CD45 and CXCR4). Therefore, our findings suggest that circulating Nestin-GFP⁺ cells participate in the Paracoccidioides brasiliensis pathogenesis in the lungs.

MiRNA Regulatory Functions in Photoreceptors

MicroRNAs (miRNAs) are important regulators of gene expression. These small, non-coding RNAs post-transcriptionally silence messenger RNAs (mRNAs) in a sequence-specific manner. In this way, miRNAs control important regulatory functions, also in the retina. If dysregulated, these molecules are involved in several retinal pathologies. For example, several miRNAs have been linked to essential photoreceptor functions, including light sensitivity, synaptic transmission, and modulation of inflammatory responses. Mechanistic miRNA knockout and knockdown studies further linked their functions to degenerative retinal diseases. Of note, the type and timing of genetic manipulation before, during, or after retinal development, is important when studying specific miRNA knockout effects. Within this review, we focus on miR-124 and the miR-183/96/182 cluster, which have assigned functions in photoreceptors in health and disease. As a single miRNA can regulate hundreds of mRNAs, we will also discuss the experimental validation and manipulation approaches to study complex miRNA/mRNA regulatory networks. Revealing these networks is essential to understand retinal pathologies and to harness miRNAs as precise therapeutic and diagnostic tools to stabilize the photoreceptors’ transcriptomes and, thereby, function.

Craniofacial skeletal response to encephalization: How do we know what we think we know?

Dramatic changes in cranial capacity have characterized human evolution. Important evolutionary hypotheses, such as the spatial packing hypothesis, assert that increases in relative brain size (encephalization) have caused alterations to the modern human skull, resulting in a suite of traits unique among extant primates, including a domed cranial vault, highly flexed cranial base, and retracted facial skeleton. Most prior studies have used fossil or comparative primate data to establish correlations between brain size and cranial form, but the mechanistic basis for how changes in brain size impact the overall shape of the skull resulting in these cranial traits remains obscure and has only rarely been investigated critically. We argue that understanding how changes in human skull morphology could have resulted from increased encephalization requires the direct testing of hypotheses relating to interaction of embryonic development of the bones of the skull and the brain. Fossil and comparative primate data have thoroughly described the patterns of association between brain size and skull morphology. Here we suggest complementing such existing datasets with experiments focused on mechanisms responsible for producing the observed patterns to more thoroughly understand the role of encephalization in shaping the modern human skull.

Structural variation during dog domestication: insights from gray wolf and dhole genomes

Several processes like phenotypic evolution, disease susceptibility and environmental adaptations, which fashion the domestication of animals, are largely attributable to structural variations (SVs) in the genome. Here, we present high-quality draft genomes of the gray wolf (Canis lupus) and dhole (Cuon alpinus) with scaffold N50 of 6.04 Mb and 3.96 Mb, respectively. Sequence alignment comprising genomes of three canid species reveals SVs specific to the dog, particularly 16 315 insertions, 2565 deletions, 443 repeats, 16 inversions and 15 translocations. Functional annotation of the dog SVs associated with genes indicates their enrichments in energy metabolisms, neurological processes and immune systems. Interestingly, we identify and verify at population level an insertion fully covering a copy of the AKR1B1 (Aldo-Keto Reductase Family 1 Member B) transcript. Transcriptome analysis reveals a high level of expression of the new AKR1B1 copy in the small intestine and liver, implying an increase in de novo fatty acid synthesis and antioxidant ability in dog compared to gray wolf, likely in response to dietary shifts during the agricultural revolution. For the first time, we report a comprehensive analysis of the evolutionary dynamics of SVs during the domestication step of dogs. Our findings demonstrate that retroposition can birth new genes to facilitate domestication, and affirm the importance of large-scale genomic variants in domestication studies.

Combined Experimental and System-Level Analyses Reveal the Complex Regulatory Network of miR-124 during Human Neurogenesis

Non-coding RNAs regulate many biological processes including neurogenesis. The brain-enriched miR-124 has been assigned as a key player of neuronal differentiation via its complex but little understood regulation of thousands of annotated targets. To systematically chart its regulatory functions, we used CRISPR/Cas9 gene editing to disrupt all six miR-124 alleles in human induced pluripotent stem cells. Upon neuronal induction, miR-124-deleted cells underwent neurogenesis and became functional neurons, albeit with altered morphology and neurotransmitter specification. Using RNA-induced-silencing-complex precipitation, we identified 98 high-confidence miR-124 targets, of which some directly led to decreased viability. By performing advanced transcription-factor-network analysis, we identified indirect miR-124 effects on apoptosis, neuronal subtype differentiation, and the regulation of previously uncharacterized zinc finger transcription factors. Our data emphasize the need for combined experimental- and system-level analyses to comprehensively disentangle and reveal miRNA functions, including their involvement in the neurogenesis of diverse neuronal cell types found in the human brain.

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miR-124 is not essential for neurogenesis from human iPSCs

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miR-124 regulation mediates neuroprotection and refines neuronal cell fates

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miRNA knockout characterization by experimental and advanced computational analyses

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Identification of 98 targets including the neuronal feature repressor ZNF787

The Biological Role of Nestin(+)-Cells in Physiological and Pathological Cardiovascular Remodeling

The intermediate filament protein nestin was identified in diverse populations of cells implicated in cardiovascular remodeling. Cardiac resident neural progenitor/stem cells constitutively express nestin and following an ischemic insult migrate to the infarct region and participate in angiogenesis and neurogenesis. A modest number of normal adult ventricular fibroblasts express nestin and the intermediate filament protein is upregulated during the progression of reparative and reactive fibrosis. Nestin depletion attenuates cell cycle re-entry suggesting that increased expression of the intermediate filament protein in ventricular fibroblasts may represent an activated phenotype accelerating the biological impact during fibrosis. Nestin immunoreactivity is absent in normal adult rodent ventricular cardiomyocytes. Following ischemic damage, the intermediate filament protein is induced in a modest population of pre-existing adult ventricular cardiomyocytes bordering the peri-infarct/infarct region and nestin⁽⁺⁾-ventricular cardiomyocytes were identified in the infarcted human heart. The appearance of nestin⁽⁺⁾-ventricular cardiomyocytes post-myocardial infarction (MI) recapitulates an embryonic phenotype and depletion of the intermediate filament protein inhibits cell cycle re-entry. Recruitment of the serine/threonine kinase p38 MAPK secondary to an overt inflammatory response after an ischemic insult may represent a seminal event limiting the appearance of nestin⁽⁺⁾-ventricular cardiomyocytes and concomitantly suppressing cell cycle re-entry. Endothelial and vascular smooth muscle cells (VSMCs) express nestin and upregulation of the intermediate filament protein may directly contribute to vascular remodeling. This review will highlight the biological role of nestin⁽⁺⁾-cells during physiological and pathological remodeling of the heart and vasculature and discuss the phenotypic advantage attributed to the intermediate filament protein.

HMGB1/Advanced Glycation End Products (RAGE) does not aggravate inflammation but promote endogenous neural stem cells differentiation in spinal cord injury

Receptor for advanced glycation end products (RAGE) signaling is involved in a series of cell functions after spinal cord injury (SCI). Our study aimed to elucidate the effects of RAGE signaling on the neuronal recovery after SCI. In vivo, rats were subjected to SCI with or without anti-RAGE antibodies micro-injected into the lesion epicenter. We detected Nestin/RAGE, SOX-2/RAGE and Nestin/MAP-2 after SCI by Western blot or immunofluorescence (IF). We found that neural stem cells (NSCs) co-expressed with RAGE were significantly activated after SCI, while stem cell markers Nestin and SOX-2 were reduced by RAGE blockade. We found that RAGE inhibition reduced nestin-positive NSCs expressing MAP-2, a mature neuron marker. RAGE blockade does not improve neurobehavior Basso, Beattie and Bresnahan (BBB) scores; however, it damaged survival of ventral neurons via Nissl staining. Through in vitro study, we found that recombinant HMGB1 administration does not lead to increased cytokines of TNF-α and IL-1β, while anti-RAGE treatment reduced cytokines of TNF-α and IL-1β induced by LPS via ELISA. Meanwhile, HMGB1 increased MAP-2 expression, which was blocked after anti-RAGE treatment. Hence, HMGB1/RAGE does not exacerbate neuronal inflammation but plays a role in promoting NSCs differentiating into mature neurons in the pathological process of SCI.

Neuronal Differentiation Capability of Nasal Polyps of Chronic Rhinosinusitis

Chronic rhinosinusitis with nasal polyps is considered a subgroup of chronic rhinosinusitis and a significant health problem, but the pathogenesis remains unclear to date. Therefore, we investigated the stemness to determine the role of stem cells in nasal polyps, with additional analysis of the neuronal differentiation potential of nasal polyp cells. We determined gene and protein expression profiles of stem cells in nasal polyp tissues, using whole genome microarray, quantitative real-time PCR (qPCR), immunohistochemistry, and flow cytometry. To evaluate the neuronal differentiation potential of nasal polyp cells, we used an efficient xenogeneic co-culture model with unsliced adult rat brain biopsies, followed by qPCR, immunohistochemistry, and growth factor antibody arrays. During gene expression analysis and immunohistochemistry, we were able to detect different stem cell markers, like Oct-4, Sox2, Klf4, c-Myc, ABCG2, Nanog, CD133, and Nestin, which confirmed the existence of stem cell like cells within nasal polyps. In addition, co-culture experiments give evidence for a guided differentiation into the neuronal lineage by overexpression of Nestin, Neurofilament, and GM-CSF. Our study demonstrated the expression of stem cell-related markers in nasal polyps. Furthermore, we characterized, for the first time, the stemness and neuronal differentiation potential of nasal polyp cells. These results gave new insights into the pathogenesis of nasal polyps and its therapeutic effectiveness could represent a promising strategy in the future.

Discovery of HAP Stem Cells

Cells expressing the stem cell marker, nestin, were selectively labeled in transgenic mice by placing green fluorescent protein (GFP) under the control of the nestin promoter in transgenic mice. In these transgenic mice, neural and other stem cells brightly expressed GFP. The mice were termed nestin-driven GFP (ND-GFP) mice. During early anagen or growth phase of the hair follicle, ND-GFP appeared in the permanent upper hair follicle immediately below the sebaceous glands in the follicle bulge. The relatively small, oval-shaped, nestin-expressing cells in the bulge area surrounded the hair shaft and were interconnected by short dendrites. The location of the nestin-expressing cells in the hair follicle varied with the hair cycle. During telogen or resting phase and in early anagen, the GFP-positive cells are mainly in the bulge area. However, in mid- and late-anagen, the GFP-expressing cells were located in the upper outer-root sheath as well as in the bulge area. The expression of the unique protein, nestin, in both neural stem cells and hair follicle stem cells, which suggested their relationship. The ND-GFP hair follicle stem cells were later termed hair-follicle-associated pluripotent (HAP) stem cells.

Transgenic mouse models for studying adult neurogenesis

The mammalian hippocampus shows a remarkable capacity for continued neurogenesis throughout life. Newborn neurons, generated by the radial neural stem cells (NSCs), are important for learning and memory as well as mood control. During aging, the number and responses of NSCs to neurogenic stimuli diminish, leading to decreased neurogenesis and age-associated cognitive decline and psychiatric disorders. Thus, adult hippocampal neurogenesis has garnered significant interest because targeting it could be a novel potential therapeutic strategy for these disorders. However, if we are to use neurogenesis to halt or reverse hippocampal-related pathology, we need to understand better the core molecular machinery that governs NSC and their progeny. In this review, we summarize a wide variety of mouse models used in adult neurogenesis field, present their advantages and disadvantages based on specificity and efficiency of labeling of different cell types, and review their contribution to our understanding of the biology and the heterogeneity of different cell types found in adult neurogenic niches.

Nestin-Based Reporter Transgenic Mouse Lines

Nestin expression marks stem and progenitor cells of the neural lineage. Transgenic mouse lines, originally generated to identify neural stem cells, can also help to identify, track, and isolate stem and progenitor cells in a range of tissues of the ectodermal, endodermal, and mesodermal origin. Here, we describe the generation of transgenic mouse lines expressing fluorescent proteins (FP) under the control of critical regulatory elements of the nestin gene and their use for identifying and analyzing adult stem and progenitor cells in various tissues.

Nestin involvement in tissue injury and cancer--a potential tumor marker?

BACKGROUND

In eukaryotic cells, the cytoskeleton contains three major filamentous components: actin microfilaments, microtubules and intermediate filaments. Nestin represents one of the class VI intermediate filament proteins. Clinical and molecular analyses have revealed substantial information regarding the presence of Nestin in cells with progenitor or stem cell properties. During tissue injury Nestin is expressed in cells with progenitor cell-like properties. These cells may serve as a tissue reserve and, as such, may contribute to tissue repair. Based on currently available data, Nestin also appears to be implicated in two oncogenic processes. First, Nestin has been found to be expressed in cancer stem-like cells and poorly differentiated cancer cells and, as such, Nestin is thought to contribute to the aggressive behavior of these cells. Second, Nestin has been found to be involved in tumor angiogenesis through an interaction of cancer cells and blood vessel endothelial cells and, as such, Nestin is thought to facilitate tumor growth.

CONCLUSIONS

We conclude that Nestin may serve as a promising tumor marker and as a potential therapeutic target amenable to tumor suppression and angiogenesis inhibition.

Multipotent nestin-positive stem cells reside in the stroma of human eccrine and apocrine sweat glands and can be propagated robustly in vitro

Human skin harbours multiple different stem cell populations. In contrast to the relatively well-characterized niches of epidermal and hair follicle stem cells, the localization and niches of stem cells in other human skin compartments are as yet insufficiently investigated. Previously, we had shown in a pilot study that human sweat gland stroma contains Nestin-positive stem cells. Isolated sweat gland stroma-derived stem cells (SGSCs) proliferated in vitro and expressed Nestin in 80% of the cells. In this study, we were able to determine the precise localization of Nestin-positive cells in both eccrine and apocrine sweat glands of human axillary skin. We established a reproducible isolation procedure and characterized the spontaneous, long-lasting multipotent differentiation capacity of SGSCs. Thereby, a pronounced ectodermal differentiation was observed. Moreover, the secretion of prominent cytokines demonstrated the immunological potential of SGSCs. The comparison to human adult epidermal stem cells (EpiSCs) and bone marrow stem cells (BMSCs) revealed differences in protein expression and differentiation capacity. Furthermore, we found a coexpression of the stem cell markers Nestin and Iα6 within SGSCs and human sweat gland stroma. In conclusion the initial results of the pilot study were confirmed, indicating that human sweat glands are a new source of unique stem cells with multilineage differentiation potential, high proliferation capacity and remarkable self renewal. With regard to the easy accessibility of skin tissue biopsies, an autologous application of SGSCs in clinical therapies appears promising.

Sensory cortex limits cortical maps and drives top-down plasticity in thalamocortical circuits

Primary somatosensory cortex (S1) contains a complete body map that mirrors subcortical maps developed by peripheral sensory input projecting to sensory hindbrain, thalamus, then S1. Peripheral changes during development alter these maps through ‘bottom-up’ plasticity. Unknown is how S1 size influences map organization and if an altered S1 map feedbacks to affect subcortical maps. We show in mice that S1 is significantly reduced by cortex-specific deletion of Pax6, resulting in a reduced body map and loss of body representations by exclusion of later-differentiating sensory thalamocortical input. An initially normal sensory thalamus was re-patterned to match the aberrant S1 map by apoptotic deletion of thalamic neurons representing body parts with axons excluded from S1. Deleted representations were rescued by altering competition between thalamocortical axons by sensory deprivation or increasing S1. Thus, S1 size determined resolution and completeness of body maps and engaged ‘top-down’ plasticity that re-patterned sensory thalamus to match S1.

Transgenic studies on homeobox genes in nervous system development: spina bifida in Isl1 transgenic mice

To develop in vivo assays for homeobox gene function in neural development, we generated transgenic mice in which the expression of a homeobox gene is altered only within the nervous system, in neurons or neuronal precursor cells. Transgenic expression of Hoxc8 did not result in gross abnormalities, while a Hoxd4 transgene caused death shortly after birth. In neural progenitor cells, the motorneuron-specific homeodomain transcription factor Isl1 induced early developmental defects, including absence of anterior neural structures, profound defects in the neuroepithelium and defective neural tube closure. A fraction of Isl1 transgenic mice exhibited spina bifida. Isl1 transgene expression was also associated with decreased proliferation and increased Pbx1 expression in the ventral neural tube. Our results suggest a function for some homeobox genes in development of the nervous system, and that cell-type- and region-specific transgenic models will be useful to identify the cellular and molecular targets of homeobox transcription factors in nervous system development.

Quantitative proteomic analysis of amniocytes reveals potentially dysregulated molecular networks in Down syndrome

BACKGROUND

Down syndrome (DS), caused by an extra copy of chromosome 21, affects 1 in 750 live births and is characterized by cognitive impairment and a constellation of congenital defects. Currently, little is known about the molecular pathogenesis and no direct genotype-phenotype relationship has yet been confirmed. Since DS amniocytes are expected to have a distinct biological behaviour compared to normal amniocytes, we hypothesize that relative quantification of proteins produced from trisomy and euploid (chromosomally normal) amniocytes will reveal dysregulated molecular pathways.

RESULTS

Chromosomally normal- and Trisomy 21-amniocytes were quantitatively analyzed by using Stable Isotope Labeling of Amino acids in Cell culture and tandem mass spectrometry. A total of 4919 unique proteins were identified from the supernatant and cell lysate proteome. More specifically, 4548 unique proteins were identified from the lysate, and 91% of these proteins were quantified based on MS/MS spectra ratios of peptides containing isotope-labeled amino acids. A total of 904 proteins showed significant differential expression and were involved in 25 molecular pathways, each containing a minimum of 16 proteins. Sixty of these proteins consistently showed aberrant expression from trisomy 21 affected amniocytes, indicating their potential role in DS pathogenesis. Nine proteins were analyzed with a multiplex selected reaction monitoring assay in an independent set of Trisomy 21-amniocyte samples and two of them (SOD1 and NES) showed a consistent differential expression.

CONCLUSIONS

The most extensive proteome of amniocytes and amniotic fluid has been generated and differentially expressed proteins from amniocytes with Trisomy 21 revealed molecular pathways that seem to be most significantly affected by the presence of an extra copy of chromosome 21.

Epigenetic regulation of nestin expression during neurogenic differentiation of adipose tissue stem cells

Adipose-tissue-derived stem cells (ASCs) have received considerable attention due to their easy access, expansion potential, and differentiation capacity. ASCs are believed to have the potential to differentiate into neurons. However, the mechanisms by which this may occur remain largely unknown. Here, we show that culturing ASCs under active proliferation conditions greatly improves their propensity to differentiate toward osteogenic, adipogenic, and neurogenic lineages. Neurogenic-induced ASCs express early neurogenic genes as well as markers of mature neurons, including voltage-gated ion channels. Nestin, highly expressed in neural progenitors, is upregulated by mitogenic stimulation of ASCs, and as in neural progenitors, then repressed during neurogenic differentiation. Nestin gene (NES) expression under these conditions appears to be regulated by epigenetic mechanisms. The neural-specific, but not muscle-specific, enhancer regions of NES are DNA demethylated by mitogenic stimulation, and remethylated upon neurogenic differentiation. We observe dynamic changes in histone H3K4, H3K9, and H3K27 methylation on the NES locus before and during neurogenic differentiation that are consistent with epigenetic processes involved in the regulation of NES expression. We suggest that ASCs are epigenetically prepatterned to differentiate toward a neural lineage and that this prepatterning is enhanced by demethylation of critical NES enhancer elements upon mitogenic stimulation preceding neurogenic differentiation. Our findings provide molecular evidence that the differentiation repertoire of ASCs may extend beyond mesodermal lineages.

Constitutive activation of β-catenin in neural progenitors results in disrupted proliferation and migration of neurons within the central nervous system

Wnt signaling is known to play crucial roles in the development of multiple organs as well as in cancer. In particular, constitutive activation of Wnt/β-Catenin signaling in distinct populations of forebrain or brainstem precursor cells has previously been shown to result in dramatic brain enlargement during embryonic stages of development as well as in the formation of medulloblastoma, a malignant brain tumor in childhood. In order to extend this knowledge to postnatal stages of both cerebral and cerebellar cortex development, we conditionally activated Wnt signaling by introducing a dominant active form of β-catenin in hGFAP-positive neural precursors. Such mutant mice survived up to 21 days postnatally. While the mice revealed enlarged ventricles and an initial expansion of the Pax6-positive ventricular zone, Pax6 expression and proliferative activity in the ventricular zone was virtually lost by embryonic day 16.5. Loss of Pax6 expression was not followed by expression of the subventricular zone marker Tbr2, indicating insufficient neuronal differentiation. In support of this finding, cortical thickness was severely diminished in all analyzed stages from embryonic day 14.5 to postnatal day 12, and appropriate layering was not detectable. Similarly, cerebella of hGFAP-cre::Ctnnb1(ex3)(Fl/+) mice were hypoplastic and displayed severe lamination defects. Constitutively active β-Catenin induced inappropriate proliferation of granule neurons and inadequate development of Bergmann glia, thereby preventing regular migration of granule cells and normal cortical layering. We conclude that Wnt signaling has divergent roles in the central nervous system and that Wnt needs to be tightly controlled in a time- and cell type-specific manner.

Targeted deletion of Hand2 in enteric neural precursor cells affects its functions in neurogenesis, neurotransmitter specification and gangliogenesis, causing functional aganglionosis

Targeted deletion of the bHLH DNA-binding protein Hand2 in the neural crest, impacts development of the enteric nervous system (ENS), possibly by regulating the transition from neural precursor cell to neuron. We tested this hypothesis by targeting Hand2 deletion in nestin-expressing neural precursor (NEP) cells. The mutant mice showed abnormal ENS development, resulting in lethal neurogenic pseudo-obstruction. Neurogenesis of neurons derived from NEP cells identified a second nestin non-expressing neural precursor (NNEP) cell in the ENS. There was substantial compensation for the loss of neurons derived from the NEP pool by the NNEP pool but this was insufficient to abrogate the negative impact of Hand2 deletion. Hand2-mediated regulation of proliferation affected both neural precursor and neuron numbers. Differentiation of glial cells derived from the NEP cells was significantly decreased with no compensation from the NNEP pool of cells. Our data indicate differential developmental potential of NEPs and NNEPs; NNEPs preferentially differentiate as neurons, whereas NEPs give rise to both neurons and glial cells. Deletion of Hand2 also resulted in complete loss of NOS and VIP and a significant decrease in expression of choline acetyltransferase and calretinin, demonstrating a role for Hand2 in neurotransmitter specification and/or expression. Loss of Hand2 resulted in a marked disruption of the developing neural network, exemplified by lack of a myenteric plexus and extensive overgrowth of fibers. Thus, Hand2 is essential for neurogenesis, neurotransmitter specification and neural network patterning in the developing ENS.

Nestin+ cells and healing the infarcted heart

Scar formation following an ischemic insult to the heart is referred to as reparative fibrosis and represents an essential physiological response to heal the damaged myocardium. The biological events of reparative fibrosis include inflammation, the deposition of collagen by myofibroblasts, sympathetic innervation, and angiogenesis. Several studies have further reported that scar formation was associated with the recruitment of neural crest-derived cardiac resident nestin(+) cells that display characteristics consistent with a neural progenitor/stem cell phenotype. During the reparative fibrotic response, these nestin(+) cells participate in neural remodeling and represent a novel cellular substrate of angiogenesis. In addition, a subpopulation of nestin(+) cells identified in the normal heart expressed cardiac progenitor transcriptional factors and may directly contribute to myocardial regeneration following ischemic damage. Nestin protein was also detected in endothelial cells of newly formed blood vessels in the scar and may represent a marker of revascularization. Lastly, nestin was induced in a subpopulation of smooth muscle α-actin(+) scar-derived myofibroblasts, and the expression of the intermediate filament protein may provide a proliferative advantage. Collectively, these data demonstrate that diverse populations of nestin(+) cells participate in cardiac wound healing.

A novel xenogeneic co-culture system to examine neuronal differentiation capability of various adult human stem cells

Background

Targeted differentiation of stem cells is mainly achieved by the sequential administration of defined growth factors and cytokines, although these approaches are quite artificial, cost-intensive and time-consuming. We now present a simple xenogeneic rat brain co-culture system which supports neuronal differentiation of adult human stem cells under more in vivo-like conditions.

Methods and Findings

This system was applied to well-characterized stem cell populations isolated from human skin, parotid gland and pancreas. In addition to general multi-lineage differentiation potential, these cells tend to differentiate spontaneously into neuronal cell types in vitro and are thus ideal candidates for the introduced co-culture system. Consequently, after two days of co-culture up to 12% of the cells showed neuronal morphology and expressed corresponding markers on the mRNA and protein level. Additionally, growth factors with the ability to induce neuronal differentiation in stem cells could be found in the media supernatants of the co-cultures.

Conclusions

The co-culture system described here is suitable for testing neuronal differentiation capability of numerous types of stem cells. Especially in the case of human cells, it may be of clinical relevance for future cell-based therapeutic applications.

Nestin reporter transgene labels multiple central nervous system precursor cells

Embryonic neuroepithelia and adult subventricular zone (SVZ) stem and progenitor cells express nestin. We characterized a transgenic line that expresses enhanced green fluorescent protein (eGFP) specified to neural tissue by the second intronic enhancer of the nestin promoter that had several novel features. During embryogenesis, the dorsal telencephalon contained many and the ventral telencephalon few eGFP+ cells. eGFP+ cells were found in postnatal and adult neurogenic regions. eGFP+ cells in the SVZ expressed multiple phenotype markers, glial fibrillary acidic protein, Dlx, and neuroblast-specific molecules suggesting the transgene is expressed through the lineage. eGFP+ cell numbers increased in the SVZ after cortical injury, suggesting this line will be useful in probing postinjury neurogenesis. In non-neurogenic regions, eGFP was strongly expressed in oligodendrocyte progenitors, but not in astrocytes, even when they were reactive. This eGFP+ mouse will facilitate studies of proliferative neuroepithelia and adult neurogenesis, as well as of parenchymal oligodendrocytes.

A genetic and functional relationship between T cells and cellular proliferation in the adult hippocampus

A large correlation between variation in T cell subsets and hippocampal neurogenesis suggests that the immune system has an unexpectedly large influence on the brain.

Neurogenesis continues through the adult life of mice in the subgranular zone of the dentate gyrus in the hippocampus, but its function remains unclear. Measuring cellular proliferation in the hippocampus of 719 outbred heterogeneous stock mice revealed a highly significant correlation with the proportions of CD8+ versus CD4+ T lymphocyte subsets. This correlation reflected shared genetic loci, with the exception of the H-2Ea locus that had a dominant influence on T cell subsets but no impact on neurogenesis. Analysis of knockouts and repopulation of TCRα-deficient mice by subsets of T cells confirmed the influence of T cells on adult neurogenesis, indicating that CD4+ T cells or subpopulations thereof mediate the effect. Our results reveal an organismal impact, broader than hitherto suspected, of the natural genetic variation that controls T cell development and homeostasis.

In adult mice new neurons are produced in the hippocampus, where they are thought to influence learning, memory, and emotional regulation. The mechanisms and functions of this neurogenesis, however, remain unclear. Here we report that in different strains of mice, variation in cellular proliferation in the hippocampus (an index of neurogenesis) correlates with variation in the relative proportions of the ratio of CD4+ to CD8+ T cells (an immunology phenotype). We also show that T cells can influence neurogenesis (but that neurogenesis does not influence T cells) by analyzing knockouts, depleting mice of T cells, and repopulating alymphoid animals. The strong genetic correlation between T cells and cellular proliferation in the hippocampus contrasts with the weak, often non-significant, correlation with behavioral phenotypes. Of significance, the findings here suggest that modulation of the functions of the hippocampus to influence behavior is not the primary role of neurogenesis.

Identification of the Tctex-1 regulatory element that directs expression to neural stem/progenitor cells in developing and adult brain

Previous studies showed that Tctex-1 immunoreactivity is selectively enriched in the germinal zones of adult brain. In this report we identify a regulatory region of the Tctex-1 gene that is capable of directing transgenic expression of green fluorescent protein (GFP) reporter that recapitulates the spatial and temporal expression pattern of endogenous Tctex-1. This construct specifically targeted expression to the nestin(+)/Pax6(+)/GLAST(+) radial glial cells and Tbr2(+) intermediate progenitors when the reporter construct was delivered to developing mouse neocortex via in utero electroporation. Characterization of mice transgenically expressing GFP under the same regulatory element showed that the GFP expression is faithful to endogenous Tctex-1 at the subgranular zone (SGZ) of dentate gyrus, ventricular/subventricular zone of lateral ventricles, and ependymal layer of 3rd ventricle of adult brains. Immunolocalization and bromodeoxyuridine incorporation studies of adult SGZ in four independent mouse lines showed that Tctex-1:GFP reporter selectively marks nestin(+)/GFAP(+)/Sox2(+) neural stem-like cells in two mouse lines (4 and 13). In two other mouse lines (17 and 18), Tctex-1:GFP is selectively expressed in Type-2 and Type-3 transient amplifying progenitors and a small subset of young neuronal progeny. The P/E-Tctex-1 reporter mouse studies independently confirmed the specific enrichment of Tctex-1 at adult SGZ stem/progenitor cells. Furthermore, these studies supported the notion that an analogous transcriptional program may be used to regulate neurogenesis in embryonic cerebral cortex and adult hippocampus. Finally, the genomic sequences and the reporter mouse lines described here provide useful experimental tools to advance adult neural stem cell research.

Description of distributed features of the nestin-containing cells in brains of adult mice: a potential source of neural precursor cells

The distribution of neural precursor cells (NPCs) in adult mice brain has so far not been described. Therefore, we investigated the distribution of NPCs by analyzing the nestin-containing cells (NCCs) in distinct brain regions of adult nestin second-intron enhancer-controlled LacZ reporter transgenic mice through LacZ staining. Results showed that NCCs existed in various regions of adult mouse brain. In cerebellum, the greatest number of NCCs existed in cortex of the simple lobule, followed by cortex of the cerebellar lobule. In olfactory bulb, NCCs were most numerous in the granular cell layer, followed by the mitral cell layer and the internal plexiform, glomerular, and external plexiform layers. In brain nuclei (nu), NCCs were most numerous in the marginal nu, followed by the brainstem and diencephalon nu. NCCs in sensory nu of brainstem were more numerous than in motor nu, and NCCs in the dorsal of sensory nu were more numerous than in the ventral part. In brain ventricle systems, NCCs were largely distributed in the center of and external to the lateral ventricle, the inferior part of the third ventricle, the dorsal and inferior parts of the fourth ventricle, and the gray matter around the cerebral aqueduct. NCCs in the left vs. right brain were not significantly different. These data collectively indicate that NCCs were extensively distributed in the cerebellum and olfactory bulb, the partial nu of the marginal system, the partial brain nu adjacent to brain ventricle systems, the subependymal zone, and the cerebral cortex around the marginal lobe and were a potential source of NPCs.

Evaluation of the frequency of putative prostate cancer stem cells in primary and metastatic prostate cancer

BACKGROUND

Tumour cells with a stem cell-like phenotype have recently been identified in prostate tumors and it has been suggested that this population may be responsible for the diversity of cell types within tumors and also for the initiation of metastases. These cells carry a number of defined markers: they are cd133 and cd44+ve and express high levels of alpha2beta1 integrin. In this study we have, for the first time, assessed matched primary and bone marrow biopsies from prostate cancer patients for the distribution of cells carrying these and a number of other putative stem cell markers.

METHODS

Eleven matched (primary and bone metastasis) specimens from prostate cancer patients were assessed for the presence of cd133, cd44, alpha2beta1 integrin, CXCR4, c-met, alpha6 integrin, and nestin using immunohistochemistry and stain intensity and distribution scored.

RESULTS

In the bone metastases, tumor cells staining positively for cd133 were detected at low frequency in approximately 50% of samples. Staining for nestin was confined to endothelium. Positive staining of tumor cells for the other antigens was present at variable frequency in >70% of metastases with the exception of CXCR4 which was absent from all but 2 specimens. Where positive staining of tumor cells was present in the metastasis, cells staining for each antigen were present in the matched primary with the exception of cd44 which was absent in all but 2/11 matched primary tissues.

CONCLUSIONS

In established metastases no single or combination of marker expression profiles identify the established metastatic phenotype, although cd44 expression was shown to be more frequent in metastases that in primary cancers.

'In vivo' optical approaches to angiogenesis imaging

In recent years, molecular imaging gained significant importance in biomedical research. Optical imaging developed into a modality which enables the visualization and quantification of all kinds of cellular processes and cancerous cell growth in small animals. Novel gene reporter mice and cell lines and the development of targeted and cleavable fluorescent "smart" probes form a powerful imaging toolbox. The development of systems collecting tomographic bioluminescence and fluorescence data enabled even more spatial accuracy and more quantitative measurements. Here we describe various bioluminescent and fluorescent gene reporter models and probes that can be used to specifically image and quantify neovascularization or the angiogenic process itself.

Type 1 insulin-like growth factor receptor signaling is essential for the development of the hippocampal formation and dentate gyrus

Type 1 insulin-like growth factor receptor (IGF1R) signaling in neuronal development was studied in mutant mice with blunted igf1r gene expression in nestin-expressing neuronal precursors. At birth [postnatal (P) day 0] brain weights were reduced to 37% and 56% of controls in mice homozygous (nes-igf1r(-/-)) and heterozygous (nes-igf1r(-/Wt)) for the null mutation, respectively, and this brain growth retardation persisted postnatally. Stereological analysis demonstrated that the volumes of the hippocampal formation, CA fields 1-3, dentate gyrus (DG), and DG granule cell layer (GCL) were decreased by 44-54% at P0 and further by 65-69% at P90 in nes-igf1r(-/Wt) mice. In nes-igf1r(-/-) mice, volumes were 29-31% of controls at P0 and, in the two mice that survived to P90, 6-19% of controls, although the hilus could not be identified. Neuron density did not differ among the mice at any age studied; therefore, decreased volumes were due to reduced cell number. In postnatal nes-igf1r(-/Wt) mice, the percentage of apoptotic cells, as judged by activated caspase-3 immunostaining, was increased by 3.5-5.3-fold. The total number of proliferating DG progenitors (labeled by BrdU incorporation and Ki67 staining) was reduced by approximately 50%, but the percentage of these cells was similar to the percentages in littermate controls. These findings suggest that 1) the postnatal reduction in DG size is due predominantly to cell death, pointing to the importance of the IGF1R in regulating postnatal apoptosis, 2) surviving DG progenitors remain capable of proliferation despite reduced IGF1R expression, and 3) IGF1R signaling is necessary for normal embryonic brain development.

Identification of regulatory elements in the Isl1 gene locus

Isl1 is a LIM/homeodomain transcription factor with critical roles for the development of the heart, the nervous system and the pancreas. Both deficiency and mis-expression of Isl1 cause profound developmental defects, demonstrating the importance of proper regulation of Isl1 gene expression during development. In order to understand the mechanisms that control Isl1 expression during embryogenesis and in tissue differentiation, we initiated a screen for gene regulatory elements in the Isl1 locus using a novel dual reporter gene vector that allows screens of large genomic regions through reporter gene assays in vitro and in vivo. We identified regions from the Isl1 gene locus that confer transcriptional activity in pancreatic cell lines in vitro. Using transgenic mice, we furthermore discovered an enhancer with in vivo specificity for the developing heart, as well as visceral and posterior mesoderm. Our findings further suggest that Foxo1 as well as Gata4 contribute to the activity of this enhancer in the developing embryo. We conclude that Isl1 gene expression is controlled in modular fashion by several elements with distinct functionality. Embryonic Isl1 expression in several tissues of mesodermal origin is driven by a specific enhancer that is located 3-6kb downstream of the gene.

High-density microwell chip for culture and analysis of stem cells

With recent findings on the role of reprogramming factors on stem cells, in vitro screening assays for studying (de)-differentiation is of great interest. We developed a miniaturized stem cell screening chip that is easily accessible and provides means of rapidly studying thousands of individual stem/progenitor cell samples, using low reagent volumes. For example, screening of 700,000 substances would take less than two days, using this platform combined with a conventional bio-imaging system. The microwell chip has standard slide format and consists of 672 wells in total. Each well holds 500 nl, a volume small enough to drastically decrease reagent costs but large enough to allow utilization of standard laboratory equipment. Results presented here include weeklong culturing and differentiation assays of mouse embryonic stem cells, mouse adult neural stem cells, and human embryonic stem cells. The possibility to either maintain the cells as stem/progenitor cells or to study cell differentiation of stem/progenitor cells over time is demonstrated. Clonality is critical for stem cell research, and was accomplished in the microwell chips by isolation and clonal analysis of single mouse embryonic stem cells using flow cytometric cell-sorting. Protocols for practical handling of the microwell chips are presented, describing a rapid and user-friendly method for the simultaneous study of thousands of stem cell cultures in small microwells. This microwell chip has high potential for a wide range of applications, for example directed differentiation assays and screening of reprogramming factors, opening up considerable opportunities in the stem cell field.

Epigenetic hierarchy governing Nestin expression

Nestin is an intermediate filament protein expressed specifically in neural stem cells and progenitor cells of the central nervous system. DNA demethylation and histone modifications are two types of epigenetic modifications working in a coordinate or synergistic manner to regulate the expression of various genes. This study investigated and elucidated the epigenetic regulation of Nestin gene expression during embryonic differentiation along the neural cell lineage. Nestin exhibits differential DNA methylation and histone acetylation patterns in Nestin-expressing and nonexpressing cells. In P19 embryonic carcinoma cells, activation of Nestin expression is mediated by both trichostatin A and 5-aza-2'-deoxycytidine treatment, concomitant with histone acetylation, but not with DNA demethylation. Nestin transcription is also mediated by treatment with retinoic acid, again in the absence of DNA demethylation. Thus, histone acetylation is sufficient to mediate the activation of Nestin transcription. This study proposed that the regulation of Nestin gene expression can be used as a model to study the epigenetic regulation of gene expression mediated by histone acetylation, but not by DNA demethylation.

Nestin modulates glucocorticoid receptor function by cytoplasmic anchoring

Nestin is the characteristic intermediate filament (IF) protein of rapidly proliferating progenitor cells and regenerating tissue. Nestin copolymerizes with class III IF-proteins, mostly vimentin, into heteromeric filaments. Its expression is downregulated with differentiation. Here we show that a strong nestin expression in mouse embryo tissue coincides with a strong accumulation of the glucocorticoid receptor (GR), a key regulator of growth and differentiation in embryonic development. Microscopic studies on cultured cells show an association of GR with IFs composed of vimentin and nestin. Cells lacking nestin, but expressing vimentin, or cells expressing vimentin, but lacking nestin accumulate GR in the nucleus. Completing these networks with an exogenous nestin, respectively an exogenous vimentin restores cytoplasmic anchoring of GR to the IF system. Thus, heteromeric filaments provide the basis for anchoring of GR. The reaction pattern with phospho-GR specific antibodies and the presence of the chaperone HSC70 suggest that specifically the unliganded receptor is anchored to the IF system. Ligand addition releases GR from IFs and shifts the receptor into the nucleus. Suppression of nestin by specific shRNA abolishes anchoring of GR, induces its accumulation in the nucleus and provokes an irreversible G1/S cell cycle arrest. Suppression of GR prior to that of nestin prevents entry into the arrest. The data give evidence that nestin/vimentin specific anchoring modulates growth suppression by GR. We hypothesize that expression of nestin is a major determinant in suppression of anti-proliferative activity of GR in undifferentiated tissue and facilitates activation of this growth control in a precise tissue and differentiation dependent manner.

Conditional ablation and recovery of forebrain neurogenesis in the mouse

Forebrain neurogenesis persists throughout life in the rodent subventricular zone (SVZ) and hippocampal dentate gyrus (DG). Several strategies have been employed to eliminate adult neurogenesis and thereby determine whether depleting adult-born neurons disrupts specific brain functions, but some approaches do not specifically target neural progenitors. We have developed a transgenic mouse line to reversibly ablate adult neural stem cells and suppress neurogenesis. The nestin-tk mouse expresses herpes simplex virus thymidine kinase (tk) under the control of the nestin 2nd intronic enhancer, which drives expression in neural progenitors. Administration of ganciclovir (GCV) kills actively dividing cells expressing this transgene. We found that peripheral GCV administration suppressed SVZ-olfactory bulb and DG neurogenesis within 2 weeks but caused systemic toxicity. Intracerebroventricular GCV infusion for 28 days nearly completely depleted proliferating cells and immature neurons in both the SVZ and DG without systemic toxicity. Reversibility of the effects after prolonged GCV infusion was slow and partial. Neurogenesis did not recover 2 weeks after cessation of GCV administration, but showed limited recovery 6 weeks after GCV that differed between the SVZ and DG. Suppression of neurogenesis did not inhibit antidepressant responsiveness of mice in the tail suspension test. These findings indicate that SVZ and DG neural stem cells differ in their capacity for repopulation, and that adult-born neurons are not required for antidepressant responses in a common behavioral test of antidepressant efficacy. The nestin-tk mouse should be useful for studying how reversible depletion of adult neurogenesis influences neurophysiology, other behaviors, and neural progenitor dynamics.

Different transcription factors regulate nestin gene expression during P19 cell neural differentiation and central nervous system development

Nestin is a molecular marker for neural progenitor cells. Rat and human nestin genes possess a central nervous system-specific enhancer within their second introns. However, the transcription factors that bind to the nestin enhancer have not been fully elucidated. Here, we show that the second intron of the mouse nestin gene is sufficient to drive reporter gene expression in the developing nervous system. The core sequence of this central nervous system-specific enhancer localizes to the 3' 320-bp region. The cis-elements for Sox and POU family transcription factors and the hormone-responsive element are essential for nestin expression during embryonic carcinoma P19 cell neural differentiation and in the developing chick neural tube. Interestingly, different transcription factors bind to the nestin enhancer at different stages of P19 cell neural differentiation and central nervous system development. Sox2 and SF1 may mediate basal nestin expression in undifferentiated P19EC cells, whereas Sox2, Brn1, and Brn2 bind to the enhancer in P19 neural progenitor cells. Similarly, in vivo, Oct1 binds to the nestin enhancer in embryonic day 8.5 (E8.5) mouse embryos, and Oct1, Brn1, and Brn2 bind to this enhancer in E10.5 and E12.5 mouse embryos. Our studies therefore suggest a temporal coordination of transcription factors in determining nestin gene expression.

Adenomatous polyposis coli is required for early events in the normal growth and differentiation of the developing cerebral cortex

Background

Adenomatous polyposis coli (Apc) is a large multifunctional protein known to be important for Wnt/β-catenin signalling, cytoskeletal dynamics, and cell polarity. In the developing cerebral cortex, Apc is expressed in proliferating cells and its expression increases as cells migrate to the cortical plate. We examined the consequences of loss of Apc function for the early development of the cerebral cortex.

Results

We used Emx1^Cre to inactivate Apc specifically in proliferating cerebral cortical cells and their descendents starting from embryonic day 9.5. We observed reduction in the size of the mutant cerebral cortex, disruption to its organisation, and changes in the molecular identity of its cells. Loss of Apc leads to a decrease in the size of the proliferative pool, disrupted interkinetic nuclear migration, and increased apoptosis. β-Catenin, pericentrin, and N-cadherin proteins no longer adopt their normal high concentration at the apical surface of the cerebral cortical ventricular zone, indicating that cell polarity is disrupted. Consistent with enhanced Wnt/β-catenin signalling resulting from loss of Apc we found increased levels of TCF/LEF-dependent transcription and expression of endogenous Wnt/β-catenin target genes (Axin2 (conductin), Lef1, and c-myc) in the mutant cerebral cortex. In the Apc mutant cerebral cortex the expression of transcription factors Foxg1, Pax6, Tbr1, and Tbr2 is drastically reduced compared to normal and many cells ectopically express Pax3, Wnt1, and Wt1 (but not Wnt2b, Wnt8b, Ptc, Gli1, Mash1, Olig2, or Islet1). This indicates that loss of Apc function causes cerebral cortical cells to lose their normal identity and redirect to fates normally found in more posterior-dorsal regions of the central nervous system.

Conclusion

Apc is required for multiple aspects of early cerebral cortical development, including the regulation of cell number, interkinetic nuclear migration, cell polarity, and cell type specification.

A novel embryonic nestin-expressing radial glia-like progenitor gives rise to zonally restricted olfactory and vomeronasal neurons

Persistent neurogenesis is maintained throughout development and adulthood in the mouse olfactory epithelium (OE). Despite this, the identity and origin of different embryonic OE progenitors, their spatiotemporal induction and contribution to patterning during development, has yet to be delineated. Here, we show that the embryonic OE contains a novel nestin-expressing radial glia-like progenitor (RGLP) that is not found in adult OE, which is antigenically distinct from embryonic CNS radial glia. Nestin-cre-mediated lineage tracing with three different reporters reveals that only a subpopulation of nestin-expressing RGLPs activate "CNS-specific" nestin regulatory elements, and produce spatially restricted olfactory receptor neurons (ORNs) in zone 1 of the OE, and vomeronasal receptor neurons restricted to the VR1 zone. This dorsal-medial restriction of transgene-activating cells is also seen in the embryonic OE of Nestin-GFP transgenic mice, in which green fluorescent protein (GFP) is found in a subpopulation of GFP+Mash1+ neuronal progenitors, despite the fact that endogenous Nestin expression is found in RGLPs throughout the OE. Embryonic OE progenitors produce three biologically distinct colony subtypes in vitro, a subpopulation of which include nestin-expressing RGLPs during in vitro colony formation. When generated from Nestin-cre/ZEG mice, neurogenic colonies also produce GFP+Mash1+ progenitors and ORNs. We thus identify a novel neurogenic precursor, the RGLP of the OE and vomeronasal organ (VNO), and provide the first evidence for intrinsic differences in the origin and spatiotemporal potential of distinct progenitors during development of the OE and VNO.

Rapid promoter analysis in developing mouse brain and genetic labeling of young neurons by doublecortin-DsRed-express

Characterization of neural promoter/enhancers is essential for understanding gene regulation during brain development and provides useful genetic tools. However, it relies on the use of transgenic mice. We report a method for the rapid in vivo analysis of neural promoter/enhancers in the developing mouse brain and its application in the isolation of the doublecortin (DCX) promoter/enhancer for genetic labeling of young neurons. In the present study, we demonstrated that reporter genes introduced into the developing mouse cerebral cortex by in utero electroporation can achieve promoter/enhancer-specific patterns of expression. We used the in utero electroporation system to isolate a genomic fragment of the doublecortin gene that can direct reporter expression faithful to doublecortin in young neurons of the cerebral cortex. Finally, we showed that the DCX promoter identified via electroporation could reproduce doublecortin expression in the entire central nervous system in DCX-DsRed-express transgenic mice. The results of our study provide a convenient, reliable, and rapid method for in vivo analysis of neural promoter/enhancers in the developing mouse brain.

Identifying and quantitating neural stem and progenitor cells in the adult brain

Adult brain contains neural stem and progenitor cells that are capable of generating new neurons. Active continuous neurogenesis is limited to the subventricular zone of the lateral ventricles and the subgranular zone of the hippocampal dentate gyrus. Newborn neurons gradually become fully functional and integrated into the existing circuitry of the olfactory bulb and the hippocampus. Transition from stem cells to fully differentiation neurons, the neuronal differentiation cascade, occurs through defined steps, and different classes of neuronal precursors can be distinguished by their morphology, expressed markers, and mitotic activity. Cells in these classes can be identified by immunophenotyping, labeling with thymidine analogues, and infection with retro- and lentiviral vectors. We here describe a transgenic approach that allows identification, in vivo visualization, isolation, and accurate enumeration of various classes of stem and progenitor cells in the adult brain. We generated a series of reporter mouse lines in which neural stem and progenitor cells express various fluorescent proteins (GFP, CFPnuc, H2B-GFP, DsRedTimer, and mCherry) under the control of the regulatory elements of the nestin gene. Using these lines, we were able to dissect the neuronal differentiation cascade into several discrete steps and to evaluate the changes induced by various neurogenic and antineurogenic stimuli. In particular, nuclear localization of the fluorescent signal in nestin-CFPnuc mice greatly simplifies the distribution pattern of neural stem and progenitor cells and allows accurate quantitation of changes induced by neurogenic agents in distinct classes of neuronal precursors. We present protocols for applying confocal microscopy, stereology, and electron microscopy to evaluate changes in the neurogenic compartments of the adult brain.

Dynamic features of postnatal subventricular zone cell motility: a two-photon time-lapse study

Neuroblasts migrate long distances in the postnatal subventricular zone (SVZ) and rostral migratory stream (RMS) to the olfactory bulbs. Many fundamental features of SVZ migration are still poorly understood, and we addressed several important questions using two-photon time-lapse microscopy of brain slices from postnatal and adult eGFP(+) transgenic mice. 1) Longitudinal arrays of neuroblasts, so-called chain migration, have never been dynamically visualized in situ. We found that neuroblasts expressing doublecortin-eGFP (Dcx-eGFP) and glutamic acid decarboxylase-eGFP (Gad-eGFP) remained within arrays, which maintained their shape for many hours, despite the fact that there was a wide variety of movement within arrays. 2) In the dorsal SVZ, neuroblasts migrated rostrocaudally as expected, but migration shifted to dorsoventral orientations throughout ventral regions of the lateral ventricle. 3) Whereas polarized bipolar morphology has been a gold standard for inferring migration in histologic sections, our data indicated that migratory morphology was not predictive of motility. 4) Is there local motility in addition to long distance migration? 5) How fast is SVZ migration? Unexpectedly, one-third of motile neuroblasts moved locally in complex exploratory patterns and at average speeds slower than long distance movement. 6) Finally, we tested, and disproved, the hypothesis that all motile cells in the SVZ express doublecortin, indicating that Dcx is not required for migration of all SVZ cell types. These data show that cell motility in the SVZ and RMS is far more complex then previously thought and involves multiple cell types, behaviors, speeds, and directions.

Ablation of central nervous system progenitor cells in transgenic rats using bacterial nitroreductase system

Specific ablation of central nervous system (CNS) progenitor cells in the brain of live animals is a powerful method to determine the functions of these cells and to reveal novel avenues for the treatment of several CNS-related disorders. To achieve this goal, we generated a line of transgenic rats expressing a bacterial enzyme, Escherichia coli nitroreductase gene (NTR), under control of the nestin promoter. In this system, NTR(+) cells are selectively eliminated upon application of prodrug CB1954, through activation of programmed cell death machineries. At 5 days of age, which is a time when cerebellar development is occurring, transgenic rats bearing the nestin-NTR/green fluorescent protein (GFP) gene are overtly normal and express NTR/GFP in neuronal stem cells, without any toxicity in these cells. The functional consequence of progenitor cell ablation was demonstrated by administering prodrug CB1954 into the cerebellum at this 5-day time point. Stem cell ablation in these neonates resulted in sensorimotor abnormalities, cerebellar degeneration, overall reduction in cerebellar seize, and manifestation of ataxia. In adult rats, GFP expression was not seen in the hippocampal progenitor cells and seen only at very low levels in the lateral ventricles, indicating a different NTR/GFP expression pattern between neonates and adults. In addition, application of CB1954 by intraventricular delivery reduced the number of 5-bromo-2'-deoxyuridine-labeled proliferating cells in the lateral ventricle but not hippocampus of NTR/GFP rats. These findings shows that targeted expression of NTR under a specific promoter might be of significant value in addressing the function of distinct cell population in vivo.

Genetic modification does not affect the stemness of neural stem cells in nestin promoter-GFP transgenic mice

Because nestin promoter-GFP mice have frequently been used in neural stem cell (NSC) research, it is essential to prove that there is no alteration in the stemness of NSCs derived from this transgenic model for the interpretation and validity of the data. We compared the stemness of NSCs derived from transgenic mice expressing GFP driven by the nestin enhancer with those from wild-type (C57BL/6) mice with respect to the general gene expression profile, expression of neural stem cell markers as nestin and Sox2, and responsiveness to neurotrophins (BDNF, PDGF-BB, and NT-3). The gene expression profile analysis showed that the coefficient of correlation between the two groups was very high (r=0.9865) in the total genes. We found that 23 genes were either up- or down-regulated more than two-fold in the NSCs from the transgenic mice (p<0.05), without any obvious functional relatedness among them. Likewise, there was no difference between the two mouse groups in the expression of nestin or Sox2, the ability to form neurospheres and the neuronal differentiation of NSCs by neurotrophins. Taken together, the self-renewal and neuronal differentiation ability of NSCs from the transgenic mice showed the great similarity to those from wild-type mice. Such information will be useful when the properties of NSCs are evaluated following genetic modification in such a nestin-GFP Tg model.