Scientific Resources

To understand the mechanism of the sequential restriction of multipotency of stem cells during development,we have established culture conditions that allow the differentiation of neuroepithelial precursor cells from embryonic stem (ES) cells. A highly enriched population of neuroepithelial precursor cells derived from ES cells proliferates in the presence of basic fibroblast growth factor (bFGF). These cells differentiate into both neurons and glia following withdrawal of bFGF. By further differentiating the cells in serum-containing medium,the neurons express a wide variety of neuron-specific genes and generate both excitatory and inhibitory synaptic connections. The expression pattern of position-specific neural markers suggests the presence of a variety of central nervous system (CNS) neuronal cell types. These findings indicate that neuronal precursor cells can be isolated from ES cells and that these cells can efficiently differentiate into functional post-mitotic neurons of diverse CNS structures. View Publication

Under appropriate conditions in culture,embryonic stem cells will differentiate and form embryoid bodies that have been shown to contain cells of the hematopoietic,endothelial,muscle and neuronal lineages. Many aspects of the lineage-specific differentiation programs observed within the embryoid bodies reflect those found in the embryo,indicating that this model system provides access to early cell populations that develop in a normal fashion. Recent studies involving the differentiation of genetically altered embryonic stem cells highlight the potential of this in vitro differentiation system for defining the function of genes in early development. View Publication

Mouse embryonic stem (ES) cells cultured as aggregates and exposed to retinoic acid are induced to express multiple phenotypes normally associated with neurons. A large percentage of treated aggregates produce a rich neuritic outgrowth. Dissociating the induced aggregates with trypsin and plating the cells as a monolayer results in cultures in which a sizable percentage of the cells have a neuronal appearance. These neuron-like cells express class III beta-tubulin and the neurofilament M subunit. Induced cultures express transcripts for neural-associated genes including the neurofilament L subunit,glutamate receptor subunits,the transcription factor Brn-3,and GFAP. Levels of neurofilament L and GAD67 and GAD65 transcripts rise dramatically upon induction. Physiological studies show that the neuron-like cells generate action potentials and express TTX-sensitive sodium channels,as well as voltage-gated potassium channels and calcium channels. We conclude that a complex system of neuronal gene expression can be activated in cultured ES cells. This system should be favorable for investigating some of the mechanisms that regulate neuronal differentiation. View Publication

The electrophoretic pattern of the large microtubule-associated protein,MAP2,changes during rat brain development. Immunoblots of NaDodSO4 extracts obtained from the cerebral cortex,cerebellum,and thalamus at 10-15 days after birth reveal only a single electrophoretic species when probed with any of three MAP2 monoclonal antibodies. By contrast,adult MAP2 contains two immunoreactive species,MAP2a and MAP2b. The single band of MAP2 from immature brain electrophoretically comigrates with adult MAP2b. Between postnatal days 17 and 18,immature MAP2 simultaneously resolves into two species in both the cerebellum and cerebral cortex. Immunoblots of NaDodSO4 extracts from spinal cord demonstrate the adult complement of MAP2 by day 10,indicating that MAP2 does not change coordinately throughout the entire central nervous system. In vitro cAMP-dependent phosphorylation of immature MAP2 causes a band split reminiscent of that seen during brain development in vivo. The possibility that the developmentally regulated changes observed in MAP2 during brain maturation are due to timed phosphorylation events is discussed. View Publication

In dissociated-cell cultures prepared from the embryonic rat hippocampus,neurons establish both axons and dendrites,which differ in geometry,in ultrastructure,and in synaptic polarity. We have used immunocytochemistry with monoclonal antibodies to study the regional distribution of beta-tubulin and micro-tubule-associated protein 2 (MAP2) in hippocampal cultures and their localization during early stages of axonal and dendritic development. After development for a week or more in culture,when axons and dendrites were well-differentiated,the distribution of these two proteins was quite different. Beta-tubulin was present throughout the nerve cell,in soma,dendrites,and axon. It was also present in all classes of non-neuronal cells,astrocytes,fibroblasts,and a presumptive glial progenitor cell. In contrast,MAP2 was preferentially localized to nerve cells; within neurons,MAP2 was present in soma and dendrites,but little or no immunostaining was detectable in axons. Both beta-tubulin and MAP2 were present in nerve cells at the time of plating. From the earliest stages of process extension,beta-tubulin was present in all neuronal processes,both axons and dendrites. Surprisingly,MAP2 was also initially present in both axons and dendrites,extending as far as the axonal growth cone. With subsequent development,MAP2 staining was selectively lost from the axon so that after 1 week in vitro little or no axonal staining remained. Taken together with earlier results (Cáceres et al.,1984a),these data indicate that the establishment of neuronal polarity,as manifested by the molecular differentiation of the axonal and dendritic cytoskeleton,occurs largely under endogenous control,even under culture conditions in which cell interactions are greatly restricted.(ABSTRACT TRUNCATED AT 250 WORDS) View Publication

Using a monoclonal antibody against the microtubule-associated protein tau we compared the distribution and the biochemical maturation of this protein in hippocampal pyramidal neurons in the rat in tau and in culture. In tissue sections from mature animals tau was localized heterogeneously within neurons. It was concentrated in axons; dendrites and somata showed little or no staining. In hippocampal cultures ranging from 12 h to 4 weeks in vitro tau was present in neurons but not in glial cells,as it is in situ. Within cultured neurons,however,tau was not compartmentalized but was present throughout the dendrites,axons and somata. Immunoblotting experiments showed that the biochemical maturation of tau that occurs in situ also failed to occur in culture. The young form of tau persisted,and the adult forms did not develop. In contrast the biochemical maturation and the compartmentalization of microtubule-associated protein 2 occurred normally in hippocampal cultures. These results show that the biochemical maturation and the intraneuronal compartmentalization of these two microtubule-associated proteins are independently controlled. Despite the non-restricted distribution of tau in hippocampal neurons in culture,and despite the presence of only the immature isoform which has a lessened stimulatory effect on microtubule polymerization,axons and dendrites appear to grow normally and to exhibit appropriate functional properties. View Publication

Neural stem cells (NSCs) have the ability to self-renew and to differentiate into various cell types of the central nervous system. This potential can be recapitulated by human induced pluripotent stem cells (hiPSCs) in vitro. The differentiation capacity of hiPSCs is characterized by several stages with distinct morphologies and the expression of various marker molecules. We used the monoclonal antibodies (mAbs) 487(LeX),5750(LeX) and 473HD to analyze the expression pattern of particular carbohydrate motifs as potential markers at six differentiation stages of hiPSCs. Mouse ESCs were used as a comparison. At the pluripotent stage,487(LeX)-,5750(LeX)- and 473HD-related glycans were differently expressed. Later,cells of the three germ layers in embryoid bodies (hEBs) and,even after neuralization of hEBs,subpopulations of cells were labeled with these surface antibodies. At the human rosette-stage of NSCs (hR-NSC),LeX- and 473HD-related epitopes showed antibody-specific expression patterns. We also found evidence that these surface antibodies could be used to distinguish the hR-NSCs from the hSR-NSCs stages. Characterization of hNSCs(FGF-2/EGF) derived from hSR-NSCs revealed that both LeX antibodies and the 473HD antibody labeled subpopulations of hNSCs(FGF-2/EGF). Finally,we identified potential LeX carrier molecules that were spatiotemporally regulated in early and late stages of differentiation. Our study provides new insights into the regulation of glycoconjugates during early human stem cell development. The mAbs 487(LeX),5750(LeX) and 473HD are promising tools for identifying distinct stages during neural differentiation. View Publication

Ion channels and transporters have increasingly recognized roles in cancer progression through the regulation of cell proliferation,migration,and death. Glioblastoma stem-like cells (GSCs) are a source of tumor formation and recurrence in glioblastoma multiforme,a highly aggressive brain cancer,suggesting that ion channel expression may be perturbed in this population. However,little is known about the expression and functional relevance of ion channels that may contribute to GSC malignancy. Using RNA sequencing,we assessed the enrichment of ion channels in GSC isolates and non-tumor neural cell types. We identified a unique set of GSC-enriched ion channels using differential expression analysis that is also associated with distinct gene mutation signatures. In support of potential clinical relevance,expression of selected GSC-enriched ion channels evaluated in human glioblastoma databases of The Cancer Genome Atlas and Ivy Glioblastoma Atlas Project correlated with patient survival times. Finally,genetic knockdown as well as pharmacological inhibition of individual or classes of GSC-enriched ion channels constrained growth of GSCs compared to normal neural stem cells. This first-in-kind global examination characterizes ion channels enriched in GSCs and explores their potential clinical relevance to glioblastoma molecular subtypes,gene mutations,survival outcomes,regional tumor expression,and experimental responses to loss-of-function. Together,the data support the potential biological and therapeutic impact of ion channels on GSC malignancy and provide strong rationale for further examination of their mechanistic and therapeutic importance. View Publication

Although human induced pluripotent stem cells (hiPSCs) hold great potential for the study of human diseases affecting disparate cell types,they have been underutilized in seeking mechanistic insights into the pathogenesis of congenital craniofacial disorders. Craniofrontonasal syndrome (CFNS) is a rare X-linked disorder caused by mutations in EFNB1 and characterized by craniofacial,skeletal,and neurological anomalies. Heterozygous females are more severely affected than hemizygous males,a phenomenon termed cellular interference that involves mosaicism for EPHRIN-B1 function. Although the mechanistic basis for cellular interference in CFNS has been hypothesized to involve Eph/ephrin-mediated cell segregation,no direct evidence for this has been demonstrated. Here,by generating hiPSCs from CFNS patients,we demonstrate that mosaicism for EPHRIN-B1 expression induced by random X inactivation in heterozygous females results in robust cell segregation in human neuroepithelial cells,thus supplying experimental evidence that Eph/ephrin-mediated cell segregation is relevant to pathogenesis in human CFNS patients. View Publication