Calcium Sensors STIM1 and STIM2 Regulate Different Calcium Functions in Cultured Hippocampal Neurons

There are growing indications for the involvement of calcium stores in the plastic properties of neurons and particularly in dendritic spines of central neurons. The store-operated calcium entry (SOCE) channels are assumed to be activated by the calcium sensor stromal interaction molecule (STIM)which leads to activation of its associated Orai channel. There are two STIM species, and the differential role of the two in SOCE is not entirely clear. In the present study, we were able to distinguish between transfected STIM1, which is more mobile primarily in young neurons, and STIM2 which is less mobile and more prominent in older neurons in culture. STIM1 mobility is associated with spontaneous calcium sparks, local transient rise in cytosolic [Ca2+]i, and in the formation and elongation of dendritic filopodia/spines. In contrast, STIM2 is associated with older neurons, where it is mobile and moves into dendritic spines primarily when cytosolic [Ca2+]i levels are reduced, apparently to activate resident Orai channels. These results highlight a role for STIM1 in the regulation of [Ca2+]i fluctuations associated with the formation of dendritic spines or filopodia in the developing neuron, whereas STIM2 is associated with the maintenance of calcium entry into stores in the adult neuron.

A Perfused Microfluidic System to Study the Differentiation of Neural Stem Cells in vitro

Introduction: Due to the ability to mimic in vivo cellular microenvironments, the development of multicell culture systems has received increasing interest for use as research models and serving as platforms for drug evaluation. Methods: In this study, we developed a perfused microfluidic system to resemble the in vivo intercellular environment and applied it to study the differentiation from neural stem cells into neurons. Results: As determined by immunofluorescence chemistry and quantitative real-time PCR, the neural stem cells grown in this microfluidic system showed an elevated differentiation rate toward the formation of neurons as determined by the increased level of βIII-tubulin production, which is 4 times higher than that of culturing neural stem cells only. Conclusion: These results revealed that some factors secreted into the intercellular microenvironment by adult neuron cells can stimulate the differentiation of neural stem cells, pointing to the importance of developing multicellular culture systems such as the perfused microfluidic system we report here to better resemble the in vivo situation.

Adhesion Molecules and Axon Pathfinding

Developing neurons extend neurites, which become the axons and dendrites of the adult neuron. These neurites follow specific paths and branch in characteristic ways. The leading tip of the neurite, the growth cone, appears to sample the extracellular environment and contribute to decisions about the direction of extension. Various molecules are essential for appropriate pathfinding by growing neurites. For example, neurites grow selectively toward or away from guidance molecules such as semaphorins, netrins, slits, and ephrins. In addition, adhesion molecules such as fibronectin and laminin mediate specific adhesion of the neurite to the substrate over which it is growing, while CAMs and cadherins promote the adhesion of neurites of different cells to each other in specific patterns. Some molecules and mechanisms that regulate neuronal development and differentiation may also regulate neurite outgrowth in adult nervous systems, either during recovery from injury or in response to novel stimuli from the environment.