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Three-dimensional Ca2+ imaging advances understanding of astrocyte biology

Jue, 05/18/2017 - 11:28

Astrocyte communication is typically studied by two-dimensional calcium ion (Ca2+) imaging, but this method has not yielded conclusive data on the role of astrocytes in synaptic and vascular function. We developed a three-dimensional two-photon imaging approach and studied Ca2+ dynamics in entire astrocyte volumes, including during axon-astrocyte interactions. In both awake mice and brain slices, we found that Ca2+ activity in an individual astrocyte is scattered throughout the cell, largely compartmented between regions, preponderantly local within regions, and heterogeneously distributed regionally and locally. Processes and endfeet displayed frequent fast activity, whereas the soma was infrequently active. In awake mice, activity was higher than in brain slices, particularly in endfeet and processes, and displayed occasional multifocal cellwide events. Astrocytes responded locally to minimal axonal firing with time-correlated Ca2+ spots.

Ephrin B1-mediated repulsion and signaling control germinal center T cell territoriality and function

Jue, 05/18/2017 - 11:28

Follicular T helper (TFH) cells orchestrate the germinal center (GC) reaction locally. Local mechanisms regulating their dynamics and helper functions are not well defined. Here we found that GC-expressed ephrin B1 (EFNB1) repulsively inhibited T cell to B cell adhesion and GC TFH retention by signaling through TFH-expressed EPHB6 receptor. At the same time, EFNB1 promoted interleukin-21 production from GC TFH cells by signaling predominantly through EPHB4. Consequently, EFNB1-null GCs were associated with defective production of plasma cells despite harboring excessive TFH cells. In a competitive GC reaction, EFNB1-deficient B cells more efficiently interacted with TFH cells and produced more bone-marrow plasma cells, likely as a result of gaining more contact-dependent help. Our results reveal a contact-dependent repulsive guidance system that controls GC TFH dynamics and effector functions locally.

Migration--the choices we face

Jue, 05/18/2017 - 11:28

News at a glance

Jue, 05/18/2017 - 11:28

Sea trash traps face doubts

Jue, 05/18/2017 - 11:28

Island extinctions weren't inevitable

Jue, 05/18/2017 - 11:28

People on the move

Jue, 05/18/2017 - 11:28

Busting myths of origin

Jue, 05/18/2017 - 11:28

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