Robotic multi-probe single-actuator inchworm neural microdrive.

A wide range of techniques in neuroscience involve placing individual probes at precise locations in the brain. However, large-scale measurement and manipulation of the brain using such methods have been severely limited by the inability to miniaturize systems for probe positioning. Here, we present a fundamentally new, remote-controlled micropositioning approach composed of novel phase-change material-filled resistive heater micro-grippers arranged in an inchworm motor configuration. The microscopic dimensions, stability, gentle gripping action, individual electronic control, and high packing density of the grippers allow micrometer-precision independent positioning of many arbitrarily shaped probes using a single piezo actuator. This multi-probe single-actuator design significantly reduces the size and weight and allows for potential automation of microdrives. We demonstrate accurate placement of multiple electrodes into the rat hippocampus in vivo in acute and chronic preparations. Our robotic microdrive technology should therefore enable the scaling up of many types of multi-probe applications in neuroscience and other fields.

The B-cell receptor controls fitness of MYC-driven lymphoma cells via GSK3ß inhibition.

Similar to resting mature B cells, where the B-cell antigen receptor (BCR) controls cellular survival, surface BCR expression is conserved in most mature B-cell lymphomas. The identification of activating BCR mutations and the growth disadvantage upon BCR knockdown of cells of certain lymphoma entities has led to the view that BCR signalling is required for tumour cell survival. Consequently, the BCR signalling machinery has become an established target in the therapy of B-cell malignancies. Here we study the effects of BCR ablation on MYC-driven mouse B-cell lymphomas and compare them with observations in human Burkitt lymphoma. Whereas BCR ablation does not, per se, significantly affect lymphoma growth, BCR-negative (BCR-) tumour cells rapidly disappear in the presence of their BCR-expressing (BCR+) counterparts in vitro and in vivo. This requires neither cellular contact nor factors released by BCR+ tumour cells. Instead, BCR loss induces the rewiring of central carbon metabolism, increasing the sensitivity of receptor-less lymphoma cells to nutrient restriction. The BCR attenuates glycogen synthase kinase 3 beta (GSK3ß) activity to support MYC-controlled gene expression. BCR- tumour cells exhibit increased GSK3ß activity and are rescued from their competitive growth disadvantage by GSK3ß inhibition. BCR- lymphoma variants that restore competitive fitness normalize GSK3ß activity after constitutive activation of the MAPK pathway, commonly through Ras mutations. Similarly, in Burkitt lymphoma, activating RAS mutations may propagate immunoglobulin-crippled tumour cells, which usually represent a minority of the tumour bulk. Thus, while BCR expression enhances lymphoma cell fitness, BCR-targeted therapies may profit from combinations with drugs targeting BCR- tumour cells.

Head-anchored whole-cell recordings in freely moving rats.

Intracellular recordings are routinely used to study the synaptic and intrinsic properties of neurons in vitro. A key requirement for these recordings is a mechanically very stable preparation; thus their use in vivo had been limited previously to head-restrained animals. We have recently demonstrated that anchoring the electrode rigidly in place with respect to the skull provides sufficient stabilization for long-lasting, high-quality whole-cell recordings in awake, freely moving rats. This protocol describes our procedure in detail, adds specific instructions for targeting hippocampal CA1 pyramidal neurons and updates it with changes that facilitate patching and improve the success rate. The changes involve combining a standard, nonhead-mounted micromanipulator with a gripper to firmly hold the recording pipette during the anchoring process then gently release it afterwards. The procedure from the beginning of surgery to the end of a recording takes approximately 5 h. This technique allows new studies of the mechanisms underlying neuronal integration and cellular/synaptic plasticity in identified cells during natural behaviors.