Kir4.1 is specifically expressed and active in non-myelinating Schwann cells.

Non-myelinating Schwann cells (NMSC) play important roles in peripheral nervous system formation and function. However, the molecular identity of these cells remains poorly defined. We provide evidence that Kir4.1, an inward-rectifying K+ channel encoded by the KCNJ10 gene, is specifically expressed and active in NMSC. Immunostaining revealed that Kir4.1 is present in terminal/perisynaptic SCs (TPSC), synaptic glia at neuromuscular junctions (NMJ), but not in myelinating SCs (MSC) of adult mice. To further examine the expression pattern of Kir4.1, we generated BAC transgenic Kir4.1-CreERT2 mice and crossed them to the tdTomato reporter line. Activation of CreERT2 with tamoxifen after the completion of myelination onset led to robust expression of tdTomato in NMSC, including Remak Schwann cells (RSC) along peripheral nerves and TPSC, but not in MSC. In contrast, activating CreERT2 before and during the onset of myelination led to tdTomato expression in NMSC and MSC. These observations suggest that immature SC express Kir4.1, and its expression is then downregulated selectively in myelin-forming SC. In support, we found that while activating CreERT2 induces tdTomato expression in immature SC, it fails to induce tdTomato in MSC associated with sensory axons in culture. NMSC derived from neonatal sciatic nerve were shown to express Kir4.1 and exhibit barium-sensitive inwardly rectifying macroscopic K+ currents. Thus, this study identified Kir4.1 as a potential modulator of immature SC and NMSC function. Additionally, it established a novel transgenic mouse line to introduce or delete genes in NMSC.

Context-dependent modulation of natural approach behaviour in mice.

Specific features of visual objects innately draw approach responses in animals, and provide natural signals of potential reward. However, visual sampling behaviours and the detection of salient, rewarding stimuli are context and behavioural state-dependent and it remains unclear how visual perception and orienting responses change with specific expectations. To start to address this question, we employed a virtual stimulus orienting paradigm based on prey capture to quantify the conditional expression of visual stimulus-evoked innate approaches in freely moving mice. We found that specific combinations of stimulus features selectively evoked innate approach or freezing responses when stimuli were unexpected. We discovered that prey capture experience, and therefore the expectation of prey in the environment, selectively modified approach frequency, as well as altered those visual features that evoked approach. Thus, we found that mice exhibit robust and selective orienting responses to parameterized visual stimuli that can be robustly and specifically modified via natural experience. This work provides critical insight into how natural appetitive behaviours are driven by both specific features of visual motion and internal states that alter stimulus salience.

The relationship between visual orienting and interlimb synchrony in a patient with a superior parietal infarction: a case study.

Much work indicates that parietal cortex mediates the transformation of visual information into the motor commands necessary for successful performance of many unimanual tasks. Accumulating evidence suggests that parietal cortex also mediates the coordination of bimanual movements, during which the natural tendency is to couple the limbs temporally. However, the extent to which parietal oculomotor and/or visual processes contribute to temporal coupling of the limbs during bimanual task performance is unknown. In the current study, we monitored the eye movements of a patient with a left parietal infarction as she performed a series of bimanual visuomotor tasks. We demonstrate the impact of an ipsilesional (leftward) orientation bias on her ability to synchronize the onset of bimanual limb movements; the movements were performed in serial fashion, i.e., left limb before right, when the patient was permitted to freely shift saccades and the visual target cuing the left (ipsilesional) limb movement was presented at greater (leftward) eccentricities. Disruption of interlimb synchrony as such was not, however, evident when the patient was required to fixate or when visual targets were presented at lesser ipsilesional eccentricities. Additionally, despite the disruptive influence of oculomotor and visual factors on interlimb synchrony, the patient appeared capable of using visual feedback to straighten the right (contralesional) limb trajectory, thus improving the spatial component of task performance. Results suggest that parietal cortex plays an important role in the coordination of limb movements during performance of bimanual visuomotor tasks. This role appears to involve orienting gaze or attention to the goals of each limb so that the nervous system can synchronize the activity of both limbs and thereby ensure successful task completion.