Beadex, the Drosophila LIM only protein, is required for the growth of the larval neuromuscular junction.

The appropriate growth of the neurons, accurate organization of their synapses, and successful neurotransmission are indispensable for sensorimotor activities. These processes are highly dynamic and tightly regulated. Extensive genetic, molecular, physiological, and behavioral studies have identified many molecular candidates and investigated their roles in various neuromuscular processes. In this paper, we show that Beadex (Bx), the Drosophila LIM only (LMO) protein, is required for motor activities and neuromuscular growth of Drosophila. The larvae bearing Bx7, a null allele of Bx, and the RNAi-mediated neuronal-specific knockdown of Bx show drastically reduced crawling behavior, a diminished synaptic span of the neuromuscular junctions (NMJ) and an increased spontaneous neuronal firing with altered motor patterns in the central pattern generators (CPGs). Microarray studies identified multiple targets of Beadex that are involved in different cellular and molecular pathways, including those associated with the cytoskeleton and mitochondria, that could be responsible for the observed neuromuscular defects. With genetic interaction studies, we further show that Highwire (Hiw), a negative regulator of synaptic growth at the NMJs, negatively regulates Bx, as the latter's deficiency was able to rescue the phenotype of the Hiw null mutant, HiwDN. Thus, our data indicates that Beadex functions downstream of Hiw to regulate the larval synaptic growth and physiology.

Compact ring resonator enhanced silicon metal-semiconductor-metal photodetector in SiN-on-SOI platform.

We present a compact on-chip resonator enhanced silicon metal-semiconductor-metal (MSM) photodetector in 850 nm wavelength band for communication and lab-on-chip bio-sensing applications. We report the highest responsivity of 0.81 A/W for a 5 µm long device. High responsivity is achieved by integrating the detector in a silicon nitride ring resonator. The resonance offers 100X responsivity improvement over a single-pass photodetector due to cavity enhancement. We also present a detailed study of the high-speed response of the cavity and single-pass detector. We report an electro-optic bandwidth of 7.5 GHz measured using a femtosecond optical excitation. To the best of our knowledge, we report for the first time silicon nitride resonator integrated Si-MSM detector in SiN-SOI platform.

Probing multiplexed basal dendritic computations using two-photon 3D holographic uncaging.

Basal dendrites of layer 5 cortical pyramidal neurons exhibit Na+ and N-methyl-D-aspartate receptor (NMDAR) regenerative spikes and are uniquely poised to influence somatic output. Nevertheless, due to technical limitations, how multibranch basal dendritic integration shapes and enables multiplexed barcoding of synaptic streams remains poorly mapped. Here, we combine 3D two-photon holographic transmitter uncaging, whole-cell dynamic clamp, and biophysical modeling to reveal how synchronously activated synapses (distributed and clustered) across multiple basal dendritic branches are multiplexed under quiescent and in vivo-like conditions. While dendritic regenerative Na+ spikes promote millisecond somatic spike precision, distributed synaptic inputs and NMDAR spikes regulate gain. These concomitantly occurring dendritic nonlinearities enable multiplexed information transfer amid an ongoing noisy background, including under back-propagating voltage resets, by barcoding the axo-somatic spike structure. Our results unveil a multibranch dendritic integration framework in which dendritic nonlinearities are critical for multiplexing different spatial-temporal synaptic input patterns, enabling optimal feature binding.

A Translaminar Spacetime Code Supports Touch-Evoked Traveling Waves.

Linking sensory-evoked traveling waves to underlying circuit patterns is critical to understanding the neural basis of sensory perception. To form this link, we performed simultaneous electrophysiology and two-photon calcium imaging through transparent NeuroGrids and mapped touch-evoked cortical traveling waves and their underlying microcircuit dynamics. In awake mice, both passive and active whisker touch elicited traveling waves within and across barrels, with a fast early component followed by a variable late wave that lasted hundreds of milliseconds post-stimulus. Strikingly, late-wave dynamics were modulated by stimulus value and correlated with task performance. Mechanistically, the late wave component was i) modulated by motor feedback, ii) complemented by a sparse ensemble pattern across layer 2/3, which a balanced-state network model reconciled via inhibitory stabilization, and iii) aligned to regenerative Layer-5 apical dendritic Ca 2+ events. Our results reveal a translaminar spacetime pattern organized by cortical feedback in the sensory cortex that supports touch-evoked traveling waves. GRAPHICAL ABSTRACT AND HIGHLIGHTS: Whisker touch evokes both early- and late-traveling waves in the barrel cortex over 100's of millisecondsReward reinforcement modulates wave dynamics Late wave emergence coincides with network sparsity in L23 and time-locked L5 dendritic Ca 2+ spikes Experimental and computational results link motor feedback to distinct translaminar spacetime patterns.