Differential Expression Analysis Identifies Candidate Synaptogenic Molecules for Wiring Direction-Selective Circuits in the Retina.

An organizational feature of neural circuits is the specificity of synaptic connections. A striking example is the direction-selective (DS) circuit of the retina. There are multiple subtypes of DS retinal ganglion cells (DSGCs) that prefer motion along one of four preferred directions.

Gut enterochromaffin cells drive visceral pain and anxiety.

Gastrointestinal (GI) discomfort is a hallmark of most gut disorders and represents an important component of chronic visceral pain. For the growing population afflicted by irritable bowel syndrome, GI hypersensitivity and pain persist long after tissue injury has resolved. Irritable bowel syndrome also exhibits a strong sex bias, afflicting women three times more than men.

A Dense Starburst Plexus Is Critical for Generating Direction Selectivity.

Starburst amacrine cell (SAC) morphology is considered central to retinal direction selectivity. In Sema6A mice, SAC dendritic arbors are smaller and no longer radially symmetric, leading to a reduction in SAC dendritic plexus density. Sema6A mice also have a dramatic reduction in the directional tuning of retinal direction-selective ganglion cells (DSGCs).

Motion Vision: Cortical Preferences Influenced by Retinal Direction Selectivity.

A recent study shows that retinal direction selectivity influences a subset of cells in primary visual cortex which respond to the optic flow associated with forward motion, while other cortical direction selective cells perform this computation independently.

Contributions of Rod and Cone Pathways to Retinal Direction Selectivity Through Development.

Unlabelled: Direction selectivity is a robust computation across a broad stimulus space that is mediated by activity of both rod and cone photoreceptors through the ON and OFF pathways. However, rods, S-cones, and M-cones activate the ON and OFF circuits via distinct pathways and the relative contribution of each to direction selectivity is unknown. Using a variety of stimulation paradigms, pharmacological agents, and knockout mice that lack rod transduction, we found that inputs from the ON pathway were critical for strong direction-selective (DS) tuning in the OFF pathway.

Development of synaptic connectivity in the retinal direction selective circuit.

Direction selectivity is a classic neuronal computation that has been described in many different sensory systems. The circuit basis of this computation is perhaps best understood in the retina, where direction selectivity is the result of asymmetric connectivity patterns between excitatory and inhibitory circuit components. Retinal direction selective circuits emerge before eye-opening, though components of the circuit undergo refinement after vision begins.

A Role for Synaptic Input Distribution in a Dendritic Computation of Motion Direction in the Retina.

The starburst amacrine cell in the mouse retina presents an opportunity to examine the precise role of sensory input location on neuronal computations. Using visual receptive field mapping, glutamate uncaging, two-photon Ca(2+) imaging, and genetic labeling of putative synapses, we identify a unique arrangement of excitatory inputs and neurotransmitter release sites on starburst amacrine cell dendrites: the excitatory input distribution is skewed away from the release sites. By comparing computational simulations with Ca(2+) transients recorded near release sites, we show that this anatomical arrangement of inputs and outputs supports a dendritic mechanism for computing motion direction.

An Asymmetric Increase in Inhibitory Synapse Number Underlies the Development of a Direction Selective Circuit in the Retina.

Neural circuits rely upon a precise wiring of their component neurons to perform meaningful computations. To compute the direction of motion in the visual scene, the direction selective circuit in the mouse retina depends on an asymmetry in the inhibitory neurotransmission from starburst amacrine cells (SACs) to direction selective ganglion cells (DSGCs). Specifically, depolarization of a SAC on the null side of a DSGC causes a threefold greater unitary inhibitory conductance than depolarization of a SAC on the preferred side.

Visual stimulation switches the polarity of excitatory input to starburst amacrine cells.

Direction-selective ganglion cells (DSGCs) are tuned to motion in one direction. Starburst amacrine cells (SACs) are thought to mediate this direction selectivity through precise anatomical wiring to DSGCs. Nevertheless, we previously found that visual adaptation can reverse DSGCs's directional tuning, overcoming the circuit anatomy.

Rab GTPases are required for early orientation of the left-right axis in Xenopus.

The earliest steps of left-right (LR) patterning in Xenopus embryos are driven by biased intracellular transport that ensures a consistently asymmetric localization of maternal ion channels and pumps in the first 2-4 blastomeres. The subsequent differential net efflux of ions by these transporters generates a bioelectrical asymmetry; this LR voltage gradient redistributes small signaling molecules along the LR axis that later regulate transcription of the normally left-sided Nodal. This system thus amplifies single cell chirality into a true left-right asymmetry across multi-cellular fields.

V-ATPase-dependent ectodermal voltage and pH regionalization are required for craniofacial morphogenesis.

Using voltage and pH reporter dyes, we have discovered a never-before-seen regionalization of the Xenopus ectoderm, with cell subpopulations delimited by different membrane voltage and pH. We distinguished three courses of bioelectrical activity. Course I is a wave of hyperpolarization that travels across the gastrula.