Biology subjects

Rangel Olguin, A. G.

Publications and source records attributed to Rangel Olguin, A. G..

3 recordsLinked to original sources

bioRxiv2025

Visual field specializations in mouse dLGN

Neural circuits throughout the visual system process features differently depending on where they appear in the visual field. While such location-specific processing exists in retina and in superior colliculus, the dorsal lateral geniculate nucleus (dLGN) is thought to lack this specialization. Here, we show systematic visual field biases in dLGNs representation of spatial frequency, orientation, direction, and temporal frequency. Using axon-localized calcium indicators and widefield imaging, we discovered that dLGN boutons show systematic gradients in feature selectivity across the visual cortex (V1), while its retinal inputs lack such gradients for these features. Selective disruption of V1 feedback to dLGN perturbed gradient structure and magnitude. These results suggest that dLGN circuits transform uniformly distributed retinal feature inputs into spatially-biased representations along with cortical feedback. dLGN feature biases would allow a functional stream to detect ethologically salient visual inputs.

neuroscience↗

bioRxiv2021

The cell adhesion molecule Sdk1 shapes assembly of a retinal circuit that detects localized edges.

Nearly 50 different mouse retinal ganglion cell (RGC) types sample the visual scene for distinct features. RGC feature selectivity arises from its synapses with a specific subset of amacrine (AC) and bipolar cell (BC) types, but how RGC dendrites arborize and collect input from these specific subsets remains poorly understood. Here we examine the hypothesis that RGCs employ molecular recognition systems to meet this challenge. By combining calcium imaging and type-specific histological stains we define a family of circuits that express the recognition molecule Sidekick 1 (Sdk1) which include a novel RGC type (S1-RGC) that responds to local edges. Genetic and physiological studies revealed that Sdk1 loss selectively disrupts S1-RGC visual responses which result from a loss of excitatory and inhibitory inputs and selective dendritic deficits on this neuron. We conclude that Sdk1 shapes dendrite growth and wiring to help S1-RGCs become feature selective.

neuroscience↗

bioRxiv2019

Evolution of Phototransduction Genes in Lepidoptera

Vision is underpinned by phototransduction, a signaling cascade that converts light energy into an electrical signal. Among insects, phototransduction is best understood in Drosophila melanogaster. A survey of phototransduction genes in four insect genomes found gains and losses between D. melanogaster and other insects; this study did not include lepidopterans. Diurnal butterflies and nocturnal moths occupy different light environments and have distinct eye morphologies, which might impact the expression of their phototransduction genes. Here, we used transcriptomics and phylogenetics to identify phototransduction genes that vary between D. melanogaster and Lepidoptera, and between moths and butterflies. Most phototransduction genes were conserved between D. melanogaster and Lepidoptera, with some exceptions. We found two lepidopteran opsins lacking a D. melanogaster ortholog, and using antibodies found that one, a candidate retinochrome which we name unclassified opsin (UnRh), is expressed in the crystaline cone cells and the pigment cells of the butterfly Heliconius melpomene. We also found differences between Lepidoptera and D. melanogaster phototransduction in diacylglycerol regulation where a lepidopteran paralog, DAG{beta}, may be taking on a role in vision. Lastly, butterflies express similar amounts of trp and trpl channel mRNAs, while moths express approximately 50x less trp. Since TRP/TRPL channels allow Ca2+ and Na+ influx this might explain why moths appear to express less Calx and Nckx30C Na+/Ca2+ channel mRNAs. Our findings suggest that while many single-copy D. melanogaster phototransduction genes are conserved in lepidopterans, phototransduction gene expression differences exist between moths and butterflies that may be linked to their visual light environment.

evolutionary biology↗