Ito, S. | bioRxiv Science

bioRxiv2018

GIMLET: Identifying Biological Modulators in Context-Specific Gene Regulation Using Local Energy Statistics

The regulation of transcription factor activity dynamically changes across cellular conditions and disease subtypes. The identification of biological modulators contributing to context-specific gene regulation is one of the challenging tasks in systems biology, which is necessary to understand and control cellular responses across different genetic backgrounds and environmental conditions. Previous approaches for identifying biological modulators from gene expression data were restricted to the capturing of a particular type of a three-way dependency among a regulator, its target gene, and a modulator; these methods cannot describe the complex regulation structure, such as when multiple regulators, their target genes, and modulators are functionally related. Here, we propose a statistical method for identifying biological modulators by capturing multivariate local dependencies, based on energy statistics, which is a class of statistics based on distances. Subsequently, our method assigns a measure of statistical significance to each candidate modulator through a permutation test. We compared our approach with that of a leading competitor for identifying modulators, and illustrated its performance through both simulations and real data analysis. Our method, entitled genome-wide identification of modulators using local energy statistical test (GIMLET), is implemented with R ([≥] 3.2.2) and is available from github (https://github.com/tshimam/GIMLET).

bioinformatics↗

bioRxiv2016

Neurons in the mouse deep superior colliculus encode orientation/direction through suppression and extract selective visual features

The superior colliculus (SC) is an integrative sensorimotor structure that contributes to multiple visiondependent behaviors. It is a laminated structure; the superficial SC layers (sSC) contain cells that respond to visual stimuli, while the deep SC layers (dSC) contain cells that also respond to auditory and somatosensory stimuli. Despite the increasing interest in mice for visual system study, the differences in the visual response properties between the sSC and the dSC are largely unknown. Here we used a large-scale silicon probe recording system to examine the visual response properties of neurons within the SC of head-fixed, awake and behaving mice. We find that both the sSC and dSC cells respond to visual stimuli, but dSC cells have three key differences. (1) The majority of the dSC orientation/direction selective (OS/DS) cells have their firing rate suppressed by drifting sinusoidal gratings (negative OS/DS cells) rather than being stimulated like the sSC cells (positive OS/DS cells). (2) Almost all the dSC cells have complex-cell-like spatial summation nonlinearity, and a significantly smaller fraction of the positive OS/DS cells in the dSC respond to flashing spots than those in the sSC. (3) The dSC cells lack Y-like spatial summation nonlinearity unlike the sSC cells. These results provide the first description of cells that are suppressed by a visual stimulus with a specific orientation or direction, show that neurons in the dSC have properties analogous to cortical complex cells, and show the presence of Y-like nonlinearity in the sSC but their absence in the dSC.\n\nSignificance statementThe superior colliculus receives visual input from the retina in its superficial layers (sSC) and induces eye/head orientating movements and innate defensive responses in its deeper layers (dSC). Despite their importance, very little is known about the visual response properties of dSC neurons. Using highdensity electrode recordings and novel model-based analysis, we find that the dSC contains cells with a novel property; they are suppressed by the orientation or direction of specific stimuli. We also show that dSC cells have properties similar to cortical \"complex\" cells. Conversely, cells with Y-like nonlinear spatial summation properties are located only in the sSC. These findings contribute to our understanding of how the SC processes visual inputs, a critical step in comprehending visually-guided behaviors.\n\nAcknowledgementsThis work was supported by the Brain Research Seed Funding provided by UCSC and from the National Institutes of Health Grant NEI R21EYO26758 to D. A. F. and A. M. L. We thank Michael Stryker for training on the electrophysiology experiments and his very helpful comments on the manuscript, Sotiris Masmanidis for providing us with the silicon probes, Forest Martinez-McKinney and Serguei Kachiguin for their technical contributions to the silicon probe system, Jeremiah Tsyporin for taking an image of neural tissues and the training of mice, Jena Yamada, Anahit Hovhannisyan, Corinne Beier, and Sydney Weiser, for their helpful comments on the manuscript.

neuroscience↗