Biology subjects

Gonzalez, K. C.

Publications and source records attributed to Gonzalez, K. C..

5 recordsLinked to original sources

bioRxiv2024

Functional architecture of intracellular oscillations in hippocampal dendrites

Fast electrical signaling in dendrites is central to neural computations that support adaptive behaviors. Conventional techniques lack temporal and spatial resolution and the ability to track underlying membrane potential dynamics present across the complex three-dimensional dendritic arbor in vivo. Here, we perform fast two-photon imaging of dendritic and somatic membrane potential dynamics in single pyramidal cells in the CA1 region of the mouse hippocampus during awake behavior. We study the dynamics of subthreshold membrane potential and suprathreshold dendritic events throughout the dendritic arbor in vivo by combining voltage imaging with simultaneous local field potential recording, post hoc morphological reconstruction, and a spatial navigation task. We systematically quantify the modulation of local event rates by locomotion in distinct dendritic regions and report an advancing gradient of dendritic theta phase along the basal-tuft axis, then describe a pre-dominant hyperpolarization of the dendritic arbor during sharp-wave ripples. Finally, we find spatial tuning of dendritic representations dynamically reorganizes following place field formation. Our data reveal how the organization of electrical signaling in dendrites maps onto the anatomy of the dendritic tree across behavior, oscillatory network, and functional cell states.

neuroscience↗

bioRxiv2023

Synaptic Basis of Behavioral Timescale Plasticity

Learning and memory are fundamental to adaptive behavior and cognition. Various forms of synaptic plasticity have been proposed as cellular substrates for the emergence of feature selectivity in neurons underlying episodic memory. However, despite decades of work, our understanding of how synaptic plasticity underlies memory encoding remains limited, largely due to a shortage of tools and technical challenges associated with the visualization of synaptic plasticity at single-neuron resolution in awake-behaving animals. Behavioral Timescale Synaptic Plasticity (BTSP) postulates that synaptic inputs active during a seconds-long time window preceding and immediately following a large depolarizing plateau spike are potentiated, while synaptic inputs active outside this time window are depressed. We experimentally tested this model in vivo in awake-behaving mice using an all-optical approach by inducing place fields (PFs) in single CA1 pyramidal neurons (CA1PNs) while monitoring the spatiotemporal tuning of individual dendritic spines and changes in their corresponding synaptic weights. We identified an asymmetric synaptic plasticity kernel resulting from bidirectional modifications of synaptic weights around plateau burst induction. Surprisingly, our work also uncovered compartment-specific differences in the magnitude and temporal expression of synaptic plasticity between basal and oblique dendrites of CA1PNs. Our results provide the first experimental evidence linking synaptic plasticity to the rapid emergence of spatial selectivity in hippocampal neurons, a critical prerequisite for episodic memory.

neuroscience↗

bioRxiv2023

Activity-dependent subcellular compartmentalization of dendritic mitochondria structure in CA1 pyramidal neurons

Neuronal mitochondria play important roles beyond ATP generation, including Ca2+ uptake, and therefore have instructive roles in synaptic function and neuronal response properties. Mitochondrial morphology differs significantly in the axon and dendrites of a given neuronal subtype, but in CA1 pyramidal neurons (PNs) of the hippocampus, mitochondria within the dendritic arbor also display a remarkable degree of subcellular, layer- specific compartmentalization. In the dendrites of these neurons, mitochondria morphology ranges from highly fused and elongated in the apical tuft, to more fragmented in the apical oblique and basal dendritic compartments, and thus occupy a smaller fraction of dendritic volume than in the apical tuft. However, the molecular mechanisms underlying this striking degree of subcellular compartmentalization of mitochondria morphology are unknown, precluding the assessment of its impact on neuronal function. Here, we demonstrate that this compartment-specific morphology of dendritic mitochondria requires activity-dependent, Camkk2- dependent activation of AMPK and its ability to phosphorylate two direct effectors: the pro-fission Drp1 receptor Mff and the recently identified anti-fusion, Opa1-inhibiting protein, Mtfr1l. Our study uncovers a new activity- dependent molecular mechanism underlying the extreme subcellular compartmentalization of mitochondrial morphology in dendrites of neurons in vivo through spatially precise regulation of mitochondria fission/fusion balance.

cell biology↗

bioRxiv2020

Early cis-regulatory events in the formation of retinal horizontal cells

During retinal development, multipotent and restricted progenitor cells generate all of the neuronal cells of the retina. Among these are horizontal cells, which are interneurons that modulate the light-induced signal from photoreceptors. This study utilizes the identification of novel cis-regulatory elements as a method to examine the gene regulatory networks that direct the development of horizontal cells. Here we describe a screen for cis-regulatory elements, or enhancers, for the horizontal cell-associated genes PTF1A, ONECUT1 (OC1), TFAP2A (AP2A), and LHX1. The OC1ECR22 and Tfap2aACR5 elements were shown to be potential enhancers for OC1 and TFAP2A, respectively, and to be specifically active in developing horizontal cells. The OC1ECR22 element is activated by PTF1A and RBPJ, which translates to regulation of OC1 expression and suggests that PTF1A is a direct activator of OC1 expression in developing horizontal cells. The region within the Tfap2aACR5 element that is responsible for its activation was determined to be a 100 bp sequence named Motif 4. Both OC1ECR22 and Tfap2aACR5 are negatively regulated by the nuclear receptors THRB and RXRG, as is the expression of OC1 and AP2A, suggesting that nuclear receptors may have a role in the negative regulation of horizontal cell development.

developmental biology↗

bioRxiv2019

Single cell profiling of CRISPR/Cas9-induced OTX2 deficient retinas reveals fate switch from restricted progenitors

Development of the vertebrate eye, like many developmental systems, depends on genes that are used iteratively in multiple distinct processes. The OTX2 transcription factor is one such gene, with a requirement for eye formation, photoreceptor formation, and retinal pigment epithelium specification, among others. Recent evidence has suggested that OTX2 is also expressed in subsets of retinal progenitor cells with restricted fate choices. However, given the multiple roles for OTX2 and limitations of conventional conditional knockout strategies, the functional significance of this expression is unknown. Here we use CRISPR/Cas9 gene editing to produce mutations of OTX2, identifying similar phenotypes to those observed in human patients. In addition, we use single cell RNA sequencing to determine the functional consequences of OTX2 gene editing by CRISPR/Cas9 on the population of cells derived from OTX2-expressing retinal progenitor cells. We not only confirm that OTX2 is required for the generation of photoreceptors, but also for maintaining the proliferative potential of cells and suppressing the formation of specific retinal fates. These include subtypes of retinal ganglion and horizontal cells normally associated with these progenitor types, suggesting that in this context OTX2 functions to repress sister cell fate choices. Upregulation of key transcription factors involved in the formation of these cells was observed suggesting that OTX2 is upstream of critical nodes of gene regulatory networks of these alternative fates.

developmental biology↗