ABSTRACT
Hippocampal pyramidal cells possess elaborate dendritic arbors with distinct domains that are targeted with input-specific synaptic sites. This synaptic arrangement is facilitated by synaptic cell-adhesion molecules that act as recognition elements to connect presynaptic and postsynaptic neurons. In this study, we investigate the organization of the synaptic recognition molecule latrophilin-2 at the surface of pyramidal neurons classified by spatial positioning and action potential firing patterns. Surveying two hippocampal neurons that highly express latrophilin-2, late-bursting CA1 pyramidal cells and early-bursting subiculum pyramidal cells, we found the molecule to be differentially positioned on their respective dendritic compartments. Investigating this latrophilin-2 positioning at the synaptic level, we found that the molecule is not present within either the pre- or postsynaptic terminal but rather is tightly coupled to synapses at a perisynaptic location. Together these findings indicate that hippocampal latrophilin-2 distribution patterning is cell-type specific, and requires multiple postsynaptic neurons for its synaptic localization.
ABSTRACT
Brain circuits are comprised of distinct interconnected neurons that are assembled by synaptic recognition molecules presented by defined pre- and post-synaptic neurons. This cell-cell recognition process is mediated by varying cellular adhesion molecules, including the latrophilin family of adhesion G-protein-coupled receptors. Focusing on parahippocampal circuitry, we find that latrophilin-2 (Lphn2; gene symbol ADGRL2) is specifically enriched in interconnected subregions of the medial entorhinal cortex (MEC), presubiculum (PrS), and parasubiculum (PaS). Retrograde viral tracing from the Lphn2-enriched region of the MEC reveals unique topographical patterning of inputs arising from the PrS and PaS that mirrors Lphn2 expression. Using a Lphn2 conditional knockout mouse model, we find that deletion of MEC Lphn2 expression selectively impairs retrograde viral labeling of inputs arising from the ipsilateral PrS. Combined with analysis of Lphn2 expression within the MEC, this study reveals Lphn2 to be selectively expressed by defined cell types and essential for MEC-PrS circuit connectivity.
Subject(s)
Entorhinal Cortex/physiology , Receptors, Peptide/genetics , Animals , Entorhinal Cortex/metabolism , Female , Gene Expression/genetics , Gene Expression Regulation/genetics , Hippocampus/physiology , Male , Mice , Mice, 129 Strain , Mice, Inbred C57BL , Mice, Knockout , Neural Pathways/cytology , Neurons/physiology , Parahippocampal Gyrus/metabolism , Receptors, Peptide/metabolismABSTRACT
We report on the development of bioinspired cardiac scaffolds made from electroconductive acid-modified silk fibroin-poly(pyrrole) (AMSF+PPy) substrates patterned with nanoscale ridges and grooves reminiscent of native myocardial extracellular matrix (ECM) topography to enhance the structural and functional properties of cultured human pluripotent stem cells (hPSC)-derived cardiomyocytes. Nanopattern fidelity was maintained throughout the fabrication and functionalization processes, and no loss in conductive behavior occurred due to the presence of the nanotopographical features. AMSF+PPy substrates were biocompatible and stable, maintaining high cell viability over a 21-day culture period while displaying no signs of PPy delamination. The presence of anisotropic topographical cues led to increased cellular organization and sarcomere development, and electroconductive cues promoted a significant improvement in the expression and polarization of connexin 43 (Cx43), a critical regulator of cell-cell electrical coupling. The combination of biomimetic topography and electroconductivity also increased the expression of genes that encode key proteins involved in regulating the contractile and electrophysiological function of mature human cardiac tissue.
