Biology subjects

Powers, K. G.

Publications and source records attributed to Powers, K. G..

3 recordsLinked to original sources

bioRxiv2025

EBF1 regulates sensory establishment in the cochlea by positioning the medial boundary of the prosensory domain and restricting proliferation of the sensory progenitor population

In our previous study, we reported that Ebf1 excision throughout the inner ear epithelium and before the onset of cochlear development leads to dramatic sensory expansion in the cochlea by neonatal stages. Ebf1 conditional knockout cochleae possess over twice as many sensory cells as littermate controls and develop ectopic sensory patches in their Kollikers organs. To better understand the mechanism behind EBF1s role in restricting sensory establishment, we performed multiome sequencing in our current study. EBF1 is a transcription factor best known for its importance in B cell lineage specification, during which it acts as both an activator and a repressor. Our results indicate that EBF1 prevents the Kollikers organ cells from being recruited to the prosensory domain by promoting expression of Prdm16 and repressing expression of Jag1 and Sox2. We also found that EBF1 may promote cell cycle exit by repressing Ccnjl expression. In summary, medial expansion of the prosensory domain, together with delayed cell cycle exit in the developing cochlear epithelium, underlies the robust increase in sensory cells seen in Ebf1 conditional knockouts. SUMMARY STATEMENTMultiome sequencing reveals EBF1 regulates prosensory domain establishment by: (1) positioning the medial boundary of the prosensory domain and (2) restricting the proliferative capacity of the sensory progenitor pool.

developmental biology↗

bioRxiv2020

A Single Membrane Protein Required for Atrial Secretory Granule Formation

The discovery of atrial secretory granules and the natriuretic peptides stored in them identified the atrium as an endocrine organ. Although neither atrial nor brain natriuretic peptide (ANP, BNP) is amidated, the major membrane protein in atrial granules is Peptidylglycine -Amidating Monooxygenase (PAM), an enzyme essential for amidated peptide biosynthesis. Mice lacking cardiomyocyte PAM (PamMyh6-cKO/cKO) are viable, but a gene dosage-dependent drop in atrial ANP and BNP content occurred. Ultrastructural analysis of adult PamMyh6-cKO/cKO atria revealed a 20-fold drop in the volume fraction of secretory granules and a decrease in peripherally localized Golgi complexes. When primary cultures of Pam0-Cre-cKO/cKO atrial myocytes (PAM floxed, no Cre recombinase) were transduced with Cre-GFP lentivirus, PAM protein levels dropped, followed by a decline in proANP levels. Expression of exogenous PAM in PamMyh6-cKO/cKO atrial myocytes produced a dose-dependent increase in proANP content. Strikingly, rescue of proANP content did not require the monooxygenase activity of PAM. Unlike many prohormones, atrial proANP is stored intact and its basal secretion is stimulated by drugs that inhibit Golgi-localized Arf activators. Increased basal secretion of proANP was a major contributor to its reduced levels in PamMyh6-cKO/cKO myocytes; the inability of these drugs to inhibit basal proANP secretion by PamMyh6-cKO/cKO myocytes revealed a role for COPI-mediated recycling of PAM to the endoplasmic reticulum. Analysis of atrial coated vesicles and the ability PAM to make fluorescently-tagged proANP accumulate in the cis-Golgi region of cells lacking secretory granules revealed a non-catalytic role for PAM in soluble cargo trafficking early in the secretory pathway. SignificanceTransmission electron microscopy of atrial cardiomyocytes revealed dense granules resembling those in endocrine cells and neurons, leading to the discovery of the natriuretic peptides stored in these granules. Subsequent studies revealed features unique to atrial granules, including high level expression of Peptidylglycine -Amidating Monooxygenase (PAM), an enzyme required for the synthesis of many neuropeptides, but not for the synthesis of natriuretic peptides. The discovery that atrial myocytes lacking PAM are unable to produce granules and that PAM lacking its monooxygenase activity can rescue granule formation provides new information about the proANP secretory pathway. A better understanding of the unique features of atrial cell biology should provide insight into atrial fibrillation, the most common cardiac arrhythmia, atrial amyloidosis and heart failure.

cell biology↗

bioRxiv2019

Identifying Novel Roles for Peptidergic Signaling in Mice

Despite accumulating evidence demonstrating the essential roles played by neuropeptides, it has proven challenging to use this information to develop therapeutic strategies. Peptidergic signaling can involve juxtacrine, paracrine, endocrine and neuronal signaling, making it difficult to define physiologically important pathways. One of the final steps in the biosynthesis of many neuropeptides requires a single enzyme, peptidylglycine -amidating monooxygenase (PAM), and lack of amidation renders most of these peptides biologically inert. PAM, an ancient integral membrane enzyme that traverses the biosynthetic and endocytic pathways, also affects cytoskeletal organization and gene expression. While mice, zebrafish and flies lacking Pam (PamKO/KO) are not viable, we reasoned that cell-type specific elimination of Pam expression would generate mice that could be screened for physiologically important and tissue-specific deficits. PamcKO/cKO mice, with loxP sites flanking the 2 exons deleted in the global PamKO/KO mouse, were indistinguishable from wildtype mice. Eliminating Pam expression in excitatory forebrain neurons reduced anxiety-like behavior, increased locomotor responsiveness to cocaine and improved thermoregulation in the cold. A number of amidated peptides play essential roles in each of these behaviors. Although atrial natriuretic peptide (ANP) is not amidated, Pam expression in the atrium exceeds levels in any other tissue. Eliminating Pam expression in cardiomyocytes increased anxiety-like behavior and improved thermoregulation. Atrial and serum levels of ANP fell sharply PamMyh6-cKO/cKO in mice and RNASeq analysis identified changes in gene expression in pathways related to cardiac function. Use of this screening platform should facilitate the development of new therapeutic approaches targeted to peptidergic pathways.\n\nSIGNIFICANCEPeptidergic signaling, which plays key roles in the many pathways that control thermoregulation, salt and water balance, metabolism, anxiety, pain perception and sexual reproduction, is essential for the maintenance of homeostasis. Despite the fact that peptides generally signal through G protein coupled receptors, it has proven difficult to use knowledge about peptide synthesis, storage and secretion to develop effective therapeutics. Our goal was to develop an in vivo bioassay system that would reveal physiologically meaningful deficits associated with disturbed peptidergic signaling. We did so by developing a system in which an enzyme essential for the production of many bioactive peptides could be eliminated in a tissue-specific manner.

neuroscience↗