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Item Correction to: Probing the multimodal fungiform papilla: complex peripheral nerve endings of chorda tympani taste and mechanosensitive fibers before and after Hedgehog pathway inhibition(Springer, 2022) Donnelly, Christopher R.; Kumari, Archana; Li, Libo; Vesela, Iva; Bradley, Robert M.; Mistretta, Charlotte M.; Pierchala, Brian A.; Anatomy, Cell Biology and Physiology, School of MedicineThis corrects the article "Probing the multimodal fungiform papilla: complex peripheral nerve endings of chorda tympani taste and mechanosensitive fibers before and after Hedgehog pathway inhibition" in Cell Tissue Res, volume 387 on page 225.Item EGR4 is critical for cell-fate determination and phenotypic maintenance of geniculate ganglion neurons underlying sweet and umami taste(National Academy of Science, 2023) Banik, Debarghya Dutta; Martin, Louis J.; Tang, Tao; Soboloff, Jonathan; Tourtellotte, Warren G.; Pierchala, Brian A.; Anatomy, Cell Biology and Physiology, School of MedicineThe sense of taste starts with activation of receptor cells in taste buds by chemical stimuli which then communicate this signal via innervating oral sensory neurons to the CNS. The cell bodies of oral sensory neurons reside in the geniculate ganglion (GG) and nodose/petrosal/jugular ganglion. The geniculate ganglion contains two main neuronal populations: BRN3A+ somatosensory neurons that innervate the pinna and PHOX2B+ sensory neurons that innervate the oral cavity. While much is known about the different taste bud cell subtypes, considerably less is known about the molecular identities of PHOX2B+ sensory subpopulations. In the GG, as many as 12 different subpopulations have been predicted from electrophysiological studies, while transcriptional identities exist for only 3 to 6. Importantly, the cell fate pathways that diversify PHOX2B+ oral sensory neurons into these subpopulations are unknown. The transcription factor EGR4 was identified as being highly expressed in GG neurons. EGR4 deletion causes GG oral sensory neurons to lose their expression of PHOX2B and other oral sensory genes and up-regulate BRN3A. This is followed by a loss of chemosensory innervation of taste buds, a loss of type II taste cells responsive to bitter, sweet, and umami stimuli, and a concomitant increase in type I glial-like taste bud cells. These deficits culminate in a loss of nerve responses to sweet and umami taste qualities. Taken together, we identify a critical role of EGR4 in cell fate specification and maintenance of subpopulations of GG neurons, which in turn maintain the appropriate sweet and umami taste receptor cells.Item Probing the multimodal fungiform papilla: complex peripheral nerve endings of chorda tympani taste and mechanosensitive fibers before and after Hedgehog pathway inhibition(Springer, 2022) Donnelly, Christopher R.; Kumari, Archana; Li, Libo; Vesela, Iva; Bradley, Robert M.; Mistretta, Charlotte M.; Pierchala, Brian A.; Anatomy, Cell Biology and Physiology, School of MedicineThe fungiform papilla (FP) is a gustatory and somatosensory structure incorporating chorda tympani (CT) nerve fibers that innervate taste buds (TB) and also contain somatosensory endings for touch and temperature. Hedgehog (HH) pathway inhibition eliminates TB, but CT innervation remains in the FP. Importantly, after HH inhibition, CT neurophysiological responses to taste stimuli are eliminated, but tactile responses remain. To examine CT fibers that respond to tactile stimuli in the absence of TB, we used Phox2b-Cre; Rosa26LSL-TdTomato reporter mice to selectively label CT fibers with TdTomato. Normally CT fibers project in a compact bundle directly into TB, but after HH pathway inhibition, CT fibers reorganize and expand just under the FP epithelium where TB were. This widened expanse of CT fibers coexpresses Synapsin-1, β-tubulin, S100, and neurofilaments. Further, GAP43 expression in these fibers suggests they are actively remodeling. Interestingly, CT fibers have complex terminals within the apical FP epithelium and in perigemmal locations in the FP apex. These extragemmal fibers remain after HH pathway inhibition. To identify tactile end organs in FP, we used a K20 antibody to label Merkel cells. In control mice, K20 was expressed in TB cells and at the base of epithelial ridges outside of FP. After HH pathway inhibition, K20 + cells remained in epithelial ridges but were eliminated in the apical FP without TB. These data suggest that the complex, extragemmal nerve endings within and disbursed under the apical FP are the mechanosensitive nerve endings of the CT that remain after HH pathway inhibition.