Differentially expressed genes in the rat cochlear nucleus
NEUROSCIENCE
Authors: Friedland, D. R.; Popper, P.; Eernisse, R.; Cioffi, J. A.
Abstract
The cochlear nucleus is the first central pathway involved in the processing of peripheral auditory activity. The anterior ventral cochlear nucleus (AVCN), posterior ventral cochlear nucleus (PVCN) and dorsal cochlear nucleus (DCN) each contain predominant populations of neurons that have been well characterized regarding their morphological and electrophysiological properties. Little is known, however, of the underlying genetic factors that contribute to these properties and the initial steps in auditory processing. Serial analysis of gene expression (SAGE), supported by microarray experiments, was performed on each subdivision of the rat cochlear nucleus to identify genes that may sub-serve specialized roles in the central auditory system. Pair-wise comparisons between SAGE libraries from the AVCN, PVCN and DCN were correlated with microarray experiments to identify individual transcripts with significant differential expression. Twelve highly correlated genes were identified representing cytoskeletal, vesicular, metabolic and g-protein regulating proteins. Among these were Rgs4 which showed higher expression in the DCN, Sst and Cyp11b1 with very high expression in the AVCN and Calb2 with preferential expression in the PVCN. The differential expression of these genes was validated with real-time reverse transcriptase-polymerase chain reaction. These experiments provide a basis for understanding normal auditory processing on a molecular level and a template for investigating changes that may occur in the cochlear nucleus with hearing loss, the generation and percept of tinnitus, and central auditory processing disorders. (c) 2006 IBRO. Published by Elsevier Ltd. All rights reserved.
Developmental plasticity of epithelial stem cells in tooth and taste bud renewal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Authors: Bloomquist, Ryan F.; Fowler, Teresa E.; An, Zhengwen; Yu, Tian Y.; Abdilleh, Kawther; Fraser, Gareth J.; Sharpe, Paul T.; Streelman, J. Todd
Abstract
In Lake Malawi cichlids, each tooth is replaced in one-for-one fashion every similar to 20 to 50 d, and taste buds (TBs) are continuously renewed as in mammals. These structures are colocalized in the fish mouth and throat, from the point of initiation through adulthood. Here, we found that replacement teeth (RT) share a continuous band of epithelium with adjacent TBs and that both organs coexpress stem cell factors in subsets of label-retaining cells. We used RNA-seq to characterize transcriptomes of RT germs and TB-bearing oral epithelium. Analysis revealed differential usage of developmental pathways in RT compared to TB oral epithelia, as well as a repertoire of genome paralogues expressed complimentarily in each organ. Notably, BMP ligands were expressed in RT but excluded from TBs. Morphant fishes bathed in a BMP chemical antagonist exhibited RT with abrogated shh expression in the inner dental epithelium (IDE) and ectopic expression of calb2 (a TB marker) in these very cells. In the mouse, teeth are located on the jaw margin while TBs and other oral papillae are located on the tongue. Previous study reported that tongue intermolar eminence (IE) oral papillae of Follistatin (a BMP antagonist) mouse mutants exhibited dysmorphic invagination. We used these mutants to demonstrate altered transcriptomes and ectopic expression of dental markers in tongue IE. Our results suggest that vertebrate oral epithelium retains inherent plasticity to form tooth and taste-like cell types, mediated by BMP specification of progenitor cells. These findings indicate underappreciated epithelial cell populationswith promising potential in bioengineering and dental therapeutics.