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The peripheral and central auditory subsystems together form a complex sensory network that allows an organism to hear. The genetic programs of the two subsystems must therefore be tightly coordinated during development. Yet, their interactions and common expression pathways have never been systematically explored. MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression and are essential for normal development of the auditory system. We performed mRNA and small-RNA sequencing of organs from both auditory subsystems at three critical developmental timepoints (E16, P0, P16) to obtain a comprehensive and unbiased insight of their expression profiles. Our analysis reveals common and organ-specific expression patterns for differentially regulated mRNAs and miRNAs, which could be clustered with a particular selection of functions such as inner ear development, Wnt signalling, K+ transport, and axon guidance, based on gene ontology. Bioinformatics detected enrichment of predicted targets of specific miRNAs in the clusters and predicted regulatory interactions by monitoring opposite trends of expression of miRNAs and their targets. This approach identified six miRNAs as strong regulatory candidates for both subsystems. Among them was miR-96, an established critical factor for proper development in both subsystems, demonstrating the strength of our approach. We suggest that other miRNAs identified by this analysis are also common effectors of proper hearing acquirement. This first combined comprehensive analysis of the developmental program of the peripheral and central auditory systems provides important data and bioinformatics insights into the shared genetic program of the two sensory subsystems and their regulation by miRNAs.

Abstract Background Plasmodium falciparum (Pf) is the leading protozoan causing malaria, the most devastating parasitic disease. To ensure transmission, a small subset of Pf parasites differentiate into the sexual forms (gametocytes). Since the abundance of these essential parasitic forms is extremely low within the human host, little is currently known about the molecular regulation of their sexual differentiation, highlighting the need to develop tools to investigate Pf gene expression during this fundamental mechanism. Methods We developed a high-throughput quantitative Reverse-Transcription PCR (RT-qPCR) platform to robustly monitor Pf transcriptional patterns, in particular, systematically profiling the transcriptional pattern of a large panel of gametocyte-related genes (GRG). Initially, we evaluated the technical performance of the systematic RT-qPCR platform to ensure it complies with the accepted quality standards for: (i) RNA extraction, (ii) cDNA synthesis and (iii) evaluation of gene expression through RT-qPCR. We then used this approach to monitor alterations in gene expression of a panel of GRG upon treatment with gametocytogenesis regulators. Results We thoroughly elucidated GRG expression profiles under treatment with the antimalarial drug dihydroartemisinin (DHA) or the metabolite choline over the course of a Pf blood cycle (48 h). We demonstrate that both significantly alter the expression pattern of PfAP2-G, the gametocytogenesis master regulator. However, they also markedly modify the developmental rate of the parasites and thus might bias the mRNA expression. Additionally, we screened the effect of the metabolites lactate and kynurenic acid, abundant in severe malaria, as potential regulators of gametocytogenesis. Conclusions Our data demonstrate that the high-throughput RT-qPCR method enables studying the immediate transcriptional response initiating gametocytogenesis of the parasites from a very low volume of malaria-infected RBC samples. The obtained data expand the current knowledge of the initial alterations in mRNA profiles of GRG upon treatment with reported regulators. In addition, using this method emphasizes that asexual parasite stage composition is a crucial element that must be considered when interpreting changes in GRG expression by RT-qPCR, specifically when screening for novel compounds that could regulate Pf sexual differentiation. Graphical Abstract

Prolonged exposure to loud noise has been shown to affect inner ear sensory hair cells in a variety of deleterious manners, including damaging the stereocilia core. The damaged sites can be visualized as ‘gaps’ in phalloidin staining of F-actin, and the enrichment of monomeric actin at these sites, along with an actin nucleator and crosslinker, suggests that localized remodeling occurs to repair the broken filaments. Herein, we show that gaps in mouse auditory hair cells are largely repaired within 1 week of traumatic noise exposure through the incorporation of newly synthesized actin. We provide evidence that Xin actin binding repeat containing 2 (XIRP2) is required for the repair process and facilitates the enrichment of monomeric γ-actin at gaps. Recruitment of XIRP2 to stereocilia gaps and stress fiber strain sites in fibroblasts is force-dependent, mediated by a novel mechanosensor domain located in the C-terminus of XIRP2. Our study describes a novel process by which hair cells can recover from sublethal hair bundle damage and which may contribute to recovery from temporary hearing threshold shifts and the prevention of age-related hearing loss.