Mutations of SLC26A4 are a common cause of hearing loss associated with enlargement of the endolymphatic sac (EES). Slc26a4 expression in the developing mouse endolymphatic sac is required for acquisition of normal inner ear structure and function. Here, we show that the mouse endolymphatic sac absorbs fluid in an SLC26A4-dependent fashion. Fluid absorption was sensitive to ouabain and gadolinium but insensitive to benzamil, bafilomycin and S3226. Single-cell RNA-seq analysis of pre-and postnatal endolymphatic sacs demonstrates two types of differentiated cells. Early ribosome-rich cells (RRCs) have a transcriptomic signature suggesting expression and secretion of extracellular proteins, while mature RRCs express genes implicated in innate immunity. The transcriptomic signature of mitochondria-rich cells (MRCs) indicates that they mediate vectorial ion transport. We propose a molecular mechanism for resorption of NaCl by MRCs during development, and conclude that disruption of this mechanism is the root cause of hearing loss associated with EES.
Second language teacher education (SLTE) has undergone considerable change over the past 25 years. The question of how language teaching is learnt and how programmes of professional preparation can contribute to this process now elicits quite different answers. A new agenda of theory and practice has emerged as SLTE has incorporated many of the ideas and practices of reflection (Schön 1983). At the same time, it has drawn increasingly on feeder fields of research and practice such as teacher cognition and professional cultures. These have augmented, and to some extent displaced, the original roots of SLTE in Applied Linguistics and Psychology, and a new knowledge base (Freeman & Johnson 1998) has been established, contributing to the formulation of theory about language teachers' learning-to-teach, and its practices. The focus of this review is on the extent to which the new agenda has influenced SLTE practices in recent years. It examines accounts of activities teacher educators and student teachers engage in during SLTE programmes in formal learning experiences. The paper identifies a thriving practitioner research culture in SLTE but argues that much more research is required to establish the true extent to which new conceptualisations of the process of learning-to-teach second languages guides SLTE practice.
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