Dhasakumar S. Navaratnam

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In humans, the absence of Fragile X mental retardation protein (FMRP), an RNA-binding protein, results in Fragile X syndrome, the most common inherited form of intellectual disability. Using biochemical and electrophysiological studies, we found that FMRP binds to the C terminus of the Slack sodium-activated potassium channel to activate the channel in(More)
We have cloned from the receptor epithelium of the chick cochlea a family of alternatively spliced cDNAs derived from cslo, which encodes a Ca2+-activated K+ channel like those shown to help determine the resonant frequency of electrically tuned hair cells. Our results from PCRs using template RNAs from both tonotopically subdivided receptor epithelia and(More)
The outer hair cell lateral membrane motor, prestin, drives the cell's mechanical response that underpins mammalian cochlear amplification. Little is known about the protein's structure-function relations. Here we provide evidence that prestin is a 10-transmembrane domain protein whose membrane topology differs from that of previous models. We also present(More)
The integral membrane protein prestin, a member of the SLC26 anion transporter family, is responsible for the voltage-driven electromotility of mammalian outer hair cells. It was argued that the evolution of prestin's motor function required a loss of the protein's transport capabilities. Instead, it was proposed that prestin manages only an abortive(More)
BACKGROUND Chloride is the major anion in cells, with many diseases arising from disordered Cl- regulation. For the non-invasive investigation of Cl- flux, YFP-H148Q and its derivatives chameleon and Cl-Sensor previously were introduced as genetically encoded chloride indicators. Neither the Cl- sensitivity nor the pH-susceptibility of these modifications(More)
The development of motor protein activity in the lateral membrane of the mouse outer hair cell (OHC) from postnatal day 5 (P5) to P18 was investigated under whole-cell voltage clamp. Voltage-dependent, nonlinear capacitance (C (v)), which represents the conformational fluctuations of the motor molecule, progressively increased during development. At P12,(More)
A gelatinous otolithic membrane (OM) couples a single calcified otolith to the sensory epithelium in the bluegill sunfish (Lepomis macrochirus) saccule, one of the otolithic organs in the inner ear. Though the OM is an integral part of the anatomic network of endorgan structures that result in vestibular function in the inner ear, the identity of the(More)
OVERVIEW This review considers the "tween twixt and twain" of hair cell physiology, specifically the signaling elements and membrane conductances which underpin forward and reverse transduction at the input stage of hair cell function and neurotransmitter release at the output stage. Other sections of this review series outline the advances which have been(More)
To identify receptor tyrosine kinases (RTKs) present in the murine inner ear, a degenerate polymerase chain reaction (PCR) methodology was employed to clone partial cDNAs encoding RTKs from embryonic day-17.5 mouse whole inner ear RNA. At least 20 distinct TKs were identified within the first 50 subcloned PCR products obtained by this analysis (Davis/Lee et(More)
Electrical resonance is a mechanism used by birds and many vertebrates to discriminate between frequencies of sound, and occurs when the intrinsic oscillation in the membrane potential of a specific hair cell corresponds to a specific stimulus sound frequency. This intrinsic oscillation results from an interplay between an inward Ca(2+) current and the(More)