The varitint-waddler (Va) deafness mutation in TRPML3 generates constitutive, inward rectifying currents and causes cell degeneration

Keiichi Nagata, Lili Zheng, Thomas Madathany, Andrew J. Castiglioni, James R. Bartles, Jaime García-Añoveros*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

Varitint-waddler (Va and VaJ) mice are deaf and have vestibular impairment, with inner ear defects that include the degeneration and loss of sensory hair cells. The semidominant Va mutation results in an alanine-to-proline substitution at residue 419 (A419P) of the presumed ion channel TRPML3. Another allele, VaJ, has the A419P mutation in addition to an I362T mutation. We found that hair cells, marginal cells of stria vascularis, and other cells lining the cochlear and vestibular endolymphatic compartments express TRPML3. When heterologously expressed in LLC-PK1-CL4 epithelial cells, a culture model for hair cells, TRPML3 accumulated in lysosomes and in espin-enlarged microvilli that resemble stereocilia. We also demonstrated that wild-type TRPML3 forms channels that are blocked by Gd 3+, have a conductance of 50-70 pS and, like many other TRP channels, open at very positive potentials and thus rectify outwardly. In addition to this outward current, TRPML3(419P) and (I362T+A419P) generated a constitutive inwardly rectifying current that suggests a sensitivity to hyperpolarizing negative potentials and that depolarized the cells. Cells expressing TRPML3(A419P) or (I362T+A419P), but not wild-type TRPML3, died and were extruded from the epithelium in a manner reminiscent of degenerating hair cells in Va mice. The increased open probability of TRPML3(A419P) and (I362T+A419P) at physiological potentials likely underlies hair cell degeneration and deafness in Va and VaJ mice.

Original languageEnglish (US)
Pages (from-to)353-358
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number1
DOIs
StatePublished - Jan 8 2008

Keywords

  • Channelopathy
  • Espin
  • Hair cell
  • MCOLN3
  • Mucolipin

ASJC Scopus subject areas

  • General

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