A helix-breaking mutation in TRPML3 leads to constitutive activity underlying deafness in the varitint-waddler mouse

Proc Natl Acad Sci U S A. 2007 Dec 4;104(49):19583-8. doi: 10.1073/pnas.0709846104. Epub 2007 Nov 28.


Homozygote varitint-waddler (Va) mice, expressing a mutant isoform (A419P) of TRPML3 (mucolipin 3), are profoundly deaf and display vestibular and pigmentation deficiencies, sterility, and perinatal lethality. Here we show that the varitint-waddler isoform of TRPML3 carrying an A419P mutation represents a constitutively active cation channel that can also be identified in native varitint-waddler hair cells as a distinct inwardly rectifying current. We hypothesize that the constitutive activation of TRPML3 occurs as a result of a helix-breaking proline substitution in transmembrane-spanning domain 5 (TM5). A proline substitution scan demonstrated that the inner third of TRPML3's TM5 is highly susceptible to proline-based kinks. Proline substitutions in TM5 of other TRP channels revealed that TRPML1, TRPML2, TRPV5, and TRPV6 display a similar susceptibility at comparable positions, whereas other TRP channels were not affected. We conclude that the molecular basis for deafness in the varitint-waddler mouse is the result of hair cell death caused by constitutive TRPML3 activity. To our knowledge, our study provides the first direct mechanistic link of a mutation in a TRP ion channel with mammalian hearing loss.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Apoptosis
  • Cell Line
  • Hearing Loss / genetics*
  • Mice
  • Molecular Sequence Data
  • Proline / chemistry
  • Proline / genetics
  • Protein Structure, Secondary / genetics
  • Protein Structure, Tertiary / genetics
  • TRPM Cation Channels / genetics*
  • Transient Receptor Potential Channels


  • Mcoln3 protein, mouse
  • TRPM Cation Channels
  • Transient Receptor Potential Channels
  • Proline