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Sci Rep. 2018 Nov 9;8(1):16659. doi: 10.1038/s41598-018-34876-9.

Whole-exome sequencing identifies two novel mutations in KCNQ4 in individuals with nonsyndromic hearing loss.

Author information

1
Department of Otorhinolaryngology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 03722, Korea.
2
Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, 16419, Korea.
3
Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 03722, Korea.
4
Department of Otorhinolaryngology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 03722, Korea. jychoi@yuhs.ac.
5
Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, 16419, Korea. tongmkang@skku.edu.
6
Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 03722, Korea. hygee@yuhs.ac.kr.

Abstract

Mutations in potassium voltage-gated channel subfamily Q member 4 (KCNQ4) are etiologically linked to a type of nonsyndromic hearing loss, deafness nonsyndromic autosomal dominant 2 (DFNA2). We performed whole-exome sequencing for 98 families with hearing loss and found mutations in KCNQ4 in five families. In this study, we characterized two novel mutations in KCNQ4: a missense mutation (c.796G>T; p.Asp266Tyr) and an in-frame deletion mutation (c.259_267del; p.Val87_Asn89del). p.Asp266Tyr located in the channel pore region resulted in early onset and moderate hearing loss, whereas p.Val87_Asn89del located in the N-terminal cytoplasmic region resulted in late onset and high frequency-specific hearing loss. When heterologously expressed in HEK 293 T cells, both mutant proteins did not show defects in protein trafficking to the plasma membrane or in interactions with wild-type (WT) KCNQ4 channels. Patch-clamp analysis demonstrated that both p.Asp266Tyr and p.Val87_Asn89del mutant channels lost conductance and were completely unresponsive to KCNQ activators, such as retigabine, zinc pyrithione, and ML213. Channels assembled from WT-p.Asp266Tyr concatemers, like those from WT-WT concatemers, exhibited conductance and responsiveness to KCNQ activators. However, channels assembled from WT-p.Val87_Asn89del concatemers showed impaired conductance, suggesting that p.Val87_Asn89del caused complete loss-of-function with a strong dominant-negative effect on functional WT channels. Therefore, the main pathological mechanism may be related to loss of K+ channel activity, not defects in trafficking.

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