Liang Gui-Hua, Jin Zhe, Ulfendahl Mats, Järlebark Leif
Department of Clinical Neuroscience, Center for Hearing and Communication ResearchKarolinska Institutet Karolinska University Hospital, Stockholm, Sweden.
Acta Otolaryngol. 2006 Apr;126(4):346-52. doi: 10.1080/00016480500416777.
Expression of neuronal Kcnq gene family transcripts in the inner ear provides further evidence for cochlear M-type currents and for complex molecular heterogeneities of voltage-gated potassium channels composed of various KCNQ subunits and/or alternative splice variants. Furthermore, important roles in regulation of cellular excitability in the auditory system, and hearing disorders related to (hyper)excitability, e.g. tinnitus, are implied.
Voltage-gated potassium channels play key roles in hearing, as evidenced by deafness resulting from disruption of genes encoding, for example, KCNQ1 or KCNQ4 subunits. Other members of the Kcnq gene family (Kcnq2, 3, and 5) are the molecular correlates of M currents, which regulate neuronal excitability. The expression of the latter has not previously been thoroughly investigated in the inner ear.
The aim of this study was to identify genetic correlates of M currents, previously identified in cochlear hair cells by electrophysiological methods.
Expression of Kcnq genes was investigated by reverse transcription-polymerase chain reaction (RT-PCR) using subtype-specific primers with total RNA isolated from whole guinea pig or rat cochlea as template. PCR products were confirmed by direct DNA sequencing.
All members of the Kcnq family were expressed in guinea pig and rat cochlea. Cochlear expression of Kcnq2 exhibited two alternatively spliced forms, lacking exons 8, 15a, and 8, 12a, 15a, respectively. Novel molecular sequence data, e.g. guinea pig Kcnq cDNA sequences, were deposited in GenBank (AY684985-AY684990).
内耳中神经元Kcnq基因家族转录本的表达为耳蜗M型电流以及由各种KCNQ亚基和/或可变剪接变体组成的电压门控钾通道的复杂分子异质性提供了进一步证据。此外，这暗示了其在调节听觉系统细胞兴奋性以及与（过度）兴奋性相关的听力障碍（如耳鸣）中发挥重要作用。
电压门控钾通道在听力中起关键作用，例如编码KCNQ1或KCNQ4亚基的基因破坏导致耳聋就证明了这一点。Kcnq基因家族的其他成员（Kcnq2、3和5）是M电流的分子相关物，可调节神经元兴奋性。此前尚未在内耳中对后者的表达进行深入研究。
本研究的目的是确定先前通过电生理方法在耳蜗毛细胞中鉴定出的M电流的基因相关物。
使用亚型特异性引物通过逆转录-聚合酶链反应（RT-PCR）研究Kcnq基因的表达，以从整个豚鼠或大鼠耳蜗中分离的总RNA为模板。PCR产物通过直接DNA测序进行确认。
Kcnq家族的所有成员均在豚鼠和大鼠耳蜗中表达。Kcnq2在耳蜗中的表达表现出两种可变剪接形式，分别缺失外显子8、15a和8、12a、15a。新的分子序列数据，如豚鼠Kcnq cDNA序列，已存入GenBank（AY684985-AY684990）。
