The novel mouse mutation Oblivion inactivates the PMCA2 pump and causes progressive hearing loss.
The novel mouse mutation Oblivion inactivates the PMCA2 pump and causes progressive hearing loss.
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DOI：
10.1371/journal.pgen.1000238
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发表时间：
2008-10
期刊：
影响因子：
4.5
通讯作者：
Steel KP
中科院分区：
文献类型：
--
作者：
Spiden SL;Bortolozzi M;Di Leva F;de Angelis MH;Fuchs H;Lim D;Ortolano S;Ingham NJ;Brini M;Carafoli E;Mammano F;Steel KP
进行性听力损失在人类中很常见，但我们对其分子基础知之甚少。进行性听力损失的小鼠突变提供了有价值的见解，ENU(N-乙基-N-亚硝脲)突变是一种有用的模型生成方法。我们描述了一种新的ENU诱导的小鼠突变体Oblivion(等位基因符号OBL)，显示出听力障碍的半显性遗传。从出生后第20天到第90天，Obl/+突变体表现出听力障碍的增加，听功能丧失之后是相应的毛细胞退化的基点到顶端的进展。Obl/Obl突变体体型较小，2周龄时表现出严重的前庭功能障碍，从出生起就完全耳聋；感觉毛细胞在耳蜗底回部完全退化，但顶端毛细胞看起来正常。突变分析显示，Atp2b2基因外显子15存在错义突变(2630C→T)，导致毛细胞立体纤毛中驻留的钙泵PMCA2泵的跨膜区6的丝氨酸取代苯丙氨酸(S877F)。这些泵中的跨膜区突变通常被认为与蛋白质对质膜的正常靶向不相容。然而，对OBL/OBL小鼠培养的椭圆形黄斑中的毛细胞和模型细胞中突变的OBL泵的分析表明，该蛋白正确地定位于质膜。生化和生物物理特性表明，该泵失去了很大一部分非刺激性钙输出能力。这些发现可以解释听觉功能的进行性丧失，并表明我们仅从序列预测机制的能力是有限的。进行性听力损失在人类中非常常见，但我们对其原因知之甚少。环境和遗传因素各有可能起到作用。了解与听力损失有关的遗传变异并了解其作用的分子和细胞机制将有助于开发更好的治疗方法。已知的为数不多的在老鼠和人类中都参与其中的基因之一是Atp2b2，它编码一个钙泵。我们已经在这个基因中发现了一种新的突变，在突变的小鼠遗忘中导致听力损失。该突变导致跨膜区的丝氨酸到苯丙氨酸的取代。影响跨膜结构域的突变通常被认为会干扰蛋白质插入细胞膜并将其运输到细胞质膜上的最终目的地的正常过程。令人惊讶的是，这种泵是在表达突变基因的培养细胞和遗忘突变内耳的感觉毛细胞中产生的，并针对质膜。然而，我们发现它损害了钙泵能力，这可以解释我们在突变体中观察到的进行性听力损失以及感觉毛细胞的进行性退化。
Progressive hearing loss is common in the human population, but we have few clues to the molecular basis. Mouse mutants with progressive hearing loss offer valuable insights, and ENU (N-ethyl-N-nitrosourea) mutagenesis is a useful way of generating models. We have characterised a new ENU-induced mouse mutant, Oblivion (allele symbol Obl), showing semi-dominant inheritance of hearing impairment. Obl/+ mutants showed increasing hearing impairment from post-natal day (P)20 to P90, and loss of auditory function was followed by a corresponding base to apex progression of hair cell degeneration. Obl/Obl mutants were small, showed severe vestibular dysfunction by 2 weeks of age, and were completely deaf from birth; sensory hair cells were completely degenerate in the basal turn of the cochlea, although hair cells appeared normal in the apex. We mapped the mutation to Chromosome 6. Mutation analysis of Atp2b2 showed a missense mutation (2630C→T) in exon 15, causing a serine to phenylalanine substitution (S877F) in transmembrane domain 6 of the PMCA2 pump, the resident Ca2+ pump of hair cell stereocilia. Transmembrane domain mutations in these pumps generally are believed to be incompatible with normal targeting of the protein to the plasma membrane. However, analyses of hair cells in cultured utricular maculae of Obl/Obl mice and of the mutant Obl pump in model cells showed that the protein was correctly targeted to the plasma membrane. Biochemical and biophysical characterisation showed that the pump had lost a significant portion of its non-stimulated Ca2+ exporting ability. These findings can explain the progressive loss of auditory function, and indicate the limits in our ability to predict mechanism from sequence alone. Progressive hearing loss is very common in the human population, but we know little about the causes. Environmental and genetic factors each may contribute. Knowledge of the genetic variants involved in hearing loss and understanding of the molecular and cellular mechanism of their action will aid the development of better treatments. One of the few genes known to be involved, in both mouse and humans, is Atp2b2, which encodes a calcium pump. We have discovered a new mutation in this gene leading to hearing loss in the mouse mutant oblivion. The mutation leads to a serine to phenylalanine substitution in a transmembrane domain. Mutations affecting such transmembrane domains are usually expected to interfere with the normal process of inserting the protein in the membrane and transporting it to its final destination on the plasma membrane of the cell. Surprisingly, the pump is produced and is targeted to the plasma membrane, in both cultured cells expressing the mutant gene and sensory hair cells from the oblivion mutant inner ear. However, we show it has impaired calcium pumping ability, which can account for the progressive hearing loss as well as the progressive degeneration of the sensory hair cells that we observe in the mutants.
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影响因子：
5.3
作者：
Dumont, RA;Lins, U;Gillespie, PG
通讯作者：
Gillespie, PG
影响因子：
64.8
作者：
BOSHER, SK;WARREN, RL
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WARREN, RL
影响因子：
4.8
作者：
Elwess, NL;Filoteo, AG;Penniston, JT
通讯作者：
Penniston, JT
影响因子：
4.8
作者：
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影响因子：
5.3
作者：
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