Department of Anatomy, Yonsei University College of Medicine, Seoul, South Korea.
Dev Dyn. 2013 Mar;242(3):269-80. doi: 10.1002/dvdy.23917. Epub 2013 Jan 28.
Carbonic anhydrases (CAs), which catalyze CO(2) hydration to bicarbonate and protons, have been suggested to regulate potassium homeostasis and endocochlear potential in the mammalian cochlea. Sixteen mammalian CA isozymes are currently known. To understand the specific roles of CA isozymes in the inner ear, a systematic survey was conducted to reveal temporal and spatial expression patterns of all 16 CA isozymes during inner ear development.
Our quantitative reverse transcriptase-polymerase chain reaction results showed that different tissues express unique combinations of CA isozymes. During inner ear development, transcripts of four cytosolic isozymes (Car1, Car2, Car3, and Car13), two membrane-bound isozymes (Car12 and Car14), and two CA-related proteins (Car8 and Car11) were expressed at higher levels than other isozymes. Spatial expression patterns of these isozymes within developing inner ears were determined by in situ hybridization. Each isozyme showed a unique expression pattern during development. For example, Car12 and Car13 expression closely overlapped with Pendrin, an anion exchanger, while Car2 overlapped with Na-K-ATPase in type II and IV otic fibrocytes, suggesting functional relationships in the inner ear.
The temporal and spatial expression patterns of each CA isozyme suggest unique and differential roles in inner ear development and function.
碳酸酐酶（CA）可催化 CO2 水合为碳酸氢根和质子，据认为其可调节哺乳动物耳蜗中的钾离子稳态和内淋巴电位。目前已知有 16 种哺乳动物 CA 同工酶。为了了解 CA 同工酶在内耳中的特定作用，我们进行了系统调查，以揭示所有 16 种 CA 同工酶在耳内发育过程中的时空表达模式。
我们的定量逆转录聚合酶链反应结果表明，不同组织表达独特的 CA 同工酶组合。在内耳发育过程中，四种胞质同工酶（Car1、Car2、Car3 和 Car13）、两种膜结合同工酶（Car12 和 Car14）和两种 CA 相关蛋白（Car8 和 Car11）的转录本表达水平高于其他同工酶。通过原位杂交确定了这些同工酶在发育中的内耳中的空间表达模式。每种同工酶在发育过程中都表现出独特的表达模式。例如，Car12 和 Car13 的表达与阴离子交换蛋白 Pendrin 紧密重叠，而 Car2 与 II 型和 IV 型耳纤维中的 Na-K-ATPase 重叠，这表明它们在内耳中具有功能关系。
每种 CA 同工酶的时空表达模式表明其在内耳发育和功能中具有独特和不同的作用。
