Roles of GABA in neural development and plasticity : produciton and analysis of GABA-synthesizing enzyme (GAD) -deficient mice

为了阐明γ -氨基丁酸（GABA）在神经和非神经组织发育以及各脑区各种功能中的作用，通过基因靶向法对小鼠γ -氨基丁酸合成酶谷氨酸脱羧酶（GAD）编码基因进行了破坏。GAD有GAD65和GAD67两种同工异构体，它们各自的作用，迄今为止尚不清楚，有望得到澄清。gad65缺失小鼠能正常生长，未出现严重的行为异常。他们的大脑含有正常水平的GABA，没有表现出组织学异常。另一方面，gad67缺陷小鼠如预期般出生，但出生后不久就死于严重的腭裂。他们的大脑只含有野生型大脑中7%的GABA，尽管他们的组织学是正常的。这些结果表明GAD67是小鼠大脑中GAD的一个重要亚型。我们正在研究GABA在腭裂和其他非神经组织发育中的作用，以及利用诱导敲除技术修复gad67缺陷小鼠的生产。由于GAD65基因敲除小鼠对惊厥和抗精神病药物的反应性表现出中度变化，我们现在正在分析GAD65缺陷纹状体、昼夜节律系统和其他大脑区域的功能。

In order to elucidate the roles of gamma-aminobutyric acid (GABA) in the development of the neural and non-neural tissues and in the various functions of each brain region, the genes encoding GABA-synthesizing enzyme, glutamic acid decarboxylase (GAD) in the mice were disrupted by gene targeting. GAD has two isoforms, GAD65 and GAD67, and expectedly their respective roles, so far unknown, would be clarified. GAD65-deficient mice could grow normally and did not show serious behavioral abnormailites. Their brain contained normal level of GABA and did not show histological abnormalities. On the other hand, GAD67-deficient mice were born as expected but died of severe cleft palate soon after birth. Their brain contained only 7% of GABA found in the wild-type brain in spite of their norman histoloy. These results have shown that GAD67 is an important isoform of GAD in the mouse brain. We are investigating on 1 involvement of GABA in development of palate and other non neural tissue and 2 production of GAD67-deficient mice rescued from cleft palate using inducible knockout technique. As GAD65 knockout mice showed moderate changes in responsiveness to convulsant and antipsychotic drugs, we are now analyzing the functions of the GAD65-deficient striatum, circadian system and other brain areas.