Cloning of MAO (monoamine oxidase) A and B has demonstrated unequivocally that these enzymes are made up of different polypeptides, and our understanding of MAO structure, regulation, and function has been significantly advanced by studies using their cDNA. MAO A and B genes are located on the X-chromosome (Xp11.23) and comprise 15 exons with identical intron-exon organization, which suggests that they are derived from the same ancestral gene. MAO A and B knock-out mice exhibit distinct differences in neurotransmitter metabolism and behavior. MAO A knock-out mice have elevated brain levels of serotonin, norephinephrine, and dopamine and manifest aggressive behavior similar to human males with a deletion of MAO A. In contrast, MAO B knock-out mice do not exhibit aggression and only levels of phenylethylamine are increased. Mice lacking MAO B are resistant to the Parkinsongenic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine. Both MAO A and B knock-out mice show increased reactivity to stress. These knock-out mice are valuable models for investigating the role of monoamines in psychoses and neurodegenerative and stress-related disorders.

中文翻译：

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单胺氧化酶：从基因到行为。

克隆MAO（单胺氧化酶）A和B明确表明这些酶是由不同的多肽组成的，并且通过使用它们的cDNA进行研究，我们对MAO的结构，调控和功能的了解已大大提高。MAO A和B基因位于X染色体（Xp11.23）上，包含15个外显子，具有相同的内含子-外显子组织，这表明它们源自相同的祖先基因。MAO A和B敲除小鼠在神经递质的代谢和行为方面表现出明显的差异。MAO A基因敲除小鼠的脑中血清素，去甲肾上腺素和多巴胺水平升高，并且表现出与人类男性相似的攻击行为，但MAO A缺失。相反，MAO B基因敲除小鼠不表现出侵略性，仅表现出苯乙胺水平增加。缺乏MAO B的小鼠对帕金森氏神经毒素1-甲基-4-苯基-1,2,3,6-四氢吡啶具有抗性。MAO A和B敲除小鼠均显示出对应激的反应性增加。这些敲除小鼠是用于研究单胺在精神病和神经退行性疾病以及与压力有关的疾病中的作用的有价值的模型。