Genetic ablation of VIAAT in glycinergic neurons causes a severe respiratory phenotype and perinatal death
Genetic ablation of VIAAT in glycinergic neurons causes a severe respiratory phenotype and perinatal death
复制标题
DOI：
10.1007/s00429-014-0829-2
复制
发表时间：
2015-09-01
影响因子：
3.1
通讯作者：
Huelsmann, Swen
中科院分区：
文献类型：
--
作者：
Rahman, Jamilur;Besser, Stefanie;Huelsmann, Swen
甘氨酸能神经元和GABA能神经元都需要囊泡抑制性氨基酸转运体（VIAAT）来填充突触囊泡。突触前GABA浓度由GABA合成酶谷氨酸脱羧酶（GAD）65和GAD 67决定，而突触前甘氨酸含量取决于质膜甘氨酸转运蛋白2（GlyT 2）。虽然严重受损，甘氨酸能传输是不是完全不存在的GlyT 2基因敲除小鼠，表明其他途径的甘氨酸摄取或从头合成的甘氨酸存在于突触前末梢。为了研究甘氨酸能传递完全丧失的后果，我们通过将具有loxP侧翼VIAAT等位基因的小鼠与GlyT 2-Cre转基因小鼠系杂交，产生了在甘氨酸能神经元中具有条件性VIAAT消融的小鼠系。有趣的是，条件性VIAAT敲除（VIAAT cKO）小鼠在出生时不能存活。除了显性呼吸衰竭外，VIAAT cKO还显示出脐疝和腭裂。免疫组织化学显示脑干中的VIAAT几乎完全耗尽。电生理结果显示，缺乏自发性甘氨酸和GABA能抑制性突触后电流从舌下运动神经元。我们的研究结果表明，GlyT 2-Cre表达神经元中VIAAT的缺失也强烈影响GABA能传递，并表明在大脑尾部的早期发育过程中，甘氨酸能和GABA能神经元群体有很大的重叠。
Both glycinergic and GABAergic neurons require the vesicular inhibitory amino acid transporter (VIAAT) for synaptic vesicle filling. Presynaptic GABA concentrations are determined by the GABA-synthesizing enzymes glutamate decarboxylase (GAD)65 and GAD67, whereas the presynaptic glycine content depends on the plasma membrane glycine transporter 2 (GlyT2). Although severely impaired, glycinergic transmission is not completely absent in GlyT2-knockout mice, suggesting that other routes of glycine uptake or de novo synthesis of glycine exist in presynaptic terminals. To investigate the consequences of a complete loss of glycinergic transmission, we generated a mouse line with a conditional ablation of VIAAT in glycinergic neurons by crossing mice with loxP-flanked VIAAT alleles with a GlyT2-Cre transgenic mouse line. Interestingly, conditional VIAAT knockout (VIAAT cKO) mice were not viable at birth. In addition to the dominant respiratory failure, VIAAT cKO showed an umbilical hernia and a cleft palate. Immunohistochemistry revealed an almost complete depletion of VIAAT in the brainstem. Electrophysiology revealed the absence of both spontaneous glycinergic and GABAergic inhibitory postsynaptic currents from hypoglossal motoneurons. Our results demonstrate that the deletion of VIAAT in GlyT2-Cre expressing neurons also strongly affects GABAergic transmission and suggest a large overlap of the glycinergic and the GABAergic neuron population during early development in the caudal parts of the brain.