Department of Physiology, Keio University School of Medicine, Tokyo, Japan.
Laboratory for Marmoset Neural Architecture, Center for Brain Science, RIKEN, Wako, Japan.
Sci Rep. 2020 Dec 9;10(1):21516. doi: 10.1038/s41598-020-78608-4.
GPR56, a member of the adhesion G protein-coupled receptor family, is abundantly expressed in cells of the developing cerebral cortex, including neural progenitor cells and developing neurons. The human GPR56 gene has multiple presumptive promoters that drive the expression of the GPR56 protein in distinct patterns. Similar to coding mutations of the human GPR56 gene that may cause GPR56 dysfunction, a 15-bp homozygous deletion in the cis-regulatory element upstream of the noncoding exon 1 of GPR56 (e1m) leads to the cerebral cortex malformation and epilepsy. To clarify the expression profile of the e1m promoter-driven GPR56 in primate brain, we generated a transgenic marmoset line in which EGFP is expressed under the control of the human minimal e1m promoter. In contrast to the endogenous GPR56 protein, which is highly enriched in the ventricular zone of the cerebral cortex, EGFP is mostly expressed in developing neurons in the transgenic fetal brain. Furthermore, EGFP is predominantly expressed in GABAergic neurons, whereas the total GPR56 protein is evenly expressed in both GABAergic and glutamatergic neurons, suggesting the GABAergic neuron-preferential activity of the minimal e1m promoter. These results indicate a possible pathogenic role for GABAergic neuron in the cerebral cortex of patients with GPR56 mutations.
GPR56 是黏附 G 蛋白偶联受体家族的成员，在包括神经祖细胞和发育中的神经元在内的大脑皮质发育细胞中大量表达。人类 GPR56 基因有多个假定的启动子，它们以不同的模式驱动 GPR56 蛋白的表达。类似于可能导致 GPR56 功能障碍的人类 GPR56 基因突变，GPR56 非编码外显子 1 上游顺式调控元件中的 15 个碱基对同源缺失 (e1m) 导致大脑皮质畸形和癫痫。为了阐明 e1m 启动子驱动的 GPR56 在灵长类动物大脑中的表达谱，我们生成了一个转基因狨猴系，其中 EGFP 在人类最小 e1m 启动子的控制下表达。与在大脑皮质室管膜区高度富集的内源性 GPR56 蛋白不同，EGFP 在转基因胎脑发育中的神经元中主要表达。此外，EGFP 主要表达在 GABA 能神经元中，而总 GPR56 蛋白在 GABA 能和谷氨酸能神经元中均匀表达，提示最小 e1m 启动子的 GABA 能神经元优先活性。这些结果表明，GPR56 突变患者的大脑皮质中 GABA 能神经元可能具有致病性作用。
