Sheen Volney L, Ganesh Vijay S, Topcu Meral, Sebire Guillaume, Bodell Adria, Hill R Sean, Grant P Ellen, Shugart Yin Yao, Imitola Jaime, Khoury Samia J, Guerrini Renzo, Walsh Christopher A
Division of Neurogenetics and Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA.
Nat Genet. 2004 Jan;36(1):69-76. doi: 10.1038/ng1276. Epub 2003 Nov 30.
Disruption of human neural precursor proliferation can give rise to a small brain (microcephaly), and failure of neurons to migrate properly can lead to an abnormal arrest of cerebral cortical neurons in proliferative zones near the lateral ventricles (periventricular heterotopia). Here we show that an autosomal recessive condition characterized by microcephaly and periventricular heterotopia maps to chromosome 20 and is caused by mutations in the gene ADP-ribosylation factor guanine nucleotide-exchange factor-2 (ARFGEF2). By northern-blot analysis, we found that mouse Arfgef2 mRNA levels are highest during embryonic periods of ongoing neuronal proliferation and migration, and by in situ hybridization, we found that the mRNA is widely distributed throughout the embryonic central nervous system (CNS). ARFGEF2 encodes the large (>200 kDa) brefeldin A (BFA)-inhibited GEF2 protein (BIG2), which is required for vesicle and membrane trafficking from the trans-Golgi network (TGN). Inhibition of BIG2 by BFA, or by a dominant negative ARFGEF2 cDNA, decreases cell proliferation in vitro, suggesting a cell-autonomous regulation of neural expansion. Inhibition of BIG2 also disturbed the intracellular localization of such molecules as E-cadherin and beta-catenin by preventing their transport from the Golgi apparatus to the cell surface. Our findings show that vesicle trafficking is an important regulator of proliferation and migration during human cerebral cortical development.
人类神经前体细胞增殖的破坏可导致小脑（小头畸形），而神经元迁移异常可导致大脑皮质神经元在侧脑室附近的增殖区异常停滞（脑室周围异位）。我们在此表明，一种以小头畸形和脑室周围异位为特征的常染色体隐性疾病定位于20号染色体，是由ADP核糖基化因子鸟嘌呤核苷酸交换因子2（ARFGEF2）基因突变引起的。通过Northern印迹分析，我们发现小鼠Arfgef2 mRNA水平在神经元持续增殖和迁移的胚胎期最高，通过原位杂交，我们发现该mRNA广泛分布于整个胚胎中枢神经系统（CNS）。ARFGEF2编码大的（>200 kDa）布雷菲德菌素A（BFA）抑制的鸟嘌呤核苷酸交换因子2蛋白（BIG2），它是从反式高尔基体网络（TGN）进行囊泡和膜运输所必需的。用BFA或显性负性ARFGEF2 cDNA抑制BIG2会降低体外细胞增殖，提示对神经扩张存在细胞自主调节。抑制BIG2还会通过阻止E-钙黏蛋白和β-连环蛋白等分子从高尔基体运输到细胞表面而干扰其细胞内定位。我们的研究结果表明，囊泡运输是人类大脑皮质发育过程中增殖和迁移的重要调节因子。
