Blackshear P J, Lai W S, Tuttle J S, Stumpo D J, Kennington E, Nairn A C, Sulik K K
Howard Hughes Medical Institute Laboratories, Duke University Medical Center, Durham, NC 27710, USA.
Brain Res Dev Brain Res. 1996 Oct 23;96(1-2):62-75. doi: 10.1016/0165-3806(96)00097-1.
The roles of protein kinase C and its substrates in development are poorly understood. Recently, we disrupted the mouse gene for a major cellular substrate for protein kinase C, the MARCKS protein (Proc. Natl. Acad. Sci. USA, 92, 944-948, 1995). The resulting phenotype consisted of universal perinatal lethality, agenesis of the corpus callosum and other forebrain commissures, and neuronal ectopia and other cortical and retinal lamination disturbances. These mice also had high frequencies of exencephaly (25% overall, 35% in females). In the present study, we have examined the normal expression of MARCKS and the various isozymes of protein kinase C at the time of cranial neural tube closure, in an attempt to correlate MARCKS expression in time and anatomical location with the exencephaly characteristic of MARCKS deficiency. Failure of neural tube closure occurred at various sites in the cranial neural tube, suggesting a cellular functional defect that was not limited to a specific location. Non-exencephalic MARCKS-deficient embryos appeared to be anatomically normal on embryonic day (E) 8.5-9.5. MARCKS and PKC alpha were expressed at the plasma membrane of the neuroepithelial cells comprising the future neural tube, as well as in the surface ectoderm and underlying mesenchyme. Endogenous protein kinase C species, comprising either or both alpha and delta, were capable of phosphorylating MARCKS in intact E8.5 embryos. Thus, MARCKS is expressed at the plasma membranes of the specific cell types involved in cranial neurulation; its deficiency presumably results in a still-to-be-elucidated functional defect in these cells that leads to exencephaly in a high proportion of cases.
蛋白激酶C及其底物在发育过程中的作用仍知之甚少。最近，我们破坏了蛋白激酶C的一种主要细胞底物——MARCKS蛋白的小鼠基因（《美国国家科学院院刊》，92卷，944 - 948页，1995年）。所产生的表型包括普遍的围产期致死率、胼胝体和其他前脑连合的发育不全，以及神经元异位和其他皮质及视网膜分层紊乱。这些小鼠还具有较高的无脑畸形发生率（总体为25%，雌性为35%）。在本研究中，我们检查了颅神经管闭合时MARCKS和蛋白激酶C各种同工酶的正常表达情况，试图将MARCKS在时间和解剖位置上的表达与MARCKS缺乏所特有的无脑畸形相关联。神经管闭合失败发生在颅神经管的不同部位，提示存在一种不限于特定位置的细胞功能缺陷。在胚胎第（E）8.5 - 9.5天，非无脑畸形的MARCKS缺陷胚胎在解剖学上似乎是正常的。MARCKS和PKCα在构成未来神经管的神经上皮细胞的质膜上表达，也在表面外胚层和下方的间充质中表达。由α和δ中的一种或两种组成的内源性蛋白激酶C能够在完整的E8.5胚胎中磷酸化MARCKS。因此，MARCKS在参与颅神经形成的特定细胞类型的质膜上表达；其缺乏可能导致这些细胞中仍有待阐明的功能缺陷，从而在很大比例的病例中导致无脑畸形。
