Department of Medical Genetics, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Mamm Genome. 2010 Feb;21(1-2):64-76. doi: 10.1007/s00335-009-9245-y. Epub 2010 Jan 3.
Mammalian epidermis is a stratified epithelium that serves as a barrier protecting the organism from mechanical stress and dehydration. Previous studies have demonstrated the importance of the actin cytoskeleton in the establishment of a functional skin epithelium. Despite what is known about the actin cytoskeleton in epithelial sheet formation, the molecules important for controlling the actin cytoskeleton during epidermal development have not been determined. Serum response factor (SRF) is a transcription factor that is considered to be an important regulator of the actin cytoskeleton. To examine the role of SRF in the developing mouse epidermis, we have employed gene targeting to ablate Srf in keratinocytes. Conditional inactivation of Srf during the embryonic timepoint leads to a defect in the organization of the epidermis. Immunohistochemical analyses demonstrated a marked loss of the filamentous actin cytoskeleton and E-cadherin localization in epidermis, as well as an aberration in the localization of tight junction proteins. Moreover, impairment of the "inside-out" epidermal barrier was shown. Srf conditional knockout keratinocytes are unable to establish proper intercellular connections or form an epithelial sheet as shown by histological examination and induced keratinocyte differentiation experiments. Our results demonstrate that Srf is essential for the actin-mediated sealing of epithelial cell-cell contacts and the development of functional stratified skin epithelium in vivo.
哺乳动物表皮是一种分层上皮，作为保护机体免受机械应激和脱水的屏障。先前的研究表明，肌动蛋白细胞骨架在功能性皮肤上皮的建立中起着重要作用。尽管人们已经了解了上皮片形成过程中的肌动蛋白细胞骨架，但对于控制表皮发育过程中肌动蛋白细胞骨架的重要分子仍未确定。血清反应因子（SRF）是一种转录因子，被认为是肌动蛋白细胞骨架的重要调节因子。为了研究 SRF 在发育中的小鼠表皮中的作用，我们利用基因靶向技术使角质形成细胞中的 Srf 失活。在胚胎时期条件性地使 Srf 失活会导致表皮组织的缺陷。免疫组织化学分析表明，表皮中的丝状肌动蛋白细胞骨架和 E-钙黏蛋白定位明显丢失，以及紧密连接蛋白的定位异常。此外，还显示出“内-外”表皮屏障的损伤。如组织学检查和诱导角质形成细胞分化实验所示，条件性敲除 Srf 的角质形成细胞无法建立适当的细胞间连接或形成上皮片。我们的结果表明，SRF 对于上皮细胞间连接的肌动蛋白介导的密封以及功能性分层皮肤上皮的体内发育是必需的。
