SPINE MORPHOLOGY IN AN ANIMAL MODEL OF FRAGILE X SYNDROME

点击翻译按钮获取中文摘要

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Golgi-impregnation studies of human autopsy tissue and of a mouse model of fragile X mental retardation syndrome suggest that dendritic spines have an underdeveloped appearance ¿ a tendency towards elongated, tortuous spine morphology. Fragile X mental retardation, a genetically-linked disorder, results from the inability to produce the protein FMRP. The lack of FMRP expression has been associated with altered dendritic spine morphology in human post-mortem tissue and a mouse model of the disorder. Moreover, stability of spine shape has been shown to be dependent upon the filamentous form of actin, F-actin. In this study we compared spine morphology in mice with knockout (KO) of the FMRP gene to that of wild-type (WT) controls. We used of phalloidin conjugated flurophores followed by photooxidation for correlative analysis of F-actin stained spines at the light and electron microscope levels and advanced structural imaging tomography after cell filling with Lucifer yellow and photoconversion. All tomography was performed on the 3MeV UHVEM microscope in Osaka Univerisity on sections 4-5 ¿m thick. The thicker sections were necessary in order to sample a reasonable length of dendrite and to capture larger spines in their entirety. We report three primary observations. First, pedunculated spines in KO mice are much more likely to stain for F-actin than in WT. Second, the mean spine length of F-actin stained spines in KO mice is longer than WT. Third, tomography data enable us to better correlate these findings, and others, to more accurately characterize the morphological phenotype expressed in this disorder. These findings are consistent with previous reports using Golgi impregnation while those from the tomography offer tremendous potential to accurately and efficiently elucidate the morphological profile of this dis