(Over)correction of FMR1 deficiency with YAC transgenics: behavioral and physical features
(Over)correction of FMR1 deficiency with YAC transgenics: behavioral and physical features
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DOI：
10.1093/hmg/9.8.1145
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发表时间：
2000-05-01
影响因子：
3.5
通讯作者：
Nelson, DL
中科院分区：
文献类型：
--
作者：
Peier, AM;McIlwain, KL;Nelson, DL
脆性X综合征是导致精神发育迟滞的常见原因，涉及FMR1基因的表达缺失。FMR1的作用仍未确定，但该蛋白似乎参与了RNA的代谢。FMR1基因敲除小鼠的表型与人类有一些相似之处，如大症和行为异常。为了了解Fmr1的功能和确定治疗脆性X综合征的可能性，我们建立了酵母人工染色体(YAC)转基因小鼠，以确定Fmr1基因敲除小鼠的表型是否可以挽救。产生了几个转基因株系，它们携带整个FMR1基因座和大量的侧翼序列。我们观察到YAC转基因支持人类蛋白(FMRP)的产生，该蛋白的水平是内源蛋白的10到15倍，并以细胞和组织特异性的方式表达。在携带YAC转基因的基因敲除小鼠中，没有出现大症，这表明人类蛋白具有功能挽救作用。考虑到脆性X患者的复杂行为表型和之前报道的Fmr1基因敲除小鼠的温和表型，我们使用以前没有报道过的其他行为分析方法对Fmr1基因敲除表型进行了更彻底的评估。随着探索行为的增加，老鼠表现出与焦虑相关的反应减少。过量表达人类蛋白的FMR1 YAC转基因小鼠确实产生了相反的行为反应，并观察到了额外的异常行为。这些发现对脆性X综合征的基因治疗具有重要意义，因为该基因的过度表达可能具有其自身的表型。
Fragile X syndrome is a common cause of mental retardation involving loss of expression of the FMR1 gene. The role of FMR1 remains undetermined but the protein appears to be involved in RNA metabolism. Fmr1 knock-out mice exhibit a phenotype with some similarities to humans, such as macroorchidism and behavioral abnormalities. As a step toward understanding the function of FMR1 and the determination of the potential for therapeutic approaches to fragile X syndrome, yeast artificial chromosome (YAC) transgenic mice were generated in order to determine whether the Fmr1 knockout mouse phenotype could be rescued. Several transgenic lines were generated that carried the entire FMR1 locus with extensive amounts of flanking sequence. We observed that the YAC transgene supported production of the human protein (FMRP) which was present at levels 10 to 15 times that of endogenous protein and was expressed in a cell- and tissue-specific manner. Macroorchidism was absent in knockout mice carrying the YAC transgene indicating functional rescue by the human protein. Given the complex behavioral phenotype in fragile X patients and the mild phenotype previously reported for the Fmr1 knockout mouse, we performed a more thorough evaluation of the Fmr1 knockout phenotype using additional behavioral assays that had not previously been reported for this animal model. The mouse displayed reduced anxiety-related responses with increased exploratory behavior. FMR1 YAC transgenic mice overexpressing the human protein did produce opposing behavioral responses and additional abnormal behaviors were also observed. These findings have significant implications for gene therapy for fragile X syndrome since overexpression of the gene may harbor its own phenotype.