Mouse survival motor neuron alleles that mimic SMN2 splicing and are inducible rescue embryonic lethality early in development but not late.
Mouse survival motor neuron alleles that mimic SMN2 splicing and are inducible rescue embryonic lethality early in development but not late.
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DOI：
10.1371/journal.pone.0015887
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发表时间：
2010-12-29
期刊：
影响因子：
3.7
通讯作者：
DiDonato CJ
中科院分区：
文献类型：
--
作者：
Hammond SM;Gogliotti RG;Rao V;Beauvais A;Kothary R;DiDonato CJ
脊髓性肌萎缩症(SMA)是由低水平的存活运动神经元(SMN)引起的，患者的临床谱系主要是由于存活运动神经元-2(SMN2)基因的不同拷贝所致。患者和动物研究表明，随着SMN水平的增加，疾病的严重性被取消。由于目前正在进行的治疗是针对SMN的诱导，因此了解SMN的剂量、时间和细胞需求对于疾病病因和潜在的治疗干预将是重要的。这就需要能够在时间和/或空间上诱发SMN的新的小鼠模型。在这里，我们描述了两个亚型SMN等位基因SMNC-T-Neo和Smn2B-Neo的产生。这些等位基因模拟SMN2外显子7的剪接，滴度为SMN水平，并且是可诱导的。它们是专门设计的，所以最多可以产生三个独立的小鼠品系，在这里我们描述两个。在纯合状态下，每个等位基因都会导致胚胎死亡。对这些突变体的分析表明，正常发育所需的SMN蛋白超过5%。这些等位基因的严重亚型性是由于SMN内含子7中含有一个loxP侧翼的新霉素基因选择盒，该盒可以用Cre重组酶去除。体外和体内实验证明这些是可诱导的SMN等位基因。当与可诱导的CRE小鼠结合时，低SMN水平导致的胚胎死亡可以在怀孕早期得到挽救，但不能晚些时候。这为SMN诱导疗法可能存在的治疗窗口提供了直接的遗传学证据。重要的是，这些品系填补了可诱导的SMN等位基因的空白。它们还提供了一个基础，当与其他SMN等位基因或含有SMN的小鼠结合时，可以产生不同疾病严重程度的SMA模型的大型谱系。
Spinal muscular atrophy (SMA) is caused by low survival motor neuron (SMN) levels and patients represent a clinical spectrum due primarily to varying copies of the survival motor neuron-2 (SMN2) gene. Patient and animals studies show that disease severity is abrogated as SMN levels increase. Since therapies currently being pursued target the induction of SMN, it will be important to understand the dosage, timing and cellular requirements of SMN for disease etiology and potential therapeutic intervention. This requires new mouse models that can induce SMN temporally and/or spatially. Here we describe the generation of two hypomorphic Smn alleles, SmnC-T-Neo and Smn2B-Neo. These alleles mimic SMN2 exon 7 splicing, titre Smn levels and are inducible. They were specifically designed so that up to three independent lines of mice could be generated, herein we describe two. In a homozygous state each allele results in embryonic lethality. Analysis of these mutants indicates that greater than 5% of Smn protein is required for normal development. The severe hypomorphic nature of these alleles is caused by inclusion of a loxP-flanked neomycin gene selection cassette in Smn intron 7, which can be removed with Cre recombinase. In vitro and in vivo experiments demonstrate these as inducible Smn alleles. When combined with an inducible Cre mouse, embryonic lethality caused by low Smn levels can be rescued early in gestation but not late. This provides direct genetic evidence that a therapeutic window for SMN inductive therapies may exist. Importantly, these lines fill a void for inducible Smn alleles. They also provide a base from which to generate a large repertoire of SMA models of varying disease severities when combined with other Smn alleles or SMN2-containing mice.
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