Two mouse models carrying truncating mutations in Magel2 show distinct phenotypes
Two mouse models carrying truncating mutations in Magel2 show distinct phenotypes
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DOI：
10.1371/journal.pone.0237814
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发表时间：
2020-08-17
期刊：
影响因子：
3.7
通讯作者：
Saitoh, Shinji
中科院分区：
文献类型：
--
作者：
Ieda, Daisuke;Negishi, Yutaka;Saitoh, Shinji
Schaaf-Yang综合征（Schaaf-Yang syndrome，简称XSS）是由位于Prader-Willi临界区15 q11-q13的MAGEL 2父方等位基因的截短变异引起的神经发育障碍。虽然PADI的表型与Prader-Willi综合征（PWS）的表型重叠，包括新生儿张力减退、喂养问题和发育迟缓/智力残疾，但PADI患者表现出自闭症谱系障碍和关节挛缩，这是PWS的非典型表型。因此，我们假设截短的Magel 2蛋白可能产生功能获得性毒性作用。为了验证这一假设，我们生成了两种工程小鼠模型;一种是表达Magel 2 N-末端区域的过表达模型，该区域是用强普遍存在的启动子标记的FLAG，另一种是使用CRISPR/Cas9系统生成的Magel 2中携带截短变体的基因组编辑模型。在过表达模型中，所有转基因小鼠在胎儿或新生儿期死亡，表明转基因的胚胎或新生儿致死性。因此，过表达截短的Magel 2可能显示毒性作用。在基因组编辑的模型中，我们生成了在Magel 2中携带移码变体（c.1690_1924del; p（Glu 564 Serfs *130））的小鼠模型。将在Magel 2的父系或母系等位基因中携带移码变体的模型小鼠分别命名为Magel 2（P：fs）和Magel 2（M：fs）。截断Magel 2转录本在脑内的印迹表达和空间分布得以维持。尽管Magel 2（P：fs）小鼠比野生型同窝小鼠轻，但Magel 2（P：fs）雄性和雌性在8周龄和4周龄时的体重分别与其野生型同窝小鼠相同。总的来说，过表达小鼠模型可能重演胎儿或新生儿死亡，这是最常见的表型。相比之下，基因组编辑的小鼠模型保持了大脑中截断Magel 2转录物的基因组印记和分布，但仅部分重现了基因组表型。因此，我们的研究结果表明，简单的功能获得性毒性效应可能无法解释糖尿病的病理机制，而是表明了Magel 2变体在人类糖尿病患者中的一系列效应。
Schaaf-Yang syndrome (SYS) is a neurodevelopmental disorder caused by truncating variants in the paternal allele ofMAGEL2, located in the Prader-Willi critical region, 15q11-q13. Although the phenotypes of SYS overlap those of Prader-Willi syndrome (PWS), including neonatal hypotonia, feeding problems, and developmental delay/intellectual disability, SYS patients show autism spectrum disorder and joint contractures, which are atypical phenotypes for PWS. Therefore, we hypothesized that the truncatedMagel2protein could potentially produce gain-of-function toxic effects. To test the hypothesis, we generated two engineered mouse models; one, an overexpression model that expressed the N-terminal region ofMagel2that was FLAG tagged with a strong ubiquitous promoter, and another, a genome-edited model that carried a truncating variant inMagel2generated using the CRISPR/Cas9 system. In the overexpression model, all transgenic mice died in the fetal or neonatal period indicating embryonic or neonatal lethality of the transgene. Therefore, overexpression of the truncatedMagel2could show toxic effects. In the genome-edited model, we generated a mouse model carrying a frameshift variant (c.1690_1924del; p(Glu564Serfs*130)) inMagel2. Model mice carrying the frameshift variant in the paternal or maternal allele ofMagel2were termedMagel2(P:fs)andMagel2(M:fs), respectively. The imprinted expression and spatial distribution of truncatingMagel2transcripts in the brain were maintained. Although neonatalMagel2(P:fs)mice were lighter than wildtype littermates,Magel2(P:fs)males and females weighed the same as their wildtype littermates by eight and four weeks of age, respectively. Collectively, the overexpression mouse model may recapitulate fetal or neonatal death, which are the severest phenotypes for SYS. In contrast, the genome-edited mouse model maintains genomic imprinting and distribution of truncatedMagel2transcripts in the brain, but only partially recapitulates SYS phenotypes. Therefore, our results imply that simple gain-of-function toxic effects may not explain the patho-mechanism of SYS, but rather suggest a range of effects due toMagel2variants as in human SYS patients.