A targeted partial invalidation of the insulin-like growth factor I receptor gene in mice causes a postnatal growth deficit.
A targeted partial invalidation of the insulin-like growth factor I receptor gene in mice causes a postnatal growth deficit.
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DOI：
10.1210/endo.141.7.7550
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发表时间：
2000-07
期刊：
影响因子：
4.8
通讯作者：
M. Holzenberger;P. Leneuve;G. Hamard;B. Ducos;L. Périn;M. Binoux;Y. Bouc
中科院分区：
文献类型：
--
作者：
M. Holzenberger;P. Leneuve;G. Hamard;B. Ducos;L. Périn;M. Binoux;Y. Bouc
胰岛素样生长因子(IGF)系统是脊椎动物体细胞生长的主要调节因子。两种配体(IGF-I和IGF-II)通过相同的IGF受体(IGF-IR)传递信号。经典的IGF-IR失效在出生时是致命的，因此需要条件模型来研究这种受体在出生后的作用。为了建立一种在遗传上可诱导的IGF-IR失效，我们使用了一种在内含子2中引入新霉素抗性盒的构建方法来靶向IGF-IR基因，而保持基因的其余部分不变。这种新霉素抗性盒干扰了初级转录本的处理，导致杂合小鼠细胞表面IGF结合位点减少12%，纯合子小鼠细胞表面IGF结合位点减少41%。杂合和纯合子后代的生长速度比野生型后代慢。这一差异从出生后4周开始明显，男性从出生后5周开始显著。在女性中，插入NEO盒式磁带对出生后生长的影响不显著。在男性中，IGF-I水平适度升高(+26%)，但显著增加，表明IGF系统的反馈调节有效。用Western Ligand blotting估计，纯合子中IGFBP-4的水平很低(-38%)，而IGFBP-1、-2和-3的水平不受影响。在雌性动物中，IGF-I和IGFBP-1、-2、-3和-4水平在杂合子、纯合子和野生型动物之间没有显著差异。我们研究了相关的分子机制，并描述了两个RNA剪接事件，它们可以解释IGF-IR的下降。这些小鼠的表型完全是在出生后发育的，身体比例保持不变。IGF-IRneo小鼠构成了一种新的人类出生后生长缺陷模型。
The insulin-like growth factor (IGF) system is a major regulator of somatic growth in vertebrates. Both ligands (IGF-I and IGF-II) signal via the same IGF receptor (IGF-IR). Classical IGF-IR invalidation is lethal at birth, so that conditional models are needed to study the postnatal role of this receptor. To establish a genetically inducible invalidation of IGF-IR, we targeted the IGF-IR gene using a construct that introduced a neomycin resistance cassette into intron 2, leaving the rest of the gene intact. This neomycin resistance cassette interfered with the processing of the primary transcript, resulting in there being 12% fewer IGF-binding sites at the cell surface in heterozygous mice and 41% fewer in homozygous mice. Hetero- and homozygous offspring grew more slowly than their wild-type littermates. This difference was noticeable from 4 weeks after birth and was significant from 5 weeks after birth in males. In females, the effect on postnatal growth of insertion of the neo cassette was not significant. In males, IGF-I levels increased moderately (+26%) but significantly, indicating effective feedback regulation of the IGF system. IGF-binding protein-4 (IGFBP-4) levels, estimated by Western ligand blotting, were low in homozygotes (-38%), whereas IGFBP-1, -2, and -3 levels were unaffected. In females, IGF-I and IGFBP-1, -2, -3, and -4 levels did not differ significantly among heterozygous, homozygous, and wild-type animals. We investigated the molecular mechanism involved and characterized two RNA-splicing events that could account for the decrease in IGF-IR. The phenotype of these mice developed exclusively postnatally, and body proportions were maintained. IGF-IRneo mice constitute a new model for human postnatal growth deficiency.