Kawashima Yuki, Kanzaki Susumu, Yang Fan, Kinoshita Tomoe, Hanaki Keiichi, Nagaishi Jun-Ichi, Ohtsuka Yoshihiko, Hisatome Ichirou, Ninomoya Haruaki, Nanba Eiji, Fukushima Toshiaki, Takahashi Shin-Ichiro
Division of Pediatrics and Perinatology, Tottori University, 36-1, Nishi-machi, Yonago 683-8504, Japan.
J Clin Endocrinol Metab. 2005 Aug;90(8):4679-87. doi: 10.1210/jc.2004-1947. Epub 2005 May 31.
Mouse knockout models have clearly demonstrated the critical importance of IGF-I and IGF receptor type 1 (IGF-IR) for embryonic growth as well as postnatal growth.
We hypothesized that mutations of IGF-IR gene might predispose to short stature in children born with intrauterine growth retardation (IUGR).
Twenty-four children with unexplained IUGR (birth weight < -1.5 SD) and short stature (<-2.0 SD) were screened for abnormalities of the IGF-IR gene.
Direct DNA sequencing was used to identify IGF-IR gene mutations. Unprocessed IGF-IR proreceptor in fibroblasts was detected by immunoblot analysis. Functions of mutated IGF-IR in fibroblasts were evaluated by IGF-I binding, and IGF-I-stimulated DNA synthesis and beta-subunit autophosphorylation.
We found the following results: 1) a heterozygous mutation (R709Q) changing the cleavage site from Arg-Lys-Arg-Arg to Arg-Lys-Gln-Arg was identified in a 6-yr-old Japanese girl (case 1) and her mother who also had IUGR with short stature (case 2); 2) fibroblasts from case 2 contained more IGF-IR proreceptor protein (189 +/- 26% of normal) and less mature beta-subunit protein (63 +/- 12%); 3) [125I]IGF-I binding to fibroblasts from case 2 was reduced, compared with normal control (0.61 +/- 0.16 x 10(6) vs. 1.14 +/- 0.12 x 10(6) sites per cell; P < 0.05); and 4) both IGF-I-stimulated [3H]thymidine incorporation and IGF-IR beta-subunit autophosphorylation were low in fibroblasts from case 2, compared with those of control (P < 0.05).
These findings strongly suggest that this mutation leads to failure of processing of the IGF-IR proreceptor to mature IGF-IR and causes short stature and IUGR.
小鼠基因敲除模型已清楚地证明胰岛素样生长因子-I（IGF-I）和1型胰岛素样生长因子受体（IGF-IR）对胚胎生长以及出生后生长至关重要。
我们推测IGF-IR基因突变可能使宫内生长迟缓（IUGR）患儿易患身材矮小。
对24例不明原因的IUGR（出生体重＜-1.5标准差）和身材矮小（＜-2.0标准差）儿童进行IGF-IR基因异常筛查。
采用直接DNA测序法鉴定IGF-IR基因突变。通过免疫印迹分析检测成纤维细胞中未加工的IGF-IR前体受体。通过IGF-I结合、IGF-I刺激的DNA合成和β亚基自身磷酸化评估成纤维细胞中突变IGF-IR的功能。
我们发现以下结果：1）在一名6岁日本女孩（病例1）及其同样患有IUGR和身材矮小的母亲（病例2）中鉴定出一种杂合突变（R709Q），该突变将切割位点从精氨酸-赖氨酸-精氨酸-精氨酸变为精氨酸-赖氨酸-谷氨酰胺-精氨酸；2）病例2的成纤维细胞含有更多的IGF-IR前体受体蛋白（正常的189±26%）和更少的成熟β亚基蛋白（63±12%）；3）与正常对照相比，[125I]IGF-I与病例2的成纤维细胞的结合减少（每个细胞0.61±0.16×10⁶个位点对1.14±0.12×10⁶个位点；P＜0.05）；4）与对照相比，病例2的成纤维细胞中IGF-I刺激的[³H]胸腺嘧啶掺入和IGF-IRβ亚基自身磷酸化均较低（P＜0.05）。
这些发现强烈表明该突变导致IGF-IR前体受体加工成成熟IGF-IR失败，并导致身材矮小和IUGR。
