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目的通过检测巨大儿的胎盘组织中胰岛素样生长因子2(IGF_2)基因印迹状态及其mRNA 表达水平和不同启动子活性,探讨巨大儿的发生机理。方法根据 IGF_2基因第9外显子Apa Ⅰ酶切位点多态性,应用 RT-PCR 结合限制性片段长度多态性技术,对83例分娩巨大儿产妇的胎盘组织(巨大儿组)和同期分娩正常体重儿的85例产妇的胎盘组织(正常体重儿组)进行杂合子筛选,对筛选出的杂合子进行 IGF_2基因印迹状态分析,用 RT-PCR 半定量检测两组胎盘组织 IGF_2mRNA 表达水平及不同启动子的活性。结果两组胎盘组织中各有30例杂合子。在这些杂合子中,IGF_2基因均为单等位基因表达,呈维持印迹状态。巨大儿组胎盘组织中 IGF_2 mRNA 表达水平为2.2±1.2,明显高于正常体重儿组的1.6±0.6,两组比较,差异有统计学意义(P<0.05);IGF_2 4个启动子(P1、P2、P3、P4)在两组胎盘组织中均表现为:P4活性最强,P3次之,P2较弱,P1最弱,仅在两例(巨大儿组和正常体重儿组各1例)中检测到 P1起始的转录本;两组胎盘组织 IGF_2不同启动子活性检测分别为:正常体重儿组P2:0.19±0.17、P3:0.98±0.80、P4:2.05±1.27;巨大儿组P2:0.20±0.20、P3:0.99±0.72、P4:2.06±1.26,两组分别比较,差异均无统计学意义(P>0.05)。结论胎盘组织中 IGF_2 mRNA 表达水平的增加可能与巨大儿的形成有关,而 IGF_2基因印迹状态和启动子活性与巨大儿的形成无明显关系。
OBJECTIVE: To investigate the mechanism of macrosomia by detecting the imprinting status of insulin-like growth factor 2 (IGF-2) gene and its mRNA expression level and the activity of different promoters in macrophage placenta. Methods According to the polymorphism of Apa Ⅰ gene exon 9 of IGF 2 gene, RT-PCR and restriction fragment length polymorphism (PCR-RFLP) 85 cases of normal birth weight of maternal placenta (normal weight group) were heterozygous selection of heterozygous selected heterozygous IGF2 gene status analysis of the placenta, RT-PCR semi-quantitative detection of placental tissue IGF2 mRNA expression levels and Activity of different promoters. Results There were 30 heterozygotes in each group of placenta. Among these heterozygotes, IGF2 gene were all single-allele gene expression and maintained the imprinted state. The expression of IGF2 mRNA in giant placenta was 2.2 ± 1.2, which was significantly higher than that of normal children (1.6 ± 0.6). There were significant differences between the two groups (P <0.05) P2, P3, P4) showed the highest activity of P4, the second best of P3, the weaker of P2 and the weakest of P1 in the two groups of placentas, only in two cases (1 in each of macrosomia group and normal weight group) Detected the initial transcripts of P1; the activity of different promoter of IGF2 in placenta of two groups were respectively: P2: 0.19 ± 0.17, P3: 0.98 ± 0.80, P4: 2.05 ± 1.27 in normal weight group; P2: 0.20 ± 0.20, P3: 0.99 ± 0.72, and P4: 2.06 ± 1.26, respectively. There was no significant difference between the two groups (P> 0.05). Conclusion The increase of the expression of IGF2 mRNA in placenta may be related to the formation of macrosomia. However, the status of IGF2 gene imprinted and the activity of promoter are not related to the formation of giant macrophages.