[Insulin-like growth factor 2 imprinting status and promoter usage in the placenta of macrosomia].
OBJECTIVE
To study the mechanism of marcosomia by investigating insulin-like growth factor 2 (IGF(2))imprinting status, expression level and the promoter usage in the placenta of macrosomia.


METHODS
We selected heterozygous cases for Apa I polymorphism in exon 9 of IGF(2) gene and then analyzed its imprinting status in 168 placentas of macrosomia and normal pregnancies. IGF(2) transcription levels and promoter usages in macrosomic and normal placenta were evaluated by using semi-quantitative RT-PCR assay.


RESULTS
Thirty specimens of macrosomic placenta and 30 of normal placenta were identified as heterozygous for IGF(2). All of the heterozygous specimens showed maintenance of imprinting. The expression of placental IGF(2) mRNA (2.2 +/- 1.2) was significantly higher in macrosomia than that of normal weight group (1.6 +/- 0.6, P < 0.05). Of four promoters, P4 was the most powerful, P3 was the second, and P2 was weakest. Transcripts from P1 were the fewest, and they were only detected in two specimens. The value of P4 was 2.06 +/- 1.26, P3 0.99 +/- 0.72, P2 0.20 +/- 0.20 in macrosomia group and P4 2.05 +/- 1.27, P3 0.98 +/- 0.80, P2 0.19 +/- 0.17 in normal group. There were no significant differences between two groups (P > 0.05).


CONCLUSIONS
It is possible that over expression of IGF(2) in placenta contributes to macrosomia while the promoter usage and imprinting status are not associated with macrosomia.
Department of Obstetrics and Gynecology, Affiliated Drum Tower Hospital, Nanjing University Medical School, Nanjing 210008, China.
Jin-Cui
JC
Yao
Ya-Li
YL
Hu
Zhi-Qun
ZQ
Wang
Yi-Min
YM
Dai
Jing-Xian
JX
Ling
Xiao-Dong
XD
Ye
D000328:Adult; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005320:Fetal Macrosomia / Q000235:genetics* / Q000473:pathology; D018392:Genomic Imprinting; D006801:Humans; D007231:Infant, Newborn; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D012333:RNA, Messenger; D007335:Insulin-Like Growth Factor II