The CpG island of the FMR-1 gene is methylated differently among embryonic tissues: implication for prenatal diagnosis.
We studied the methylation status of the CpG island of the FMR-1 (fragile X syndrome) gene to recognize the possibility of its prenatal diagnosis with early pregnant subjects. Southern hybridization using EcoRI/BssHII restriction enzymes double digestion was performed in the brain and chorionic villi of 8th week embryos, and the placenta and cord blood of newborns. No methylation of the FMR-1 gene occurred in both of the tissues examined in males, while 50% of the cells in females were methylated in both the brain and the cord blood, indicating that methylation occurs with inactivation of the X-chromosome in accordance with the literature. However, there was no methylation in either the chorionic villi or placenta in female as well as in males. Some extra-embryonic tissues such as the chorionic villi and the placenta escape X-chromosome FMR-1 gene inactivation and it can be the exception in the lyonization. To assess the methylation status in prenatal diagnosis, precautions are needed and they are not suitable for prenatal diagnosis.
Iida
T
T
Department of Obstetrics and Gynaecology, Faculty of Medicine, University of Tokyo, Japan.
Nakahori
Y
Y
Tsutsumi
O
O
Taketani
Y
Y
Nakagome
Y
Y
D015139:Blotting, Southern; D001921:Brain / Q000196:embryology / Q000378:metabolism; D002824:Chorionic Villi / Q000378:metabolism; D004247:DNA / Q000032:analysis / Q000378:metabolism*; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000378:metabolism*; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics*; D006801:Humans; D008297:Male; D008745:Methylation; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012727:Sex Characteristics
D004247:DNA; D015226:Dinucleoside Phosphates; C015772:CpG dinucleotide