Epigenetic status of the H19 locus in human oocytes following in vitro maturation.
Imprinting is an epigenetic modification that is reprogrammed in the germ line and leads to the monoallelic expression of some genes. Imprinting involves DNA methylation. Maternal imprint is reset during oocyte growth and maturation. In vitro maturation (IVM) of oocytes may, therefore, interfere with imprint acquisition and/or maintenance. To evaluate if maturing human oocytes in vitro would be hazardous at the epigenetic level, we first determined the methylation profile of the H19 differentially methylated region (DMR). The methylation status of the H19 DMR seems particularly vulnerable to in vitro culture conditions. We analyzed oocytes at different stages of maturation following IVM, germinal vesicle (GV), metaphase I (MI), and metaphase II (MII), using the bisulfite mutagenesis technique. Our results indicated that the unmethylated specific maternal profile for the H19 DMR was stably established at the GV stage. The majority of MI-arrested oocytes exhibited an altered pattern of methylation, the CTCF-binding site being methylated in half of the DNA strands analyzed. Of the 20 MII oocytes analyzed, 15 showed the normal unmethylated maternal pattern, while 5 originating from two different patients exhibited a methylated pattern. These findings highlight the need for extended analysis on MII-rescued oocytes to appreciate the epigenetic safety of the IVM procedure, before it becomes a routine and practical assisted reproductive procedure.
Borghol
Nada
N
INSERM U 418/INRA UA 953, Hopital Debrousse, 29 rue Soeur Bouvier, 69322 Lyon Cedex 05, France.
Lornage
Jacqueline
J
Blachère
Thierry
T
Sophie Garret
Anne
A
Lefèvre
Annick
A
D000328:Adult; D001665:Binding Sites / Q000235:genetics; D000076246:CCCTC-Binding Factor; D018899:CpG Islands / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics; D008677:Metaphase; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism*; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics*; D012097:Repressor Proteins / Q000378:metabolism; D013997:Time Factors
D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D004268:DNA-Binding Proteins; C094335:H19 long non-coding RNA; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D012097:Repressor Proteins; D007335:Insulin-Like Growth Factor II; D004247:DNA; D004262:DNA Restriction Enzymes