Dynamics of Dnmt1 methyltransferase expression and intracellular localization during oogenesis and preimplantation development.
The imprinting of mammalian genes depends on the maintenance of DNA methylation patterns during pre- and postimplantation development. Dnmt1o is a variant form of the somatically expressed Dnmt1 cytosine methyltransferase that is synthesized and stored in the oocyte cytoplasm and trafficks to the eight-cell nucleus during preimplantation development, where it maintains DNA methylation patterns on alleles of imprinted genes. Transcripts encoding Dnmt1 are present in preimplantation embryos, suggesting that Dnmt1 protein is also expressed in the preimplantation embryo, and may account for maintenance methylation at preimplantation stages other than the eight-cell embryo. However, using an antibody that detects Dnmt1, but not Dnmt1o, no Dnmt1 protein was detected on immunoblots or by immunocytochemical staining in wildtype preimplantation embryos. Moreover, Dnmt1 protein produced in the oocyte from a modified Dnmt1 allele, Dnmt1(1s/1o), trafficked to nuclei of eight-cell embryos, but not to nuclei of other stages. The highly restricted nuclear localization patterns of oocyte-derived Dnmt1o and Dnmt1 during preimplantation development add further support to the notion that DNA methyltransferases other than Dnmt1 are required for maintaining imprints during preimplantation development.
Ratnam
Sarayu
S
Department of Human Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Mertineit
Carmen
C
Ding
Feng
F
Howell
Carina Y
CY
Clarke
Hugh J
HJ
Bestor
Timothy H
TH
Chaillet
J Richard
JR
Trasler
Jacquetta M
JM
D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001755:Blastocyst / Q000201:enzymology*; D003001:Cloning, Molecular; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics* / Q000378:metabolism*; D005314:Embryonic and Fetal Development; D018507:Gene Expression Regulation, Developmental; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000201:enzymology; D009866:Oogenesis; D009928:Organ Specificity; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012727:Sex Characteristics
D007527:Isoenzymes; D012333:RNA, Messenger; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619381:Dnmt1 protein, mouse