DNA methylation of retrotransposon genes is regulated by Piwi family members MILI and MIWI2 in murine fetal testes.
Silencing of transposable elements occurs during fetal gametogenesis in males via de novo DNA methylation of their regulatory regions. The loss of MILI (miwi-like) and MIWI2 (mouse piwi 2), two mouse homologs of Drosophila Piwi, activates retrotransposon gene expression by impairing DNA methylation in the regulatory regions of the retrotransposons. However, as it is unclear whether the defective DNA methylation in the mutants is due to the impairment of de novo DNA methylation, we analyze DNA methylation and Piwi-interacting small RNA (piRNA) expression in wild-type, MILI-null, and MIWI2-null male fetal germ cells. We reveal that defective DNA methylation of the regulatory regions of the Line-1 (long interspersed nuclear elements) and IAP (intracisternal A particle) retrotransposons in the MILI-null and MIWI2-null male germ cells takes place at the level of de novo methylation. Comprehensive analysis shows that the piRNAs of fetal germ cells are distinct from those previously identified in neonatal and adult germ cells. The expression of piRNAs is reduced under MILI- and MIWI2-null conditions in fetal germ cells, although the extent of the reduction differs significantly between the two mutants. Our data strongly suggest that MILI and MIWI2 play essential roles in establishing de novo DNA methylation of retrotransposons in fetal male germ cells.
Kuramochi-Miyagawa
Satomi
S
Department of Pathology, Medical School, Graduate School of Frontier Biosciences, Research Institute for Microbial Diseases, Osaka University, Yamada-oka 2-2 Suita, Osaka 565-0871, Japan.
Watanabe
Toshiaki
T
Gotoh
Kengo
K
Totoki
Yasushi
Y
Toyoda
Atsushi
A
Ikawa
Masahito
M
Asada
Noriko
N
Kojima
Kanako
K
Yamaguchi
Yuka
Y
Ijiri
Takashi W
TW
Hata
Kenichiro
K
Li
En
E
Matsuda
Yoichi
Y
Kimura
Tohru
T
Okabe
Masaru
M
Sakaki
Yoshiyuki
Y
Sasaki
Hiroyuki
H
Nakano
Toru
T
D000818:Animals; D060565:Argonaute Proteins; D015152:Blotting, Northern; D016000:Cluster Analysis; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D011485:Protein Binding; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics; D018626:Retroelements / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013737:Testis / Q000166:cytology / Q000196:embryology / Q000378:metabolism*
D060565:Argonaute Proteins; C448522:Piwil1 protein, mouse; C448521:Piwil2 protein, mouse; D011506:Proteins; D022661:RNA, Untranslated; D018626:Retroelements