Peg3 Mutational Effects on Reproduction and Placenta-Specific Gene Families

Abstract

Peg3 (paternally expressed gene 3) is an imprinted gene encoding a DNA-binding protein. This gene plays important roles in controlling fetal growth rates and nurturing behaviors. In the current study, a new mutant mouse model has been generated to further characterize the functions of this DNA-binding protein. Besides known phenotypes, this new mutant model also revealed potential roles of Peg3 in mammalian reproduction. Female heterozygotes produce a much smaller number of mature oocytes than the wild-type littermates, resulting in reduced litter sizes. According to genome-wide expression analyses, several placenta-specific gene families are de-repressed in the brain of Peg3 heterozygous embryos, including prolactin, cathepsin and carcinoembryonic antigen cell adhesion molecule (Ceacam) families. The observed de-repression is more pronounced in females than in males. The de-repression of several members of these gene families is observed even in the adult brain, suggesting potential defects in epigenetic setting of the placenta-specific gene families in the Peg3 mutants. Overall, these results indicate that Peg3 likely controls the transcription of several placenta-specific gene families, and further suggest that this predicted transcriptional control by Peg3 might be mediated through unknown epigenetic mechanisms.

PEG3 binds to H19-ICR as a transcriptional repressor

“…Second, we used a mutant model targeting the Peg3 locus as a negative control. 12 In this knockout (KO) model, transcription of Peg3 was truncated by 2 poly(A) signals inserted into intron 5 as part of an expression cassette; thus, the PEG3 protein is depleted in these cells (Fig. 1A).…”

“…11 This possibility has been further supported by the observation that many placenta-specific gene families associated with H3K9me3 modification are de-repressed in mutant embryos lacking PEG3. 12 Although premature at the moment, a series of these recent studies suggested that PEG3 was a transcriptional repressor for its downstream genes through H3K9me3-mediated mechanisms. 11,12 As an ongoing effort, in the current study we performed a new series of ChIP-seq experiments using mouse embryonic fibroblast (MEF) cells.…”

“…12 Although premature at the moment, a series of these recent studies suggested that PEG3 was a transcriptional repressor for its downstream genes through H3K9me3-mediated mechanisms. 11,12 As an ongoing effort, in the current study we performed a new series of ChIP-seq experiments using mouse embryonic fibroblast (MEF) cells. This series of analyses identified a set of 16 potential downstream genes, and the majority of these genes appear to be expressed in oocytes.…”

Epigenetic instability at imprinting control regions in a KrasG12D-induced T-cell neoplasm

“…Second, the Peg3 floxed allele features the 6 th exon flanked by 2 loxP sites and thus is excised upon Cre-mediated recombination. 15,16 The PEG3 protein cannot be translated from the modified ORF of Peg3 del6 due to a frame shift and subsequent nonsense mutation. Therefore, when the recombined allele (Peg3 del6 ) is paternally transmitted, the result is the abrogation of PEG3 protein due to the introduced mutation on the paternal allele and the silencing of the maternal allele by genomic imprinting (Fig.…”

“…Two publically available mouse strains, B6.129-Kras tm4Tyj /Nci (LSL-Kras G12D ) and STOCK Tg (MMTV-Cre)4Mam/J (MMTV-Cre), were purchased from Jackson Laboratories. 13,14,15 The third strain, Peg3 floxed , was generated in the lab. 16,17 The order of breeding was carried out as follows: first, the Peg3 floxed allele was bred with the LSL-Kras G12D model to generate double heterozygous mice.…”