DNA methyltransferase loading, but not de novo methylation, is an oocyte-autonomous process stimulated by SCF signalling

Diane Lees Murdock, Ho-Tak Lau, Diego H. Castrillon, Massimo De Felici, Colum Walsh

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Epigenetic reprogramming occurs during oocyte growth in mice, a stage where a number of important events are occurring, including transcription of maternal mRNAs for storage in the mature egg, global transcriptional silencing an the acquisition of meiotic competence. Oocyte growth occurs in conjunction with follicular development over a period of many days. The signals involved in initiating different stages in oocyte and follicular development and the concurrent epigenetic changes are poorly understood. Here we examine the role of stern cell factor (SCF or Kit ligand) on the early- to mid-stages of oocyte growth and on DNA methyltransferase expression and function using a one-step in vitro culture system. Our results show that SCF promotes early oocyte growth and development to the multilaminar follicle stage. Oocyte growth is Sufficient to trigger transcription of Dnmt 1 and Dnmt3L from dedicated oocyte promoters, and we show that eggs undergoing growth in the absence of follicle development in Foxo3 mutants show elevated levels of Dnmt1. The methyltransferase proteins undergo sequential relocalisation in the oocyte, with DNMT1 being exported from the nucleus at the bilaminar follicle stage, while DNMT3A is transported into the nucleus at the multi laminar stage, indicating an important role for trafficking in controlling imprinting. SCF is thought to signal partly through the phophostidylinositol 3 (P13) kinase pathway: inhibiting this path was previously shown to prevent FOXO3 nuclear export and we could show here that it also prevented DNMT1 export. Some oocytes reached full size (70 mu M) in this in vitro system, but no secondary follicles were formed, most likely due to failure of the thecal layer to form properly. De novo methylation of imprinted genes was seen in some oocyte Cultures, with methylation levels being highest for Snrpn and lgf2r which are methylated early in vivo, while Peg1, which is methylated late, showed little or no methylation. SCF treatment did not increase the number of cultures showing methylation. We saw no evidence for de novo methylation of IAP repeats in our Cultures, These results suggest that while methyltransferase loading is triggered by oocyte growth, in which SCF plays an important role, complete methylation probably requires progression to the secondary follicle stage and is unlikely to be affected by SCF. (C) 2008 Elsevier Inc. All rights reserved.
LanguageEnglish
Pages238-250
JournalDevelopmental Biology
Volume321
Issue number1
DOIs
Publication statusPublished - Sep 2008

Fingerprint

Methyltransferases
Methylation
Oocytes
DNA
Growth
Epigenomics
Protein Methyltransferases
Stored Messenger RNA
Stem Cell Factor
Cell Nucleus Active Transport
Growth and Development
Mental Competency
Eggs
Ovum
Phosphotransferases

Cite this

@article{e3beb0bfdc5e45ccb3ecb200a1fa21bf,
title = "DNA methyltransferase loading, but not de novo methylation, is an oocyte-autonomous process stimulated by SCF signalling",
abstract = "Epigenetic reprogramming occurs during oocyte growth in mice, a stage where a number of important events are occurring, including transcription of maternal mRNAs for storage in the mature egg, global transcriptional silencing an the acquisition of meiotic competence. Oocyte growth occurs in conjunction with follicular development over a period of many days. The signals involved in initiating different stages in oocyte and follicular development and the concurrent epigenetic changes are poorly understood. Here we examine the role of stern cell factor (SCF or Kit ligand) on the early- to mid-stages of oocyte growth and on DNA methyltransferase expression and function using a one-step in vitro culture system. Our results show that SCF promotes early oocyte growth and development to the multilaminar follicle stage. Oocyte growth is Sufficient to trigger transcription of Dnmt 1 and Dnmt3L from dedicated oocyte promoters, and we show that eggs undergoing growth in the absence of follicle development in Foxo3 mutants show elevated levels of Dnmt1. The methyltransferase proteins undergo sequential relocalisation in the oocyte, with DNMT1 being exported from the nucleus at the bilaminar follicle stage, while DNMT3A is transported into the nucleus at the multi laminar stage, indicating an important role for trafficking in controlling imprinting. SCF is thought to signal partly through the phophostidylinositol 3 (P13) kinase pathway: inhibiting this path was previously shown to prevent FOXO3 nuclear export and we could show here that it also prevented DNMT1 export. Some oocytes reached full size (70 mu M) in this in vitro system, but no secondary follicles were formed, most likely due to failure of the thecal layer to form properly. De novo methylation of imprinted genes was seen in some oocyte Cultures, with methylation levels being highest for Snrpn and lgf2r which are methylated early in vivo, while Peg1, which is methylated late, showed little or no methylation. SCF treatment did not increase the number of cultures showing methylation. We saw no evidence for de novo methylation of IAP repeats in our Cultures, These results suggest that while methyltransferase loading is triggered by oocyte growth, in which SCF plays an important role, complete methylation probably requires progression to the secondary follicle stage and is unlikely to be affected by SCF. (C) 2008 Elsevier Inc. All rights reserved.",
author = "{Lees Murdock}, Diane and Ho-Tak Lau and Castrillon, {Diego H.} and {De Felici}, Massimo and Colum Walsh",
year = "2008",
month = "9",
doi = "10.1016/j.ydbio.2008.06.024",
language = "English",
volume = "321",
pages = "238--250",
journal = "Developmental Biology",
issn = "0012-1606",
publisher = "Elsevier",
number = "1",

}

DNA methyltransferase loading, but not de novo methylation, is an oocyte-autonomous process stimulated by SCF signalling. / Lees Murdock, Diane; Lau, Ho-Tak; Castrillon, Diego H.; De Felici, Massimo; Walsh, Colum.

In: Developmental Biology, Vol. 321, No. 1, 09.2008, p. 238-250.

Research output: Contribution to journalArticle

TY - JOUR

T1 - DNA methyltransferase loading, but not de novo methylation, is an oocyte-autonomous process stimulated by SCF signalling

AU - Lees Murdock, Diane

AU - Lau, Ho-Tak

AU - Castrillon, Diego H.

AU - De Felici, Massimo

AU - Walsh, Colum

PY - 2008/9

Y1 - 2008/9

N2 - Epigenetic reprogramming occurs during oocyte growth in mice, a stage where a number of important events are occurring, including transcription of maternal mRNAs for storage in the mature egg, global transcriptional silencing an the acquisition of meiotic competence. Oocyte growth occurs in conjunction with follicular development over a period of many days. The signals involved in initiating different stages in oocyte and follicular development and the concurrent epigenetic changes are poorly understood. Here we examine the role of stern cell factor (SCF or Kit ligand) on the early- to mid-stages of oocyte growth and on DNA methyltransferase expression and function using a one-step in vitro culture system. Our results show that SCF promotes early oocyte growth and development to the multilaminar follicle stage. Oocyte growth is Sufficient to trigger transcription of Dnmt 1 and Dnmt3L from dedicated oocyte promoters, and we show that eggs undergoing growth in the absence of follicle development in Foxo3 mutants show elevated levels of Dnmt1. The methyltransferase proteins undergo sequential relocalisation in the oocyte, with DNMT1 being exported from the nucleus at the bilaminar follicle stage, while DNMT3A is transported into the nucleus at the multi laminar stage, indicating an important role for trafficking in controlling imprinting. SCF is thought to signal partly through the phophostidylinositol 3 (P13) kinase pathway: inhibiting this path was previously shown to prevent FOXO3 nuclear export and we could show here that it also prevented DNMT1 export. Some oocytes reached full size (70 mu M) in this in vitro system, but no secondary follicles were formed, most likely due to failure of the thecal layer to form properly. De novo methylation of imprinted genes was seen in some oocyte Cultures, with methylation levels being highest for Snrpn and lgf2r which are methylated early in vivo, while Peg1, which is methylated late, showed little or no methylation. SCF treatment did not increase the number of cultures showing methylation. We saw no evidence for de novo methylation of IAP repeats in our Cultures, These results suggest that while methyltransferase loading is triggered by oocyte growth, in which SCF plays an important role, complete methylation probably requires progression to the secondary follicle stage and is unlikely to be affected by SCF. (C) 2008 Elsevier Inc. All rights reserved.

AB - Epigenetic reprogramming occurs during oocyte growth in mice, a stage where a number of important events are occurring, including transcription of maternal mRNAs for storage in the mature egg, global transcriptional silencing an the acquisition of meiotic competence. Oocyte growth occurs in conjunction with follicular development over a period of many days. The signals involved in initiating different stages in oocyte and follicular development and the concurrent epigenetic changes are poorly understood. Here we examine the role of stern cell factor (SCF or Kit ligand) on the early- to mid-stages of oocyte growth and on DNA methyltransferase expression and function using a one-step in vitro culture system. Our results show that SCF promotes early oocyte growth and development to the multilaminar follicle stage. Oocyte growth is Sufficient to trigger transcription of Dnmt 1 and Dnmt3L from dedicated oocyte promoters, and we show that eggs undergoing growth in the absence of follicle development in Foxo3 mutants show elevated levels of Dnmt1. The methyltransferase proteins undergo sequential relocalisation in the oocyte, with DNMT1 being exported from the nucleus at the bilaminar follicle stage, while DNMT3A is transported into the nucleus at the multi laminar stage, indicating an important role for trafficking in controlling imprinting. SCF is thought to signal partly through the phophostidylinositol 3 (P13) kinase pathway: inhibiting this path was previously shown to prevent FOXO3 nuclear export and we could show here that it also prevented DNMT1 export. Some oocytes reached full size (70 mu M) in this in vitro system, but no secondary follicles were formed, most likely due to failure of the thecal layer to form properly. De novo methylation of imprinted genes was seen in some oocyte Cultures, with methylation levels being highest for Snrpn and lgf2r which are methylated early in vivo, while Peg1, which is methylated late, showed little or no methylation. SCF treatment did not increase the number of cultures showing methylation. We saw no evidence for de novo methylation of IAP repeats in our Cultures, These results suggest that while methyltransferase loading is triggered by oocyte growth, in which SCF plays an important role, complete methylation probably requires progression to the secondary follicle stage and is unlikely to be affected by SCF. (C) 2008 Elsevier Inc. All rights reserved.

U2 - 10.1016/j.ydbio.2008.06.024

DO - 10.1016/j.ydbio.2008.06.024

M3 - Article

VL - 321

SP - 238

EP - 250

JO - Developmental Biology

T2 - Developmental Biology

JF - Developmental Biology

SN - 0012-1606

IS - 1

ER -