title: Expression ofEgr3in mouse gonads and its localization and function in oocytes.
abstract: OBJECTIVE
  The early growth response (Egr) family consists of four members (Egr1, Egr2, Egr3, and Egr4) that are zinc finger transcription factors. Among them, Egr3 is involved in transcriptional regulation of target genes during muscle spindle formation and neurite outgrowth. We previously showed that the immunoreactive Egr3 is localized on oocyte spindle and accumulate near the microtubule organizing center during meiosis I in mice. Egr3 was also shown to be localized on spermatocytes. We herein investigated ifEgr3is expressed in mouse gonads and if Egr3 blockade results in any defect in oocyte maturation.
  
  
  METHODS
  Expression ofEgr3in mouse gonads was examined by reverse transcription-polymerase chain reaction. Full-length Egr3 and truncatedEgr3(ΔEgr3) complementary RNAs (cRNAs) with Xpress tag at N-terminus and DsRed2 at C-terminus, and small interfering RNA (siRNA) targetingEgr3were microinjected into mouse oocytes at germinal vesicle stage. Localization of microinjected Egr3 was examined by confocal live imaging and immunofluorescence staining.
  
  
  RESULTS
  Egr3mRNA was detected in mouse ovaries and testes from 1 to 4 week-old mice. An uncharacterized longer transcript containing 5'untranslated region was also detected in 3 and 4 week-old gonads. Microinjected Xpress-Egr3-DsRed2 or Xpress-ΔEgr3-DsRed2 localized to nuclei and chromosomes during meiotic progression. Microinjection of these cRNAs orEgr3siRNA in oocytes did not affect meiotic maturation. Immunofluorescence staining of Egr3 in Xpress-ΔEgr3-DsRed2-injected oocytes showed a positive signal only on meiotic spindle, suggesting that this antibody does not detect endogenous or exogenous Egr3 in mouse oocytes.
  
  
  CONCLUSIONS
  The results show that Egr3 localizes to chromosomes during meiotic progression and that certain antibodies may not faithfully represent localization of target proteins in oocytes. Egr3 seems to be dispensable during oocyte maturation in mice.
authors.affiliation: Department of Biomedical Science and Technology, Institute of Biomedical Science and Technology, Konkuk University, Seoul 05029, Korea.
authors.forename: Hyejin
authors.initials: H
authors.lastname: Shin
authors.affiliation: Department of Biomedical Science, CHA University, Seongnam 13884, Korea.
authors.forename: Dong-Won
authors.initials: DW
authors.lastname: Seol
authors.affiliation: Department of Biomedical Science and Technology, Institute of Biomedical Science and Technology, Konkuk University, Seoul 05029, Korea.
authors.forename: Minyeong
authors.initials: M
authors.lastname: Nam
authors.affiliation: Department of Biomedical Science, CHA University, Seongnam 13884, Korea.
authors.forename: Haengseok
authors.initials: H
authors.lastname: Song
authors.affiliation: Department of Biomedical Science, CHA University, Seongnam 13884, Korea.
authors.forename: Dong Ryul
authors.initials: DR
authors.lastname: Lee
authors.affiliation: Department of Biomedical Science and Technology, Institute of Biomedical Science and Technology, Konkuk University, Seoul 05029, Korea.|Department of Veterinary Medicine, Konkuk University, Seoul 05029, Korea.
authors.forename: Hyunjung Jade
authors.initials: HJ
authors.lastname: Lim
keywords: Egr3; Mouse; Oocytes; Ovary; Testis