ABSTRACT
Fetal and adult Leydig cells develop in mammalian prenatal and postnatal testes, respectively. In mice, fetal Leydig cells (FLCs) emerge in the interstitial space of the testis at embryonic day 12.5 and thereafter increase in number, possibly through differentiation from progenitor cells. However, the progenitor cells have not yet been identified. Previously, we established transgenic mice in which FLCs are labeled strongly with enhanced green fluorescent protein (EGFP). Interestingly, fluorescence-activated cell sorting provided us with weakly EGFP-labeled cells as well as strongly EGFP-labeled FLCs. In vitro reconstruction of fetal testes demonstrated that weakly EGFP-labeled cells contain FLC progenitors. Transcriptome from the 2 cell populations revealed, as expected, marked differences in the expression of genes required for growth factor/receptor signaling and steroidogenesis. In addition, genes for energy metabolisms such as glycolytic pathways and the citrate cycle were activated in strongly EGFP-labeled cells, suggesting that metabolism is activated during FLC differentiation.
Subject(s)
Citric Acid Cycle/genetics , Fetus/metabolism , Gene Expression Regulation, Developmental , Glycolysis/genetics , Leydig Cells/metabolism , RNA, Messenger/metabolism , Stem Cells/metabolism , Animals , Cell Differentiation , Energy Metabolism/genetics , Gene Expression Profiling , Gonadal Steroid Hormones/biosynthesis , Green Fluorescent Proteins/genetics , Immunohistochemistry , Leydig Cells/cytology , Male , Mice , Mice, Transgenic , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction/genetics , Stem Cells/cytologyABSTRACT
It has been established that two developmentally and functionally distinct cell types emerge within the mammalian testis and adrenal gland throughout life. Fetal and adult types of steroidogenic cells (i.e., testicular Leydig cells and adrenocortical cells) develop in the prenatal and postnatal period, respectively. Although the ovary synthesizes steroids postnatally, the presence of fetal-type steroidogenic cells has not been described. We had previously established transgenic mouse lines in which fetal Leydig cells were labeled with an EGFP reporter gene by the FLE (fetal Leydig enhancer) of the Ad4BP/SF-1 (Nr5a1) gene. In the present study, we examined the reporter gene expression in females and found that the reporter gene is turned on in postnatal ovaries. A comparison of the expressions of the EGFP and marker genes revealed that EGFP is expressed in not all but rather a proportion of steroidogenic theca and in interstitial gland cells in the ovary. This finding was further supported by experiments using BAC transgenic mice in which reporter gene expression recapitulated endogenous Ad4BP/SF-1 gene expression. In conclusion, our observations from this study strongly suggest that ovarian theca and interstitial gland cells in mice consist of at least two cell types.
Subject(s)
Adrenal Glands/cytology , Cell Lineage/genetics , Leydig Cells/cytology , Pituitary Gland/cytology , Steroidogenic Factor 1/genetics , Theca Cells/cytology , Adrenal Glands/growth & development , Adrenal Glands/metabolism , Aging , Animals , Animals, Newborn , Female , Fetus , Gene Expression Regulation, Developmental , Genes, Reporter , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Leydig Cells/metabolism , Luminescent Proteins/genetics , Luminescent Proteins/metabolism , Male , Mice , Mice, Transgenic , Pituitary Gland/growth & development , Pituitary Gland/metabolism , Signal Transduction , Steroidogenic Factor 1/metabolism , Theca Cells/classification , Theca Cells/metabolism , Red Fluorescent ProteinABSTRACT
We previously showed that circadian genes clock, bmal1, cry1, cry2, per1, and per2 are expressed and function as maternal mRNA regulating events in the oocytes and preimplantation embryos of mice. Recent evidence indicates however that either or both expression profiles of circadian genes in some tissues, and transcript sequences of circadian genes, differ to generate the physiological differences between diurnal and nocturnal species. We therefore investigated the expression profiles of circadian genes in oocytes and preimplantation embryos of species other than mice, namely cattle and rabbits, representing diurnal and nocturnal species, respectively, and determined the protein sequences of circadian genes in these species. Quantitative real-time PCR revealed that all circadian genes considered in this study were present in the oocytes and preimplantation embryos of both species, and the transcript amounts of clock, cry1 and per1 contained in oocytes were significantly higher than in preimplantation embryos of both species. The transcripts of clock, cry1, and per1 of cattle and rabbits were determined by primer walking, and functional domains in the estimated amino acid sequences were compared between cattle and rabbits and with those of humans and mice. The sequences of clock, cry1, and per1 in cattle and rabbits closely resembled those in mice (85-100% homologies), and no difference based on diurnality or nocturnality was observed. These findings suggest that circadian genes in the oocytes and preimplantation embryos of mammals fulfill the same functions across species as maternal mRNA.
