PGC meiosis marker. The Transcriptome and DNA Methylome Landscapes of Human Primordial Germ Cells. Guo F et al. (2015) Germ cells are vital for transmitting genetic information from one generation to the next and for maintaining the continuation of species. Here, we analyze the transcriptome of human primordial germ cells (PGCs) from the migrating stage to the gonadal stage at single-cell and single-base resolutions. Human PGCs show unique transcription patterns involving the simultaneous expression of both pluripotency genes and germline-specific genes, with a subset of them displaying developmental-stage-specific features. Furthermore, we analyze the DNA methylome of human PGCs and find global demethylation of their genomes. Approximately 10 to 11 weeks after gestation, the PGCs are nearly devoid of any DNA methylation, with only 7.8% and 6.0% of the median methylation levels in male and female PGCs, respectively. Our work paves the way toward deciphering the complex epigenetic reprogramming of the germline with the aim of restoring totipotency in fertilized oocytes.//////////////////
Synaptonemal complexes are meiosis-specific nuclear organelles that appear to be involved at the meiotic prophase in
chromosome rearrangements such as chromosome pairing and recombination.
General function
Cell organization, Chromosome organization
Comment
Cellular localization
Nuclear
Comment
Ovarian function
Follicle endowment, Germ cell development
Comment
Kerr SM, et al 1996 reported that the homologue of the rat
synaptonemal complex protein gene SCP1 is expressed in embryonic ovary, adult brain and testis.
Loss of SCP1, a Synaptonemal Complex Protein, Contributes to the Initiation of Follicular Assembly in the Developing Rat Ovary Paredes A, et al .
In the rat ovary, germ and somatic cells become organized into primordial follicles 48-72 h after birth. Although several genes have been implicated in the control of early follicular growth, less is known about the factors involved in the formation of primordial follicles. Using the method of differential display (DD) of messenger RNAs, we found several genes differentially expressed at the time of follicular assembly. One of them encodes Synaptonemal Complex Protein-1 (SCP1), a core component of the protein complex that maintains recombining chromosomes together during prophase I of the first meiotic division in germ cells. This association, evident during the pachytene stage, ends when chromosomal desynapsis begins in the diplotene stage at the end of prophase I. Oocytes become arrested in the diplotene/dictate stage before becoming enclosed into primordial follicles, suggesting that oocytes must complete meiotic prophase I before becoming competent to direct follicle assembly. We now show that attainment of the diplotene stage results in follicular formation. In developing rat ovaries, SCP1 mRNA expression is confined to oocytes and decreases precipitously within 24 h after birth, preceding the organization of primordial follicles. The premature loss of SCP1, achieved via treatment with an antisense oligodeoxynucleotide targeting SCP1 mRNA, resulted in more oocytes reaching the diplotene stage, as evidenced by a decrease in the number of oocytes containing germ cell nuclear antigen-1 (GCNA1, a nuclear protein whose expression ceases in diplotene), and an increase in the number of oocytes expressing MSY2 (a cytoplasmic Y box protein expressed in oocytes that have become arrested in diplotene). SCP1-deficient ovaries exhibited and increased number of newly formed follicles, suggesting that completion of meiotic prophase I endows oocytes with the capability of orchestrating follicular assembly.
Expression regulated by
Comment
Ovarian localization
Primordial Germ Cell, Oocyte
Comment
A Promoter Fragment of the sycp1 Gene Is Sufficient to Drive Transgene Expression in Male and Female Meiotic Germ Cells in Zebrafish. Gautier A 2013 et al.
The synaptonemal complex protein 1 (Sycp1) is required for the formation of crossovers that occurs during the meiotic prophase. The tissue and cell-specific expression pattern of the Sycp1 protein have been studied in mammals and fish but data on the corresponding transcript remain scarce. In this report, we described for the first time in zebrafish the tissue- and cell-specific expression pattern of the sycp1 gene. In ovary, the expression of the sycp1 transcript was restricted to the early primary oocytes. In testis, the sycp1 transcript was observed in primary spermatocytes in agreement with a previous report describing the localization of the Sycp1 protein in those cells. Unexpectedly, sycp1 transcript expression remained high in spermatids. To gain insight on the genomic region responsible for the sycp1 gene expression pattern, we generated four independent Dr_sycp1:eGFP transgenic zebrafish lines carrying the -1482/+338 gene fragment fused to the enhanced green fluorescent protein reporter gene. We demonstrate that this promoter fragment contains the information required for the cell specific expression of the endogenous sycp1 gene in males and in females. However the GFP protein and its associated fluorescence persist in spermatozoa and maturing oocytes. The Dr_sycp1:eGFP zebrafish lines have the potential to be valuable models to trace meiosis onset in zebrafish and constitute the first transgenic lines expressing the GFP reporter protein only in the male meiotic and post-meiotic cells in fish.
/////////////////////////A Promoter Fragment of the sycp1 Gene Is Sufficient to Drive Transgene Expression in Male and Female Meiotic Germ Cells in Zebrafish. Gautier A 2013 et al.
The synaptonemal complex protein 1 (Sycp1) is required for the formation of crossovers that occurs during the meiotic prophase. The tissue and cell-specific expression pattern of the Sycp1 protein have been studied in mammals and fish but data on the corresponding transcript remain scarce. In this report, we described for the first time in zebrafish the tissue- and cell-specific expression pattern of the sycp1 gene. In ovary, the expression of the sycp1 transcript was restricted to the early primary oocytes. In testis, the sycp1 transcript was observed in primary spermatocytes in agreement with a previous report describing the localization of the Sycp1 protein in those cells. Unexpectedly, sycp1 transcript expression remained high in spermatids. To gain insight on the genomic region responsible for the sycp1 gene expression pattern, we generated four independent Dr_sycp1:eGFP transgenic zebrafish lines carrying the -1482/+338 gene fragment fused to the enhanced green fluorescent protein reporter gene. We demonstrate that this promoter fragment contains the information required for the cell specific expression of the endogenous sycp1 gene in males and in females. However the GFP protein and its associated fluorescence persist in spermatozoa and maturing oocytes. The Dr_sycp1:eGFP zebrafish lines have the potential to be valuable models to trace meiosis onset in zebrafish and constitute the first transgenic lines expressing the GFP reporter protein only in the male meiotic and post-meiotic cells in fish.
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Follicle stages
Comment
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: type: null mutation fertility: infertile - ovarian defect Comment: Mouse Sycp1 functions in synaptonemal complex assembly, meiotic recombination, and XY body formation. de Vries FA et al. (2005) In meiotic prophase, synaptonemal complexes (SCs) closely appose homologous chromosomes (homologs) along their length. SCs are assembled from two axial elements (AEs), one along each homolog, which are connected by numerous transverse filaments (TFs). We disrupted the mouse gene encoding TF protein Sycp1 to analyze the role of TFs in meiotic chromosome behavior and recombination. Sycp1(-/-) mice are infertile, but otherwise healthy. Sycp1(-/-) spermatocytes form normal AEs, which align homologously, but do not synapse. Most Sycp1(-/-) spermatocytes arrest in pachynema, whereas a small proportion reaches diplonema, or, exceptionally, metaphase I. In leptotene Sycp1(-/-) spermatocytes, gammaH2AX (indicative of DNA damage, including double-strand breaks) appears normal. In pachynema, Sycp1(-/-) spermatocytes display a number of discrete gammaH2AX domains along each chromosome, whereas gammaH2AX disappears from autosomes in wild-type spermatocytes. RAD51/DMC1, RPA, and MSH4 foci (which mark early and intermediate steps in pairing/recombination) appear in similar numbers as in wild type, but do not all disappear, and MLH1 and MLH3 foci (which mark late steps in crossing over) are not formed. Crossovers were rare in metaphase I of Sycp1(-/-) mice. We propose that SYCP1 has a coordinating role, and ensures formation of crossovers. Unexpectedly, Sycp1(-/-) spermatocytes did not form XY bodies.//////////////////Sycp1-/- ovaries weighed on average 35% less than Sycp1+/- or Sycp1+/+ ovaries. Growing follicles and oocytes were lacking in sections of Sycp1-/- ovaries, which suggests a disruption of oocyte development during meiosis, followed by apoptosis.