Project description:How germ cells faithfully pass genetic material to the next generation despite undergoing several developmental transitions during maturation is poorly understood. Here we identify a novel factor in C. elegans, OEF-1, that is highly germline-specific, with early expression in the embryonic germ lineage and differential expression in larvae and adults depending on the gametogenesis program. OEF-1 is nuclear and associates with autosomal germline-expressed genes. Loss of OEF-1 triggers accelerated germ cell progression, leading to defects at multiple points during germline development. Thus OEF-1 may act to coordinate the timely progression of germ cells through proliferation, meiotic entry, and gametogenesis.
Project description:Sex-determining chromosomes exhibit complex global regulation in germ cells, in part due to the absence of dosage compensatory mechanisms found in the soma. In the XX hermaphrodite germ line of C. elegans, the X chromosome houses few germline-expressed genes [1] and is poorly expressed, though not completely silent, through most of germ cell development [2]. A chromatin-modifying pathway consisting of the histone methyltransferase (HMT) MES-4 and the Polycomb Repressive Complex 2 (PRC2) orthologs MES-2/3/6 contributes to X silencing in C. elegans germ cells [3-5]. MES-4 promotes H3K36me3 accumulation on autosomes, which leads to concentration of H3K27me3 on the X by MES-2/3/6 [5]. Loss of MES activity results in inappropriate activation of X-linked genes and second-generation sterility [5, 6]. The two marks occupy mutually exclusive domains of the genome [5, 7], leading to a model in which the presence of one modification prevents the accumulation of the other at specific loci. However, further details about how this repulsion mechanism between H3K27me3 and H3K36me3 is established remain mysterious. Here we implicate the zinc-finger protein OEF-1 in counterbalancing the accumulation of H3K27me3 throughout the genome, particularly on the X chromosome. Strikingly OEF-1, like MES-4, is localized to sites of active gene expression in the germ line, and promotes H3K36me3 levels in mes-4 mutants. Our data thus identify OEF-1 as a novel modulator of the fundamental relationship between gene activation and gene silencing in the C. elegans germ line.
Project description:In animals with germ plasm, specification of the germline involves “germ granules”, cytoplasmic condensates that enrich maternal transcripts in the germline founder cells. In C. elegans embryos, P granules enrich maternal transcripts, but surprisingly P granules are not essential for germ cell fate specification. Here we describe a second condensate in the C. elegans germ plasm. Like canonical P-bodies found in somatic cells, “germline P-bodies” contain regulators of mRNA decapping and deadenylation and, in addition, the intrinsically-disordered proteins MEG-1 and MEG-2 and the TIS11-family RNA-binding protein POS-1. Embryos lacking meg-1 and meg-2 do not stabilize P-body components, miss-regulate POS-1 targets, miss-specify the germline founder cell, and do not develop a germline. Our findings suggest that specification of the germ line involves at least two distinct condensates that independently enrich and regulate maternal mRNAs in the germline founder cells.
Project description:Germ granules are membrane-less organelles essential for small RNA biogenesis and germline development. Among the conserved properties of germ granules is their association with the nuclear membrane. Recent studies demonstrated that LOTUS domain proteins, EGGD-1 and EGGD-2 (also known as MIP-1 and MIP-2 respectively), promote the formation of perinuclear germ granules in C. elegans. This finding presents a unique opportunity to evaluate the significance of perinuclear localization of germ granules. Here we show that loss of eggd-1 causes the coalescence of germ granules and formation of abnormal cytoplasmic aggregates. Impairment of perinuclear granules affects certain germline classes of small RNAs including Piwi-interacting RNAs. Transcriptome profiling reveals overexpression of spermatogenic and cuticle-related genes in eggd-1 hermaphrodites. We further demonstrate that disruption of germ granules activates HLH-30-mediated transcriptional program in somatic tissues. Collectively, our findings underscore the essential role of EGGD-1 in germ granule organization and reveal an unexpected germ granule-to-soma communication.
Project description:Germ granules are membrane-less organelles essential for small RNA biogenesis and germline development. Among the conserved properties of germ granules is their association with the nuclear membrane. Recent studies demonstrated that LOTUS domain proteins, EGGD-1 and EGGD-2 (also known as MIP-1 and MIP-2 respectively), promote the formation of perinuclear germ granules in C. elegans. This finding presents a unique opportunity to evaluate the significance of perinuclear localization of germ granules. Here we show that loss of eggd-1 causes the coalescence of germ granules and formation of abnormal cytoplasmic aggregates. Impairment of perinuclear granules affects certain germline classes of small RNAs including Piwi-interacting RNAs. Transcriptome profiling reveals overexpression of spermatogenic and cuticle-related genes in eggd-1 hermaphrodites. We further demonstrate that disruption of germ granules activates HLH-30-mediated transcriptional program in somatic tissues. Collectively, our findings underscore the essential role of EGGD-1 in germ granule organization and reveal an unexpected germ granule-to-soma communication.
Project description:This SuperSeries is composed of the following subset Series: GSE35775: The H3K27 demethylase Utx facilitates somatic and germ cell epigenetic reprogramming to pluripotency [Affymetrix gene expression] GSE37821: The H3K27 demethylase Utx facilitates somatic and germ cell epigenetic reprogramming to pluripotency [ChIP-Seq] Refer to individual Series
Project description:A number of environmental factors (e.g. toxicants) have been shown to promote the epigenetic transgenerational inheritance of disease and phenotypic variation. Transgenerational inheritance requires the germline transmission of altered epigenetic information between generations in the absence of direct environmental exposures. The primary periods for epigenetic programming of the germline is associated with primordial germ cell development and during fetal gonadal sex determination. The current study examined the actions of an agricultural fungicide vinclozolin on gestating female (F0 generation) progeny in regards to the primordial germ cell (PGC) epigenetic reprogramming of the F3 generation (i.e. great-grandchildren). The F3 generation primordial germ cell transcriptome and epigenome (DNA methylation) was altered transgenerationally. Interestingly, the differential DNA methylation regions (DMR) and altered transcriptomes were distinct between the onset of gonadal sex determination at embryonic day 13 (E13) and after cord formation in the testis at embryonic day 16 (E16). A larger number of DMR and transcriptional alterations were observed in the E13 PGC than E16 germ cells. Observations demonstrate an altered transgenerational epigenetic reprogramming and function of the primordial germ cells and subsequent male germline is a component of vinclozolin induced epigenetic transgenerational inheritance of disease. Insights into the molecular control of germline transmitted epigenetic inheritance are provided. The combined observations demonstrate ancestral exposure of a gestating female during fetal gonadal sex determination can promote transgenerational alterations in the primordial germ cell and subsequent male germline epigenetic and transcriptional programming. This altered germline programming leads to the epigenetic transgenerational inheritance of disease and phenotypic variation. Observations support the role of the primordial germ cell programming in the molecular mechanism involved and provides insights into the molecular mechanisms that control the epigenetic transgenerational inheritance phenomena. Results suggest a cascade of epigenetic and transcriptional events during germ cell development is needed to obtain the mature germline epigenome that is then transmitted transgenerationally. RNA samples from PGC of 2 F3-control lineage groups were compared to PGC of 2 F3-vinclozolin lineage groups for two embryonic age E13 and E16
Project description:Fertility requires the faithful proliferation of germ cells and their differentiation into gametes. Controlling these cellular states demands precise timing and expression of gene networks. Transcription factors (TFs) play critical roles in gene expression networks that influence germ cell development. There has, however, been no functional analysis of the entire TF repertoire in controlling in vivo germ cell development. Here, we analyzed germ cell states and germline architecture to systematically investigate the function of 364 germline-expressed TFs in the Caenorhabditis elegans germ line. Using germline-specific knockdown, automated germ cell counting, and high-content analysis of germ cell nuclei and plasma membrane organization, we identify 156 TFs with discrete autonomous germline functions. By identifying TFs that control the germ cell cycle, proliferation, differentiation, germline structure and fertility, we have created an atlas for mechanistic dissection of germ cell behavior and gamete production.