Biology subjects

Cincotta, S. A.

Publications and source records attributed to Cincotta, S. A..

4 recordsLinked to original sources

bioRxiv2024

Sustained fertility from first-wave follicle oocytes that pause their growth

Ovulation results from the cyclical recruitment of non-renewing, quiescent oocytes for growth. Therefore, the primordial follicles that are established during development from an oocyte encapsulated by granulosa cells are thought to comprise the lifelong ovarian reserve 1-4. However, using oocyte lineage tracing in mice, we observed that a subset of oocytes recruited for growth in the first juvenile wave remain paused for many months before continuing growth, ovulation, fertilization and development into healthy offspring. This small subset of genetically-labeled fetal oocytes, labeled with Sycp3-CreERT2, is distinguished by earlier entry and slower dynamics of meiotic prophase I. While labeled oocytes were initially found in both primordial follicles and growing follicles of the first wave, they disappeared from primordial follicles by puberty. Unexpectedly, these first-wave labeled growing oocytes persisted throughout reproductive lifespan and contributed to offspring at a steady rate beyond 12 months of age, suggesting that follicles can pause mid-growth for extended periods then successfully resume. These results challenge the conclusion from lineage tracing of granulosa cells that first-wave follicles make a limited contribution to fertility5 and furthermore suggest that growth-paused oocytes comprise a second and previously unrecognized ovarian reserve.

developmental biology↗

bioRxiv2023

Differential susceptibility of male and female germ cells to glucocorticoid-mediated signaling

While physiologic stress has long been known to impair mammalian reproductive capacity through hormonal dysregulation, mounting evidence now suggests that stress experienced prior to or during gestation may also negatively impact the health of future offspring. Rodent models of gestational physiologic stress can induce neurologic and behavioral changes that persist for up to three generations, suggesting that stress signals can induce lasting epigenetic changes in the germline. Treatment with glucocorticoid stress hormones is sufficient to recapitulate the transgenerational changes seen in physiologic stress models. These hormones are known to bind and activate the glucocorticoid receptor (GR), a ligand-inducible transcription factor, thus implicating GR-mediated signaling as a potential contributor to the transgenerational inheritance of stress-induced phenotypes. Here we demonstrate dynamic spatiotemporal regulation of GR expression in the mouse germline, showing expression in the fetal oocyte as well as the perinatal and adult spermatogonia. Functionally, we find that fetal oocytes are intrinsically buffered against changes in GR signaling, as neither genetic deletion of GR nor GR agonism with dexamethasone altered the transcriptional landscape or the progression of fetal oocytes through meiosis. In contrast, our studies revealed that the male germline is susceptible to glucocorticoid-mediated signaling, specifically by regulating RNA splicing within the spermatogonia, although this does not abrogate fertility. Together, our work suggests a sexually dimorphic function for GR in the germline, and represents an important step towards understanding the mechanisms by which stress can modulate the transmission of genetic information through the germline.

developmental biology↗

bioRxiv2023

TET1 Catalytic Activity is Required for Reprogramming of Imprinting Control Regions and Patterning of Sperm-Specific Hypomethylated Regions

DNA methylation erasure is required for mammalian primordial germ cell reprogramming. TET enzymes iteratively oxidize 5-methylcytosine to generate 5-hyroxymethylcytosine (5hmC), 5-formylcytosine, and 5-carboxycytosine to facilitate active genome demethylation. Whether these bases are required to promote replication-coupled dilution or activate base excision repair during germline reprogramming remains unresolved due to the lack of genetic models that decouple TET activities. Here, we generated two mouse lines expressing catalytically inactive TET1 (Tet1-HxD) and TET1 that stalls oxidation at 5hmC (Tet1-V). Tet1-/-, Tet1V/V, and Tet1HxD/HxD sperm methylomes show that TET1V and TET1HxD rescue most Tet1-/- hypermethylated regions, demonstrating the importance of TET1s extra-catalytic functions. Imprinted regions, in contrast, require iterative oxidation. We further reveal a broader class of hypermethylated regions in sperm of Tet1 mutant mice that are excluded from de novo methylation during male germline development and depend on TET oxidation for reprogramming. Our study underscores the link between TET1-mediated demethylation during reprogramming and sperm methylome patterning.

developmental biology↗

bioRxiv2018

Heterogeneity of transposon expression and activation of the repressive network in human fetal germ cells

Epigenetic resetting in germ cells during development leads to the de-repression of transposable elements (TEs). piRNAs protect fetal germ cells from potentially harmful TEs by targeted destruction of mRNA and deposition of repressive epigenetic marks. Here we provide the first evidence for an active piRNA pathway and TE repression in germ cells of human fetal testis. We identify pre-pachytene piRNAs with features of secondary amplification that map most abundantly to L1 family TEs. We find that L1-ORF1p expression is heterogeneous in fetal germ cells, peaks at mid-gestation and declines concomitantly with increasing levels of piRNAs and H3K9me3, as well as nuclear localization of HIWI2. Surprisingly, following this decline, the same cells with accumulation of L1-ORF1p display highest levels of HIWI2 and H3K9me3, whereas L1-ORF1p low cells are also low in HIWI2 and H3K9me3. Conversely, earlier in development, the germ cells lacking L1-ORF1p express high levels of the chaperone HSP90a. We propose that a subset of HSP90a-armed germ cells resists L1 expression, whereas only those vulnerable L1-expressing germ cells activate the PIWI-piRNA repression pathway which leads to epigenetic silencing of L1 via H3K9me3.

developmental biology↗