Biology subjects

Marcet-Ortega, M.

Publications and source records attributed to Marcet-Ortega, M..

5 recordsLinked to original sources

bioRxiv2025

TRIP13 fosters both transcriptional silencing and DSB repair during meiosis

During meiosis, the coordinated suppression of global gene transcription and induction of double-strand breaks (DSBs) genome wide is crucial for successful gamete formation. The AAA+ ATPase TRIP13 is a master meiotic regulator involved in numerous cellular processes, including DSB repair, organization of the meiotic chromosome axis, and meiotic silencing of unsynapsed axes. Here, we examine the involvement of TRIP13 in transcription suppression and DSB repair during meiotic prophase I in mice. Because TRIP13 is required for silencing of sex chromosomes at pachynema, we hypothesized that it may also be involved in the global transcription suppression that begins at the onset of meiotic prophase. Indeed, as predicted, we observed increased incorporation of 5-ethynyl uridine in early stages of meiotic prophase I and a higher presence of the active form of RNA polymerase II in Trip13 mutant spermatocytes. RNA sequencing data revealed that more than two-thirds of upregulated transcripts came from the sex chromosomes. Given this more general role in transcription silencing, we also tested whether TRIP13 promotes the transcription block that causes meiotic arrest in synapsis-deficient oocytes. However, Trip13 ablation did not rescue Spo11-/- oocytes, which experience asynapsis without DSB repair defects. Instead, Trip13 mutation did increase the number of oocytes in Dmc1-/- Chk2-/- mice, in which DSBs persist unrepaired. This rescue seems attributable to a previously unknown function of TRIP13 in preventing DSB repair by non-canonical pathways, as we observed fewer homologous recombination markers along with an increased presence of non-homologous end joining markers in the triple mutant cells. These findings underscore TRIP13s multifaceted role in transcription and DSB repair regulation during meiosis, highlighting its importance and potential for further meiotic regulation and fertility research.

cell biology↗

bioRxiv2024

The MRE11-RAD50-NBS1 complex both starts and extends DNA end resection in mouse meiosis

Nucleolytic resection of DNA ends is critical for homologous recombination, but its mechanism is not fully understood, particularly in mammalian meiosis. Here we examine roles of the conserved MRN complex (MRE11, RAD50, and NBS1) through genome-wide analysis of meiotic resection in mice with various MRN mutations, including several that cause chromosomal instability in humans. Meiotic DSBs form at elevated levels but remain unresected if Mre11 is conditionally deleted, thus MRN is required for both resection initiation and regulation of DSB numbers. Resection lengths are reduced to varying degrees in MRN hypomorphs or if MRE11 nuclease activity is attenuated in a conditional nuclease-dead Mre11 model. These findings unexpectedly establish that MRN is needed for longer-range extension of resection, not just resection initiation. Finally, resection defects are additively worsened by combining MRN and Exo1 mutations, and mice that are unable to initiate resection or have greatly curtailed resection lengths experience catastrophic spermatogenic failure. Our results elucidate multiple functions of MRN in meiotic recombination, uncover unanticipated relationships between short- and long-range resection, and establish the importance of resection for mammalian meiosis.

genetics↗

bioRxiv2024

BEND2 is a crucial player in oogenesis and reproductive aging

Infertility affects up to 12% of couples globally, with genetic factors contributing to nearly half of the cases. Advances in genomic technologies have led to the discovery of genes like Bend2, which plays a crucial role in gametogenesis. In the testis, Bend2 expresses two protein isoforms: full-length and a smaller one. Ablation of both proteins results in an arrested spermatogenesis. Because the Bend2 locus is on the X chromosome, and the Bend2-/y mutants are sterile, BEND2s role in oogenesis remained elusive. In this study, we employed a novel Bend2 mutation that blocks the expression of the full-length BEND2 protein but allows the expression of the smaller BEND2 isoform. Interestingly, this mutation does not confer male sterility and mildly affects spermatogenesis. Thus, it allowed us to study the role of BEND2 in oogenesis. Our findings demonstrate that full-length BEND2 is dispensable for male fertility, and its ablation leads to a reduced establishment of the ovarian reserve. These results reveal a critical role for full-length BEND2 in oogenesis and provide insights into the mechanisms underlying the establishment of the ovarian reserve. Furthermore, these findings hold relevance for the diagnostic landscape of human infertility.

cell biology↗

bioRxiv2019

A cancer-associated missense mutation in PP2A-Aα increases centrosome clustering during mitosis

A single incidence of whole-genome doubling (WGD) is common early in tumorigenesis. In addition to increasing ploidy, WGD doubles centrosome number. In the ensuing mitoses, excess centrosomes form a multipolar spindle, resulting in a lethal multipolar cell division. To survive, cells must cluster centrosomes into two poles to allow a bipolar cell division. Cancer cells are typically more proficient at centrosome clustering than untransformed cells, but the mechanism behind increased clustering ability is not well understood. Heterozygous missense mutations in PPP2R1A, which encodes the alpha isoform of the A-subunit of protein phosphatase 2A (PP2A-A), positively correlate with WGD. To understand this correlation, we introduced a heterozygous hotspot mutation, P179R, in endogenous PP2A-A in human tissue culture cells. We find that PP2A-AP179R decreases PP2A assembly and targeting. Strikingly, when centrosome number is increased, either through cytokinesis failure or centrosome amplification, PP2A-A mutant cells are more proficient than WT cells at centrosome clustering, likely due to PP2A-A loss-of-function. PP2A-AP179R appears to enhance centrosome clustering by altering the interactions between centrosomes and the cell cortex. Thus, cancer-associated mutations in PP2A-A may increase cellular fitness after WGD by enhancing centrosome clustering.

cell biology↗

bioRxiv2017

ATR Is Required To Complete Meiotic Recombination In Mice

Precise execution of recombination during meiosis is essential for forming chromosomally balanced gametes. Meiotic recombination initiates with the formation and resection of DNA double-strand breaks (DSBs). Binding of replication protein A (RPA) at resected DSBs fosters association of RAD51 and DMC1, the primary effectors of homology search. It is well appreciated that cellular responses to meiotic DSBs are critical for efficient repair and quality control, but molecular features of these responses remain poorly understood, particularly in mammals. Here we provide evidence that the DNA damage response protein kinase ATR is crucial for meiotic recombination and completion of meiotic prophase in mice. Using a hypomorphic Atr mutation and pharmacological inhibition of ATR in vivo and in cultured spermatocytes, we show that ATR, through its effector kinase CHK1, promotes efficient RAD51 and DMC1 assembly at RPA-coated DSB sites and establishment of interhomolog connections during meiosis. Furthermore, our findings suggest that ATR promotes local accumulation of recombination markers on unsynapsed axes during meiotic prophase to favor homologous chromosome synapsis. These data reveal that ATR plays multiple roles in mammalian meiotic recombination.

cell biology↗