Evolutionarily conserved mechanisms of male germline development in flowering plants and animals

Sexual reproduction is the main reproductive strategy of the overwhelming majority of eukaryotes. This suggests that the last eukaryotic common ancestor was able to reproduce sexually. Sexual reproduction reflects the ability to perform meiosis, and ultimately generating gametes, which are cells that carry recombined half sets of the parental genome and are able to fertilize. These functions have been allocated to a highly specialized cell lineage: the germline. Given its significant evolutionary conservation, it is to be expected that the germline programme shares common molecular bases across extremely divergent eukaryotic species. In the present review, we aim to identify the unifying principles of male germline establishment and development by comparing two very disparate kingdoms: plants and animals. We argue that male meiosis defines two temporally regulated gene expression programmes: the first is required for meiotic commitment, and the second is required for the acquisition of fertilizing ability. Small RNA pathways are a further key communality, ultimately ensuring the epigenetic stability of the information conveyed by the male germline

An SNF2 helicase-like protein links mitotic transcription termination to sister chromatid resolution

Mitotic chromatin is largely assumed incompatible with transcription due to changes in the transcription machinery and chromosome architecture. However, the mechanisms of mitotic transcriptional inactivation and their interplay with chromosome assembly remain largely unknown. By monitoring ongoing transcription in Drosophila early embryos, we reveal that eviction of nascent mRNAs from mitotic chromatin occurs after substantial chromosome compaction and is not promoted by condensin I. Instead, we show that the timely removal of transcripts from mitotic chromatin is driven by the SNF2 helicase-like protein Lodestar (Lds), identified here as a modulator of sister chromatid cohesion defects. In addition to transcriptional termination, we uncovered that Lds cooperates with Topoisomerase 2 to ensure efficient sister chromatid resolution and mitotic fidelity. We conclude that mitotic transcriptional termination is not a passive consequence of cell cycle progression and/or chromosome compaction but occurs via dedicated mechanisms with functional parallelisms to sister chromatid resolution.info:eu-repo/semantics/publishedVersio

A dual-function SNF2 protein drives chromatid resolution and nascent transcripts removal in mitosis

Mitotic chromatin is largely assumed incompatible with transcription due to changes in the transcription machinery and chromosome architecture. However, the mechanisms of mitotic transcriptional inactivation and their interplay with chromosome assembly remain largely unknown. By monitoring ongoing transcription in Drosophila early embryos, we reveal that eviction of nascent mRNAs from mitotic chromatin occurs after substantial chromosome compaction and is not promoted by condensin I. Instead, we show that the timely removal of transcripts from mitotic chromatin is driven by the SNF2 helicase-like protein Lodestar (Lds), identified here as a modulator of sister chromatid cohesion defects. In addition to the eviction of nascent transcripts, we uncover that Lds cooperates with Topoisomerase 2 to ensure efficient sister chromatid resolution and mitotic fidelity. We conclude that the removal of nascent transcripts upon mitotic entry is not a passive consequence of cell cycle progression and/or chromosome compaction but occurs via dedicated mechanisms with functional parallelisms to sister chromatid resolution.info:eu-repo/semantics/publishedVersio

Biomechanical Basis of Bone Fracture and Fracture Osteosynthesis in Small Animals

The mastery of concepts related to biomechanics in bone fracture is crucial for the surgical success of osteosynthesis. The understanding of the basics of bone fracture is a skill fundamental to the choice of the correct method of osteosynthesis. Deep knowledge of implants, namely, their mechanic characteristics, and the correct technical use following the recommended guidelines for each type are crucial factors to decrease surgical failure and complications rate. This chapter reviews the biomechanical parameters of fracture repair that influence construct stiffness and strength. The authors also provided practical examples of the biomechanics concepts applied in clinical practice during this chapter. Metal alloys used in orthopedic implants are also fundamentally reviewed in their physical properties during this chapter. Fracture patterns vary hugely among patients and contributed to the difficult understanding of forces acting in fracture lines. However, fracture biomechanics basic knowledge and how osteosynthesis methods counteract the forces acting on fractures are key to surgical success

N-terminal acetylation shields proteins from degradation and promotes age-dependent motility and longevity

Most eukaryotic proteins are N-terminally acetylated, but the functional impact on a global scale has remained obscure. Using genome-wide CRISPR knockout screens in human cells, we reveal a strong genetic dependency between a major N-terminal acetyltransferase and specific ubiquitin ligases. Biochemical analyses uncover that both the ubiquitin ligase complex UBR4-KCMF1 and the acetyltransferase NatC recognize proteins bearing an unacetylated N-terminal methionine followed by a hydrophobic residue. NatC KO-induced protein degradation and phenotypes are reversed by UBR knockdown, demonstrating the central cellular role of this interplay. We reveal that loss of Drosophila NatC is associated with male sterility, reduced longevity, and age-dependent loss of motility due to developmental muscle defects. Remarkably, muscle-specific overexpression of UbcE2M, one of the proteins targeted for NatC KO-mediated degradation, suppresses defects of NatC deletion. In conclusion, NatC-mediated N-terminal acetylation acts as a protective mechanism against protein degradation, which is relevant for increased longevity and motility. The most common protein modification in eukaryotes is N-terminal acetylation, but its functional impact has remained enigmatic. Here, the authors find that a key role for N-terminal acetylation is shielding proteins from ubiquitin ligase-mediated degradation, mediating motility and longevity.Association Francaise contre les Myopathies 261981, Canadian Institutes of Health Research (CIHR) 249843, United States Department of Health & Human Services National Institutes of Health (NIH) - USA F-12540, Portuguese national funding through Fundaco para a Ciencia e a Tecnologia (FCT) 171752-PR-2009-0222, National Funds through Fundaco para a Ciencia e a Tecnologia (FCT) G008018N, G002721N, University of Bergen MC_UU_00028/6, FDN-143264, FDN-143265, PJT-180285, PJT-463531, R01HG005853, R01HG005084, DL 57/2016/CP1361/CT0019, 2022.01782.PTDC,PTDC/BIA-BID/28441/2017,PTDC/BIA-BID/1606/2020, ALG-01-0145-FEDER-028441, PPBI-POCI-01-0145-FEDER-022122, LISBOA-01-0145-FEDER-022170info:eu-repo/semantics/publishedVersio

Genetic and Epigenetic Regulation of <i>Drosophila</i> Oocyte Determination

Primary oocyte determination occurs in many organisms within a germ line cyst, a multicellular structure composed of interconnected germ cells. However, the structure of the cyst is itself highly diverse, which raises intriguing questions about the benefits of this stereotypical multicellular environment for female gametogenesis. Drosophila melanogaster is a well-studied model for female gametogenesis, and numerous genes and pathways critical for the determination and differentiation of a viable female gamete have been identified. This review provides an up-to-date overview of Drosophila oocyte determination, with a particular emphasis on the mechanisms that regulate germ line gene expression

Drosophila melanogaster as a model to study the role of gut microbiota in inflammaging

The aging process is characterized by a variety of events, including microbiota dysbiosis and increased inflammation, the so-called inflammaging. While it remains unknown whether this dysbiosis is a cause or consequence of inflammaging, it has been hinted that gut microbiota homeostasis is crucial for healthy aging and hence restoration of this homeostasis might be a route to maintain health in old age. Here, the model organism Drosophila melanogaster is being used to ascertain causality between alterations in gut microbiota and the inflammatory status of the host contributing to aging. To address this, we aim to perform fecal transplantation experiments from old donor mice with different inflammatory status to germ-free flies. Compared to mice, D. melanogaster has a shorter lifespan, is easier to rear in large populations, has cheaper husbandry costs and no ethical implications. Furthermore, germ-free animals, amenable to gnotobiotic experiments with controlled microbiotas, are incomparably easier to obtain. Following microbiota transplantation, we will score the appearance of age-associated signs, based on phenotypes such as the negative geotactic response, longevity, gut permeability and inflammation. With this model, we expect to detect differences in age-associated traits of D. melanogaster that recapitulate the different levels of dysbiosis of the donor microbiota. This will help understand the extent to which microbiota influences inflammaging.Not Publishe

Regulation of Fertilization and Early Seed Development Evolutionarily conserved mechanisms of male germline development in flowering plants and animals

Abstract Sexual reproduction is the main reproductive strategy of the overwhelming majority of eukaryotes. This suggests that the last eukaryotic common ancestor was able to reproduce sexually. Sexual reproduction reflects the ability to perform meiosis, and ultimately generating gametes, which are cells that carry recombined half sets of the parental genome and are able to fertilize. These functions have been allocated to a highly specialized cell lineage: the germline. Given its significant evolutionary conservation, it is to be expected that the germline programme shares common molecular bases across extremely divergent eukaryotic species. In the present review, we aim to identify the unifying principles of male germline establishment and development by comparing two very disparate kingdoms: plants and animals. We argue that male meiosis defines two temporally regulated gene expression programmes: the first is required for meiotic commitment, and the second is required for the acquisition of fertilizing ability. Small RNA pathways are a further key communality, ultimately ensuring the epigenetic stability of the information conveyed by the male germline. Male germline establishment and development The life cycle of plants alternates between two morphologically distinct generations: the sporophyte and the gametophytes. During the course of evolution, the sporophytic phase became dominant, with the short-lived gametophytes arising, at the end of ontogeny, within structures on the sporophyte. It is during the development of the gametophytes that the plant germline is specified. Animals also display considerable variation in the timing of germline specification; this lineage can be established during early or late embryogenesis or even throughout adult life, as seen in plants (for a review, see In flowering plants, male gametophytes are formed in specialized reproductive organs of the flower: the anthers. Archesporial cells in the stamen primordium divide periclinally to produce an outer PPC (primary parietal cell) and an inner PSC (primary sporogenous cell) Abbreviations: DCL1, DICER-LIKE1; DUO1, DUO POLLEN1; GCS1, GENERATIVE CELL-SPECIFIC PROTEIN 1; HAP2, HAPLESS2; MGH3, MALE GAMETE-SPECIFIC HISTONE H3 ; MGU, male germ unit; piRNA, Piwi-interacting RNA; PLCζ , phospholipase Cζ ; PMC, pollen mother cell; PM, pollen mitosis; PPC, primary parietal cell; PSC, primary sporogenous cell; SC, sperm cell; SSP, SHORT SUSPENSOR; TE, transposable element; VN, vegetative nucleus. 1 To whom correspondence should be addressed (email [email protected]). PPC differentiates into the tapetum, a sterile nourishing tissue that is essential for the early stages of pollen development. Consecutive divisions of the PSC generate a central mass of microsporocytes, the PMCs (pollen mother cells). PMCs remain interconnected by cytoplasmic bridges, the cytomictic channels. These channels result from the continuity of the inner side of the cytoplasmic membrane (symplast) of neighbouring cells and are believed to be necessary for the subsequent synchronization of PMC development. Such synchronization will regulate meiosis, a process that will ultimately result in the formation of four microspores (for a review, se

Analysis of mammalian native elongating transcript sequencing (mNET-seq) high-throughput data

Mammalian Native Elongating Transcript sequencing (mNET-seq) is a recently developed technique that generates genome-wide profiles of nascent transcripts associated with RNA polymerase II (Pol II) elongation complexes. The ternary transcription complexes formed by Pol II, DNA template and nascent RNA are first isolated, without crosslinking, by immunoprecipitation with antibodies that specifically recognize the different phosphorylation states of the polymerase large subunit C-terminal domain (CTD). The coordinate of the 3' end of the RNA in the complexes is then identified by high-throughput sequencing. The main advantage of mNET-seq is that it provides global, bidirectional maps of Pol II CTD phosphorylation-specific nascent transcripts and coupled RNA processing at single nucleotide resolution. Here we describe the general pipeline to prepare and analyse high-throughput data from mNET-seq experiments.UID/BIM/50005/2019/ PTDC/BEX-BID/0395/2014/ PTDC/BIA-BID/28441/2017/ UID/BIM/04773/2013 CBMR 1334info:eu-repo/semantics/publishedVersio