Non-coding RNAs enter mitosis: functions, conservation and implications

Nuage (or commonly known as chromatoid body in mammals) is a conserved germline-specific organelle that has been linked to the Piwi-interacting RNA (piRNA) pathway. piRNAs are a class of gonadal-specific RNAs that are ~23-29 nucleotides in length and protect genome stability by repressing the expression of deleterious retrotransposons. More recent studies in Drosophila have implicated the piRNA pathway in other functions including canalization of embryonic development, regulation of maternal gene expression and telomere protection. We have recently shown that Vasa (known as Mouse Vasa Homolog in mouse), a nuage component, plays a mitotic role in promoting chromosome condensation and segregation by facilitating robust chromosomal localization of condensin I in the Drosophila germline. Vasa functions together with Aubergine (a PIWI family protein) and Spindle-E/mouse TDRD-9, two other nuage components that are involved in the piRNA pathway, therefore providing a link between the piRNA pathway and mitotic chromosome condensation. Here, we propose and discuss possible models for the role of Vasa and the piRNA pathway during mitosis. We also highlight relevant studies implicating mitotic roles for RNAs and/or nuage in other model systems and their implications for cancer development

Drosophila MARF1 ensures proper oocyte maturation by regulating nanos expression.

Meiosis and oocyte maturation are tightly regulated processes. The meiosis arrest female 1 (MARF1) gene is essential for meiotic progression in animals; however, its detailed function remains unclear. In this study, we examined the molecular mechanism of dMarf1, a Drosophila homolog of MARF1 encoding an OST and RNA Recognition Motif (RRM) -containing protein for meiotic progression and oocyte maturation. Although oogenesis progressed in females carrying a dMarf1 loss-of-function allele, the dMarf1 mutant oocytes were found to contain arrested meiotic spindles or disrupted microtubule structures, indicating that the transition from meiosis I to II was compromised in these oocytes. The expression of the full-length dMarf1 transgene, but none of the variants lacking the OST and RRM motifs or the 47 conserved C-terminal residues among insect groups, rescued the meiotic defect in dMarf1 mutant oocytes. Our results indicate that these conserved residues are important for dMarf1 function. Immunoprecipitation of Myc-dMarf1 revealed that several mRNAs are bound to dMarf1. Of those, the protein expression of nanos (nos), but not its mRNA, was affected in the absence of dMarf1. In the control, the expression of Nos protein became downregulated during the late stages of oogenesis, while it remained high in dMarf1 mutant oocytes. We propose that dMarf1 translationally represses nos by binding to its mRNA. Furthermore, the downregulation of Nos induces cycB expression, which in turn activates the CycB/Cdk1 complex at the onset of oocyte maturation

The expression profile of purified Drosophila germline stem cells

AbstractWe developed a method to highly purify germline stem cells (GSCs) from the Drosophila ovary, one of the best understood types of adult stem cell. GSCs express variant isoforms of general transcriptional components, translation initiation factors, and several variant ribosomal proteins, including RpL22, a protein enriched in several mammalian stem cells. These novel isoforms may help regulate stem cell gene expression because a reversion assay indicated that at least four were specific for GSCs. By comparative analysis, we identify additional genes enriched in GSCs, including Psc, the Drosophila homolog of the Bmi-1 Polycomb group gene, as well as genes that may delay cytokinesis in pre-meiotic germ cells. By comparing GSCs arrested by BMP over-expression and bam mutation, we hypothesize that mRNA utilization is modulated in differentiating GSC daughters. Our findings suggest that Drosophila and mammalian stem cells utilize at least two regulatory mechanisms in common

miRNA/siRNA-directed pathway to produce noncoding piRNAs from endogenous protein-coding regions ensures Drosophila spermatogenesis

PIWI-interacting RNA (piRNA) pathways control transposable elements (TEs) and endogenous genes, playing important roles in animal gamete formation. However, the underlying piRNA biogenesis mechanisms remain elusive. Here, we show that endogenous protein coding sequences (CDSs), which are normally used for translation, serve as origins of noncoding piRNA biogenesis in Drosophila melanogaster testes. The product, namely, CDS-piRNAs, formed silencing complexes with Aubergine (Aub) in germ cells. Proximity proteome and functional analyses show that CDS-piRNAs and cluster/TE-piRNAs are distinct species occupying Aub, the former loading selectively relies on chaperone Cyclophilin 40. Moreover, Argonaute 2 (Ago2) and Dicer-2 activities were found critical for CDS-piRNA production. We provide evidence that Ago2-bound short interfering RNAs (siRNAs) and microRNAs (miRNAs) specify precursors to be processed into piRNAs.We further demonstrate that Aub is crucial in spermatid differentiation, regulating chromatins through mRNA cleavage. Collectively, our data illustrate a unique strategy used by male germ line, expanding piRNA repertoire for silencing of endogenous genes during spermatogenesis.Iki T., Kawaguchi S., Kai T.. miRNA/siRNA-directed pathway to produce noncoding piRNAs from endogenous protein-coding regions ensures Drosophila spermatogenesis. Science Advances 9, eadh0397 (2023); https://doi.org/10.1126/sciadv.adh0397

ポストコロナジダイ ニ オケル ヨコレンケイ キョウカガタ コクサイ コウリュウ カツドウ ノ テンカイ タヨウナ ブンカ ゲンゴケン カラ ノ リュウガクセイ リクルート ヲ ソクシン スル オオサカダイガク バーチャル ダイガク ツアー ノ ジッセン

新型コロナウイルス感染症拡大等により，全世界で海外留学を取り巻く環境が激変している．多種多様なオンラインイベント，膨大な情報やオンラインコミュニティを選択できる環境におかれている留学希望者及び大学の需要に合わせて，新たなプログラムの企画と開発が必要になっている．大阪大学は2020年春よりオンライン留学説明会を企画，実施し，また大学のブランディング活動を継続しつつ，バーチャル留学プログラムを設立することにより，バーチャルおよび対面での国際学生交流活動を企画，開催してきた．大阪大学は，新たに展開したこれらの活動と，留学生の応募と入試に関するサポート，就職指導と支援なども組入れ，留学生のオンラインリクルート体制を構築した．本稿では，大学の国際化促進フォーラムの幹事校として，大阪大学が主催した「多様な文化・言語圏からの留学生リクルート：バーチャル大学ツアーの実施」の企画背景，実践事例と今後の展開方向について紹介する．大阪大学はこれまでの経験を活かし，ポストコロナを見据えた留学生のリクルート戦略としてバーチャル大学ツアーを開催し，ニューノーマルにおけるオールジャパンでの留学生リクルートの促進を図り，協力体制の構築に貢献した．本稿の目的は，このプロジェクトの実施成果と課題を分析し，横連携強化型国際交流活動の更なる発展の可能性を展望することである．The global circumstances surrounding international student recruitment and study abroad programs have changed dramatically since the disruption of international exchange during the Covid-19 pandemic. With many online events, abundant flow of information, and online communities to choose from, there is a need to plan and develop new programs that meet the needs of prospective students and universities. Osaka University has built an online international student recruitment system through the planning and implementation of online study abroad information events, virtual study abroad programs, and international student exchange activities, as well as through the establishment of a support system for international student applications and admissions and career guidance and job-hunting support. This paper describes the planning backdrop, actual practices, and future directions of the “Virtual university tours: a new tool to recruit international students with diverse linguistic and cultural backgrounds” hosted by Osaka University as a secretariat of the Japan Forum for Internationalization of Universities. Leveraging its accumulated experience, Osaka University held a virtual university tour to recruit international students aiming for the post-Covid era. The activities promote all-Japan recruitment of international students in the new normal and contribute to the construction of a cooperative framework. The purpose of this paper is to discuss the results of the implementation of this project, analyze its challenges, and look at the possibilities for further development of international exchange activities that strengthen lateral cooperation.教育実践レポートPractice Report

piRNAs mediate posttranscriptional retroelement silencing and localization to pi-bodies in the Drosophila germline

Nuage, a well-conserved perinuclear organelle found in germline cells, is thought to mediate retroelement repression in Drosophila melanogaster by regulating the production of Piwi-interacting RNAs (piRNAs). In this study, we present evidence that the nuage–piRNA pathway components can be found in cytoplasmic foci that also contain retroelement transcripts, antisense piRNAs, and proteins involved in messenger RNA (mRNA) degradation. These mRNA degradation proteins, decapping protein 1/2 (DCP1/2), Me31B (maternal expression at 31B), and pacman (PCM), are normally thought of as components of processing bodies. In spindle-E (spn-E) and aubergine (aub) mutants that lack piRNA production, piRNA pathway proteins no longer overlap the mRNA degradation proteins. Concomitantly, spn-E and aub mutant ovaries show an accumulation of full-length retroelement transcripts and prolonged stabilization of HeT-A mRNA, supporting the role of piRNAs in mediating posttranscriptional retroelement silencing. HeT-A mRNA is derepressed in mRNA degradation mutants twin, dcp1, and ski3, indicating that these enzymes also aid in removing full-length transcripts and/or decay intermediates