Systematic analysis of the role of SLC52A2 in multiple human cancers

Background In humans, riboflavin must be obtained through intestinal absorption because it cannot be synthesized by the body. SLC52A2 encodes a membrane protein belonging to the riboflavin transporter protein family and is associated with a variety of diseases. Here, we systematically explore its relevance to multiple human tumors. Methods We analyzed the association of SLC52A2 with 33 tumors using publicly available databases such as TCGA and GEO. We verified the SLC52A2 expression in hepatocellular carcinoma, gastric cancer, colon cancer, and rectal cancer using immunohistochemistry. Results We report that SLC52A2 was highly expressed in almost all tumors, and the immunohistochemical results in the hepatocellular, gastric, colon, and rectal cancers were consistent with the above. SLC52A2 expression was linked to patient overall survival, disease-specific survival, progression-free interval, diagnosis, mutations, tumor mutational burden, microsatellite instability, common immune checkpoint genes, and immune cells infiltration. Enrichment analysis showed that SLC52A2 was mainly enriched in oocyte meiosis, eukaryotic ribosome biogenesis, and cell cycle. In hepatocellular carcinoma, the SLC52A2 expression is an independent prognostic factor. The SNHG3 and THUMPD3-AS1/hsa-miR-139-5p-SLC52A2 axis were identified as potential regulatory pathways in hepatocellular carcinoma. Conclusion In conclusion, we have systematically described for the first time that SLC52A2 is closely associated with a variety of tumors, especially hepatocellular carcinoma.

ZYG-9ch-TOG promotes the stability of acentrosomal poles via regulation of spindle microtubules in C. elegans oocyte meiosis

During mitosis, centrosomes serve as microtubule organizing centers that guide the formation of a bipolar spindle. However, oocytes of many species lack centrosomes; how meiotic spindles establish and maintain these acentrosomal poles remains poorly understood. Here, we show that the microtubule polymerase ZYG-9ch-TOG is required to maintain acentrosomal pole integrity in C. elegans oocyte meiosis; following acute depletion of ZYG-9 from pre-formed spindles, the poles split apart and an unstable multipolar structure forms. Depletion of TAC-1, a protein known to interact with ZYG-9 in mitosis, caused loss of proper ZYG-9 localization and similar spindle phenotypes, further demonstrating that ZYG-9 is required for pole integrity. However, depletion of ZYG-9 surprisingly did not affect the assembly or stability of monopolar spindles, suggesting that ZYG-9 is not required for acentrosomal pole structure per se. Moreover, fluorescence recovery after photobleaching (FRAP) revealed that ZYG-9 turns over rapidly at acentrosomal poles, displaying similar turnover dynamics to tubulin itself, suggesting that ZYG-9 does not play a static structural role at poles. Together, these data support a global role for ZYG-9 in regulating the stability of bipolar spindles and demonstrate that the maintenance of acentrosomal poles requires factors beyond those acting to organize the pole structure itself.

Integrated multiple transcriptomes in oviductal tissue across the porcine oestrous cycle reveal functional roles in oocyte maturation and transport

Understanding the changes in the swine female reproductive system is important for solving issues related to reproductive failure and litter size. Elucidating the regulatory mechanisms of the natural oestrous cycle in the oviduct under non-fertilisation conditions can improve our understanding of its role in the reproductive system. Herein, whole transcriptome RNA sequencing of oviduct tissue samples was performed. The differentially expressed genes (DEGs) were identified for each time point relative to Day 0 and classified into three clusters based on their expression patterns. Clusters 1 and 2 included genes involved in the physiological changes through the oestrous cycle. Cluster 1 genes were mainly involved in PI3K-Akt signalling and steroid hormone biosynthesis pathways. Cluster 2 genes were involved in extracellular matrix-receptor interactions and protein digestion pathways. In Cluster 3, the DEGs were downregulated in the luteal phase; they were strongly associated with cell cycle, calcium signalling, and oocyte meiosis. The gene expression in the oviduct during the oestrous cycle influenced oocyte transport and fertilisation. Our findings provide a basis for successfully breeding pigs and elucidating the mechanisms underlying the changes in the pig oviduct during the oestrous cycle.

CENP-V is required for proper chromosome segregation through interaction with spindle microtubules in mouse oocytes

Proper chromosome segregation is essential to avoid aneuploidy, yet this process fails with increasing age in mammalian oocytes. Here we report a role for the scarcely described protein CENP-V in oocyte spindle formation and chromosome segregation. We show that depending on the oocyte maturation state, CENP-V localizes to centromeres, to microtubule organizing centers, and to spindle microtubules. We find that Cenp-V−/− oocytes feature severe deficiencies, including metaphase I arrest, strongly reduced polar body extrusion, increased numbers of mis-aligned chromosomes and aneuploidy, multipolar spindles, unfocused spindle poles and loss of kinetochore spindle fibres. We also show that CENP-V protein binds, diffuses along, and bundles microtubules in vitro. The spindle assembly checkpoint arrests about half of metaphase I Cenp-V−/− oocytes from young adults only. This finding suggests checkpoint weakening in ageing oocytes, which mature despite carrying mis-aligned chromosomes. Thus, CENP-V is a microtubule bundling protein crucial to faithful oocyte meiosis, and Cenp-V−/− oocytes reveal age-dependent weakening of the spindle assembly checkpoint.

The Impact of Exogenous Tetrodotoxin on the piRNAs and mRNAs Profiles of Gonads in Pufferfish Takifugu Flavidus

Tetrodotoxin (TTX) is a deadly neurotoxin and usually accumulates in large amounts in the ovaries but is non-toxic or low toxic in the testis of pufferfish. The molecular mechanism underlying sexual dimorphism of TTX accumulation in gonads is complex and unclear. Piwi/piRNA complexes are essential for germline specification, gametogenesis, and gonadal development, they also demonstrate sexual dimorphism in teleosts. Hence, the present study investigated the expression of piRNAs and mRNAs by transcriptomics in cultured pufferfish Takifugu flavidus after intramuscular administration of exogenous TTX. The results showed 80 piRNAs were down-regulated and 223 genes were up-regulated in the ovary after TTX administration. By contrast, 286 piRNAs were down-regulated and 445 genes were up-regulated after TTX administration in testis. Functional and pathway analyses indicated that the TTX up-regulated genes were enriched in the Wnt, ErbB and GnRH signaling pathways in ovary, while were enriched in the oocyte meiosis, estrogenesis biosynthesis and cell apoptosis-related pathways in testis. Interestingly, these genes were also the potential target genes of TTX downregulated piRNAs. Amhr2 and cyp19a were also identified as sex-related genes, involved in TTX administration. These results showed a certain level of consistency with the enrichment pathway analysis, which indicated that the TTX could affect the expression of sex-related genes, and work as an inhibitor for the testicular meiosis, but as a promoting factor for ovary development through piRNAs in pufferfish. In addition, TUNEL staining showed that significant apoptosis was detected in the TTX treated testis, and the role of the cell apoptotic pathway was further confirmed. Overall, this research will contribute to an understanding of the piwi function in TTX sexual dimorphism accumulation in pufferfish and provide a basis for further studies.

Pervasive 3′-UTR Isoform Switches During Mouse Oocyte Maturation

Oocyte maturation is the foundation for developing healthy individuals of mammals. Upon germinal vesicle breakdown, oocyte meiosis resumes and the synthesis of new transcripts ceases. To quantitatively profile the transcriptomic dynamics after meiotic resumption throughout the oocyte maturation, we generated transcriptome sequencing data with individual mouse oocytes at three main developmental stages: germinal vesicle (GV), metaphase I (MI), and metaphase II (MII). When clustering the sequenced oocytes, results showed that isoform-level expression analysis outperformed gene-level analysis, indicating isoform expression provided extra information that was useful in distinguishing oocyte stages. Comparing transcriptomes of the oocytes at the GV stage and the MII stage, in addition to identification of differentially expressed genes (DEGs), we detected many differentially expressed transcripts (DETs), some of which came from genes that were not identified as DEGs. When breaking down the isoform-level changes into alternative RNA processing events, we found the main source of isoform composition changes was the alternative usage of polyadenylation sites. With detailed analysis focusing on the alternative usage of 3′-UTR isoforms, we identified, out of 3,810 tested genes, 512 (13.7%) exhibiting significant switches of 3′-UTR isoforms during the process of moues oocyte maturation. Altogether, our data and analyses suggest the importance of examining isoform abundance changes during oocyte maturation, and further investigation of the pervasive 3′-UTR isoform switches in the transition may deepen our understanding on the molecular mechanisms underlying mammalian early development.

Gm364 coordinates MIB2/DLL3/Notch2 to regulate female fertility through AKT activation

Many integral membrane proteins might act as indispensable coordinators in specific functional microdomains to maintain the normal operation of known receptors, such as Notch. Gm364 is a multi-pass transmembrane protein that has been screened as a potential female fertility factor. However, there have been no reports to date about its function in female fertility. Here, we found that global knockout of Gm364 decreased the numbers of primordial follicles and growing follicles, impaired oocyte quality as indicated by increased ROS and γ-H2AX, decreased mitochondrial membrane potential, decreased oocyte maturation, and increased aneuploidy. Mechanistically, Gm364 directly binds and anchors MIB2, a ubiquitin ligase, on the membrane. Subsequently, membrane MIB2 ubiquitinates and activates DLL3. Next, the activated DLL3 binds and activates Notch2, which is subsequently cleaved within the cytoplasm to produce NICD2, the intracellular active domain of Notch2. Finally, NICD2 can directly activate AKT within the cytoplasm to regulate oocyte meiosis and quality.

Elevated STIL predicts poor prognosis in patients with hepatocellular carcinoma

Background Overexpression of STIL centriolar assembly protein (STIL) has been observed in a variety of cancers. However, the functional significance of STIL in hepatocellular carcinoma remains unknow. Results STIL expression were abnormal in HCC tissues, and HCC patients with increased STIL expression had poor prognosis. In addition, increased STIL expression was correlated with T stage, pathologic stage, histologic grade, AFP, age, tumor status. STIL was an independent predictor of poor prognosis in HCC patients, as verified with a nomogram based on a Cox regression model. STIL was involved in HCC progression by modulating the cell cycle, DNA replication, oocyte meiosis, etc. Correlation analysis indicated TUBG1 mRNA expression was correlated with immune infiltrates. Conclusion STIL plays a vital role in HCC progression and prognosis; it may, therefore, serve as an effective biomarker for the prediction of patient survival.

M-Phase oscillations in PP1 activity are essential for accurate progression through mammalian oocyte meiosis

Tightly controlled fluctuations in kinase and phosphatase activity play important roles in regulating M-Phase transitions (e.g., G2/M). Protein Phosphatase 1 (PP1) is one of these phosphatases, with oscillations in activity driving mitotic M-Phase entry, progression, and exit, with evidence from a variety of experimental systems pointing to roles in meiosis as well. Here we report that PP1 is important for M-Phase transitions through mouse oocyte meiosis. Employing a unique small-molecule approach to inhibit or activate PP1 at distinct phases of mouse oocyte meiosis, we found that aberrations in normal cyclical PP1 activity leads to meiotic abnormalities. We report here that temporal control of PP1 activity is essential for G2/M transition, metaphase I/anaphase I transition, and the formation of a normal metaphase II oocyte. Our data also reveal that inappropriate activation of PP1 is more deleterious at G2/M transition than at prometaphase I-to-metaphase I, and that an active pool of PP1 during prometaphase I is vital for metaphase I/anaphase I transition and metaphase II chromosome alignment. Taken together, these results establish that loss of oscillations in PP1 activity causes a range of severe meiotic defects, pointing to essential roles for PP1 in oocytes and female fertility, and more broadly, M-Phase regulation.

Multiple motors cooperate to establish and maintain acentrosomal spindle bipolarity in C. elegans oocyte meiosis

ABSTRACTWhile centrosomes organize spindle poles during mitosis, oocyte meiosis can occur in their absence. Spindles in human oocytes frequently fail to maintain bipolarity and consequently undergo chromosome segregation errors, making it important to understand mechanisms that promote acentrosomal spindle stability. To this end, we have optimized the auxin-inducible degron system in C. elegans to remove factors from pre-formed oocyte spindles within minutes and assess effects on spindle structure. This approach revealed that dynein is required to maintain the integrity of acentrosomal poles; removal of dynein from bipolar spindles caused pole splaying, and when coupled with a monopolar spindle induced by depletion of kinesin-12 motor KLP-18, dynein depletion led to a complete dissolution of the monopole. Surprisingly, we went on to discover that following monopole disruption, individual chromosomes were able to reorganize local microtubules and re-establish a miniature bipolar spindle that mediated chromosome segregation. This revealed the existence of redundant microtubule sorting forces that are undetectable when KLP-18 and dynein are active. We found that the kinesin-5 family motor BMK-1 provides this force, uncovering the first evidence that kinesin-5 contributes to C. elegans meiotic spindle organization. Altogether, our studies have revealed how multiple motors are working synchronously to establish and maintain bipolarity in the absence of centrosomes.