Methane seepage intensity distinguish microbial communities in sediments at the Mid-Okinawa Trough.

Shallow methane/sulfate transition zones in cold seeps are hotspots to study microbially mediated geochemical cycles due to high methane fluxes. However, our knowledge about the microbial communities in remote seafloor cold seep ecosystems with different methane seepage intensity is still sparse due to the challenge for sampling and visual observations. In this work, three remotely operated vehicle (ROV) video-guided push sediment cores were sampled from cold seep fields with different methane seepage intensity (low-intensity seepage, R5-C1; moderate-intensity seepage, R6-C2; high-intensity seepage, R6-C3) at the western slope of Mid-Okinawa Trough (Mid-OT) and subjected to high throughput sequencing of 16S rRNA genes for bacteria and archaea. Vesicomyid clams and white microbial mats are visible by video at R6-C3 with methane bubbles. The high relative abundances of anaerobic methanotrophic archaea (ANME-1, -2, and -3), δ-Proteobacteriacea and Campylobacteria in R6-C3 indicated that the processes of anaerobic methane oxidation (AOM), sulfate reduction and sulfur oxidation might occur in this active seeping site. In contrast, Bathyarchaeia, Nitrosopumilales, Sphingomonadales, and Burkholderiales were enriched in bubble-free sites, which commonly involved in the degradation of organic compounds. Principal coordinate analysis showed that both bacterial and archaeal communities were clustered according to sampling sites, also indicating the impact of methane seepage intensity on microbial communities. The co-occurrence network analysis revealed that microbes at the site with high methane fluxes mainly cooperated with each other to sustain the ecosystems, whereas competition enhanced at sites with low methane fluxes. Detection of thermophiles Thermoanaerobaculia and Hydrothermarchaeota may indicate microbial transmission from nearby hydrothermal vents, suggesting potential interactions between cold seepage and hydrothermal vent ecosystems. These results expand our knowledge about the composition and distribution of bacteria and archaea with different methane seepage intensity in cold seep field at the Mid-OT, contributing to the ongoing efforts in understanding carbon cycling in the cold seep ecosystems.

Diversity of Anaerobic Methane Oxidizers in the Cold Seep Sediments of the Okinawa Trough.

Active cold seeps in the Okinawa Trough (OT) have been widely identified, but the sediment microbial communities associated with these sites are still poorly understood. Here, we investigated the distribution and biomass of the microbial communities, particularly those associated with the anaerobic oxidation of methane (AOM), in sediments from an active cold seep in the mid-Okinawa Trough. Methane-oxidizing archaea, including ANME-1a, ANME-1b, ANME-2a/b, ANME-2c, and ANME-3, were detected in the OT cold seep sediments. Vertical stratification of anaerobic methanotrophic archaea (ANME) communities was observed in the following order: ANME-3, ANME-1a, and ANME-1b. In addition, the abundance of methyl coenzyme M reductase A (mcrA) genes corresponded to high levels of dissolved iron, suggesting that methane-metabolizing archaea might participate in iron reduction coupled to methane oxidation (Fe-AOM) in the OT cold seep. Furthermore, the relative abundance of ANME-1a was strongly related to the concentration of dissolved iron, indicating that ANME-1a is a key microbial player for Fe-AOM in the OT cold seep sediments. Co-occurrence analysis revealed that methane-metabolizing microbial communities were mainly associated with heterotrophic microorganisms, such as JS1, Bathy-1, and Bathy-15.

Suppression of NSDHL attenuates adipogenesis with a downregulation of LXR-SREBP1 pathway in 3T3-L1 cells.

Previous RNA-Seq analyses revealed that NAD(P)H steroid dehydrogenase-like (NSDHL) has a different expression during 3T3-L1 differentiation; however, its roles in adipogenesis are unknown. In the present study, using quantitative real-time PCR, we confirmed that NSDHL knockdown increased the proliferation of 3T3-L1 preadipocytes, but attenuated the differentiation of 3T3-L1 preadipocytes, as evidenced by reduced lipid accumulation and down-regulation of PPARγ gene expression. Further analyses showed that the expression peak of NSDHL was at the early stage of 3T3-L1 preadipocytes differentiation and LXR-SREBP1 signaling pathway was downregulated in NSDHL-knockdown 3T3-L1 cells. Collectively, our findings indicate that NSDHL is a novel modulator of adipogenesis. Moreover, our data provide insight into the complex relationships between sterol sensing, LXR-SREBP1 signaling pathway, and PPARγ in 3T3-L1 cells.

Adipogenesis associated Mth938 domain containing (AAMDC) protein expression is regulated by alternative polyadenylation and microRNAs.

The post-transcriptional events regulating expression of the adipogenesis associated Mth938 domain containing (AAMDC) protein are poorly understood. Here, we find that AAMDC expresses three isoforms due to alternative polyadenylation (APA) and alternative splicing (AS). Luciferase assay revealed that expression of the two isoforms with short and long 3'UTRs is differentially controlled. Further analyses showed that the short isoform displays higher translation efficiency and that miR-2428/664a reduces expression of the long isoform, indicating that APA-mediated shortening of the AAMDC 3'UTR renders the short isoform insusceptible to miRNA-mediated suppression due to loss of the binding sites for miR-2428/664a. Finally, we demonstrate that the short AAMDC isoform promotes bovine preadipocyte differentiation. Collectively, our findings indicate that AAMDC is post-transcriptionally regulated through APA and microRNAs.

RNA-Seq analysis reveals a negative role of MSMO1 with a synergized NSDHL expression during adipogenesis of 3T3-L1.

To investigate a comprehensive transcriptome information of adipogenesis, we assessed global changes in the transcriptional events during 3T3-L1 adipogenesis by RNA-Seq. Compared to the preadipocyte stage (day 0), gene expression profiling demonstrated that 2013 genes were up-regulated, and 2430 genes were down-regulated at the differentiated adipocyte stage (day 13). Among these differentially expressed genes, we found the expression of MSMO1 was down-regulated at day 13, but whether it impacts adipogenesis has not been characterized. Thus, we investigated its role in adipogenesis. Results showed that overexpression of MSMO1 inhibited the differentiation of 3T3-L1, and led to the down-regulated expression of adipogenic marker genes, while knockdown of MSMO1 had totally opposite effects. Furthermore, interaction network model allowed us to validate an unexpected role between MSMO1 and its partner, NSDHL, in regulating adipogenesis, which plays a synergized expression pattern with MSMO1. Our findings indicate that MSMO1 and NSDHL are novel modulators of adipogenesis.