Effects of salinity acclimation on histological characteristics and miRNA expression profiles of scales in juvenile rainbow trout (Oncorhynchus mykiss).

BACKGROUND: The scales serve as an ideal model for studying the regulatory mechanism of bone homeostasis in fish. To explore the effect of salinity acclimation on bone metabolism of juvenile rainbow trout (Oncorhynchus mykiss), three sampling time points during salinity acclimation (7D, 14D and 21D) were selected to detect variations in histological characteristics. In the histological analysis, osteoblast marker enzymes alkaline phosphatase (ALP), osteoclast marker tartrate-resistant acid phosphatase (TRAcP) and calcium salt deposit areas (Von Kossa's) were detected. Changes in calcium (Ca), phosphorus (P) and the molar mass ratio of calcium to phosphorus (Ca/P) in the scales were also detected by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In addition, the global MicroRNA (miRNA) expression profiles during salinity acclimation were examined using Illumina sequencing platform because of their important regulatory roles in teleost biological processes. RESULTS: Twelve independent miRNA libraries were constructed, a total of 664 known and 92 putative novel miRNAs were identified. A total of 290 differentially expressed (DE) miRNAs were found in clusters with significant trends in the cluster analysis, and five types of clustering patterns were obtained; 22,374 DE predicted target genes of the aforementioned 290 DE miRNAs were obtained, 5957 of which clustered in six types of clustering patterns with a significant trend. To better understand the functions of the DE miRNAs, GO and KEGG analysis was performed on the 5957 target genes, as a result, they were significantly enriched in bone metabolism related signaling pathways such as MAPK signaling pathway, Calcium signaling pathway, Wnt signaling pathway, Mineral absorption and NF-kappa B signaling pathway. Six DE miRNAs were randomly selected and their expression were verified by quantitative real-time PCR (qRT-PCR), the expression trends were consistent with the results of transcriptome sequencing. CONCLUSIONS: The DE miRNAs and DE target genes identified in this study might play an important role in regulation of bone metabolism during salinity acclimation, relative genes or pathways could serve as key candidates for further studies to elucidate molecular mechanism of teleost bone metabolism, and help performing salinity acclimation and developing marine culture of salmonid species.

Lysine acetyltransferase Tip60 is required for hematopoietic stem cell maintenance.

Hematopoietic stem cells (HSCs) have the potential to replenish the blood system for the lifetime of the organism. Their 2 defining properties, self-renewal and differentiation, are tightly regulated by the epigenetic machineries. Using conditional gene-knockout models, we demonstrated a critical requirement of lysine acetyltransferase 5 (Kat5, also known as Tip60) for murine HSC maintenance in both the embryonic and adult stages, which depends on its acetyltransferase activity. Genome-wide chromatin and transcriptome profiling in murine hematopoietic stem and progenitor cells revealed that Tip60 colocalizes with c-Myc and that Tip60 deletion suppress the expression of Myc target genes, which are associated with critical biological processes for HSC maintenance, cell cycling, and DNA repair. Notably, acetylated H2A.Z (acH2A.Z) was enriched at the Tip60-bound active chromatin, and Tip60 deletion induced a robust reduction in the acH2A.Z/H2A.Z ratio. These results uncover a critical epigenetic regulatory layer for HSC maintenance, at least in part through Tip60-dependent H2A.Z acetylation to activate Myc target genes.

The basic helix-loop-helix transcription factor SHARP1 is an oncogenic driver in MLL-AF6 acute myelogenous leukemia.

Acute Myeloid Leukemia (AML) with MLL gene rearrangements demonstrate unique gene expression profiles driven by MLL-fusion proteins. Here, we identify the circadian clock transcription factor SHARP1 as a novel oncogenic target in MLL-AF6 AML, which has the worst prognosis among all subtypes of MLL-rearranged AMLs. SHARP1 is expressed solely in MLL-AF6 AML, and its expression is regulated directly by MLL-AF6/DOT1L. Suppression of SHARP1 induces robust apoptosis of human MLL-AF6 AML cells. Genetic deletion in mice delays the development of leukemia and attenuated leukemia-initiating potential, while sparing normal hematopoiesis. Mechanistically, SHARP1 binds to transcriptionally active chromatin across the genome and activates genes critical for cell survival as well as key oncogenic targets of MLL-AF6. Our findings demonstrate the unique oncogenic role for SHARP1 in MLL-AF6 AML.

MOAP-1 Mediates Fas-Induced Apoptosis in Liver by Facilitating tBid Recruitment to Mitochondria.

Fas apoptotic signaling regulates diverse physiological processes. Acute activation of Fas signaling triggers massive apoptosis in liver. Upon Fas receptor stimulation, the BH3-only protein Bid is cleaved into the active form, tBid. Subsequent tBid recruitment to mitochondria, which is facilitated by its receptor MTCH2 at the outer mitochondrial membrane (OMM), is a critical step for commitment to apoptosis via the effector proteins Bax or Bak. MOAP-1 is a Bax-binding protein enriched at the OMM. Here, we show that MOAP-1-deficient mice are resistant to Fas-induced hepatocellular apoptosis and lethality. In the absence of MOAP-1, mitochondrial accumulation of tBid is markedly impaired. MOAP-1 binds to MTCH2, and this interaction appears necessary for MTCH2 to engage tBid. These findings reveal a role for MOAP-1 in Fas signaling in the liver by promoting MTCH2-mediated tBid recruitment to mitochondria.

Non-canonical NF-κB signalling and ETS1/2 cooperatively drive C250T mutant TERT promoter activation.

Transcriptional reactivation of TERT, the catalytic subunit of telomerase, is necessary for cancer progression in about 90% of human cancers. The recent discovery of two prevalent somatic mutations-C250T and C228T-in the TERT promoter in various cancers has provided insight into a plausible mechanism of TERT reactivation. Although the two hotspot mutations create a similar binding motif for E-twenty-six (ETS) transcription factors, we show that they are functionally distinct, in that the C250T unlike the C228T TERT promoter is driven by non-canonical NF-κB signalling. We demonstrate that binding of ETS to the mutant TERT promoter is insufficient in driving its transcription but this process requires non-canonical NF-κB signalling for stimulus responsiveness, sustained telomerase activity and hence cancer progression. Our findings highlight a previously unrecognized role of non-canonical NF-κB signalling in tumorigenesis and elucidate a fundamental mechanism for TERT reactivation in cancers, which if targeted could have immense therapeutic implications.

Enhanced cytotoxicity to cancer cells by mitochondria-targeting MWCNTs containing platinum(IV) prodrug of cisplatin.

Among the arsenal of nano-materials, carbon nanotubes (CNTs) are becoming more prominent due to favorable attributes including their unique shape, which promotes cellular-uptake, and large aspect-ratio that facilitates functionalization of bioactive molecules on their surface. In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized with either mitochondrial-targeting fluorescent rhodamine-110 (MWCNT-Rho) or non-targeting fluorescein (MWCNT-Fluo). Despite structural similarities, MWCNT-Rho associated well with mitochondria (ca. 80% co-localization) in contrast to MWCNT-Fluo, which was poorly localized (ca. 21% co-localization). Additionally, MWCNT-Rho entrapping platinum(IV) pro-drug of cisplatin (PtBz) displayed enhanced potency (IC50 = 0.34 ± 0.07 µM) compared to a construct based on MWCNT-Fluo (IC50 ≥ 2.64 µM). Concurrently, preliminary in vitro toxicity evaluation revealed that empty MWCNT-Rho neither decreased cell viability significantly nor interfered with mitochondrial membrane-potential, while seemingly being partially expelled from cells. Due to its targeting capability and apparent lack of cytotoxicity, MWCNT-Rho complex was used to co-encapsulate PtBz and a chemo-potentiator, 3-bromopyruvate (BP), and the resulting MWCNT-Rho(PtBz+BP) construct demonstrated superior efficacy over PtBz free drug in several cancer cell lines tested. Importantly, a 2-fold decrease in mitochondrial potential was observed, implying that mitochondrial targeting of compounds indeed incurred additional intended damage to mitochondria.