Mastl is required for timely activation of APC/C in meiosis I and Cdk1 reactivation in meiosis II

In mitosis, the Greatwall kinase (called microtubule-associated serine/threonine kinase like [Mastl] in mammals) is essential for prometaphase entry or progression by suppressing protein phosphatase 2A (PP2A) activity. PP2A suppression in turn leads to high levels of Cdk1 substrate phosphorylation. We have used a mouse model with an oocyte-specific deletion of Mastl to show that Mastl-null oocytes resume meiosis I and reach metaphase I normally but that the onset and completion of anaphase I are delayed. Moreover, after the completion of meiosis I, Mastl-null oocytes failed to enter meiosis II (MII) because they reassembled a nuclear structure containing decondensed chromatin. Our results show that Mastl is required for the timely activation of anaphase-promoting complex/cyclosome to allow meiosis I exit and for the rapid rise of Cdk1 activity that is needed for the entry into MII in mouse oocytes

Regulators of Membrane Fluidity

Caenorhabditis elegans PAQR-2 (a homolog of the mammalian AdipoR1 and AdipoR2 proteins) and IGLR-2 (homolog of the mammalian LRIG proteins) form a complex at the plasma membrane that regulates fatty acid desaturation to protect against saturated fatty acid-induced membrane rigidification. Maintenance of membrane homeostasis is fundamental for most cellular processes and, given its importance, robust regulatory mechanisms must exist that adjust lipid composition to compensate for dietary variation. To better understand this phenomenon, we performed forward genetic screens in C. elegans and isolated mutants that improve tolerance to dietary saturated fatty acids. These include eight new loss of function alleles of the novel gene fld-1, one loss of function allele of acs-13 and one gain of function allele of paqr-1. fld-1 encodes a homolog of the human TLCD1/2 transmembrane proteins. The FLD-1 protein is localized on plasma membranes and mutations in the fld-1 gene help to suppress the phenotypes of paqr-2 mutant worms, including its characteristic membrane fluidity defects. The wild-type C. elegans FLD-1 and human TLCD1/2 proteins do not regulate the synthesis of long-chain polyunsaturated fatty acids but rather limit their incorporation into phospholipids. C. elegans acs-13 encodes a homolog of the human acyl-CoA synthetase ACSL1. The ACS-13 protein is localized to mitochondrial membranes where it likely activates and channels long chain fatty acids for import. In human cells, ACSL1 activity potentiates lipotoxicity by the saturated fatty acid palmitate (16:0) because it depletes the cells of membrane-fluidizing unsaturated fatty acids. Echoing our findings in C. elegans, knockdown of ASCL1 in human cells using siRNA also protects against the membrane-rigidifying effects of palmitate and acts as a suppressor of AdipoR2 knockdown. A novel gain-of-function allele of PAQR-1, a paralog of PAQR-2, takes over the role of PAQR-2 for downstream effectors. Through genetic interaction studies and domain swapping experiments we showed that the transmembrane domains of PAQR-2 are responsible for its functional requirement for IGLR-2. Conversely, PAQR-1 itself does not require IGLR-2 for its function. The less conserved N-terminal cytoplasmic domains of PAQR-1 and PAQR-2 likely regulate the activity of these proteins, speculatively via a “ball and chain” mechanism similar to that found in certain voltage-gated channels. We conclude that inhibition of membrane fluidity regulators, such as fld-1 or acs-13, or a gain-of-function allele of paqr-1 can suppress paqr-2 mutant phenotypes through different mechanisms, which suggests that paqr-2 regulates membrane fluidity in more than one way. Despite acting differently, the effects of these three mutations converge into lowering SFA levels while increasing the PUFA levels within phospholipids, and show that membrane homeostasis is likely essential for our ability to tolerate dietary saturated fats

The Nup155-mediated organisation of inner nuclear membrane proteins is independent of Nup155 anchoring to the metazoan nuclear pore complex

The nuclear envelope (NE), an important barrier between the nucleus and the cytoplasm, is composed of three structures: the outer nuclear membrane, which is continuous with the ER, the inner nuclear membrane (INM), which interfaces with chromatin, and nuclear pore complexes (NPCs), which are essential for the exchange of macromolecules between the two compartments. The NPC protein Nup155 has an evolutionarily conserved role in the metazoan NE formation; but the in vivo analysis of Nup155 has been severely hampered by the essential function of this protein in cell viability. Here, we take advantage of the hypomorphicity of RNAi systems and use a combination of protein binding and rescue assays to map the interaction sites of two neighbouring NPC proteins Nup93 and Nup53 on Nup155, and to define the requirements of these interactions in INM protein organization. We show that different parts of Drosophila Nup155 have distinct functions: the Nup155 beta-propeller anchors the protein to the NPC, whereas the alpha-solenoid part of Nup155 is essential for the correct localisation of INM proteins lamin-B receptor (LBR) and otefin. Using chromatin extracts from semisynchronized cells, we also provide evidence that the Nup155 alpha-solenoid has a chromatin-binding activity that is stronger at the end of mitosis. Our results argue that the role of Nup155 in INM protein localisation is not mediated through the NPC anchoring activity of the protein and suggest that regions other than Nup155 beta-propeller are necessary for the targeting of proteins to the INM

Leveraging a gain-of-function allele of Caenorhabditis elegans paqr-1 to elucidate membrane homeostasis by PAQR proteins.

The C. elegans proteins PAQR-2 (a homolog of the human seven-transmembrane domain AdipoR1 and AdipoR2 proteins) and IGLR-2 (a homolog of the mammalian LRIG proteins characterized by a single transmembrane domain and the presence of immunoglobulin domains and leucine-rich repeats in their extracellular portion) form a complex that protects against plasma membrane rigidification by promoting the expression of fatty acid desaturases and the incorporation of polyunsaturated fatty acids into phospholipids, hence increasing membrane fluidity. In the present study, we leveraged a novel gain-of-function allele of PAQR-1, a PAQR-2 paralog, to carry out structure-function studies. We found that the transmembrane domains of PAQR-2 are responsible for its functional requirement for IGLR-2, that PAQR-1 does not require IGLR-2 but acts via the same pathway as PAQR-2, and that the divergent N-terminal cytoplasmic domains of the PAQR-1 and PAQR-2 proteins serve a regulatory function and may regulate access to the catalytic site of these proteins. We also show that overexpression of human AdipoR1 or AdipoR2 alone is sufficient to confer increased palmitic acid resistance in HEK293 cells, and thus act in a manner analogous to the PAQR-1 gain-of-function allele

National Trends of Endoscopic Retrograde Cholangiopancreatography Utilization and Outcomes in Decompensated Cirrhosis

BACKGROUND: Endoscopic retrograde cholangiopancreatography (ERCP) can be challenging in patients with decompensated cirrhosis (DC) due to increased risk of adverse events related to liver dysfunction. Limited data exist regarding its national utilization in patients with DC. We aim to determine the trends in utilization and outcomes of ERCP among patients with DC in US hospitalizations. METHODS: We identified hospitalizations undergoing ERCP (diagnostic and therapeutic) between 2000 and 2013 from the National Inpatient Sample (NIS) database and used validated ICD9-CM codes to identify DC hospitalizations. We utilized Cochrane-Armitage test to identify changes in trends and multivariable survey regression modeling for adjusted odds ratios (aOR) for adverse outcomes and mortality predictors. RESULTS: There were 43782 cases of ERCPs performed in DC patients during the study period. Absolute number of ERCPs performed in this population from 2000 to 2013 showed an upward trend; however, the proportion of DC patients undergoing ERCP remained stable. We noted significant decrease in utilization of diagnostic ERCP and an increase of therapeutic ERCPs (P \u3c 0.01). There was a significant decrease in the mean length of stay for DC patients undergoing ERCP from 8.2 days in 2000 to 7.2 days in 2013 (P \u3c 0.01) with an increase in the mean cost of hospitalization from $17053 to$19825 (P \u3c 0.001). Mortality rates showed a downward trend from 2000 to 2013 from 13.6 to 9.6% (P \u3c 0.01). Increasing age, Hispanic race, diagnosis of hypertension and diabetes mellitus, and private insurance were related to adverse discharges(P \u3c 0.01). Increasing age, presence of hepatic encephalopathy, and sepsis were associated with higher mortality (P \u3c 0.01). CONCLUSIONS: There is an increasing trend in therapeutic ERCP utilization in DC hospitalizations nationally. There is an overall decrease in mortality in DC hospitalizations undergoing ERCP. This improvement in mortality suggests improvement in both procedural technique and peri-procedural care as well as overall decreasing mortality in cirrhosis

MASTL is essential for anaphase entry of proliferating primordial germ cells and establishment of female germ cells in mice

10.1038/celldisc.2016.52Cell Discovery31605

Additional file 2: Table S2. of Association between probiotic and yogurt consumption and kidney disease: insights from NHANES

UAC and eGFR between frequent and infrequent consumers. (DOC 27 kb