Search

Protein phosphatase 6 (PP6) is a member of the PP2A-like subfamily, which plays a critical role in many fundamental cellular processes. We recently reported that PP6 is essential for female fertility. Here, we report that PP6 is involved in meiotic recombination and that germ cell-specific deletion of PP6 by Stra8-Cre causes defective spermatogenesis. The PP6-deficient spermatocytes were arrested at the pachytene stage and defects in DSB repair and crossover formation were observed, indicating that PP6 facilitated meiotic double-stranded breaks (DSB) repair. Further investigations revealed that depletion of PP6 in the germ cells affected chromatin relaxation, which was dependent on MAPK pathway activity, consequently preventing programmed DSB repair factors from being recruited to proper positions on the chromatin. Taken together, our results demonstrate that PP6 has an important role in meiotic recombination and male fertility.

Zygotic chromatin undergoes extensive reprogramming immediately after fertilization. It is generally accepted that maternal factors control this process. However, little is known about the underlying mechanisms. Here we report that maternal RAD9A, a key protein in DNA damage response pathway, is involved in post-zygotic embryo development, via a mouse model with conditional depletion of Rad9a alleles in oocytes of primordial follicles. Post-zygotic losses originate from delayed zygotic chromatin decondensation after depletion of maternal RAD9A. Pronucleus formation and DNA replication of most mutant zygotes are therefore deferred, which subsequently trigger the G2/M checkpoint and arrest development of most mutant zygotes. Delayed zygotic chromatin decondensation could also lead to increased reabsorption of post-implantation mutant embryos. In addition, our data indicate that delayed zygotic chromatin decondensation may be attributed to deferred epigenetic modification of histone in paternal chromatin after fertilization, as fertilization and resumption of secondary meiosis in mutant oocytes were both normal. More interestingly, most mutant oocytes could not support development beyond one-cell stage after parthenogenetic activation. Therefore, RAD9A may also play an important role in maternal chromatin reprogramming. In summary, our data reveal an important role of RAD9A in zygotic chromatin reprogramming and female fertility.

Hydroxyurea(HU) is a reducing and complexing agent that can be used in the PUREX process. Zr is an important fission product in the spent fuel and main element of concern in the nuclear fuel reprocessing. The decontamination of zirconium in the route of plutonium and uranium can be lowered by the complexation of hydroxyurea in the PUREX process. The complexation of Zr(Ⅳ) with hydroxyurea in the nitric acid system was investigated in this work. Under the condition of 0.3 mol/L HNO3, the complex ratio of Zr(Ⅳ) with HU is 1∶8 obtained by Job’s method. Combining with the half-integer method, the apparent stability constants of Zr(Ⅳ) with hydroxyurea are calculated as following: lg K1≈1.59, lg K2≈1.75, lg K3≈1.88, lg K4≈1.98, lg K5≈2.09, lg K6≈2.27, lg K7≈2.51, lg K8≈3.01. Under 1.0 mol/L HNO3, the complex ratio of Zr(Ⅳ) with hydroxyurea is 1∶4, and the apparent stability constants of Zr(Ⅳ) with hydroxyurea are lg K1≈2.33, lg K2≈2.51, lg K3≈2.78, lg K4≈3.31. Under 3.0 mol/L HNO3, the complex ratio of Zr(Ⅳ) with hydroxyurea is 1∶2, and the apparent stability constants of Zr(Ⅳ) with hydroxyurea are lg K1≈2.69 and lg K2≈2.79.

In this paper, the half-reaction time of the reaction between hydrazine and its derivatives with nitrous acid is measured using spectrophotometry and stopped-flow injection device. Using Gaussian09 and HyperChem, hydrazine and its derivatives have been structurally optimized and some quantization parameters are calculated. Combining the half-reaction time and the quantization parameters, and using statistical regression analysis, QSAR model of the reaction between hydrazine and its derivatives with nitrous acid is established. The results show that total energy of molecules is the most important influencing factor in the reaction, and the half-reaction time increases with total energy of the molecule except for allyl hydrazine, the reaction rate decreases with the increase of total energy of the molecule.

Study questionThere is an unexplored physiological role of N-WASP (neural Wiskott-Aldrich syndrome protein) in oocyte maturation that prevents completion of second meiosis.Summary answerIn mice, N-WASP deletion did not affect oocyte polarity and asymmetric meiotic division in first meiosis, but did impair midbody formation and second meiosis completion.What is known alreadyN-WASP regulates actin dynamics and participates in various cell activities through the RHO-GTPase-Arp2/3 (actin-related protein 2/3 complex) pathway, and specifically the Cdc42 (cell division cycle 42)-N-WASP-Arp2/3 pathway. Differences in the functions of Cdc42 have been obtained from in vitro compared to in vivo studies.Study design, samples/materials, methodsBy conditional knockout of N-WASP in mouse oocytes, we analyzed its in vivo functions by employing a variety of different methods including oocyte culture, immunofluorescent staining and live oocyte imaging. Each experiment was repeated at least three times, and data were analyzed by paired-samples t-test.Main results and the role of chanceOocyte-specific deletion of N-WASP did not affect the process of oocyte maturation including spindle formation, spindle migration, polarity establishment and maintenance, and homologous chromosome or sister chromatid segregation, but caused failure of cytokinesis completion during second meiosis (P

The Mississippi Embayment (ME) is one of the fastest groundwater depletion zones in the world. This study investigated stream‐aquifer water exchange in the ME over a 115‐year period (1900 to 2014) under normal and extreme climates (i.e., precipitation increased and decreased by 20%) with and without agricultural pumping for crop irrigation. The average daily water flow from the aquifer to the streams was always greater than vice versa under all climate scenarios. Under normal climate, the average daily water flow from the aquifer to the streams was 2.52 times larger without pumping than with pumping. While the extreme climate had discernable impacts, the groundwater pumping, but not extreme climate, was the major factor for low flows and drying streams in the ME. These findings are essential to groundwater resource management in the region and provide a critical reference for other parts of the world with similar conditions. [ABSTRACT FROM AUTHOR]