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The transition from spermatogonia to spermatocytes and the initiation of meiosis are key steps in spermatogenesis and are precisely regulated by a plethora of proteins. However, the underlying molecular mechanism remains largely unknown. Here, we report that Src homology domain tyrosine phosphatase 2 (Shp2; encoded by the protein tyrosine phosphatase, nonreceptor type 11 [Ptpn11] gene) is abundant in spermatogonia but markedly decreases in meiotic spermatocytes. Conditional knockout of Shp2 in spermatogonia in mice using stimulated by retinoic acid gene 8 (Stra8)-cre enhanced spermatogonial differentiation and disturbed the meiotic process. Depletion of Shp2 in spermatogonia caused many meiotic spermatocytes to die; moreover, the surviving spermatocytes reached the leptotene stage early at postnatal day 9 (PN9) and the pachytene stage at PN11-13. In preleptotene spermatocytes, Shp2 deletion disrupted the expression of meiotic genes, such as disrupted meiotic cDNA 1 (Dmc1), DNA repair recombinase rad51 (Rad51), and structural maintenance of chromosome 3 (Smc3), and these deficiencies interrupted spermatocyte meiosis. In GC-1 cells cultured in vitro, Shp2 knockdown suppressed the retinoic acid (RA)-induced phosphorylation of extracellular-regulated protein kinase (Erk) and protein kinase B (Akt/PKB) and the expression of target genes such as synaptonemal complex protein 3 (Sycp3) and Dmc1. Together, these data suggest that Shp2 plays a crucial role in spermatogenesis by governing the transition from spermatogonia to spermatocytes and by mediating meiotic progression through regulating gene transcription, thus providing a potential treatment target for male infertility.

Triple-negative breast cancer (TNBC) is a heterogeneous disease with a poor prognosis due to the lack of an effective targeted therapy. Histone lysine methyltransferases (KMTs) have emerged as attractive drug targets for cancer therapy. However, the function of the majority of KMTs in TNBC has remained largely unknown. In the current study, we found that KMT nuclear receptor binding SET domain protein 2 (NSD2) is overexpressed in TNBC tumors and that its overexpression is associated with poor survival of TNBC patients. NSD2 regulates TNBC cell survival and invasion and is required for tumorigenesis and tumor growth. Mechanistically, NSD2 directly controls the expression of EGFR and ADAM9, a member of the ADAM (a disintegrin and metalloproteinase) family that mediates the release of growth factors, such as HB-EGF. Through its methylase activity, NSD2 overexpression stimulates EGFR-AKT signaling and promotes TNBC cell resistance to the EGFR inhibitor gefitinib. Together, our results identify NSD2 as a major epigenetic regulator in TNBC and provide a rationale for targeting NSD2 alone or in combination with EGFR inhibitors as a targeted therapy for TNBC.

The friction process of the WC–Co cemented carbides in the different conditions was investigated by molecular dynamics simulation in this work. The effects of grain size, friction load, and sliding velocity on the friction and wear behavior of the cemented carbides were analyzed. The friction and wear microscopic mechanism of the cemented carbides in the atomic scale was revealed. The results show that, with the increase of grain size, the dislocation slip in the Co and WC phases gradually plays more important role in the friction-induced plastic deformation mechanism rather than the grain rotation. The increase of friction load may lead to the deformable Co bonding phase being extruded from the surface and removed first. Nonetheless, the extrusion-wear mechanism of the Co phase can be suppressed by reducing the WC grain size, and the sliding wear resistance of the cemented carbides can be improved. Besides, the increase of sliding rate may reduce the wear rate. The main reason is that, in the process of high-speed sliding, the nucleation and expansion of dislocation in each phase of the subsurface layer lacks the continuous driving stress, and the dislocation density is low. Therefore, WC is difficult to fracture, and the wear degree caused by Co phase being extruded from the surface is significantly reduced.

C10H14O6, triclinic, P1‾ $P\overline{1}$ (no. 2), a = 7.5531(2) Å, b = 9.3964(3) Å, c = 9.5089(3) Å, α = 61.8330(10)°, β = 68.6230(10)°, γ = 86.5750(10)°, V = 548.80(3) Å3, Z = 2, R gt(F) = 0.0485, wRref (F 2) = 0.1438, T = 170.0 K.

Objective To study the neuroprotective effect of levetiracetam (LEV) with hypoxia ischemia brain-damage (HIBD) model of neonatal rats. Methods The rats were randomly divided into three groups: model group, LEV low, medium and high concentration groups [gavage with 10, 30, 50 mg/(kg·d) LEV], with 10 rats in each, and another 10 rats in sham operation group. Twenty four hours after the last administration, HE staining was used to observe the pathological changes of rat brain, TUNEL method was used to detect the apoptosis of neurons, the expression of inflammatory factors interleukin-6 (IL-6), tumor necrosis factor α(TNF-α), and oxidative stress factors malondialdehyde(MDA), the content and activity of superoxide dismutas (SOD) in serum were detected by ELISA, and the protein expression of caspase-3, B-cell lymphoma-2(Bcl-2), nuclear factor erythroid 2-related factor 2(Nrf2), heme oxygenase(HO-1) in rat brain tissue were detected by Western blot. Results Compared with the sham operation group, the morphology of brain tissue cell in the model group were disordered, showed diffuse distribution, increased vacuolation and inflammatory infiltration, the apoptosis rate of neurons, the expression of IL-6, TNF-α, MDA in serum and caspase-3 in brain tissue were significantly higher(P＜0.05), and the expression of SOD in serum, Bcl-2, Nrf2 and HO-1 in brain tissue were significantly lower(P＜0.05); Compared with the model group, the above changes of LEV in low, medium and high concentration groups were significantly reduced(P＜0.05). Conclusions LEV can alleviate inflammatory reaction and oxidative stress, and play a neuroprotective role in HIBD newborn rats.