MORN2 regulates the morphology and energy metabolism of mitochondria and is required for male fertility in mice.

BACKGROUND: Mitochondria produce adenosine triphosphate through respiratory activities to power sperm differentiation and motility, and decreased mitochondrial respiratory activity can result in poor sperm motility and asthenospermia. The mitochondrial sheath is a component of the mid-piece of the sperm flagellum, and dysfunction of the sheath can reduce sperm motility and cause male infertility. The membrane occupation and recognition nexus-motif protein 2 (MORN2) is testis enriched in mice, and the MORN motif was reported to play a role in the regulation of bioelectrical signal homeostasis in cardiomyocytes. METHODS: We generated Morn2-/- mice using CRISPR/Cas9 and evaluated the potential functions of MORN2 in spermiogenesis through histological analysis, fertility examination, RT-PCR, CASA, immunofluorescence, TUNEL, electron microscopy analysis, mitochondrial energy metabolism analysis, etc. RESULTS: The Morn2-/- mice were infertile, and their sperm showed severe motility defects. Morn2-/- sperm also had abnormal morphology characterized by bent heads, aberrant mitochondrial sheath formation, lower mitochondrial membrane potential, higher levels of reactive oxygen species, and decreased mitochondrial respiratory activity. CONCLUSIONS: Our study demonstrates that MORN2 is essential for male fertility and indicates that MORN2 functions in mitochondrial sheath formation and regulates mitochondrial respiratory activity.

2-bromoacetamide exposure impairs oocyte maturation in mice and humans primarily via disrupting the cytoskeleton.

2-bromoacetamide (BAcAm) is an emerging class of unregulated disinfection by-products (DBPs), with potent cytogenetic and developmental toxicity in animals. However, whether BAcAm exerts toxic effects on mammalian oocyte quality remains to be elucidate. In this research, we investigated the effect of BAcAm on mouse and human oocyte maturation with an in vitro culture system. Our results revealed that BAcAm exposure hindered the extrusion of the first polar body, disrupted the spindle organization and reduced the competence of embryo development after fertilization in the mouse oocytes. Results of single-cell RNA sequencing (scRNA-seq) showed that 605 differentially expressed genes (DEGs) were identified in the BAcAm exposed mouse oocytes, among which 366 were up-regulated and 239 were down-regulated. Gene Ontology (GO) analysis further revealed that DEGs were mainly enriched in mitochondrial functions, oxidative stress, cytoskeleton, endoplasmic reticulum (ER), Golgi and protein synthesis, DNA damage and apoptosis. We then conducted further tests in these aspects and discovered that BAcAm exposure principally perturbed the function of microtubule and actin cytoskeleton. This finding was confirmed in human oocytes. Overall, our data suggest that BAcAm exposure disturbs the cytoskeleton function, thus impairing oocyte maturation. These data, for the first time, provide a comprehensive view for the toxic effects of BAcAm on oocyte maturation.

A neglected contributor of thermal hydrolysis to sludge anaerobic digestion: Fulvic acids release and their influences.

Fulvic acids (FAs) belong to inert organic matters in sewage sludge and their influences are often overlooked during convectional anaerobic digestion (AD). Currently, thermal hydrolysis (TH) has been widely applied on sludge pretreatment before AD processes, which makes FAs undergo drastic evolutions and aggressive to sludge AD. Results in the present study indicated that FAs concentration in the liquid was elevated by over incredible 150 folds during sludge TH, from 3.4 mg/L in raw sludge to 590.0 mg/L in hydrolyzed sludge at 180 °C. Moreover, during sludge TH, the chemical structures of FAs, including aromatic condensation degree, elemental composition and functional group, also underwent significant changes, which enhanced FAs electron transfer capability, reduced their biodegradability and promoted their roles on sludge AD. Furthermore, fortunately, the evolutions of FAs were favorable to sludge AD in general. Methane production could be promoted by about 20% under FAs concentration of 0.6 g/L, and the FAs extracted from hydrolyzed sludge presented higher promotion performances than that of the raw FAs, in which 180 °C FAs were particularly conspicuous. Furthermore, FAs evolutions would present differential influences on each phase of sludge AD, promotional to acidogenesis and methanogenesis but inhibitory to hydrolysis. Pearson correlation analysis indicated FAs influences on sludge AD, particularly the hydrolysis phase, were not only related to their concentration, but also chemical structure. The findings of this study demonstrated that FAs influences should not be negligible anymore during sludge AD with TH pretreatment. Meanwhile, since FAs promotion on sludge AD was closely related to their concentration and chemical structure, it would be significant to take FAs evolutions as auxiliary indexes for the regulations of sludge TH.

Activated sludge thermal hydrolysis for liquid fermentation to produce VFAs: Exploring the balance of carbon release between quantity, quality and recovery.

Thermal hydrolysis has been widely applied to improve organics bioconversion during sludge anaerobic treatment currently, based on which, liquid fermentation to produce volatile fatty acids (VFAs) with high concentration and good purity has been successfully developed by only using hydrolysate as the substrate to avoid the interference of "useless" residual solids. Therefore, obtaining high-quality hydrolysate is the prerequisite for VFAs production via liquid fermentation. However, previous studies on sludge thermal hydrolysis either only focused on organics release or only on sludge dewatering. Actually, the quantity, quality and recovery of the carbon released from sludge are equally important, and a balance between them should be established. Results in the present study indicated that organics concentration in sludge hydrolysate could not be arbitrarily enhanced by increasing thermal hydrolysis intensity or sludge concentration, and interestingly there seemed a threshold of around 32 g/L that the highest concentration the sludge hydrolysate could reach. Moreover, with the increase of hydrolysis intensity, the bioavailability of sludge could be promoted but reached the maximum with BOD5/COD of around 0.44 at 180 °C, while sludge dewaterability could be improved but also trended to stable after 160 °C. The findings of this study demonstrate that excessively high hydrolysis intensity would not only waste energy but also induce forms of non-biodegradable organics. The performances of sludge liquid fermentation, including VFAs production and sludge reduce, were closely related to hydrolysis intensity, the choice of which should be based on the balance of the quantity, quality and recovery of the released carbon.