T-type Ca2+ channels in sperm function

Intracellular Ca2+ regulates many fundamental physiological processes in excitable and non-excitable cells. Certainly this is the case of sperm where the local concentration of intracellular Ca2+ ([Ca2+]i) is significantly influenced by Ca2+ permeable channels present in the cell plasma membrane. Amongst these channels, the voltage dependent Ca2+ channels (CaV) of the T-type (CaV3) appear to have an eminent role in the acrosome reaction (AR) of some sperm species, though they may participate in other important functions like motility and capacitation. The AR is an exocytotic event where the acrosome vesicle in the posterior region of the head fuses with the plasma membrane. This reaction allows sperm to fuse and fertilize the egg. Here we summarize our present knowledge regarding CaV3 channels in sperm, show the first direct electrophysiological evidence for their presence in maturing mouse sperm and discuss some of the relevant unanswered questions.     

Neutralization of oxidized phospholipids attenuates age‐associated bone loss in mice

Oxidized phospholipids (OxPLs) are pro‐inflammatory molecules that affect bone remodeling under physiological conditions. Transgenic expression of a single‐chain variable fragment (scFv) of the antigen‐binding domain of E06, an IgM natural antibody that recognizes the phosphocholine (PC) moiety of OxPLs, increases trabecular and cortical bone in adult male and female mice by increasing bone formation. OxPLs increase with age, while natural antibodies decrease. Age‐related bone loss is associated with increased oxidative stress and lipid peroxidation and is characterized by a decline in osteoblast number and bone formation, raising the possibility that increased OxPLs, together with the decline of natural antibodies, contribute to age‐related bone loss. We show here that transgenic expression of E06‐scFv attenuated the age‐associated loss of spinal, femoral, and total bone mineral density in both female and male mice aged up to 22 and 24 months, respectively. E06‐scFv attenuated the age‐associated decline in trabecular bone, but not cortical bone, and this effect was associated with an increase in osteoblasts and a decrease in osteoclasts. Furthermore, RNA‐seq analysis showed that E06‐scFv increased Wnt10b expression in vertebral bone in aged mice, indicating that blocking OxPLs increases Wnt signaling. Unlike age‐related bone loss, E06‐scFv did not attenuate the bone loss caused by estrogen deficiency or unloading in adult mice. These results demonstrate that OxPLs contribute to age‐associated bone loss. Neutralization of OxPLs, therefore, is a promising therapeutic target for senile osteoporosis, as well as atherosclerosis and non‐alcoholic steatohepatitis (NASH), two other conditions shown to be attenuated by E06‐scFv in mice.     

VEGF-induced vascular permeability is mediated by FAK

Endothelial cells (ECs) form cell-cell adhesive junctional structures maintaining vascular integrity. This barrier is dynamically regulated by vascular endothelial growth factor (VEGF) receptor signaling. We created an inducible knockin mouse model to study the contribution of the integrin-associated focal adhesion tyrosine kinase (FAK) signaling on vascular function. Here we show that genetic or pharmacological FAK inhibition in ECs prevents VEGF-stimulated permeability downstream of VEGF receptor or Src tyrosine kinase activation in vivo. VEGF promotes tension-independent FAK activation, rapid FAK localization to cell-cell junctions, binding of the FAK FERM domain to the vascular endothelial cadherin (VE-cadherin) cytoplasmic tail, and direct FAK phosphorylation of β-catenin at tyrosine-142 (Y142) facilitating VE-cadherin-β-catenin dissociation and EC junctional breakdown. Kinase inhibited FAK is in a closed conformation that prevents VE-cadherin association and limits VEGF-stimulated β-catenin Y142 phosphorylation. Our studies establish a role for FAK as an essential signaling switch within ECs regulating adherens junction dynamics.     

Microglial regulation of cholinergic differentiation in the basal forebrain

Because inflammation during pregnancy can lead to neurodevelopmental anomalies, we investigated the role of inflamed microglia on cholinergic precursors in the rat embryonic basal forebrain (BF) cultured on embryonic day 15. Conditioned medium (CM) taken from microglia stimulated variously (microglial CM; MCM) increased activity of choline acetyltransferase (ChAT), the enzyme responsible for acetylcholine biosynthesis and a phenotypic hallmark of the cholinergic neuron. There was a concomitant decline in glutamic acid decarboxylase expression. Of stimulators tested, only β-amyloid failed to produce effective MCM. Infection with a Lac-Z-containing retrovirus revealed that MCM promoted cholinergic differentiation from undifferentiated precursors in the population. Several candidates were tested for their ability to mimic MCM. Mature nerve growth factor (NGF) did not mimic MCM, but acted synergistically with it to promote enormous increases in ChAT activity. However, a microglial cell line produced high-molecular weight forms of NGF (pro-NGF) that were lethal to mature cholinergic neurons. Although bone morphogenetic proteins (BMP) 2, 4, and 9 increased ChAT activity dose-dependently, noggin did not inhibit the effects of the MCM, suggesting that BMPs were not the only active factor(s) in the MCM. Embryonic microglia isolated following maternal inflammation produced a variety of immune system cytokines and chemokines. One of these, interleukin-6 (IL-6), was tested for its ability to promote cholinergic differentiation. Although IL-6 alone did not mimic the action of MCM, neutralization of it inhibited MCM effectiveness. Thus, following maternal inflammation, a complex microglial-derived cocktail of factors can promote excess cholinergic differentiation in the embryonic BF.     

Amazonian biodiversity: assessing conservation priorities with taxonomic data

Data from 3991 records of museum collections representing 421 species of plants, arthropods, amphibians, fish, and primates were analyzed with GIS to identify areas of high species diversity and endemism in Amazonia. Of the 472 1 × 1° grid cells in Amazonia, only nine cells are included in the highest species diversity category (43–67 total species) and nine in the highest endemic species diversity category (4–13 endemic species). Over one quarter of the grid cells have no museum records of any of the organisms in our study. Little correspondence exists between the centers of species diversity identified by our collections-based data and those areas recommended for conservation in an earlier qualitative study of Amazonian biodiversity. Museum collections can play a vital role in identifying species-rich areas for potential conservation in Amazonia, but a concerted and structured effort to increase the number and distribution of collections is needed to take maximum advantage of the information they contain.     

Effects of hyperoxia on biomarkers of oxidative stress in closed-circuit oxygen military divers

Oxygen toxicity is a problem in diving which can have fatal consequences in the water. When divers use closed-circuit oxygen rebreathing apparatus they are taking only oxygen 100% and this hyperoxic exposure increases the generation of reactive oxygen species (ROS) in biological tissues. The objective of the present study is to evaluate the effects of hyperoxia on biomarkers of oxidative stress in closed-circuit oxygen military divers. Fifteen professional divers of Spanish Navy Diving Center participated in a training program which consisted of one-hour immersion at seven metres of depth breathing oxygen 100% with closed-circuit oxygen rebreathing apparatus. The training went on two or three times per week for the first six weeks and once a week for the last six weeks. Serum total antioxidant status (TAS), levels of glutathione peroxidase (GPx), nitrates (NO₃ ^?) and urinary concentrations of 15-isoprostane F_2t were measured. The results show that TAS decreased significantly after 6 weeks (mean 1.38 versus 1.23 mmol/l), with a slight increase at the end (mean 1.31 mmol/l). GPx and F₂-isoprostanes were significantly lower after 6 and 12 weeks and NO₃ ^? was significantly lower after 6 weeks and remained unchanged until the end. In summary, professional divers who use closed-circuit apparatus and therefore breathe oxygen 100%, do not suffer an important oxidative hyperoxia-induced stress, probably due an adaptive process after hyperoxia. The age and good physical form of the subjects studied could probably enhance the adaptive process to hyperoxia.     

Apical membrane potentials and intracellular potassium and sodium activities in the gallbladder of the freshwater turtle Mauremys caspica

Open-tip and liquid ion-exchanger microelectrodes were used to measure transapical membrane potential (Va), fractional voltage ratio (fa) and intracellular sodium and potassium activities (aiNa, aiK) in Mauremys caspica gallbladder under open circuit conditions. The average values (+/- SEM) for Va and fa were -32 +/- 3 and 0.20 +/- 0.03 mV respectively. aiNa and aiK were, respectively, 17 +/- 4 and 82 +/- 7 mM. These results suggest that the mechanisms of Na+ and K+ transport in this tissue are essentially similar to those observed in leaky epithelia in general.     

Mice with endogenous TDP‐43 mutations exhibit gain of splicing function and characteristics of amyotrophic lateral sclerosis

TDP‐43 (encoded by the gene TARDBP) is an RNA binding protein central to the pathogenesis of amyotrophic lateral sclerosis (ALS). However, how TARDBP mutations trigger pathogenesis remains unknown. Here, we use novel mouse mutants carrying point mutations in endogenous Tardbp to dissect TDP‐43 function at physiological levels both in vitro and in vivo. Interestingly, we find that mutations within the C‐terminal domain of TDP‐43 lead to a gain of splicing function. Using two different strains, we are able to separate TDP‐43 loss‐ and gain‐of‐function effects. TDP‐43 gain‐of‐function effects in these mice reveal a novel category of splicing events controlled by TDP‐43, referred to as “skiptic” exons, in which skipping of constitutive exons causes changes in gene expression. In vivo, this gain‐of‐function mutation in endogenous Tardbp causes an adult‐onset neuromuscular phenotype accompanied by motor neuron loss and neurodegenerative changes. Furthermore, we have validated the splicing gain‐of‐function and skiptic exons in ALS patient‐derived cells. Our findings provide a novel pathogenic mechanism and highlight how TDP‐43 gain of function and loss of function affect RNA processing differently, suggesting they may act at different disease stages.