Mouse round spermatids developed in vitro from preexisting spermatocytes can produce normal offspring by nuclear injection into in vivo-developed mature oocytes

It has been shown that mature oocytes injected with nuclei from round spermatids collected from mouse testis can generate normal offspring and that round spermatids can develop in vitro. An undetermined issue is whether spermatids developed in vitro are capable of generating fertile offspring by nuclear injection into oocytes. Herein, we report the production of normal and fertile offspring by nuclear injection using haploid spermatid donors derived from mouse primary spermatocyte precursors cocultured with Sertoli cells. Cocultured spermatogonia and spermatocytes were characterized by their nuclear immunoreactive patterns determined by an antibody to phosphorylated histone H2AX (gamma-H2AX), a marker for DNA double-strand breaks. Cocultured round spermatid progenies display more than one motile flagellum, whose axonemes were recognized by antitubulin immunostaining. Flagellar wavelike movement and flagellar-driven propulsion of round spermatids developed in vitro were documented by videomicroscopy (http://www.sci.ccny.cuny.edu/ approximately kier). We also show that breeding of male and female mouse offspring generated by spermatid nuclear injection produced fertile offspring. In addition to their capacity to produce fertile offspring, cocultured, flagellated round spermatids can facilitate the analysis of the mechanisms of centriolar polarity, duplication, assembly, and flagellar growth, including the intraflagellar transport of cargo proteins.     

Synthesis of lipid A type carboxymethyl derivatives with ether chains instead of ester chains and their LPS-antagonistic activities

Synthesis of lipid A type carboxymethyl derivatives having ether chains at both the C-3 and C-3' positions and their LPS-antagonistic activities toward human U937 cells are described.     

Fibroblast growth factor (FGF)-4 can induce proliferation of cardiac cushion mesenchymal cells during early valve leaflet formation

While much has been learned about how endothelial cells transform to mesenchyme during cardiac cushion formation, there remain fundamental questions about the developmental fate of cushions. In the present work, we focus on the growth and development of cushion mesenchyme. We hypothesize that proliferative expansion and distal elongation of cushion mesenchyme mediated by growth factors are the basis of early valve leaflet formation. As a first step to test this hypothesis, we have localized fibroblast growth factor (FGF)-4 protein in cushion mesenchymal cells at the onset of prevalve leaflet formation in chick embryos (Hamburger and Hamilton stage 20-25). Ligand distribution was correlated with FGF receptor (FGFR) expression. In situ hybridization data indicated that FGFR3 mRNA was confined to the endocardial rim of the atrioventricular (AV) cushion pads, whereas FGFR2 was expressed exclusively in cushion mesenchymal cells. FGFR1 expression was detected in both endocardium and cushion mesenchyme as well as in myocardium. To determine whether the FGF pathways play regulatory roles in cushion mesenchymal cell proliferation and elongation into prevalvular structure, FGF-4 protein was added to the cushion mesenchymal cells explanted from stage 24-25 chick embryos. A significant increase in proliferative ability was strongly suggested in FGF-4-treated mesenchymal cells as judged by the incorporation of 5'-bromodeoxyuridine (BrdU). To determine whether cushion cells responded similarly in vivo, a replication-defective retrovirus encoding FGF-4 with the reporter, bacterial beta-galactosidase was microinjected into stage 18 chick cardiac cushion mesenchyme along the inner curvature where AV and outflow cushions converge. As compared with vector controls, overexpression of FGF-4 clearly induced expansion of cushion mesenchyme toward the lumen. To further test the proliferative effect of FGF-4 in cardiac cushion expansion in vivo (ovo), FGF-4 protein was microinjected into stage 18 chick inner curvature. An assay for BrdU incorporation indicated a significant increase in proliferative ability in FGF-4 microinjected cardiac cushion mesenchyme as compared with BSA-microinjected controls. Together, these results suggest a role of FGF-4 for cardiac valve leaflet formation through proliferative expansion of cushion mesenchyme.     

Cloning and characterization of a novel RING-B-box-coiled-coil protein with apoptotic function

We have identified a novel RING-B-box-coiled-coil (RBCC) protein (MAIR for macrophage-derived apoptosis-inducing RBCC protein) that consists of an N-terminal RING finger, followed by a B-box zinc finger, a coiled-coil domain, and a B30.2 domain. MAIR mRNA was expressed widely in mouse tissues and was induced by macrophage colony-stimulating factor in murine peritoneal and bone marrow macrophages. MAIR protein initially showed a granular distribution predominantly in the cytoplasm. The addition of zinc to transfectants containing MAIR cDNA as part of a heavy metal-inducible vector caused apoptosis of the cells characterized by cell fragmentation; a reduction in mitochondrial membrane potential; activation of caspase-7, -8, and -9, but not caspase-3; and DNA degradation. We also found that the RING finger and coiled-coil domains were required for MAIR activity by analysis with deletion mutants.     

Whole chloroplast genome comparison of rice,maize, and wheat: implications for chloroplast gene diversification and phylogeny of cereals

The fully sequenced chloroplast genomes of maize (subfamily Panicoideae), rice (subfamily Bambusoideae), and wheat (subfamily Pooideae) provide the unique opportunity to investigate the evolution of chloroplast genes and genomes in the grass family (Poaceae) by whole-genome comparison. Analyses of nucleotide sequence variations in 106 cereal chloroplast genes with tobacco sequences as the outgroup suggested that (1) most of the genic regions of the chloroplast genomes of maize, rice, and wheat have evolved at similar rates; (2) RNA genes have highly conservative evolutionary rates relative to the other genes; (3) photosynthetic genes have been under strong purifying selection; (4) between the three cereals, 14 genes which account for about 28% of the genic region have evolved with heterogeneous nucleotide substitution rates; and (5) rice genes tend to have evolved more slowly than the others at loci where rate heterogeneity exists. Although the mechanism that underlies chloroplast gene diversification is complex, our analyses identified variation in nonsynonymous substitution rates as a genetic force that generates heterogeneity, which is evidence of selection in chloroplast gene diversification at the intrafamilial level. Phylogenetic trees constructed with the variable nucleotide sites of the chloroplast genes place maize basal to the rice-wheat clade, revealing a close relationship between the Bambusoideae and Pooideae.     

Involvement of vertebrate polkappa in Rad18-independent postreplication repair of UV damage

DNA damage, which is left unrepaired by excision repair pathways, often blocks replication, leading to lesions such as breaks and gaps on the sister chromatids. These lesions may be processed by either homologous recombination (HR) repair or translesion DNA synthesis (TLS). Vertebrate Polkappa belongs to the DNA polymerase Y family, as do most TLS polymerases. However, the role for Polkappa in vertebrate cells is unclear because of the lack of reverse genetic studies. Here, we generated cells deficient in Polkappa (polkappa cells) from the chicken B lymphocyte line DT40. Although purified Polkappa is unable to bypass ultraviolet (UV) damage, polkappa cells exhibited increased UV sensitivity, and the phenotype was suppressed by expression of human and chicken Polkappa, suggesting that Polkappa is involved in TLS of UV photoproduct. Defects in both Polkappa and Rad18, which regulates TLS in yeast, in DT40 showed an additive effect on UV sensitivity. Interestingly, the level of sister chromatid exchange, which reflects HR-mediated repair, was elevated in normally cycling polkappa cells. This implies functional redundancy between HR and Polkappa in maintaining chromosomal DNA. In conclusion, vertebrate Polkappa is involved in Rad18-independent TLS of UV damage and plays a role in maintaining genomic stability.     

Effect of taurine on cholesterol metabolism in hamsters: up-regulation of low density lipoprotein (LDL) receptor by taurine

The effects of taurine on hepatic cholesterol metabolism were investigated in hamsters fed a high-fat diet or normal chow. Two weeks-treatment of taurine at 1% in drinking water prevented high-fat diet-induced increase in cholesterol levels of serum and liver. The decrease in serum cholesterol by taurine was due to decrease in non-HDL cholesterols. A similar tendency was noted in serum and liver cholesterol levels of hamsters fed a normal diet. In hamsters fed a high-fat diet, taurine prevented elevation in hepatic activity of acyl-CoA:cholesterol acyltransferase (ACAT) and increased the activity of cholesterol 7alpha-hydroxylase. Taurine also increased cholesterol 7alpha-hydroxylase activity in hamsters fed normal chow. Studies on liver membranes revealed that taurine increased 125I-labeled LDL binding by 52% and 58% in hamsters fed either a normal chow or high-fat diet, respectively. Furthermore, LDL kinetic analysis showed that taurine intake resulted in significant faster plasma LDL fractional catabolic rates (FCR). These results suggest that taurine elevates hepatic LDL receptor and thereby decreases serum cholesterol levels, an event which may be the result of hepatic cholesterol depletion as a consequence of increased bile acid synthesis via enhancement of cholesterol 7alpha-hydroxylase activity. Thus, up-regulation of the LDL receptor and subsequent increase in receptor- mediated LDL turnover may be a key event in the cholesterol-lowering effects of taurine in hamsters.     

The phosphatidylinositol 3-kinase (PI3K)-Akt pathway suppresses Bax translocation to mitochondria

Bax, a proapoptotic member of the Bcl-2 family, localizes largely in the cytoplasm but redistributes to mitochondria in response to apoptotic stimuli, where it induces cytochrome c release. In this study, we show that the phosphatidylinositol 3-OH kinase (PI3K)-Akt pathway plays an important role in the regulation of Bax subcellular localization. We found that LY294002, a PI3K inhibitor, blocked the effects of serum to prevent Bax translocation to mitochondria and that expression of an active form of PI3K suppressed staurosporine-induced Bax translocation, suggesting that PI3K activity is essential for retaining Bax in the cytoplasm. In contrast, both U0126, a MEK inhibitor, and active MEK had little effect on Bax localization. In respect to downstream effectors of PI3K, we found that expression of active Akt, but not serum and glucocorticoid-induced protein kinase (SGK), suppressed staurosporine-induced translocation of Bax, whereas dominant negative Akt moderately promoted Bax translocation. Expression of Akt did not alter the levels of Bax, Bcl-2, Bcl-X(L), or phosphorylated JNK under the conditions used, suggesting that there were alternative mechanisms for Akt in the suppression of Bax translocation. Collectively, these results suggest that the PI3K-Akt pathway inhibits Bax translocation from cytoplasm to mitochondria and have revealed a novel mechanism by which the PI3K-Akt pathway promotes survival.