BackgroundDefinitive erythropoiesis is a vital process throughout life. Both its basal activity under physiological conditions and its increased activity under anemia-induced stress conditions are highly stimulated by the hormone erythropoietin. The transcription factor Sox6 was previously shown to enhance fetal erythropoiesis together and beyond erythropoietin signaling, but its importance in adulthood and mechanisms of action remain unknown. We used here Sox6 conditional null mice and molecular assays to address these questions.Methodology/Principal Findings Sox6fl/flErGFPCre adult mice, which lacked Sox6 in erythroid cells, exhibited compensated anemia, erythroid cell developmental defects, and anisocytotic, short-lived red cells under physiological conditions, proving that Sox6 promotes basal erythropoiesis. Tamoxifen treatment of Sox6fl/flCaggCreER mice induced widespread inactivation of Sox6 in a timely controlled manner and resulted in erythroblast defects before reticulocytosis, demonstrating that impaired erythropoiesis is a primary cause rather than consequence of anemia in the absence of Sox6. Twenty five percent of Sox6fl/flErGFPCre mice died 4 or 5 days after induction of acute anemia with phenylhydrazine. The others recovered slowly. They promptly increased their erythropoietin level and amplified their erythroid progenitor pool, but then exhibited severe erythroblast and reticulocyte defects. Sox6 is thus essential in the maturation phase of stress erythropoiesis that follows the erythropoietin-dependent amplification phase. Sox6 inactivation resulted in upregulation of embryonic globin genes, but embryonic globin chains remained scarce and apparently inconsequential. Sox6 inactivation also resulted in downregulation of erythroid terminal markers, including the Bcl2l1 gene for the anti-apoptotic factor Bcl-xL, and in vitro assays indicated that Sox6 directly upregulates Bcl2l1 downstream of and beyond erythropoietin signaling.Conclusions/SignificanceThis study demonstrates that Sox6 is necessary for efficient erythropoiesis in adult mice under both basal and stress conditions. It is primarily involved in enhancing the survival rate and maturation process of erythroid cells and acts at least in part by upregulating Bcl2l1.

To identify Streptococcus pneumoniae genes expressed specifically during infections, a selection system based on the in vivo expression technology (IVET) was established. galU, which is critical for capsular polysaccharide biosynthesis, and lacZY encoding beta-galactosidase were employed as dual reporter genes to screen in-vivo-induced (ivi) genes of S. pneumoniae. The galU-deficient mutant of S. pneumoniae is incapable of utilizing galactose, thus failing to synthesize capsular polysaccharide, and therefore loses its ability to survive in the host. A promoter-trap library was constructed in S. pneumoniae, which was used to infect BALB/c mice in an intranostril model. Those strains recovered from lung tissue of mice and exhibiting a white colony phenotype on tryptic soy agar containing X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) were collected and identificated. A total of 15 unique sequences were obtained through in vivo screening. The ivi genes of S. pneumoniae are involved in many processes, such as colonization and adherence, energy metabolism, nutrient substance transport, transcription regulation, DNA metabolism, and cell wall synthesis. There are some hypothetical proteins whose functions are not clear. This novel IVET is a useful tool for identifying ivi genes in S. pneumoniae.

Previous reports suggest that ClpP proteolytic activity is important not only for cell physiology but also for regulation of virulence properties of Streptococcus pneumoniae (S. pneumoniae). In order to get a more comprehensive picture of the role of ClpP protease on protein expression in S. pneumoniae D39 and how it relates to physiology and virulence, a clpP mutant strain was constructed in S. pneumoniae D39, and global proteome expression was studied by 2-dimensional electrophoresis and matrix-assisted laser desorption-ionization-time of flight mass spectrometry. We report here that clpP deletion affects the expression of proteins which are involved in the general stress response, nucleotide metabolism, energy metabolism, and proteins metabolism. These provide clues for understanding the role of ClpP in the physiology and pathogenesis of pneumococcus.

Streptococcus pneumoniae resides on the mucosal surface of the upper respiratory tract and is ready to spread and trigger clinical diseases. Hence the vaccine that can eliminate the nasopharyngeal colonization was thought to be an ideal protective strategy against pneumococcal invasive diseases. Caseinolytic protease X (ClpX), a pneumococcal caseinolytic protease ATPase subunit, was shown to be a non-transmembrane protein by bioinformatics analysis. Consistent with the in silico prediction, the secretory expression of ClpX, instead of surface exposure, was further confirmed by flow cytometry and Western blot. Furthermore, ClpX was highly conserved in nine different serotypes of S. pneumoniae at both gene and protein concentrations. In addition, the anti-ClpX IgG antibody levels in human serum samples were much higher in healthy children, compared with pediatric patients, and displayed an age-related increase. Finally, ClpX protein antigen was introduced to BALB/c mice through a mucosal route, and protection against nasopharyngeal colonization and lethal infection caused by different S. pneumoniae serotypes was successfully elicited. Our findings suggest that ClpX is a potential candidate antigen that could be incorporated in pneumococcal protein vaccines.

Blood pressure (BP) is a complex trait regulated by the interaction among multiple physiologic regulatory systems, likely involving numerous genes that lead to inconsistent findings in genetic studies. One possibility of failure to replicate some single-locus results is that the underlying genetics of hypertension is based on multiple genes with minor effects. To learn the association between 17 single nucleotide polymorphisms (SNPs) in 13 cardiovascular disease-predisposing genes and blood pressure of Han males, the 17 SNPs genotypes of 375 Han males were detected and analyzed with BaiO gene chip. The relationship between the SNPs and blood pressure was analyzed with variance analysis and multiple linear regression analysis. Variance analysis and/or multiple linear regression showed that: systolic blood pressure (SBP) was increasing with the elevation of year; AGT(235)M, ApoE(112,158)E4, and SerpinA3(rs4934)A were relative to the increase of SBP; AGT(235)M, ET-2(985)G, ApoC3(3206)T, and ApoE(112,158)E4 may have had some relation with diastolic blood pressure (DBP) elevation; and ApoB(Xba) + was associated with the increase of pulse pressure (PP). These findings support the multigenic nature of the etiology of essential hypertension and propose a potential gene-gene interactive model for future studies.