Effect of all-trans-retinoic acid on the expression of primordial germ cell differentiation-associated genes in mESC-derived EBs.

atRA (all-trans-retinoic acid) is known to induce the differentiation of mESCs (mouse embryonic stem cells) into PGCs (primordial germ cells) in vitro. However, it is not clear as to what changes occur in PGC differentiation-associated genes or what mechanisms are involved when EBs (embryoid bodies) derived from mESCs are induced by atRA. EBs derived from mESCs were treated with 1, 2 or 5 µM atRA for 16 h, 2 days or 5 days. Real-time PCR and Western blot analysis were performed to detect the relative levels of PGC differentiation-associated genes (Lin28, Blimp1, Stra8 and Mvh) and the corresponding proteins respectively. Immunofluorescence was used to detect the protein location and distribution in EBs. The expression characteristics of genes could be divided into three categories: rapidly reached the peak value in 16 h and then decreased (Stra8, Lin28), initially low and then increased to reach the peak value in 5 days (Mvh) and relatively unchanged (Blimp1). A low level of Lin28 was expressed in EBs treated with atRA for 2 days or 5 days. The variation in the level of Lin28 mRNA did not influence the change in the level of Blimp1 mRNA. The changes in Stra8/Lin28 were consistent with the corresponding changes in the levels of their respective mRNAs, but the changes for Mvh/Blimp1 were not consistent with the corresponding changes in the levels of their respective mRNAs. Blimp1 expression may be independent of the effect of atRA on PGC differentiation. atRA may promote the start of a period in which there is a low level of Lin28 expression during PGC differentiation.

[Mouse-induced pluripotent stem cells have the potential to differentiate into induced primordial germ cells].

OBJECTIVE: To investigate whether mouse-induced pluripotent stem (iPS) cell line IP14D-1 has the potential to differentiate into induced primordial germ cells (iPGCs), and to explore the changes in the expression of iPGCs-differentiation associated genes and their possible mechanisms. METHODS: Undifferentiated IP14D-1 was cultured to proliferate and then differentiated to form 4-, 7- and 9-day-old induced embryoid bodies (iEBs) in vitro, respectively. RT-PCR and immunofluorescence were used to detect the expressions of Lin28, Blimpl, Stra8 and Mvh, as well as the localization of the corresponding protein in iEBs. RESULTS: The expression of Blimpl was higher than that of Lin28 in the undifferentiated IP14D-1 and mouse embryonic stem cells (mESCs). Mvh and Stra8 as well as mESCs and EBs were also expressed in IP14D-1 and iEBs, but with no significant differences. The expression of Lin28 was gradually increased in the IP14D-1-derived iEBs from 4 to 7 days, but decreased at 9 days, and the expression of Blimp1 was gradually reduced with the prolonged growing time of iEBs. CONCLUSION: A stable system was established for the culture and differentiation of IP14D-1 and IP14D-1-derived iEBs. The expressions of Lin28, Blimp1, Mvh and Stra8 were not significantly different between the undifferentiated IP14D-1 and mESCs, nor were the expressions of Mvh and Stra8 between iEBs and EBs. IP14D-1 and iEBs had the potential to differentiate into iPGCs, which increased in number in the 7-day-old iEBs, and the expression of iPGC-differentiation associated Lin28 became lower in the older iEBs.

[Extracellular matrix regulates expressions of germ cell differentiation associated genes in mouse embryonic stem cells].

OBJECTIVE: Interactions of cells with the extracellular matrix (ECM) are essential for cell differentiation. The authors sought to determine the roles of different ECMs in the expressions of germ cell differentiation associated genes after mouse embryonic stem cells (mESCs) differentiated into embryoid bodies (EBs). METHODS: EBs derived from mESCs were maintained in suspension for 3 days and then cultured on the plates coated with various ECMs, including fibronectin (F), laminin (L), matrigel (M), collagen (C) and nonadhensive agarose (A), respectively, for 1, 2, 3 or 4 days, followed by evaluation of the expressions of the genes associated with germ cell differentiation by RT-PCR. RESULTS: The EBs of the F and L groups exhibited facilitated adherent differentiation. The expressions of the Blimp-1, Stella, Mvh and Stra8 genes were increased gradually in the F and L but not obviously in the M and C groups. The overall gene expressions were low in the A group, but high and then gradually decreased in the blank control group. Endogenous fibronectin, laminin and integrin beta1 were obviously expressed in the L and control groups. CONCLUSION: Laminin /integrin beta1 signaling may play a role in regulating the differentiation of mESCs into primordial germ cells (PGCs). Exogenous laminin can facilitate the differentiation of mESC-derived EBs into PGCs by acting on the integrin beta1 subunit, while exogenous fibronectin may be involved in the regulation of the differentiation through other integrin subunit. Endogenous laminin and fibronectin secreted by EBs may also facilitate cell differentiation in the absence of exogenous ECMs.

[Analysis of human metapneumovirus genotype in Hunan, China and its attachment protein G sequence character].

OBJECTIVE: To understand the genotypes of human metapneumovirus (hMPV) and the genetic character of hMPV attachment protein G sequence in Hunan, China. METHODS: 232 nasopharyngeal aspirates (NPA) samples from hospitalized children with acute respiratory infections were collected from Hunan, China in 2005. HMPV was detected. The full length of G glycoprotein genes were amplified and sequenced. Bioinformatics soft-wares were employed to analyze the sequences. RESULTS: 17/232 (7.3%) were showed hMPV positive. And co-infection rate with other viruses is 35%. The diagnoses of these hMPV positive cases are pneumonia, bronchiolitis and bronchopneumonia. Phylogenetic analysis for G genes from 13 hMPVs revealed the existence of four major subgroups: A1, A2, B1, B2 in Hunan, China in 2005. There are four types of sequence lengths of hMPV G glycoprotein, which are 711, 675, 660, 696nt. It is different in potential N-linked glycosylation sites and number of cysteine residues among these hMPVs of Hunan, China and Beijing, China. Also it is different from those in Japan and North America. CONCLUSION: The investigation of hMPV from Hunan, China in 2005 revealed the high speed of genetic variation and the marked character of geographic epidemic differences.

Phospholipase A2-like activity of human bocavirus VP1 unique region.

Human bocavirus (HBoV) is a new parvovirus first discovered in 2005, which is associated with acute respiratory infection. Analysis of sequence homology has revealed that a putative phospholipase A2 (PLA2) motif exists in the VP1 unique region of HBoV. However, little is known about whether the VP1 unique region of HBoV has PLA2 enzymatic activity and how these critical residues contribute to its PLA2 activity. To address these issues, the VP1 unique region protein and four of its mutants, were expressed in Eschericha coli. The purified VP1 unique protein (VP1U) showed a typical Ca2+-dependent secreted PLA2-like (sPLA2) activity, which was inhibited by sPLA2-specific inhibitors in a time-dependent manner. Mutation of one of the amino acids (21Pro, 41His, 42Asp or 63Asp) in VP1U almost eliminated the sPLA2 activity of HBoV VP1U. These data indicate that VP1U of HBoV has sPLA2-like enzymatic activity, and these residues are crucial for its sPLA2-like activity. Potentially, VP1U may be a target for the development of anti-viral drugs for HBoV.

[Genome cloning and phylogenetic analysis of human bocavirus capsid gene].

The full-length genome of one human bocavirus (HBoV) and the VP1 sequences of nine HBoV were amplified from patients' samples by PCR, cloned into pGEM-T vector separately, and sequenced. In this study, the one full length gemome and nine VP1 sequences of HBoV were aligened with 14 sequences of Parvoviruses which were canonical exemplars in Parvovirinae. Phylogenetic analysis showed that HBoV capsid sequences positioned closely to B19 parvovirus, although they positioned far in phylogenetic tree based on full length genome. Many similarities were found between HBoV and B19 in capsid by alignment on secondary structural elements. Because both B19 and HBoV are the only Parvoviruses that infect mankind, so study on HBoV may be used for reference to B19 which had been studied for about 30 years. By analysis of mutational sites, HBoV capsid protein showed a highly conserved secondary structural elements, but highly active in VP1-U, leading end of VP2 and insertions between the strands of the betaG-H. This cued that HBoV inclined to immune evasion and infectant adaptive faculty.

[Clinical characteristics of bocavirus infection among children].

OBJECTIVE: To study the clinical characteristics of human bocavirus (HBoV) among children and to understand the association of HBoV with human diseases. METHOD: Totally 148 nasopharyngeal aspirate (NPA) samples were collect from hospitalized children with acute respiratory infection during Oct. 2005 to Feb. 2006. Two serum samples were obtained from HBoV positive patients. PCR was used to assay all these samples and PCR products were sequenced. RESULT: HBoV was positive in 11 of 148 NPA samples. The positive rate was 7.4 percent. The serum samples of HBoV infected patients showed that serum contained HBoV by PCR assay. All these HBoV positive patients had the clinical symptoms of bronchitis, bronchopneumonia and pneumonia. Some patients had diarrhea. CONCLUSION: All patients infected with HBoV had upper and lower respiratory tract infections. HBoV is a probable important pathogen of upper and lower respiratory tract infection. The HBoV could cause viremia. In addition, some HBoV patients had diarrhea. HBoV infection probably could also result in intestinal disease and other related symptoms.

Human bocavirus infection, People's Republic of China.

A newly identified parvovirus, human bocavirus (HBoV), was found in 21 (8.3%) of 252 nasopharyngeal aspirates from hospitalized children with lower respiratory tract infection in Hunan Province, People's Republic of China. Viral loads were 10(4) to 10(10) copies/mL. Phylogenetic analysis of the VP1 gene showed a single genetic lineage of HBoV worldwide.