A novel steroid thyroid hormone receptor-related gene inappropriately expressed in human hepatocellular carcinoma

We have previously isolated from a human hepatocellular carcinoma a hepatitis B virus integration in a 147-base-pair cellular DNA fragment, similar to steroid- and c-erb-A/thyroid-hormone receptor genes. We have now cloned the corresponding complementary DNA from a human-liver cDNA library. Nucleotide sequence analysis revealed that the overall structure of the cellular gene, which we have named hap, is similar to that of the DNA-binding hormone receptors. That is, it displays two highly conserved regions identified as the putative DNA-binding and hormone-binding domains of the c-erb A/steroid receptors. Six out of seven hepatoma and hepatoma-derived cell-lines express a 2.5-kilobase (kb) hap messenger RNA species which is undetectable in normal adult and fetal livers but present in all non-hepatic tissues analysed. The data suggest that the hap gene product may be a novel ligand-responsive regulatory protein whose inappropriate expression in liver may relate to the hepatocellular carcinogenesis.     

A phosphate transporter expressed in arbuscule-containing cells in potato.

Arbuscular mycorrhizas are the most common non-pathogenic symbioses in the roots of plants. It is generally assumed that this symbiosis facilitated the colonization of land by plants. In arbuscular mycorrhizas, fungal hyphae often extend between the root cells and tuft-like branched structures (arbuscules) form within the cell lumina that act as the functional interface for nutrient exchange. In the mutualistic arbuscular-mycorrhizal symbiosis the host plant derives mainly phosphorus from the fungus, which in turn benefits from plant-based glucose. The molecular basis of the establishment and functioning of the arbuscular-mycorrhizal symbiosis is largely not understood. Here we identify the phosphate transporter gene StPT3 in potato (Solanum tuberosum). Functionality of the encoded protein was confirmed by yeast complementation. RNA localization and reporter gene expression indicated expression of StPT3 in root sectors where mycorrhizal structures are formed. A sequence motif in the StPT3 promoter is similar to transposon-like elements, suggesting that the mutualistic symbiosis evolved by genetic rearrangements in the StPT3 promoter.     

A chloride channel widely expressed in epithelial and non-epithelial cells.

Chloride channels have several functions, including the regulation of cell volume, stabilizing membrane potential, signal transduction and transepithelial transport. The plasma membrane Cl- channels already cloned belong to different structural classes: ligand-gated channels, voltage-gated channels, and possibly transporters of the ATP-binding-cassette type (if the cystic fibrosis transmembrane regulator is a Cl- channel). The importance of chloride channels is illustrated by the phenotypes that can result from their malfunction: cystic fibrosis, in which transepithelial transport is impaired, and myotonia, in which ClC-1, the principal skeletal muscle Cl- channel, is defective. Here we report the properties of ClC-2, a new member of the voltage-gated Cl- channel family. Its sequence is approximately 50% identical to either the Torpedo electroplax Cl- channel, ClC-0 (ref. 8), or the rat muscle Cl- channel, ClC-1 (ref. 9). Isolated initially from rat heart and brain, it is also expressed in pancreas, lung and liver, for example, and in pure cell lines of fibroblastic, neuronal, and epithelial origin, including tissues and cells affected by cystic fibrosis. Expression in Xenopus oocytes induces Cl- currents that activate slowly upon hyperpolarization and display a linear instantaneous current-voltage relationship. The conductivity sequence is Cl- greater than or equal to Br- greater than I-. The presence of ClC-2 in such different cell types contrasts with the highly specialized expression of ClC-1 (ref. 9) and also with the cloned cation channels, and suggests that its function is important for most cells.     

一个小鼠睾丸特异表达新基因的克隆及表达谱分析

运用“数据库消减杂交”(digital diffrential Display)筛选出一个在小鼠睾丸中特异表达的新基因—mLrrc18(Genballk Accession No：AY775400),该基因的全长cDNA序列为2.7kb,小鼠多组织RT-PCR结果表明：该基因在睾丸中特异表达,而在其它组织中没有表达。该基因的睾丸特异性表达提示它可能在睾丸的的发育和性成熟过程中起重要作用。     

新生物活性肽-daintain/AIF-1在乳腺癌中的表达

采用免疫组织化学两步法分析了乳腺癌组织蜡块切片中daintain／AIF-1的表达．93％的乳腺癌中都有该活性肽的分布,癌旁良性组织中则没有阳性染色或染色很浅．Daintain／AIF-1在乳腺病变级别不同组织中的表达差异很大：增生组织免疫后着黄色,重度不典型增生组织着橙黄色,癌组织则染成了棕褐色．进一步用RT-PCR检测发现,乳腺癌新鲜组织中能扩增出daintain／AIF-1的mRNA,而癌旁良性乳腺组织中的daintain／AIF-1 mRNA极微量,几乎看不到扩增的核酸条带．这些研究表明,daintain／AIF-1在乳腺癌中过量表达,可能在乳腺肿瘤的发展过程起到了促进作用．因此,提示daintain／AIF-1可作为乳腺癌病变早期诊断的一个参考指标。     

A novel serine esterase expressed by cytotoxic T lymphocytes

Cytotoxic T (Tc) lymphocytes recognize and lyse target cells and are thought to serve as an important defence against viral infections and possibly against neoplasms. The nature of the receptors responsible for antigen recognition by these cells is becoming clearer, but the molecular mechanisms responsible for their cytolytic activity remain largely unknown. The possibility that proteases are involved in this process has been suggested by the effects of certain inhibitors. Here we demonstrate that clones of murine Tc cells possess considerable trypsin-like esterase activity when assayed by a sensitive colorimetric assay. This activity was blocked completely by two serine esterase inhibitors, diisopropylfluorophosphoridate (DFP) and phenylmethylsulphonyl fluoride (PMSF), but not by N alpha-tosyl lysyl chloromethyl ketone (TLCK). The use of 3H-DFP as an affinity-labelling reagent demonstrated that the esterase activity resides in a protein of relative molecular mass (Mr) 28,000 (28K). A wide variety of other lymphocytes, including those from thymus, spleen and lymph node, established lines of B cells and noncytotoxic T cells, and clones of T helper cells, had about 300-fold less esterase activity than the Tc-cell clones and far smaller amounts of the DFP-reactive 28K protein. However, in thymocytes the esterase activity increased 20-50-fold and the 28K protein became more prominent 4 days after these cells had been stimulated in vitro to generate Tc cells.     

A novel alpha-globin gene arrangement in man

The human genome has two linked alpha-globin genes on chromosome 16. Deletion of one or more of them, as occurs in alpha-thalassaemia, leads to a reduced output of alpha-globin mRNA in proportion to the number of alpha-globin genes lost. In some racial groups deletion of one of the pair of alpha-globin genes may result from unequal crossing over between the genes on homologous chromosomes by a mechanism resembling that postulated for the formation of the delta beta fusion genes of the Lepore haemoglobins. By analogy, the opposite chromosome in this cross-over should have three alpha-globin genes just as the 'anti-Lepore chromosome has three non-alpha chain genes. We describe here a Welsh family in which three members have five alpha-globn increased alpha mRNA output and it may therefore produce the phenotype of mild beta-thalassaemia.     

Mutational hotspot in the p53 gene in human hepatocellular carcinomas.

Human hepatocellular carcinomas (HCC) from patients in Qidong, an area of high incidence in China, in which both hepatitis B virus and aflatoxin B1 are risk factors, were analysed for mutations in p53, a putative tumour-suppressor gene. Eight of the 16 HCC had a point mutation at the third base position of codon 249. The G----T transversion in seven HCC DNA samples and the G----C transversion in the other HCC are consistent with mutations caused by aflatoxin B1 in mutagenesis experiments. No mutations were found in exons 5,6,8 or the remainder of exon 7. These results contrast with p53 mutations previously reported in carcinomas and sarcomas of human lung, colon, oesophagus and breast; these are primarily scattered over four of the five evolutionarily conserved domains, which include codon 249 (refs 4-9). We suggest that the mutant p53 protein may be responsible for a selective clonal expansion of hepatocytes during carcinogenesis.     

A novel abl protein expressed in Philadelphia chromosome positive acute lymphoblastic leukaemia

The Philadelphia (Ph) chromosome breakpoints in chronic myelocytic leukaemia are clustered on chromosome 22 band q11 in a 5.8-kilobase (kb) region designated bcr. The c-abl protooncogene is translocated from chromosome 9 band q34 into bcr and the biochemical consequence of this molecular rearrangement is the production of an abnormal fusion protein bcr-abl p210 with enhanced protein-tyrosine kinase activity compared to the normal p145 c-abl protein. The Ph chromosome translocation is also seen in some acute lymphoblastic leukaemias with B-cell precursor phenotypes some of which have bcr rearrangement (bcr+) and some do not (bcr-). We present evidence that the Ph+, bcr- leukaemias are associated with a novel p190 abl kinase. We propose that acute lymphoblastic leukaemias that are bcr+, p210+ are probably lymphoid blast crises following a clinically silent chronic phase of chronic myelocytic leukaemia arising in multipotential stem cells whereas bcr-, p190+ cases are de novo acute lymphoblastic leukaemias arising in more restricted precursors.     

A novel MHC class II epitope expressed in thymic medulla but not cortex

The repertoire of receptors expressed by peripheral T cells is the result of two selective events that occur during intrathymic development. Positive selection expands cells able to recognize foreign peptides presented by self MHC molecules, and negative selection eliminates cells reactive to self MHC molecules and associated self peptides. Chimaera studies suggest that, at least in the case of T cells recognizing MHC class II, interaction with thymic cortical epithelial cells is responsible for the former, whereas thymic medullary cells, of bone marrow origin, mediate the latter. This view of thymic development is supported by recent morphometric analyses, showing that autoreactive cells are found in thymic cortex but not medulla. Although numerous studies have shown that MHC class II molecules are expressed in both sites, none provides any explanation for the differential selection of T cells that is observed. Here, we describe a novel MHC class II epitope which is found on cells in thymic medulla but not cortex. The antibody to this epitope reacts with about 10% of class II molecules on B cells and may be recognizing a self peptide-MHC complex. These results provide the first evidence for differential expression of class II epitopes in different tissues and are compatible with the hypothesis that different ligands, rather than different affinity thresholds for the same ligand, are involved in positive and negative selection of the T-cell repertoire.     

A gene mapping to the sex-determining region of the mouse Y chromosome is a member of a novel family of embryonically expressed genes

A gene mapping to the sex-determining region of the mouse Y chromosome is deleted in a line of XY female mice mutant for Tdy, and is expressed at a stage during male gonadal development consistent with its having a role in testis determination. This gene is a member of a new family of at least five mouse genes, related by an amino-acid motif showing homology to other known or putative DNA-binding domains.     

A novel type of cardiac calcium channel in ventricular cells

Calcium influx is vital for several aspects of cardiac activity, so it is important to ask if heart cells possess a single or multiple types of Ca channel. Only one Ca channel type has been identified in patch-clamp studies of unitary current, despite suggestions to the contrary from whole-cell recordings in heart cells and unitary recordings from other cells. Here we describe a novel type of cardiac Ca channel with several properties that distinguish it from the hitherto-identified Ca channel in heart cells. Its conductance in isotonic Ba is small (8 pS), and is no larger in Ba than in Ca. It activates and inactivates at relatively negative potentials and remains functional long after patch excision. It is insensitive to dihydropyridines such as nimodipine and the Ca agonist Bay K 8644, and is more resistant to block by external Cd than the previously described type of cardiac Ca channel.     

Subtyping of type A influenza by sequencing the variable regions of HA gene specifically amplified with RT-PCR

The outbreak of a novel influenza A(H1N1) virus across the globe poses a threat to human health.It is of paramount importance to develop a rapid,reliable and inexpensive diagnostic procedure.Based on the bioinformatic information from public database,primers specific for influenza A virus surface protein haemagglutinin(HA) of several subtypes(including H1,H2,H3,H5,H7 and H9) were designed.Primer-specific PCR products were subjected to sequencing for accurately distinguishing H1 and H3 subtypes from others.T...     

小鼠胚肝基质细胞在体外培养中的动态演化

胚肝基质细胞是研究胚肝造血调控的重要工具,本实验对小鼠胚肝基质细胞在体外培养过程中的生长、细胞类型组成及其组成比例的演变过程进行了观察．实验显示小鼠原代培养初期基质细胞是由平滑肌样上皮细胞、巨噬细胞以及成纤维样细胞、树突状细胞、内皮细胞构成的,经过多次传代后,巨噬细胞等类型的细胞逐渐丢失,平滑肌样上皮细胞和成纤维样细胞成为主体,表明体外培养的小鼠胚肝基质细胞在4代以内都能较真实的反映体内造血微环境的构成,适用于胚肝造血研究．此为进一步研究胚肝基质细胞在胚胎期造血过程中的作用奠定了工作基础．     

成人骨髓基质细胞的体外培养

本研究从成人的髋骨抽取骨髓液，离心后将骨髓基质细胞悬液接种培养，待细胞贴壁融合后，进行传代扩增培养．并采用流式细胞术进行细胞周期分析，结果表明原代培养和传代培养的细胞均为贴壁、形态不一的骨髓基质细胞，且此体外培养的骨髓基质细胞具有很强的增殖能力．本研究成功地建立了一套完整、简单、可行的体外分离、长期培养扩增人骨髓基质细胞(Human Bone Marrow Stromal Cells hBMSCs)的系统，证明成人骨髓基质细胞能够在体外长期增殖，为人的骨髓基盾细胞的理论研究和临床应用奠定了基础.