Spermatid differentiation requires the assembly of a cell polarity complex downstream of junctional adhesion molecule-C

During spermatogenesis in the mammalian testis, stem cells (spermatogonia) differentiate into spermatocytes, which subsequently undergo two consecutive meiotic divisions to give rise to haploid spermatids. These cells are initially round but progressively elongate, condense their nuclei, acquire flagellar and acrosomal structures, and shed a significant amount of their cytoplasm to form spermatozoa (the sperm cells) in a developmental cascade termed spermiogenesis. Defects in these processes will lead to a lack of mature sperm cells (azoospermia), which is a major cause of male infertility in the human population. Here we report that a cell-surface protein of the immunoglobulin superfamily, junctional adhesion molecule-C (JAM-C), is critically required for the differentiation of round spermatids into spermatozoa in mice. We found that Jam-C is essential for the polarization of round spermatids, a function that we attribute to its role in the assembly of a cell polarity complex.     

Novel primitive lymphoid tumours induced in transgenic mice by cooperation between myc and bcl-2

The putative oncogene bcl-2 is juxtaposed to the immunoglobulin heavy chain (Igh) locus by the t(14;18) chromosomal translocation typical of human follicular B-cell lymphomas. The bcl-2 gene product is not altered by the translocation, but its expression is deregulated, presumably by the Igh enhancer E mu. Constitutive bcl-2 expression seems to augment cell survival, as infection with a bcl-2 retrovirus enables certain growth factor-dependent mouse cell lines to maintain viability when deprived of factor. Furthermore, high levels of the bcl-2 product can protect human B and T lymphoblasts under stress and thereby confer a growth advantage. Mice expressing a bcl-2 transgene controlled by the Igh enhancer accumulate small non-cycling B cells which survive unusually well in vitro but do not show a propensity for spontaneous tumorigenesis. In contrast, an analogous myc transgene, designed to mimic the myc-Igh translocation product typical of Burkitt's lymphoma and rodent plasmacytoma, promotes B lymphoid cell proliferation and predisposes mice to malignancy in pre-B and B lymphoid cells. Previous experiments have suggested that bcl-2 can cooperate with deregulated myc to improve in vitro growth of pre-B and B cells. Here we describe a marked synergy between bcl-2 and myc in doubly transgenic mice. E mu-bcl-2/myc mice show hyperproliferation of pre-B and B cells and develop tumours much faster than E mu-myc mice. Suprisingly, the tumours derive from a cell with the hallmarks of a primitive haemopoietic cell, perhaps a lymphoid-committed stem cell.     

A restricted cell population propagates glioblastoma growth after chemotherapy

Glioblastoma multiforme is the most common primary malignant brain tumour, with a median survival of about one year. This poor prognosis is due to therapeutic resistance and tumour recurrence after surgical removal. Precisely how recurrence occurs is unknown. Using a genetically engineered mouse model of glioma, here we identify a subset of endogenous tumour cells that are the source of new tumour cells after the drug temozolomide (TMZ) is administered to transiently arrest tumour growth. A nestin-ΔTK-IRES-GFP (Nes-ΔTK-GFP) transgene that labels quiescent subventricular zone adult neural stem cells also labels a subset of endogenous glioma tumour cells. On arrest of tumour cell proliferation with TMZ, pulse-chase experiments demonstrate a tumour re-growth cell hierarchy originating with the Nes-ΔTK-GFP transgene subpopulation. Ablation of the GFP+ cells with chronic ganciclovir administration significantly arrested tumour growth, and combined TMZ and ganciclovir treatment impeded tumour development. Thus, a relatively quiescent subset of endogenous glioma cells, with properties similar to those proposed for cancer stem cells, is responsible for sustaining long-term tumour growth through the production of transient populations of highly proliferative cells.     

Can transgenic rice cause ecological risks through transgene escape?

Alien transgene escape from genetically engineered rice to non-transgenic varieties or close wild relatives (including weedy rice) may lead to unpredictable ecological risks. However, for transgene escape to occur three conditions need to be met: (i) spatially, transgenic rice and its non-transgenic counterparts or wild relatives should have sympatric distributions; (ii) temporally, the flowering time of transgenic rice and the non-transgenic varieties or wild relatives should overlap; and (iii) biologically, transgenic rice and its wild relative species should have such a sufficiently close relationship that their interspecific hybrids can have normal generative reproduction. This paper presents research data on the geographic distribution, flowering habits, interspecific hybridization, and gene flow of cultivated rice (Oryza sativa) and its closely related wild relatives containing the AA genome. The objective is to estimate the possibility of transgene escape to non-transgenic rice varieties and wild relatives of rice, which may result in unpredictable ecological risks.     

Control of germ cell nuclear behaviour at fertilization by Tetrahymena intermediate filament protein

Intermediate filament protein [relative molecular mass (Mr) 49,000 (49K)] from the ciliated protozoan Tetrahymena has been shown to resemble intermediate filament proteins from mammalian cells in several respects, and to have a possible role in the oral morphogenesis preceding binary fission in Tetrahymena. Here, based on immunofluorescence localization of the 49K protein in Tetrahymena during the early stages of conjugation, we suggest that the protein is involved in some nuclear events, such as the production of four haploid nuclei by prezygotic divisions (meiosis), selection of one of the four meiotic products, formation of the gametic pronucleus by the mitotic division of the selected meiotic product, transfer of the gametic pronucleus across a cell-cell junction, and zygote formation by pronuclear fusion.     

绒山羊曲细精管生殖细胞的长期培养和精子发生过程的观察

哺乳动物精子发生过程是生殖生物学的重要研究课题之一.为了开展对山羊精子发生过程的研究,我们首次建立了绒山羊睾丸生殖细胞原代培养方法.原代生殖细胞和支持细胞(Sertolicells)由绒山羊睾丸曲细精管组织块产生,在体外共培养超过三个月.在共培养期间,观察到绒山羊的精原干细胞分化为精母细胞和精子细胞的形态变化过程.这一方法的建立为山羊精子发生过程的研究和应用打下了基础.实验结果显示,在没有添加任何生长因子的条件下,绒山羊睾丸生殖细胞长期增生分化,不断产生精子细胞.这一结果暗示了组织块和共生的支持细胞为生殖细胞的增生和分化提供了营养因子和调节因子.生成的游离精子细胞最后全部死亡,暗示这一共培养体系不能提供变态过程所需因子.     

Pre-B cells in kappa-transgenic mice

Recent experiments have shown that the microinjected kappa-chain gene of transgenic mice is expressed in a tissue-specific fashion only in B lymphocytes. The next step was to determine whether, within the B-lymphocyte lineage, the kappa-chain gene was expressed in a normal developmental fashion. Normally, only mu heavy(H)-chain genes, and not kappa-chain genes, are expressed in pre-B cells. To obtain cloned cell lines derived from early cells of the B-cell lineage, we transformed bone marrow cells from kappa-transgenic mice with Abelson murine leukaemia virus (A-MuLV) and tested the resultant cell lines for the retention of the kappa transgene and its expression in RNA and protein. We found that cells with the pre-B phenotype exist in kappa-transgenic mice. We further observed that in A-MuLV-transformed cell lines from a kappa-transgenic mouse with a high copy number of the transgene, the proportion of cell lines expressing kappa (transgenic kappa) was higher than in cell lines from normal or low copy number transgenic mice.     

Evidence that stem cells reside in the adult Drosophila midgut epithelium

Adult stem cells maintain organ systems throughout the course of life and facilitate repair after injury or disease. A fundamental property of stem and progenitor cell division is the capacity to retain a proliferative state or generate differentiated daughter cells; however, little is currently known about signals that regulate the balance between these processes. Here, we characterize a proliferating cellular compartment in the adult Drosophila midgut. Using genetic mosaic analysis we demonstrate that differentiated cells in the epithelium arise from a common lineage. Furthermore, we show that reduction of Notch signalling leads to an increase in the number of midgut progenitor cells, whereas activation of the Notch pathway leads to a decrease in proliferation. Thus, the midgut progenitor's default state is proliferation, which is inhibited through the Notch signalling pathway. The ability to identify, manipulate and genetically trace cell lineages in the midgut should lead to the discovery of additional genes that regulate stem and progenitor cell biology in the gastrointestinal tract.     

Depletion of the predominant B-cell population in immunoglobulin mu heavy-chain transgenic mice

The transgenic mouse line M54 was generated by introducing a functionally-rearranged immunoglobulin mu heavy-chain gene into the germ line of a C57B1/6 inbred mouse. Previous examination of the antibodies produced by B-cell hybridomas derived from transgenic M54 mice showed that the presence of the mu transgene grossly altered the immunoglobulin repertoire of unimmunized animals, suggesting that these mice suffer from a serious immunoregulatory perturbation. Studies presented here introduce a new perspective on this functional defect. We show that the lymphoid tissues from these transgenic mice lack virtually all conventional bone-marrow-derived B cells, which constitute the predominant B-cell population in normal mice and which typically produce primary and secondary antibody responses to T-cell-dependent antigens. Moreover, the bone marrow from transgenic M54 mice is depleted of pre-B lymphocytes, indicating a serious defect in early B-cell lymphopoiesis. In contrast, CD5 (Ly-1) B cells, a second B-cell population displaying a characteristic set of cell surface markers which are derived from distinct precursors in the peritoneum, are represented at normal frequencies in these transgenic mice. Thus, the presence of the rearranged immunoglobulin heavy-chain transgene in M54 mice results in an unexpected selective developmental defect that impairs the development of bone-marrow-derived pre-B and B cells without affecting Ly-1 B cells.     

Analysis of gene expression patterns with cDNA microarray during late stage of spermatogenesis in mice

The differentiation process of round spermatids to spermatozoa during the late stage of spermatogenesis is called spermiogenesis. To explore spermiogenesis-related genes, cDNA microarray was used to study expression patterns of 1176 genes in pachytene spermatocytes, round spermatids and elongating spermatids of Balb/c mice. The results showed that 208 genes were detected in all the three cell types. Most of them were down-regulated from pachytene spermatocytes to round spermatids and elongating spermatids. However, up-regulation of 7 genes expression in round spermatids and 3 genes in elongating spermatids were found. Expression of 7 differentially expressed genes in cDNA arrays was further confirmed by semi-quantitative RT-PCR study. The RT-PCR results indicated that the expression of 6 genes was consistent with that in cDNA arrays, only one gene did not show differential expression by RT-PCR. These results may provide important clues for studying of expression, regulation, and function of spermiogenesis-related genes.     

Follicles were reconstituted from dissociated mouse fetal ovarian cellsin vitro

Early folliculogenesis involved in the interaction of germ cells and somatic cells is a complicated physiological event. Female germ cells are committed to differentiate into oocytes and finish complete development in the functional units of follicles. Thus there will be great significance in basal research and practices to evaluate the possibility of ovarian cells to reconstitute into follicles in vitro. In the present research, 12-16 dpc (days post coitum) mouse fetal ovarian cells were respectively isolated using collagenase digestion and cultured in droplets in vitro. The results revealed that the fetal ovarian cells of 12-16 dpc appeared to form multiple cell aggregates and tissue-like pieces in vitro. However, 12-13 dpc ovarian cells failed to form the follicles. 14-15 dpc ovarian cells were competent to form a few follicle-like complexes. Furthermore many small typical follicles were reconstituted from 16 dpc ovarian cells in vitro. The results showed for the first time that mouse embryonic ovarian cells were able to form the follicles in vitro. It was a gradual progression for the female germ cells to achieve the ability to induce somatic cells differentiation and reconstitu-tion into follicles, which may directly lead to the success in reorganization and transplantation of genetically modified ovary in vitro.     

H-2-linked low-molecular weight polypeptide antigens assemble into an unusual macromolecular complex

The major histocompatibility complex (MHC) is a cluster of tightly linked genes whose products are of central importance in the functioning of the immune system. Class I and II MHC antigens are integral membrane proteins which regulate cell-surface interactions between T cells and their targets, while class III antigens are components of the complement system of serum proteins. All available evidence indicates that the structure and function of the MHC and its gene products are highly conserved among species (for review, see ref.5). We recently reported the existence in murine cells of a fourth class of MHC-linked polypeptides which are biochemically and genetically distinct from previously identified MHC gene products: BALB.B anti-BALB/c (anti-H-2d) antiserum immunoprecipitates a set of 16 cytoplasmic low-molecular weight polypeptides (LMP) from BALB/c spleen cells and from the WEHI-3 cell line. The production of these peptides is coordinately regulated (by immune interferon) with the production of the class I and II MHC antigens, suggesting that they too are functionally relevant to the immune system. We demonstrate here that these 16 polypeptides are associated with one another in vivo as a very large (580,000-molecular weight, Mr) noncovalent complex. The unusual nature of this complex has allowed the non-immunochemical identification of similar complexes from (serologically negative) H-2b murine cells and from a human cell line. Thus, LMP antigens display two properties in common with other MHC antigens: they are both polymorphic and genetically conserved across species.     

The src gene product of transformed and morphologically reverted ASV-infected mammalian cells.

Morphological revertants of avian sarcoma virus transformed vole cells contain the sarcoma gene product (pp60src) in an enzymatically active form, suggesting that the presence of pp60src protein kinase activity is infussicient to induce morphological transformation. Structural analyses of pp60src from infected vole cell clones suggest that in one of the revertant clones on alteration in pp60src may be responsible for morphological reversion while in a second clone, reversion may result from an alteration in a cell gene product with which pp60src must interact. As these morphological revertant cells are tumorigenic, different cell components are required to interact with pp60src to facilitate the two events.     

抓住高新生物技术发展契机,全面推进大连市农业现代化

20世纪 70年代以来 ,基因的体外重组和克隆技术的诞生 ,使以 DNA重组技术为核心的现代生物技术蓬勃发展 ,从而推动了农业现代化的发展 .传统的农业生产技术被高新的生物技术取代 ,基因药物、具有优良性状的转基因作物、克隆动物等出现使农业进入前所未有的现代化时代 .同时 ,计算机技术的迅猛发展 ,也使农业发展走向信息化时代 .农业的现代化、信息化使农业发展前景广阔 .大连是地处环渤海地区的主要发展城市 ,需要抓住高新生物技术所带来的巨大经济效益这一契机 ,根据实际情况致力于本市农业发展 ,走科技兴农之路 ,在农业生物、医药生物、蓝色农业、白色农业等方面取得突破 ,以获得更大的经济效益     

流式细胞技术对莱哈衣藻(Chlamydomonas reinhardi)配子形成过程的观察

应用流式细胞仪观察了不同暗交替周期对莱哈衣藻的配子形成过程影响,并采用核酸抑制剂和蛋白合成抑制剂处理,观察其配子配对情况。结果表明在缺氮诱导条件下,前期的光照对配子分化形成十分重要,而先黑暗后光照或连续黑暗诱导时,细胞或配子的分裂缺乏规律性。     

Cell attachment protein VP8* of a human rotavirus specifically interacts with A-type histo-blood group antigen

As with many other viruses, the initial cell attachment of rotaviruses, which are the major causative agent of infantile gastroenteritis, is mediated by interactions with specific cellular glycans. The distally located VP8* domain of the rotavirus spike protein VP4 (ref. 5) mediates such interactions. The existing paradigm is that 'sialidase-sensitive' animal rotavirus strains bind to glycans with terminal sialic acid (Sia), whereas 'sialidase-insensitive' human rotavirus strains bind to glycans with internal Sia such as GM1 (ref. 3). Although the involvement of Sia in the animal strains is firmly supported by crystallographic studies, it is not yet known how VP8* of human rotaviruses interacts with Sia and whether their cell attachment necessarily involves sialoglycans. Here we show that VP8* of a human rotavirus strain specifically recognizes A-type histo-blood group antigen (HBGA) using a glycan array screen comprised of 511 glycans, and that virus infectivity in HT-29 cells is abrogated by anti-A-type antibodies as well as significantly enhanced in Chinese hamster ovary cells genetically modified to express the A-type HBGA, providing a novel paradigm for initial cell attachment of human rotavirus. HBGAs are genetically determined glycoconjugates present in mucosal secretions, epithelia and on red blood cells, and are recognized as susceptibility and cell attachment factors for gastric pathogens like Helicobacter pylori and noroviruses. Our crystallographic studies show that the A-type HBGA binds to the human rotavirus VP8* at the same location as the Sia in the VP8* of animal rotavirus, and suggest how subtle changes within the same structural framework allow for such receptor switching. These results raise the possibility that host susceptibility to specific human rotavirus strains and pathogenesis are influenced by genetically controlled expression of different HBGAs among the world's population.     

Cloned goats (Gapra hircus) from foetal fibroblast cell lines

Mammalian cloning has been one of the most active research topics in the world. Cloning within vitro culured foetal fibroblast cells, in comparison with embryonic cells, can be used not only to theoretically study the embryonic or cellular development and differentiation in mammals, but also to utilize the unlimited fibroblast cells to produce large numbers of clonings. The preliminary results are as follows: (i) The division and development of the cloned embryos with embryonic donor cells and goat foetal fibroblast donor cells were 55%, 77% and 35%, 31%, respectively. There is no significant statistical difference between them, (ii) These studies result in the birth of two cloned goats derived from two 30-day foetal fibroblast cell lines, which are the first cloned mammals from somatic cells in China. This project has established a technological data base for the furture research on adult mammalian somatic cloning and nucleocytoplasmic interactions in animal development, and a novel technique for the cloning of animals with a high-level expression of transgene(s).