Breakthroughs and future challenges in left–right patterning

How left–right (LR) asymmetry emerges during development has been a classic problem in the field of developmental biology, but it is only since the 1990s that molecular and genetic approaches have become possible. Since current progress in LR patterning has been summarized in several other reviews, I would like to briefly describe how this topic developed in the early days and what remains to be solved. In particular, two breakthroughs in the mid to late 1990s made major contributions to recent progress. Despite the rapid progress, there remain many challenging issues that need to be addressed in future.     

Hormone interactions during lateral root formation

Lateral root (LR) formation, the production of new roots from parent roots, is a hormone- and environmentally-regulated developmental process in higher plants. Physiological and genetic studies using Arabidopsis thaliana and other plant species have revealed the roles of several plant hormones in LR formation, particularly the role of auxin in LR initiation and primordium development, resulting in much progress toward understanding the mechanisms of auxin-mediated LR formation. However, hormone interactions during LR formation have been relatively underexamined. Recent studies have shown that the plant hormones, cytokinin and abscisic acid negatively regulate LR formation whereas brassinosteroids positively regulate LR formation. On the other hand, ethylene has positive and negative roles during LR formation. This review summarizes recent findings on hormone-regulated LR formation in higher plants, focusing on auxin as a trigger and on the other hormones in LR formation, and discusses the possible interactions among plant hormones in this developmental process.     

海洋半知类真菌次级代谢物研究概况

海洋真菌的次级代谢物的研究在20世纪90年代以来取得了很大进展,其中主要在海洋子囊菌和半知菌的菌体和发酵液中发现了很多结构新颖、具有独特生理活性的化合物,这些研究结果表明海洋真菌中蕴含了丰富的新型化合物,将是未来新药研究的重点领域.综述了近年来海洋子囊类真菌活性次级代谢物的研究情况.     

RNA interference-mediated silencing of laminin receptor 1 (LR1) suppresses migration and invasion and down-regulates matrix metalloproteinase (MMP)-2 and MMP-9 in trophoblast cells: implication in the pathogenesis of preeclampsia

Shallow trophoblast invasion is a common pathological feature of preeclampsia. The 67 kDa laminin receptor 1 (LR1) is a laminin-binding protein that has been reported to be down-regulated in preeclamptic placentas. The aim of the present study was to determine the functional role of LR1 in the migration and invasion of the trophoblast cell line, JEG3 cells. RNA interference mediated by plasmid expressing LR1 short hairpin RNA (shRNA) was utilized to knockdown LR1 expression in JEG3 cells. We found that the mRNA and protein expression levels of LR1 were significantly reduced in LR1-specific shRNA transfected cells compared with the untransfected and control shRNA transfected cells. The wound healing and Transwell invasion assays demonstrated that LR1 knockdown remarkably suppressed the migration and invasion potential of JEG3 cells. The gelatin zymography assay showed that LR1 knockdown greatly reduced matrix metalloproteinase (MMP)-2 and MMP-9 activities in the culture supernatants. Western blot analysis showed that LR1 shRNA significantly decreased expression levels of MMP-2, MMP-9 and phospho-extracellular signal-regulated kinase, but increased expression levels of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in comparison to the control vector-transfected cells. In conclusion, our data support an important role for LR1 in regulating trophoblast invasion and migration, and suggest a possible pathological mechanism of preeclampsia.     

Challenges and opportunities in mass spectrometric analysis of proteins from dried blood spots

Dried blood spots (DBS) have been used as a clinical sample format for over 50 years, and have been analyzed for small molecules and metabolites by mass spectrometry (MS) since the early 1990s. In the meantime, MS has become the tool of choice in proteomics. Despite this obvious avenue of scientific investigation, the marriage of MS and DBS protein analysis has been comparatively recent. DBS are a potentially rich source of protein biomarkers that remain to be exploited. This article focuses on the progress made in the mass spectrometric analysis of proteins from DBS and discusses the benefits and challenges facing this emerging field.     

Vaccines against Tuberculosis: Where Are We and Where Do We Need to Go?

In this review we discuss recent progress in the development, testing, and clinical evaluation of new vaccines against tuberculosis (TB). Over the last 20 years, tremendous progress has been made in TB vaccine research and development: from a pipeline virtually empty of new TB candidate vaccines in the early 1990s, to an era in which a dozen novel TB vaccine candidates have been and are being evaluated in human clinical trials. In addition, innovative approaches are being pursued to further improve existing vaccines, as well as discover new ones. Thus, there is good reason for optimism in the field of TB vaccines that it will be possible to develop better vaccines than BCG, which is still the only vaccine available against TB.     

ABI4调控侧根发育研究(综述)

生长素是调控植物侧根发育的关键植物激素,生长素运输载体PIN蛋白介导其极性分布。ABI4抑制生长素极性运输蛋白基因PIN1的表达,影响生长素的极性运输,抑制侧根形成。本文概述ABI4转录因子调控侧根发育的研究进展。     

Recent developments in the encoding and deconvolution of combinatorial libraries

The value of molecular libraries generated by combinatorial methods is largely dependent on the ease and ability to deconvolute or decode the structure of compounds of interest after screening the library. Following the introduction of promising concepts in the early 1990s, there has been considerable progress in the development and refinement of methodologies to address this issue.     

Spread and current potential distribution of an alien grass, Eragrostis lehmanniana Nees, in the southwestern USA: comparing historical data and ecological niche models

The potential distribution of alien species in a novel habitat often is difficult to predict because factors limiting species distributions may be unique to the new locale. Eragrostis lehmanniana is a perennial grass purposely introduced from South Africa to Arizona, USA in the 1930s; by the 1980s, it had doubled its extent. Based on environmental characteristics associated with its introduced and native range, researchers believed that E. lehmanniana had reached the limits of its distribution by the early 1990s. We collected data on E. lehmanniana locations from various land management agencies throughout Arizona and western New Mexico and found new records that indicate that E. lehmanniana has continued to spread. Also, we employed two modelling techniques to determine the current potential distribution and to re-investigate several environmental variables related to distribution. Precipitation and temperature regimes similar to those indicated by past research were the most important variables influencing model output. The potential distribution of E. lehmanniana mapped by both models was 71,843 km² and covers a large portion of southeastern and central Arizona. Logistic regression (LR) predicted a potential distribution of E. lehmanniana more similar to this species current distribution than GARP based on average temperature, precipitation, and grassland species composition and recorded occurrences. Results of a cross-validation assessment and extrinsic testing showed that the LR model performed as well or better than GARP based on sensitivity, specificity, and kappa indices.     

噬菌体抗体库研究进展

治疗性抗体的发展经历了异源抗体、人源化抗体和人源性抗体几个阶段。目前,人源性抗体是治疗性抗体发展的主要方向,而噬菌体抗体库技术的出现为人源性抗体的制备提供了良好的技术平台,并且逐渐成为目前获得人源性抗体的主要手段之一。噬菌体抗体库技术是20世纪90年代初期抗体工程领域的一项重大进展,它是噬菌体展示和抗体库2种技术的集成,目前广泛应用于生物医学领域。本文对该技术的原理、类型、特点及研究进展进行了综述。     

Decade of the brain. An agenda for the nineties.

On July 25, 1989, President George Bush, in response to reports written by the National Advisory Councils of the National Institute of Neurological Disorders and Stroke and the National Institute of Mental Health and at the urging of Congress, signed a presidential declaration designating the 1990s to be the "Decade of the Brain" and called on the United States to observe the decade with appropriate activities. At mid-decade, scientific accomplishment has been spectacular; however, both public support and increases in research resources have been minimal. It can be anticipated that scientific progress will continue to be impressive for the remainder of the decade, but many research opportunities will either not be addressed or will be postponed. At mid-decade, the time has come to re-evaluate the research agenda and the public strategy for the remainder of the decade.     

Isolation and characterization of some of the proteins that shuttle between cytoplasm and nucleus in Amoeba proteus

The Rapidly Migrating Proteins (RMP) which shuttle nonrandomly between nucleus and cytoplasm and equilibrate in approximately equal amounts in each compartment, were isolated from Amoeba proteus by implanting ³H-protein containing nuclei into unlabeled cells and some time later extracting the labeled material from the cytoplasms of such cells. The labeled material was subsequently fractionated by gel filtration in Sephadex G-100 columns. The RMP are soluble in dilute salt solutions and appear as a heterogenous group of molecules, one component of which seems to be a single species of protein accounting for ca. one-third of the RMP fraction. Because of its distinctness this component, called the LR fraction, received the major attention in this study. LR was found to comprise ca. 17% of the aqueous-soluble proteins of the nucleus and ca. 3–4% of the total cell protein. LR has a very low molecular weight as determined, e.g., by its elution from a Sephadex G-100 column. Because of its low molecular weight, LR could be purified by taking advantage of the fact that LR is (1) soluble in a saturated Solution of ammonium sulfate and (2) insoluble in butanol, diethyl ether, and 10% trichloroacetic acid. LR migrates toward the anode as a single band when subjected to electrophoresis on “standard disc” and SDS polyacrylamide gels. It does not enter a gel designed to separate basic proteins (at pH 4.0). When subjected to Sephadex G-25 gel filtration LR migrates through the gel as a single band and elutes from the gel at a position in the middle of the linear separation range that indicates its molecular weight is ca. 2300. The only N-terminal amino acid found in the LR fraction is proline. Evidence is presented to show that LR is not the product of a non-specific breakdown of protein produced during its isolation, but the possibility that it results from the cleavage of a single chemical bond of a larger polypeptide, has not been eliminated. When injected into non-labeled amebae, purified radioactive LR concentrates in the nucleus — just as radioactive RMP concentrates in a recipient cell nucleus when an amino acid-labeled nucleus is implanted into an unlabeled cell.     

Left-right asymmetry in vertebrate embryogenesis

Embryonic development results in animals whose body plans exhibit a variety of symmetry types. While significant progress has been made in understanding the molecular events underlying the early specification of the antero-posterior and dorso-ventral axes, little information has been available regarding the basis for left-right (LR) differences in animal morphogenesis. Recently however, important advances have been made in uncovering the molecular mechanisms responsible for LR patterning. A number of genes (including well-known signaling molecules such as Sonic hedgehog and activin) are asymmetrically expressed in early chick embryos, well before the appearance of morphological asymmetries. One of these, nodal, is asymmetrically expressed in frogs and mice as well, and its expression is altered in mouse mutants exhibiting defects in laterality. In the chick, these genes regulate each other in a sequential cascade, which independently determines the situs of the heart and other organs.     

Green tea polyphenol epigallocatechin-3-gallate signaling pathway through 67-kDa laminin receptor

(-)-Epigallocatechin-3-gallate (EGCG), the principal polyphenol in green tea, has been shown to be a potent chemopreventive agent. Recently, 67-kDa laminin receptor (67LR) has been identified as a cell surface receptor for EGCG that mediates the anticancer activity of EGCG. Indeed, expression of 67LR confers EGCG responsiveness to tumor cells; however, the molecular basis for the anticancer activity of EGCG in vivo is not entirely understood. Here we show that (i) using a direct genetic screen, eukaryotic translation elongation factor 1A (eEF1A) is identified as a component responsible for the anticancer activity of EGCG; (ii) through both eEF1A and 67LR, EGCG induces the dephosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) at Thr-696 and activates myosin phosphatase; and (iii) silencing of 67LR, eEF1A, or MYPT1 in tumor cells results in abrogation of EGCG-induced tumor growth inhibition in vivo. Additionally, we found that eEF1A is up-regulated by EGCG through 67LR. Overall, these findings implicate both eEF1A and MYPT1 in EGCG signaling for cancer prevention through 67LR.     

微生物谷氨酰胺转胺酶的表达及分子改造研究进展

微生物谷氨酰胺转胺酶具有催化蛋白质和某些非蛋白物质交联的功能,被广泛应用于食品、医药及纺织等领域.为提高该酶的产量及建立相应的分子改造平台,上世纪90年代日本味之素公司便开展了微生物谷氨酰胺转胺酶重组菌构建的研究.目前,该酶已在多个表达系统中实现活性表达,部分重组菌较野生菌的产酶能力有显著提高.近年来,谷氨酰胺转胺酶的分子改造研究也取得了初步进展,酶的催化活力、热稳定性及底物专一性得到提升.文中对上述研究中涉及的蛋白质表达及改造策略进行了简要的总结及分析,并指出相关研究的发展趋势.     

Dissecting Arabidopsis lateral root development

Recent studies in the model plant Arabidopsis provide new insight into the regulation of root architecture, a key determinant of nutrient- and water-use efficiency in crops. Lateral root (LR) primordia originate from a subset of pericycle founder cells. Sophisticated mass-spectroscopy-based techniques have been used to map the sites of biosynthesis of auxin and its distribution in Arabidopsis seedlings, highlighting the importance of the phytohormone during LR initiation and emergence. Key components of the cell cycle and signal-transduction pathway(s) that promote and attenuate auxin-dependent LR initiation have recently been identified. Additional signals, such as abscisic acid and nitrate, also regulate LR emergence, raising intriguing questions about the cross-talk between their transduction pathways.     

Auxin reflux between the endodermis and pericycle promotes lateral root initiation

Lateral root (LR) formation is initiated when pericycle cells accumulate auxin, thereby acquiring founder cell (FC) status and triggering asymmetric cell divisions, giving rise to a new primordium. How this auxin maximum in pericycle cells builds up and remains focused is not understood. We report that the endodermis plays an active role in the regulation of auxin accumulation and is instructive for FCs to progress during the LR initiation (LRI) phase. We describe the functional importance of a PIN3 (PIN‐formed) auxin efflux carrier‐dependent hormone reflux pathway between overlaying endodermal and pericycle FCs. Disrupting this reflux pathway causes dramatic defects in the progress of FCs towards the next initiation phase. Our data identify an unexpected regulatory function for the endodermis in LRI as part of the fine‐tuning mechanism that appears to act as a check point in LR organogenesis after FCs are specified.     

A lipid raft-associated 67kDa laminin receptor mediates suppressive effect of epigallocatechin-3-O-gallate on FcepsilonRI expression

(-)-Epigallocatechin-3-O-gallate (EGCG), a major green tea polyphenol, has previously exhibited a suppressive effect on the expression of the high-affinity IgE receptor (FcepsilonRI). This effect has been shown to be elicited by interaction with the plasma membrane microdomain lipid rafts. Recently, we have identified the 67 kDa laminin receptor (67LR) as a cell surface EGCG receptor that mediates an anti-cancer action. Here we show that the 67LR is highly associated with lipid rafts on human basophilic KU812 cells. Experiments using 67LR-enhanced and -reduced cells revealed that the EGCG's ability to downregulate FcepsilonRI expression correlated with the amount of 67LR. Thus, these results suggest that the lipid raft-associated 67LR plays an important role in mediating the FcepsilonRI-suppressive action of EGCG.     

In vitro approaches to the elucidation of mechanisms of chemical teratogenesis.

This article describes some of the contributions that in vitro methods have made to our progress, albeit slow, toward understanding mechanisms of chemical teratogenesis. Emphasis is given to the painstaking and time consuming nature of approaches required to elucidate mechanisms. The examples considered are cyclophosphamide, 2-methoxyethanol, and retinoids. Some of the newer methods that take advantage of the recent advances in molecular biology and analytical chemistry have already been applied to studies on teratogenic mechanisms. Prospects for the 1990s are excellent and promise more rapid progress than during the past decade toward unraveling the mysteries of normal developmental biology. That knowledge in turn should be immediately applicable for investigations on developmental toxicant-induced abnormal development.     

植物中的RB蛋白:不表现抑肿瘤功能的抑肿瘤蛋白?

视网膜神经胶质瘤易感蛋白(RB)是人类发现的第一个抑肿瘤蛋白,它在细胞的增殖和分化过程中发挥重要的调节作用。从20世纪90年代中期发现第一个植物RB同源(RB-related,RBR)蛋白以来,植物RBR蛋白已被证明广泛分布于各种植物中。通过RB-E2F信号途径以及招募染色质重塑因子,植物RBR蛋白作为植物细胞增殖的负调控因子,可以抑制细胞的有丝分裂和核内复制以及维持细胞的分化状态,进而在不同的植物组织中表现出多样的生理功能。对于植物RBR蛋白功能的认识已经有了长足的进步,但是它的许多特性仍需要更为深入的阐明。