摘要:

AbstractThe study of haemopoiesis enables us to address one of the central questions of developmental biology, concerning the molecular mechanisms by which a multipotent cell develops into distinct differentiated progeny. Recent work(1)suggests specific roles for retinoic acid receptors at two distinct stages of haemopoiesis. Continuous cell lines of lymphohaemopoietic progenitors were established by infection with a retrovirus containing a dominant negative retinoic acid receptor. The cell lines depend on stem cell factor for their proliferation and can be induced to diffentiate into B‐lymphocytes, erythrocytes, neutrophils, monocytes, mast cells and megakaryocytes. Since lymphohaemopoietic progenitors represent less than 0.01% of nucleated marrow cells, immortalised progenitors provide a valuable system with which to study haemopoiesis on a molecular leve

ISSN:0265-9247    

DOI:10.1002/bies.950170302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractRoot nodule morphogenesis involves the induction of mitotic activity in otherwise quiescent root cortical cells, giving rise to the nodule primordium. One gene expressed during nodule initiation,ENOD40, has been implicated in nodule growth and/or differentiation(1,2). Interestingly, although the nucleotide sequence ofENOD40genes from soybean(3,4)andMedicago(1,2)are highly homologous, they are unlikely to encode a similar protein product. In fact, a remarkable feature of these genes is their apparent lack of protein coding potential. Thus,ENOD40is a member of the growing list of eukaryotic genes whose RNA product is implicated in control of cell growth and differentiation, the so called riboregulators(5).

ISSN:0265-9247    

DOI:10.1002/bies.950170303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractNeurotransmitter release takes place by the exocytosis of loaded synaptic vesicles. The vesicles then fuse to the presynaptic membrane and are recycled by an endocytotic mechanism. A quantitative optical assay that detects uptake and release of a fluorescent dye during presynaptic activity was recently developed and used on the frog neauromuscular junction. I discuss a report(1)that demonstrates the effective application of this method to aDrosophilapreparation. The authors use theshibiremutation and a spider venom to identify two intermediates in vesicle recycling. Their report, along with other recent studies, demonstrates the power and promise of the genetic approach for the understanding of mechanisms of synapse function and development.

ISSN:0265-9247    

DOI:10.1002/bies.950170304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe development of each of the four Malpighian tubules ofDrosophiladuring embryogenesis requires a special cell, the tip cell, to achieve full growth. A central question concerns how the tip cell acquires its unique properties within the tubule primordium. In a recent report(1), a sequence of key gene expression events in both the tip cell and its cellular neighbours is described. The results show that there are some significant parallels between tip cell selection and the mechanisms that help select neuroblasts within the developing neuroectoderm. Beyond these similarities between neural development and tip cell selection, the later differentiation of the tip cell shows some intriguing elements of neural cell differentiation.

ISSN:0265-9247    

DOI:10.1002/bies.950170305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractGene targeting has allowed the dissection of complex biological processes at the genetic level. Our understanding of the nuances of skeletal muscle development has been greatly increased by the analysis of mice carrying targeted null mutations in theMyf‐5,MyoDandmyogeningenes, encoding members of the myogenic regulatory factor (MRF) family. These experiments have elucidated the hierarchical relationships existing between the MRFs, and established that functional redundancy is a feature of the MRF regulatory network. Either MyoD or Myf‐5 is sufficient for the formation or survival of skeletal myoblasts. Myogenin acts later in development and plays an essentialin vivorole in the terminal differentiation of myotu

ISSN:0265-9247    

DOI:10.1002/bies.950170306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractSkeletal myoblasts have their origin early in embryogenesis within specific somites. Determined myoblasts are committed to a myogenic fate; however, they only differentiate and express a muscle‐specific phenotype after they have received the appropriate environmental signals. Once proliferating myoblasts enter the differentiation programme they withdraw from the cell cycle and form post‐mitotic multinucleated myofibres (myogenesis); this transformation is accompanied by muscle‐specific gene expression. Muscle development is associated with complex and diverse protein isoform transitions, generated by differential gene expression and mRNA splicing. The myofibres are in a state of dynamic adaptation in response to hormones, mechanical activity and motor innervation, which modulate differential gene expression and splicing during this functional acclimatisation. This review will focus on the profound effects of thyroid hormone on skeletal muscle, which produce alterations in gene and isoform expression, biochemical properties and morphological features that precipitate in modified contractile/mechanical characteristics. Insight into the molecular events that control these events was provided by the recent characterisation of theMyoDgene family, which encodes helix‐loop‐helix proteins; these activate muscle‐specific transcription and serve as targets for a variety of physiological stimuli. The current hypothesis on hormonal regulation of myogenesis is that thyroid hormones (1)directlyregulate themyoDand contractile protein gene families, and (2) induce thyroid hormone receptor‐transcription factor interactions critical to ge

ISSN:0265-9247    

DOI:10.1002/bies.950170307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractOne of the goals in developmental biology is the identification of key regulatory genes that govern the transition of embryonic cells from a pluripotent potential to a specific, committed cell fate. During vertebrate skeletal myogenesis, this transition is regulated by theMyoDfamily of genes.C. eleganshas muscle analogous to vertebrate skeletal muscle and has a gene(hlh‐1) related to theMyoDfamily. The molecular and genetic characterization ofhlh‐1shows that it is very similar to the vertebrate MyoD family in many respects, including its expression pattern and DNA binding activity. Thehlh‐1product is required for proper myogenesis, but it is not required for myogenic commitment during embryogenesis in the nematode. The role of thisMyoD‐related gene in nematode myogenesis is discussed and compared to those of the vertebrateMyo

ISSN:0265-9247    

DOI:10.1002/bies.950170308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe integrins are receptors for proteins of the extracellular matrix, both providing a physical link to the cytoskeleton and transducing signals from the extracellular matrix. Activation of integrins leads to tyrosine and serine phosphorylation of a number of proteins, elevation of cytosolic calcium levels, cytoplasmic alkalinization, changes in phospholipid metabolism and, ultimately, changes in gene expression. The recently discovered focal adhesion kinase localizes to focal contacts, which are sites of integrin clustering, and focal adhesion kinase can physically associate with integrinsin vitro. As integrins lack intrinsic catalytic activity, focal adhesion kinase is a candidate for a signaling molecule that is recruited by integrins in order to trigger the generation of intracellular second messengers. Thus, focal adhesion kinase may play a central role in signal transduction through integrins.

ISSN:0265-9247    

DOI:10.1002/bies.950170309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAlthough 80–90% of adults are seropositive for antibodies against the human parvovirus adeno‐associated virus (AAV), infection has not been associated with either symptoms or disease. In cell culture, AAV infection is not productive unless there is a coinfection with a helper virus, either adenovirus or any type of herpes virus; in the absence of a helper virus coinfection the viral genome is integrated into the genome, usually at a specific site on chromosome 19q13.3‐qter. The integrated genome can be activated and rescued by subsequent super infection by a helper virus. The high frequency of site‐specific integration by AAV and the lack of associated disease have encouraged the use of AAV as a vector for gene therapy. This review will focus on the molecular mechanisms involved in the establishment of, and rescue from, the latent state and their relevance to use of AAV as a

ISSN:0265-9247    

DOI:10.1002/bies.950170310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDuctin is the highest conserved membrane protein yet found in eukaryotes. It is multifunctional, being the subunit c or proteolipid component of the vacuolar H+‐ATPase and at the same time the protein component of a form of gap junction in metazoan animals. Analysis of its structure shows it to be a tandem repeat of two 8‐kDa domains derived from the subunit c of the F0proton pore from the F1F0ATPase. Each domain contains two transmembrane α‐helices, which together may form a four‐helix bundle. In both the V‐ATPase and gap junction channel, ductin is probably arranged as a hexamer of subunits forming a central channel of gap junction‐like proportions. The two functions appear to be seggregated by ductin having two orientations in the bilayer. Ductin is also the major component of the mediatophore, a protein complex which may aid in the release of neurotransmitters across the pre‐synaptic membrane. It is also a target for a class of poorly understood viral polypeptides. These polypeptides are small and highly hydrophobic and some have oncogenic activity. Ductin thus appears to be at the crossroads of a number of biolog

ISSN:0265-9247    

DOI:10.1002/bies.950170311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY