- Email: [email protected]
Meeting of cell-cell adhesion, communication and signalling at the junction
MISCELLANEA
Intercellular junctions localize to the outer margins of the cell. Their roles in cell-cell interactions and their different morphologies were described in a classic paper by Farquhar and Palade over 30 years ago. At this symposium*, there were many unexpected surprises as researchers described the functions of different protein constituents of junctions and how these proteins influence a diversity of cellular and tissue functions. A highlight was direct evidence that structural components of intercellular junctions play direct roles in events in the nucleus, in the determination of cellular differentiation during embryogenesis, and in organ function in the adult organism. Junction organization and structure The identity and structural organization of proteins in the tight junction have been important questions in recent years. B. Stevenson (Edmonton, Canada) and J. Anderson (Yale, USA) described the sequences of genes encoding two cytoplasmic proteins, ZO-1 and 20-2, that associate with tight junctions. These proteins have structural motifs common to the membrane-associated guanylate kinase (MACUK) family of proteins, another member of which is the product of the lethal discs-large- 7 tumour suppressor gene (d/g) found in the septate junction in Drosophila (D. Woods, Irvine, USA). Proteins of the MAGUK family have conserved discs large homology repeats (PDZ domain). Anderson noted that many membrane proteins have a conserved C-terminal amino acid motif, S/TxV, that binds to the PDZ domain. He suggested that MACUK proteins may be important in regulating a diversity of signaltransduction events and/or membranecortical-cytoskeleton interactions. The identification of membrane protein(s) that regulate tight-junction function as a barrier to paracellular diffusion has been difficult. The best candidate so far is occludin (S. Tsukita, Kyoto, Japan). Immuno-electron microscopy of freeze-fractured membranes containing occludin showed clustering of the protein in tightly apposed membrane structures reminiscent of tight junctions in the plasma membrane. Protein-protein interactions are clearly not solely responsible for tight-junction organization since the lipid environment and amount of cholesterol present in the membrane also regulate function (E. Schneeberger, Charlestown, USA). T. Fleming (Southampton, USA) de-
Meeting of cell-cell adhesion, communication and signalling at the junction W. James Nelson scribed studies on expression and assembly of tight-junction-associated proteins during preimplantation mouse development. He showed that assembly is regulated temporally at transcriptional, translational and posttranslational levels and that assembly of tight-junction proteins is a sequential process. D. Goodenough (Boston, USA) examined the correlation between tight-junction protein distribution and formation of functional diffusion barriers between cells in pregastrulation Xenopus embryos. He concluded that tight junctions formed initially at the base of cells and that they did not localize to the apex of the lateral membrane until after the 1 OOOcell stage. He suggested that assembly of the adherens junctional complex might specify tight-junction location. Adherens junctions have long been recognized as principle sites of cell-cell adhesion. Membrane proteins, members of the cadherin superfamily, and cytoplasmic proteins, catenins and actin, have been localized to them. W. Hendrickson (New York, USA) has solved the structure of the 5th repeat domain of N-cadherin. He showed that a conserved amino acid motif, HAV, is located at an important interface between dimerforming domains. Hendrickson also presented preliminary studies of the structure of the interface between the 4th and 5th extracellular domains of N-cadherin, which revealed the apposition of two amino acid motifs that have been shown to bind Ca2+. This solution structure of the N-cadherin extracellular domains suggests a model in which cadherins laterally associate with one another to form a large complex that could potentiate weak adhesion between individual cadherins on adjacent cells. W. J. Nelson (Stanford, USA) showed by retrospective immunofluorescence microscopy analysis that large puncta containing cadherin and catenins associate with actin filaments at early epithelial cell-cell contacts, which may reflect the parallel organization of cadherins into large complexes.
trends in CELL BIOLOGY (Vol. 6) August 1996
Linkage of cadherins to the actin cytoskeleton through catenins is important for regulating cadherin-mediated cell-cell adhesion. R. Kemler (Freiburg, Germany) and P. Cowin (New York, USA) presented details of protein domains involved in interactions between c1- and B-catenin/plakoglobin, and R. Kemler and W. Birchmeier (Berlin, Germany) presented evidence from mouse knockouts that catenins are absolutely required for cadherin function in cell-cell adhesion. In addition to their interactions with cadherin, catenins also bind other membrane and cytoplasmic proteins. N. Tonks (Cold Spring Harbor, USA) reported that a transmembrane protein tyrosine phosphatase (PTPP) interacts with the catenin-binding domain of cadherin, raising the possibility that PTPP might compete with catenins for binding to cadherin. W. J. Nelson also reported on the distribution of the adenomatous polyposis coli (APC) gene product that also binds catenins. APC protein is localized to the tips of membrane protrusions that contain bundles of microtubules, indicating that APC protein is involved in a specialized form of microtubule-dependent cell migration. Desmosomes are Ca*+-dependent cell adhesion junctions that contain adhesion proteins of the cadherin superfamily and associated cytoplasmic proteins that are linked to keratin intermediatefilaments. P. Cowin demonstrated that plakoglobin binds competitively to desmosomal cadherins and to a-catenin. She speculated that this competition might regulate the association of plakoglobin with different cadherin complexes in desmosomes versus adherens junctions, and of different cytoskeletal protein complexes with these junctions. In contrast to the protein complexity of the junctions discussed above, gap junctions are composed of one protein, the connexin. However, a high degree of structural and functional diversity is possible because of the large number of different genes encoding connexins. N. B. Gilula (La Jolla, USA)
0 1996 ElsevierScience Ltd PII: 50962.8924(96)30040-8
*Keystone Symposium on Molecular Approaches to the Function of Intercellular Junctions. Lake Tahoe, CA, USA; 1-7 March 1996. Organized by Bruce Nicolson, Dan Goodenough, Pam Cowin and Peter Bryant.
W. James Nelson is in the Dept of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 943055426, USA. E-mail: wjnelson@leland. stanford.edu
325
MISCELLANEA
FIGURE 1 Localization of ectopically expressed B-catenin in Xenopus blastomeres. The HA-tagged p-catenin is shown in green and the yolk platelets are stained red. Plasma membrane (arrow) and nuclear (arrowheads) localizations of the B-catenin are visible. Accumulation of p-catenin in the nucleus may account for its signalling activity, which is independent of its function in cell-cell adhesion. This image was kindly provided by Franc;ois Fagotto and Barry Cumbiner of the Sloan Kettering Institute, New York, USA. For more information, see FACOTTO, F., FUNAYAMA, N., CLUCK, U. and CUMBINER, B. M. (1996) /. Cell Rio/. 132, 1105-l 114. Bar, 50 Pm. suggested that the structural and, perhaps, functional diversity of gap junction channels could be increased if they contained only one or more different connexins, or a gap junction channel was composed of two identical or two different hemichannels. There was considerable discussion of experimental tests of these possibilities. P. Brink (Stony Brook, USA) and R. Weingart (Bern, Switzerland) showed that cells expressing a single connexin displayed a characteristic gap junction conductance and gating characteristics. Significantly, cells expressing a combination of connexin genes did not have a conductance or gating signature characteristic of any individual gap junction, suggesting that, in cells expressing more than one connexin gene, heterotypic combinations of connexin proteins occur. The structure of gap junctions was discussed by B. Nicolson (Buffalo, USA) and M. Yeager (La Jolla, USA). Nicolson used a mutational approach to study the structure of gap junctions in which specific functions were ablated or modified. Yeager described the structure of two-dimensional crystals of gap junctions, which revealed a hexagonal lattice comprised of a hexamerit cluster of connexins. Roles of junction proteins in regulating cellular differentiation One of the highlights of this meeting was the potential roles of
326
different junctional protein complexes in regulating cellular differentiation. Studies of cadherins and catenins in Drosophila, Xenopus and mammals have taken many unexpected turns. M. Peifer (Chapel Hill, USA) reviewed studies of ARMADILLO (ARM), the Drosophila homologue of B-catenin, in the wingless signal-transduction pathway. Peifer described the phenotype of embryos in which maternal ARM was reduced to very low levels in a zygotic armadillo-null embryo: the adherens junction did not assemble; cell-cell adhesion was disrupted; epithelial cells appeared to have undergone conversion to mesenchyme, together with a loss of cell polarity; and gastrulation was blocked. T. Uemura (Kyoto, Japan) described studies on the distribution and function of DE-cadherin in Drosophila development. A mutation in DE-cadherin, shotgun, caused distinct changes in the branching morphogenesis of malpighian tubules, hindgut and the tracheal system. The roles of B-catenin and plakoglobin in signalling events in Xenopus development were explored by M. Klymkowsky (Boulder, USA) and B. Cumbiner (New York, USA). They reported that ectopic expression of either plakoglobin or p-catenin in the vegetal pole of fertilized Xenopus eggs resulted in duplication of the embryonic axis. This was accompanied by translocation of plakoglobin and
p-catenin into the nucleus (Fig. 1). Klymkowsky and Gumbiner showed independently that coexpression of cadherin suppressed the translocation of plakoglobin and p-catenin from the plasma membrane/cytoplasm to the nucleus and did not result in duplication of the embryonic axis. Cumbiner suggested that B-catenin may be working through the Nieuwkoop centre and described preliminary experiments to examine downstream effecters of p-catenin signalling. He reported that a member of the Hox gene family, siamois, was localized to the Nieuwkoop centre, and overexpression gave rise to duplication of the embryonic axis similar to that of B-catenin. Studies on roles of B-catenin in signalling in mammalian cells has also proceeded at a rapid pace. W. Birchmeier described the results of a yeast two-hybrid screen for B-catenin-binding proteins that revealed LEF-1, a DNA-binding protein involved in epithelia-to-mesenchyme conversion. Birchmeier described gelshift assays showing that LEF-1 interactions with DNA change in the presence of p-catenin. He suggested that this could affect gene expression, resulting in changes in cell differentiation pathways. R. Kemler showed independently that ectopic expression of LEF-1 in mouse embryos resulted in localization of p-catenin and LEF-1 to the nucleus, loss of cell-cell contacts, and formation of cells that were mesenchymal in morphology. Significantly, homozygous knockout of the gene encoding B-catenin is embryonic lethal at approximately embryonic-day 7 (E7) owing to defects in ectoderm formation and a block in mesoderm induction (R. Kemler, W. Birchmeier). Dual localization of proteins in junctions and the nucleus was also shown by W. Franke (Heidelberg, Germany) for proteins of either tight junctions or desmosomes, suggesting that other junctional proteins might have signalling functions. Similar conclusions were drawn by M. Beckerle (Salt Lake City, USA) for zyxin, a cytoplasmic protein that is localized to focal-adhesion plaques at the cell-extracellular-matrix interface and the nucleus. The phenotypes of mice that have knockouts in a variety of the genes encoding connexins were described. These studies also show the importance of gap junctions in a wide variety of tissue-differentiation and function events. The phenotypes of mice homozygous for knockout (-/-) of
trends in CELL BIOLOGY (Vol. 6) August 1996
MISCELLANEA
specific connexin genes was, in some cases, different from that anticipated from previous studies of the tissue distribution of the protein. A. Simon (Boston, USA) described the effects of a deletion of Cx37 in mice. Although Cx37 was thought to be expressed in vascular endothelial cells, female Cx37 -/- mouse knockouts were sterile and had defects in oocyte development. K. Willecke (Bonn, Germany) described the phenotype of Cx26 -Imice, which died at E9.5E10.5. Willecke showed that Cx26 is normally expressed in the labyrinth layer of the placenta, and loss of expression likely gives rise to decreased nutrient uptake by the embryo, leading to poor growth and death. Willecke also described the phenotype of Cx32 -I-
A penny for your thoughts? Technology Transfer: Making the most of your Intellectual Property by Neil F. Sullivan, Cambridge University Press, 7 995. f40.00 (235 pages) ISBN 0 52 1 466 7 6 4 It is often argued that the UK has a poor track record in converting discoveries into commercial products. One of the many reasons for this is that academic scientists in certain branches of science are poorly informed of the processes involved - in particular, the crucial early steps necessary to recognize and protect their intellectual property. Technology Transfer is a very useful addition to the literature on this subject. It gives a clear and precise account of how to protect intellectual property and then how to develop it commercially either through licensing or a business start up. Neil Sullivan is extremely well qualified to produce a definitive work in this field. He has a PhD in Molecular Biology and is a Master of Business Administration. He has worked as a post-doctoral scientist in both the USA and the UK, and has recently acquired business development and technology-
mice, which had several abnormalities in liver metabolism and growth, and an increased incidence of spontaneous and chemical carcinogeninduced liver tumours. N. B. Cilula described the phenotype of Cx0l3 -/mice, which displayed a defect associated with lens development that resulted in cataract formation. G. Kidder (Ontario, Canada) examined Cx43 -/mice. Although Cx43 was thought to be important in development of the preimplantation embryo, Cx43 -/mice developed normally until birth at which time they died owing to occlusion of the right ventricular outflow tract caused by hyperplastic cell growth. So, what did we learn? To state the obvious, junction organization and
function remain complex. Detailed biochemical studies are elucidating structural interactions between proteins in each junctional complex, and genetic tests of protein functions are proceeding at a fast pace. Ectopic expression of mutant proteins and complete knockouts of specific genes are also revealing additional roles of junction proteins in signal transduction to the nucleus, with consequences for cell-fate determination and differentiation. To paraphrase a comment by Werner Franke, ‘we have always considered a role for these proteins in crosstalk between the plasma membrane and nucleus, but now we must consider that some have a direct role in crosswalk between these compartments.’
transfer experience as Director of Industrial Liaison at the University of Newcastle, UK. This book is written very much from the scientist’s point of view. It starts with a short description of intellectual property and what to do to ensure that you obtain the best protection. It does not describe how to file a patent-that is for a patent agent - but rather spells out what the scientist should be thinking about prior to filing a patent and describes what scientists should do both before and afterfiling to make sure that they have valuable intellectual property and retain its value. The bulk of the book is concerned with the commercial development of intellectual property. For patents or other forms of protection of intellectual property, there is a welldeveloped legal framework of practice, but for the commercial development of intellectual property there is no proscribed way. The author starts by stressing the crucial first step for any research scientist before embarking on the commercial development of his or her research. It is essential to be very clear about what one wants to achieve as this will determine what you need to do and how you should set about to do it. Sometimes, more than one person is involved and a collective object must be established. Quite correctly, Sullivan has chosen not to give a proscriptive formula 01 what to do, but rather he has laid out the issues that need to be considered and highlighted the problems that
one may face. Both for licensing and for a business start up, he touches on many of the key points and discusses the advantages and disadvantages of different approaches. There is a wealth of very useful information in these chapters to help in the preparation for negotiating a licensing agreement with a corporate partner, including a section on understanding the point of view of the other party and learning to see issues from another’s perspective. The chapters covering a business start up are not as detailed as those covering licensing agreements but, nevertheless, cover most of the key points and give a good perspective of the overall process, In reality, a business has to start before all the pieces are in place, and initially it is much more chaotic (and more fun) than would seem from the description in this book. The author is a biologist and it is appropriate that, in his conclusion, he should very briefly discuss some of the problems facing the rapidly growing business sector of biotechnology. It is important to stress, however, that this book is relevant to technology transfer in all branches of science. Finally, there are three appendices, a glossary of business terminology, sources of marketing information and a list of useful addresses. Overall, this is an excellent and informative book and will be verv, heloful to all scientists wishing to see ‘the results of their research developed commercially.
trends ir; CELL BIOLOGY (Vol. 6) August 1996
0 1996 Elsevier Science Ltd
Alan Munro Christ’s College, Cambridge, UK CB2 3BU.
327
Intercellular junctions localize to the outer margins of the cell. Their roles in cell-cell interactions and their different morphologies were described in a classic paper by Farquhar and Palade over 30 years ago. At this symposium*, there were many unexpected surprises as researchers described the functions of different protein constituents of junctions and how these proteins influence a diversity of cellular and tissue functions. A highlight was direct evidence that structural components of intercellular junctions play direct roles in events in the nucleus, in the determination of cellular differentiation during embryogenesis, and in organ function in the adult organism. Junction organization and structure The identity and structural organization of proteins in the tight junction have been important questions in recent years. B. Stevenson (Edmonton, Canada) and J. Anderson (Yale, USA) described the sequences of genes encoding two cytoplasmic proteins, ZO-1 and 20-2, that associate with tight junctions. These proteins have structural motifs common to the membrane-associated guanylate kinase (MACUK) family of proteins, another member of which is the product of the lethal discs-large- 7 tumour suppressor gene (d/g) found in the septate junction in Drosophila (D. Woods, Irvine, USA). Proteins of the MAGUK family have conserved discs large homology repeats (PDZ domain). Anderson noted that many membrane proteins have a conserved C-terminal amino acid motif, S/TxV, that binds to the PDZ domain. He suggested that MACUK proteins may be important in regulating a diversity of signaltransduction events and/or membranecortical-cytoskeleton interactions. The identification of membrane protein(s) that regulate tight-junction function as a barrier to paracellular diffusion has been difficult. The best candidate so far is occludin (S. Tsukita, Kyoto, Japan). Immuno-electron microscopy of freeze-fractured membranes containing occludin showed clustering of the protein in tightly apposed membrane structures reminiscent of tight junctions in the plasma membrane. Protein-protein interactions are clearly not solely responsible for tight-junction organization since the lipid environment and amount of cholesterol present in the membrane also regulate function (E. Schneeberger, Charlestown, USA). T. Fleming (Southampton, USA) de-
Meeting of cell-cell adhesion, communication and signalling at the junction W. James Nelson scribed studies on expression and assembly of tight-junction-associated proteins during preimplantation mouse development. He showed that assembly is regulated temporally at transcriptional, translational and posttranslational levels and that assembly of tight-junction proteins is a sequential process. D. Goodenough (Boston, USA) examined the correlation between tight-junction protein distribution and formation of functional diffusion barriers between cells in pregastrulation Xenopus embryos. He concluded that tight junctions formed initially at the base of cells and that they did not localize to the apex of the lateral membrane until after the 1 OOOcell stage. He suggested that assembly of the adherens junctional complex might specify tight-junction location. Adherens junctions have long been recognized as principle sites of cell-cell adhesion. Membrane proteins, members of the cadherin superfamily, and cytoplasmic proteins, catenins and actin, have been localized to them. W. Hendrickson (New York, USA) has solved the structure of the 5th repeat domain of N-cadherin. He showed that a conserved amino acid motif, HAV, is located at an important interface between dimerforming domains. Hendrickson also presented preliminary studies of the structure of the interface between the 4th and 5th extracellular domains of N-cadherin, which revealed the apposition of two amino acid motifs that have been shown to bind Ca2+. This solution structure of the N-cadherin extracellular domains suggests a model in which cadherins laterally associate with one another to form a large complex that could potentiate weak adhesion between individual cadherins on adjacent cells. W. J. Nelson (Stanford, USA) showed by retrospective immunofluorescence microscopy analysis that large puncta containing cadherin and catenins associate with actin filaments at early epithelial cell-cell contacts, which may reflect the parallel organization of cadherins into large complexes.
trends in CELL BIOLOGY (Vol. 6) August 1996
Linkage of cadherins to the actin cytoskeleton through catenins is important for regulating cadherin-mediated cell-cell adhesion. R. Kemler (Freiburg, Germany) and P. Cowin (New York, USA) presented details of protein domains involved in interactions between c1- and B-catenin/plakoglobin, and R. Kemler and W. Birchmeier (Berlin, Germany) presented evidence from mouse knockouts that catenins are absolutely required for cadherin function in cell-cell adhesion. In addition to their interactions with cadherin, catenins also bind other membrane and cytoplasmic proteins. N. Tonks (Cold Spring Harbor, USA) reported that a transmembrane protein tyrosine phosphatase (PTPP) interacts with the catenin-binding domain of cadherin, raising the possibility that PTPP might compete with catenins for binding to cadherin. W. J. Nelson also reported on the distribution of the adenomatous polyposis coli (APC) gene product that also binds catenins. APC protein is localized to the tips of membrane protrusions that contain bundles of microtubules, indicating that APC protein is involved in a specialized form of microtubule-dependent cell migration. Desmosomes are Ca*+-dependent cell adhesion junctions that contain adhesion proteins of the cadherin superfamily and associated cytoplasmic proteins that are linked to keratin intermediatefilaments. P. Cowin demonstrated that plakoglobin binds competitively to desmosomal cadherins and to a-catenin. She speculated that this competition might regulate the association of plakoglobin with different cadherin complexes in desmosomes versus adherens junctions, and of different cytoskeletal protein complexes with these junctions. In contrast to the protein complexity of the junctions discussed above, gap junctions are composed of one protein, the connexin. However, a high degree of structural and functional diversity is possible because of the large number of different genes encoding connexins. N. B. Gilula (La Jolla, USA)
0 1996 ElsevierScience Ltd PII: 50962.8924(96)30040-8
*Keystone Symposium on Molecular Approaches to the Function of Intercellular Junctions. Lake Tahoe, CA, USA; 1-7 March 1996. Organized by Bruce Nicolson, Dan Goodenough, Pam Cowin and Peter Bryant.
W. James Nelson is in the Dept of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 943055426, USA. E-mail: wjnelson@leland. stanford.edu
325
MISCELLANEA
FIGURE 1 Localization of ectopically expressed B-catenin in Xenopus blastomeres. The HA-tagged p-catenin is shown in green and the yolk platelets are stained red. Plasma membrane (arrow) and nuclear (arrowheads) localizations of the B-catenin are visible. Accumulation of p-catenin in the nucleus may account for its signalling activity, which is independent of its function in cell-cell adhesion. This image was kindly provided by Franc;ois Fagotto and Barry Cumbiner of the Sloan Kettering Institute, New York, USA. For more information, see FACOTTO, F., FUNAYAMA, N., CLUCK, U. and CUMBINER, B. M. (1996) /. Cell Rio/. 132, 1105-l 114. Bar, 50 Pm. suggested that the structural and, perhaps, functional diversity of gap junction channels could be increased if they contained only one or more different connexins, or a gap junction channel was composed of two identical or two different hemichannels. There was considerable discussion of experimental tests of these possibilities. P. Brink (Stony Brook, USA) and R. Weingart (Bern, Switzerland) showed that cells expressing a single connexin displayed a characteristic gap junction conductance and gating characteristics. Significantly, cells expressing a combination of connexin genes did not have a conductance or gating signature characteristic of any individual gap junction, suggesting that, in cells expressing more than one connexin gene, heterotypic combinations of connexin proteins occur. The structure of gap junctions was discussed by B. Nicolson (Buffalo, USA) and M. Yeager (La Jolla, USA). Nicolson used a mutational approach to study the structure of gap junctions in which specific functions were ablated or modified. Yeager described the structure of two-dimensional crystals of gap junctions, which revealed a hexagonal lattice comprised of a hexamerit cluster of connexins. Roles of junction proteins in regulating cellular differentiation One of the highlights of this meeting was the potential roles of
326
different junctional protein complexes in regulating cellular differentiation. Studies of cadherins and catenins in Drosophila, Xenopus and mammals have taken many unexpected turns. M. Peifer (Chapel Hill, USA) reviewed studies of ARMADILLO (ARM), the Drosophila homologue of B-catenin, in the wingless signal-transduction pathway. Peifer described the phenotype of embryos in which maternal ARM was reduced to very low levels in a zygotic armadillo-null embryo: the adherens junction did not assemble; cell-cell adhesion was disrupted; epithelial cells appeared to have undergone conversion to mesenchyme, together with a loss of cell polarity; and gastrulation was blocked. T. Uemura (Kyoto, Japan) described studies on the distribution and function of DE-cadherin in Drosophila development. A mutation in DE-cadherin, shotgun, caused distinct changes in the branching morphogenesis of malpighian tubules, hindgut and the tracheal system. The roles of B-catenin and plakoglobin in signalling events in Xenopus development were explored by M. Klymkowsky (Boulder, USA) and B. Cumbiner (New York, USA). They reported that ectopic expression of either plakoglobin or p-catenin in the vegetal pole of fertilized Xenopus eggs resulted in duplication of the embryonic axis. This was accompanied by translocation of plakoglobin and
p-catenin into the nucleus (Fig. 1). Klymkowsky and Gumbiner showed independently that coexpression of cadherin suppressed the translocation of plakoglobin and p-catenin from the plasma membrane/cytoplasm to the nucleus and did not result in duplication of the embryonic axis. Cumbiner suggested that B-catenin may be working through the Nieuwkoop centre and described preliminary experiments to examine downstream effecters of p-catenin signalling. He reported that a member of the Hox gene family, siamois, was localized to the Nieuwkoop centre, and overexpression gave rise to duplication of the embryonic axis similar to that of B-catenin. Studies on roles of B-catenin in signalling in mammalian cells has also proceeded at a rapid pace. W. Birchmeier described the results of a yeast two-hybrid screen for B-catenin-binding proteins that revealed LEF-1, a DNA-binding protein involved in epithelia-to-mesenchyme conversion. Birchmeier described gelshift assays showing that LEF-1 interactions with DNA change in the presence of p-catenin. He suggested that this could affect gene expression, resulting in changes in cell differentiation pathways. R. Kemler showed independently that ectopic expression of LEF-1 in mouse embryos resulted in localization of p-catenin and LEF-1 to the nucleus, loss of cell-cell contacts, and formation of cells that were mesenchymal in morphology. Significantly, homozygous knockout of the gene encoding B-catenin is embryonic lethal at approximately embryonic-day 7 (E7) owing to defects in ectoderm formation and a block in mesoderm induction (R. Kemler, W. Birchmeier). Dual localization of proteins in junctions and the nucleus was also shown by W. Franke (Heidelberg, Germany) for proteins of either tight junctions or desmosomes, suggesting that other junctional proteins might have signalling functions. Similar conclusions were drawn by M. Beckerle (Salt Lake City, USA) for zyxin, a cytoplasmic protein that is localized to focal-adhesion plaques at the cell-extracellular-matrix interface and the nucleus. The phenotypes of mice that have knockouts in a variety of the genes encoding connexins were described. These studies also show the importance of gap junctions in a wide variety of tissue-differentiation and function events. The phenotypes of mice homozygous for knockout (-/-) of
trends in CELL BIOLOGY (Vol. 6) August 1996
MISCELLANEA
specific connexin genes was, in some cases, different from that anticipated from previous studies of the tissue distribution of the protein. A. Simon (Boston, USA) described the effects of a deletion of Cx37 in mice. Although Cx37 was thought to be expressed in vascular endothelial cells, female Cx37 -/- mouse knockouts were sterile and had defects in oocyte development. K. Willecke (Bonn, Germany) described the phenotype of Cx26 -Imice, which died at E9.5E10.5. Willecke showed that Cx26 is normally expressed in the labyrinth layer of the placenta, and loss of expression likely gives rise to decreased nutrient uptake by the embryo, leading to poor growth and death. Willecke also described the phenotype of Cx32 -I-
A penny for your thoughts? Technology Transfer: Making the most of your Intellectual Property by Neil F. Sullivan, Cambridge University Press, 7 995. f40.00 (235 pages) ISBN 0 52 1 466 7 6 4 It is often argued that the UK has a poor track record in converting discoveries into commercial products. One of the many reasons for this is that academic scientists in certain branches of science are poorly informed of the processes involved - in particular, the crucial early steps necessary to recognize and protect their intellectual property. Technology Transfer is a very useful addition to the literature on this subject. It gives a clear and precise account of how to protect intellectual property and then how to develop it commercially either through licensing or a business start up. Neil Sullivan is extremely well qualified to produce a definitive work in this field. He has a PhD in Molecular Biology and is a Master of Business Administration. He has worked as a post-doctoral scientist in both the USA and the UK, and has recently acquired business development and technology-
mice, which had several abnormalities in liver metabolism and growth, and an increased incidence of spontaneous and chemical carcinogeninduced liver tumours. N. B. Cilula described the phenotype of Cx0l3 -/mice, which displayed a defect associated with lens development that resulted in cataract formation. G. Kidder (Ontario, Canada) examined Cx43 -/mice. Although Cx43 was thought to be important in development of the preimplantation embryo, Cx43 -/mice developed normally until birth at which time they died owing to occlusion of the right ventricular outflow tract caused by hyperplastic cell growth. So, what did we learn? To state the obvious, junction organization and
function remain complex. Detailed biochemical studies are elucidating structural interactions between proteins in each junctional complex, and genetic tests of protein functions are proceeding at a fast pace. Ectopic expression of mutant proteins and complete knockouts of specific genes are also revealing additional roles of junction proteins in signal transduction to the nucleus, with consequences for cell-fate determination and differentiation. To paraphrase a comment by Werner Franke, ‘we have always considered a role for these proteins in crosstalk between the plasma membrane and nucleus, but now we must consider that some have a direct role in crosswalk between these compartments.’
transfer experience as Director of Industrial Liaison at the University of Newcastle, UK. This book is written very much from the scientist’s point of view. It starts with a short description of intellectual property and what to do to ensure that you obtain the best protection. It does not describe how to file a patent-that is for a patent agent - but rather spells out what the scientist should be thinking about prior to filing a patent and describes what scientists should do both before and afterfiling to make sure that they have valuable intellectual property and retain its value. The bulk of the book is concerned with the commercial development of intellectual property. For patents or other forms of protection of intellectual property, there is a welldeveloped legal framework of practice, but for the commercial development of intellectual property there is no proscribed way. The author starts by stressing the crucial first step for any research scientist before embarking on the commercial development of his or her research. It is essential to be very clear about what one wants to achieve as this will determine what you need to do and how you should set about to do it. Sometimes, more than one person is involved and a collective object must be established. Quite correctly, Sullivan has chosen not to give a proscriptive formula 01 what to do, but rather he has laid out the issues that need to be considered and highlighted the problems that
one may face. Both for licensing and for a business start up, he touches on many of the key points and discusses the advantages and disadvantages of different approaches. There is a wealth of very useful information in these chapters to help in the preparation for negotiating a licensing agreement with a corporate partner, including a section on understanding the point of view of the other party and learning to see issues from another’s perspective. The chapters covering a business start up are not as detailed as those covering licensing agreements but, nevertheless, cover most of the key points and give a good perspective of the overall process, In reality, a business has to start before all the pieces are in place, and initially it is much more chaotic (and more fun) than would seem from the description in this book. The author is a biologist and it is appropriate that, in his conclusion, he should very briefly discuss some of the problems facing the rapidly growing business sector of biotechnology. It is important to stress, however, that this book is relevant to technology transfer in all branches of science. Finally, there are three appendices, a glossary of business terminology, sources of marketing information and a list of useful addresses. Overall, this is an excellent and informative book and will be verv, heloful to all scientists wishing to see ‘the results of their research developed commercially.
trends ir; CELL BIOLOGY (Vol. 6) August 1996
0 1996 Elsevier Science Ltd
Alan Munro Christ’s College, Cambridge, UK CB2 3BU.
327