No abstract

Scatter factor is a fibroblast-derived protein that causes separation of contiguous epithelial cells and increased local mobility of unanchored cells. Highly purified scatter factor has been obtained by a combination of ionexchange and reverse-phase chromatography from serum-free medium conditioned by a ras-transformed clone (D4) of mouse NIH 3T3 fibroblasts. Under nonreducing conditions scatter factor has a pI of -9.5 and migrates in SDS/polyacrylamide gels as a single band at -62 kDa from which epithelial scatter activity can be recovered. Treatment with reducing agents destroys biological activity and is associated with the appearance of two major bands at "57 and "30 kDa. Whether both the 57-kDa and 30-kDa polypeptides are required for biological activity remains to be established. All the activities observed in crude medium conditioned by cells producing scatter factor are retained by highly purified preparations of scatter factor.These include (i) increased local movement, modulation of morphology, and inhibition of junction formation by single epithelial cells and (it) disruption of epithelial interactions and cell scattering from preformed epithelial sheets. These changes occur with picomolar concentrations of purified scatter factor and without an effect on cell growth.Cell movement is restricted by the interaction with basement and extracellular membrane proteins (1) and, in certain tissues, by cell-cell interactions that involve cell-specific adhesion molecules (2). Movement of epithelial cells is further limited by cell-cell (desmosomes, tight and gap junctions) and cell-substratum (hemidesmosomes) junctional systems. Cytokines are also involved in the regulation of cell movement, as it appears that certain growth factors, including nerve growth factor (3), platelet-derived growth factor (4), and epidermal growth factor (5, 6) may stimulate cell movement as well as cell growth.There is increasing evidence, however, for a new group of cytokines that regulate cell movement with little or no effect on cell growth. Pioneering studies by Yoshida et al. (7) indicated that certain mouse and rat hepatoma lines and mouse and human leukemias produced a protein of 70 kDa that was chemotactic for the producer cells as well as for other tumor cells but not for polymorphonuclear cells (7). More recently, another motility factor has been isolated from serum-free medium conditioned by the human melanoma line A2058. This 55-kDa protein has both chemotactic and chemokinetic activity for the producer cells (but not for polymorphonuclear cells) and has been designated autocrine motility factor (AMF) (8). ras-transformed derivatives of mouse NIH 3T3 fibroblasts also produce AMF and respond to it and, interestingly, normal NIH 3T3 firboblasts, which do not produce AMF, are able to respond to the AMF secreted by ras-tranformed cells (8). A factor similar to AMF has been isolated from serum-free medium conditioned by a highly metastatic clone (MTLn3) of rat mammary adenocarcinoma (9). This factor (53 kDa) is chemota...

Huntington's disease (HD) is thought to show true dominance, since subjects with two mutant alleles have been reported to have similar ages at onset of disease compared to heterozygous sibs. We have investigated this phenomenon using a cell culture model. Protein aggregate formation was used as an indicator for pathology, as intraneuronal huntingtin inclusions are associated with pathology in vitro and in vivo. We showed that cytoplasmic and nuclear aggregates are formed by constructs comprising part of exon 1 of huntingtin with 41, 51, 66, or 72 CAG repeats, in a rate that correlates with repeat number. No inclusions were seen with 21 CAG repeat constructs. Mutant and wild type huntingtin fragments can be sequestered into inclusions seeded by a mutant huntingtin. Wild type huntingtin did not enhance or interfere with protein aggregation. The rate of protein aggregation was dose dependent for all mutant constructs tested. These experiments suggested a model for the dominance observed in HD; the decrease in the age at onset of a mutant homozygote may be small compared to the variance in the age at onset for that specific repeat number in heterozygotes. Our experiments also provide a model, which may explain the diVerent repeat size ranges seen in patients and healthy controls for the diVerent polyglutamine diseases. (J Med Genet 1999;36:739-746)