Regulated expression of vimentin cDNA in cells in the presence and absence of a preexisting vimentin filament network.

Human cells were transfected with a mouse vimentin cDNA expression vector containing the hormone response element of mouse mammary tumor virus. The distribution of mouse vimentin after induction with dexamethasone was examined by indirect immunofluorescence with antivimentin antibodies specific for either mouse or human vimentin. In stably transfected HeLa cells, which contain vimentin filaments, addition of dexamethasone resulted in the initial appearance of mouse vimentin in discrete areas, usually perinuclear, that always corresponded to areas of the human filament network with the most intense fluorescence. Within 20 h after addition of dexamethasone, the mouse and human vimentin immunofluorescence patterns were identical. However, in stably transfected MCF-7 cells, which lack vimentin filaments, induction of mouse vimentin synthesis resulted in assembly of vimentin filaments throughout the cytoplasm without any obvious local concentrations. Transient expression experiments with SW-13 cell subclones that either lack or contain endogenous vimentin filaments yielded similar results to those obtained with MCF-7 and HeLa transfectants, respectively. Further experiments with HeLa transfectants were conducted to follow the fate of the mouse protein after synthesis had dropped after withdrawal of dexamethasone. The mouse vimentin-specific fluorescence was initially lost from peripheral areas of the cells while the last detectable mouse vimentin always corresponded to the human filament network with the most intense fluorescence. These studies are consistent with a uniform assembly of vimentin filaments throughout the cytoplasm and suggest that previous observations of polarized or vectorial assembly from a perinuclear area to more peripheral areas in cells may be attributable to the nonuniformly distributed appearance of vimentin filaments in immunofluorescence microscopy.

A functional role for vimentin intermediate filaments in the metabolism of lipoprotein-derived cholesterol in human SW-13 cells.

Numerous studies have indicated that cytoplasmic intermediate filaments (cIFs) can associate with cellular lipids. To determine if these interactions might have functional consequences, we have studied the lipid metabolism of human SW-13 adrenal tumor cell lines that either contain vimentin-type cIFs (vim+) or lack any detectable cIF network (vim-). Although there were no significant differences in phospholipid or glyceride synthesis, vim- cell lines had elevated levels of cholesterol synthesis and decreased cholesterol esterification, compared with vim+ cells. These differences in cholesterol synthesis and esterification were found to be due to an impaired ability of vim- cells to utilize low density lipoprotein (LDL)-derived cholesterol, although receptor-mediated endocytosis of LDL and the capacity of these cells to esterify endogenously produced cholesterol were not affected. Expression of a mouse vimentin cDNA in stably transfected cell lines, derived from vim- cells, restored the capacity of these cells to utilize LDL cholesterol. The uptake and metabolism of [3H]cholesterol linoleate-loaded LDL showed that the impaired ability of vim- cells to esterify LDL cholesterol was not associated with an accumulation of cellular free cholesterol but rather an increase in the appearance of [3H]cholesterol in the culture medium. These studies indicate that in SW-13 cells, the intracellular movement of LDL-derived cholesterol from the lysosome to the site of esterification is a vimentin-dependent process.

The presence or absence of a vimentin-type intermediate filament network affects the shape of the nucleus in human SW-13 cells.

Human SW-13 cells express the intermediate filament protein vimentin in a mosaic pattern (Hedberg, K. K. and Chen, L. B. (1986). Exp. Cell Res. 163, 509-517). We have isolated SW-13 clones that do (vim+) or do not (vim-) synthesize vimentin as analyzed using anti-intermediate filament immunofluorescence, electron microscopy and two-dimensional gel analysis of detergent-extracted preparations. Vimentin is the only cytoplasmic intermediate filament protein present in the vim+ cells, and the vim- cells do not contain any detectable cytoplasmic intermediate filament system. The presence or absence of intermediate filaments did not observably affect the distribution of mitochondria, endoplasmic reticulum, microtubules or actin stress fibers when these structures were visualized by fluorescence microscopy. However, electron microscopy and anti-lamin A/C immunofluorescence studies showed that nuclear morphology in vim- cells was frequently characterized by large folds or invaginations, while vim+ cells had a more regular or smooth nuclear shape. When vim- cells were transfected with a mouse vimentin expression plasmid, the synthesis of a mouse vimentin filament network restored the smooth nuclear morphology characteristic of vim+ cells. Conversely, when vim+ cells were transfected with a carboxy-terminally truncated mutant vimentin, expression of the mutant protein disrupted the organization of the endogenous vimentin filaments and resulted in nuclei with a prominently invaginated morphology. These results indicated that in SW-13 cells the vimentin filament system affects the shape of the nucleus.

Detection of three rare (G377S, T134P and 1451delAC), and two novel mutations (G195W and Rec[1263del55;1342G>C]] in Spanish Gaucher disease patients. Mutation in brief no. 251. Online.

To study glucocerebrosidase mutations causing Gaucher disease, we have screened 30 apparently unrelated patients for the presence of 7 previous described mutations. N370S (1226A>G) was the most common mutation (43%), followed by L444P (1448T>C) (23%). To identify the other unknown mutations, we screened regions of the glucocerebrosidase gene (GBA), by SSCP and sequencing. These analyses allowed identification of one novel G195W (700G>T), and two rare T134P (517A>C) and G377S (1246G>A) missense mutations. Mutation T134P (517A>C) was present in a type I patient, while G195W (700G>T), was encountered in two patients (types I, and III). The prevalence of mutation G377S (1246G>A), previously undetected in Spain, was found to be high (8%) making it a good candidate for routine genetic screening in patients from Spanish descent. Two null mutations have been identified as well Rec[1263del55;1342G>C], and 1451delAC). The Rec[1263del55;1342G>C] is a novel chimeric allele in which the gene sequence between nucleotides 5878-6272 [sequence numbering according to Horowitz et al.(1989)] has been replaced by the homologous region of the pseudogene, and consequently it carries the 1263del55 and D409H (1342G>C) mutations. The functional equivalence of this allele to a 1263del55 allele previously described, suggest the potencial existence of a group of four distinct 55 bp deletion harboring alleles with identical clinical consequences.