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Biomedical subjects

F Propst

Publications and source records attributed to F Propst.

At least 19 recordsLinked to original sources
PubMed1998

Evidence against structural and functional identity of microtubule-associated protein 1B and proteoglycan claustrin.

Recently, the concept of microtubule-associated protein 1B as an intracellular 2460 amino acid protein was challenged by the suggestion that only the N-terminal 1022 codons are utilized and encode the core protein of the extracellular proteoglycan claustrin (Burg and Cole (1994) J. Neurobiol. 25, 1-22). We expressed this N-terminal MAP1B fragment in tissue culture cells and found that it bound to microtubules and was not localized in the extracellular matrix. In addition, epitope mapping demonstrated that MAP1B consisted of more than 1022 amino acids and that the reported cDNA of claustrin is incomplete.

3T3 Cells↗
PubMed1997

Targeted inactivation of plectin reveals essential function in maintaining the integrity of skin, muscle, and heart cytoarchitecture.

Previous studies suggest that plectin, a versatile cytoskeletal linker protein, has an important role in maintaining the structural integrity of diverse cells and tissues. To establish plectin's function in a living organism, we have disrupted its gene in mice. Plectin (-/-) mice died 2-3 days after birth exhibiting skin blistering caused by degeneration of keratinocytes. Ultrastructurally, hemidesmosomes and desmosomes appeared unaffected. In plectin-deficient mice, however, hemidesmosomes were found to be significantly reduced in number and apparently their mechanical stability was altered. The skin phenotype of these mice was similar to that of patients suffering from epidermolysis bullosa simplex (EBS)-MD, a hereditary skin blistering disease with muscular dystrophy, caused by defects in the plectin gene. In addition, plectin (-/-) mice revealed abnormalities reminiscent of minicore myopathies in skeletal muscle and disintegration of intercalated discs in heart. Our results clearly demonstrate a general role of plectin in the reinforcement of mechanically stressed cells. Plectin (-/-) mice will provide a useful tool for the study of EBS-MD, and possibly other types of plectin-related myopathies involving skeletal and cardiac muscle, in an organism amenable to genetic manipulation.

Animals↗
PubMed1997

Serum starved v-mos-transformed cells are unable to appropriately downregulate cyclins and CDKs.

Serum deprived v-mos-transformed NIH3T3 cells are unable to enter a true quiescent state, but instead, arrest in the early G1 phase of the cell cycle. We have analysed several cell cycle regulatory proteins in these G1 arrested cells and show altered regulation in the expression and activity of certain cyclins and cyclin-dependent kinases. In particular, p34cdc2, cyclin A, cyclin D and cyclin E are not appropriately down-regulated in serum starved, G1 arrested, v-mos-transformed cells as compared with quiescent NIH3T3 cells. Furthermore, serum starved v-mos-transformed cells have elevated histone H1 kinase activity associated with cyclin A, cyclin E, p33cdk2, and p34cdc2. Using a metallothionein-inducible c-mos(mu) expression system, we show that c-mos(mu) induction in quiescent NIH3T3 cells causes elevated expression of p34cdc2. However, this induction of c-mos(mu) and subsequent expression of p34cdc2 was not sufficient to promote significant entry of cells into S phase. Analysis of extracts from serum starved v-H-ras, v-src, and tpr-met transformed NIH3T3 cells demonstrates that these oncogene-transformed cells also contain elevated levels of p34cdc2. We propose that the altered regulation of these critical cell cycle regulatory molecules, and specifically the inability to fully downregulate their activity, contributes significantly to neoplastic transformation and subsequent unregulated growth of tumor cells.

3T3 Cells↗
PubMed1995

Kinase activities of c-Mos and v-Mos proteins: a single amino acid exchange is responsible for constitutive activation of the 124 v-Mos kinase.

The Mos protein kinase is a serine-/threonine-specific protein kinase with a crucial role in meiotic cell divisions in vertebrates. Several oncogenic derivatives of the c-Mos protein have been discovered in murine retroviruses. These proteins have acquired mutations and exhibit different degrees of protein kinase activity in vitro. In an attempt to understand the factors governing Mos protein kinase activity we have compared the kinase activities of the wild-type c-Mos protein and two v-Mos proteins (strain HT1 and MSV124) after expression in insect cells. Only the 124 v-Mos protein showed kinase activity in vitro as measured by autophosphorylation, vimentin phosphorylation or by phosphorylation and activation of MAP kinase kinase. By domain swapping and site-directed mutagenesis we identified a single point mutation in the 124 v-Mos protein (Arg145-->Gly) which is responsible for its constitutive activity. This residue is located in the alpha-helix C of the kinase domain close to the ATP binding fold and is conserved in all known c-Mos proteins. Introduction of the corresponding mutation into HT1 v-Mos and into murine c-Mos activated both proteins for autophosphorylation, vimentin phosphorylation and for signalling via MAP kinase kinase in vitro. We hypothesize that the Arg145-->Gly mutation found in 124 v-Mos mimicks a conformational change which might be an obligatory step in the activation of c-Mos in vivo.

Amino Acid Sequence↗
PubMed1995

Expression of the v-Mos oncogene in male meiotic germ cells of transgenic mice results in metaphase arrest.

To explore the role of pp39mos in male germ cell meiosis, we have constructed transgenic mice carrying either the c-Mos or v-Mos genes linked to the human male germ cell-specific phosphoglycerate kinase-2 promoter. All male transgenic mice bearing the v-Mos but not the c-Mos construct were sterile due to arrest of germ cells at metaphase I. Immunocytochemistry performed on sections from control and c-Mos transgenic testes with eight different monoclonal and polyclonal antisera against either alpha-, beta- or gamma-tubulins demonstrated that all could recognize MI spermatocyte spindles from control and c-Mos transgenics, but only one monoclonal anti-microtubule sera decorated the spindles of v-Mos-arrested meiotic figures. Western blot analyses with this one serum revealed a change in proteins in the v-Mos samples. Immunocytochemistry with the MPM-2 monoclonal antibody, which is specific for epitopes phosphorylated during mitosis, demonstrated an increase in cytoplasmic and spindle-associated phosphoproteins in arrested v-Mos spermatocytes. Western analysis with MPM-2 showed an increase in a M(r) 50,000-55,000 and a M(r) 25,000-29,000 protein in Mos transgenic testes when compared to controls. An anti-MAP kinase antibody demonstrated an increase in all four MAP kinases in testes of transgenic mice. Thus, overexpression of pp39v-mos during male germ cell meiosis resulted in an alteration of various cell cycle related kinases and cytostatic factor-like arrest at MI.

Animals↗
PubMed1994

v-mos-transformed cells fail to enter quiescence but growth arrest in G1 following serum withdrawal.

The product of the mos protooncogene normally functions in the induction of meiosis and regulation of cell-cycle progression in oocytes. Here we have investigated the cell-cycle progression of NIH3T3 cells transformed by the v-mos gene. Flow cytometric analysis showed that logarithmically growing v-mos-transformed cells do not differ from their nontransformed counterparts in the distribution of cells in the G1, S, and G2/M phases. Likewise, after serum withdrawal for 48 h, both normal and v-mos-transformed NIH3T3 cells have essentially ceased proliferation, as analyzed by flow cytometry, [3H]thymidine and BrdU incorporation into newly synthesized DNA, and mitotic indexes. However, while the normal NIH3T3 cells are arrested in a quiescent state, the v-mos-transformed cells are arrested in early to mid G1, prior to the point where cells require certain amino acids for proliferation (V point). In agreement with these different arrest points, the v-mos-transformed cells enter S phase following serum stimulation within about 8 h, without the additional 4- to 6-h lag period characteristically displayed by the parental NIH3T3 cells. In addition, we show a lack of expression of a growth arrest-specific gene product, gas1, in the serum-arrested v-mos-transformed cells. These data demonstrated that v-mos-transformed cells display growth characteristics that differ fundamentally from those of normal cells or cells transformed by overexpression of myc [1]. Our results suggest that the v-mos oncoprotein transforms cells, at least in part, by preventing exit from the cell cycle into quiescence.

3T3 Cells↗
PubMed1992

Harderian gland hyperplasia in c-mos transgenic mice.

Transgenic mice carrying the mouse mos proto-oncogene linked to a retroviral LTR develop hyperplasia of the Harderian glands. Enlargement of the glands is evident as early as 18 weeks after birth, with glands reaching up to 10 times their normal weight. Approximately 65% of the cases of hyperplasia occur bilaterally, and the majority of mice affected are male (66%). Elevated levels of mos expression are found in all Harderian glands of mice from the affected transgenic line, but not in glands of normal mice or a non-affected transgenic line, indicating that hyperplasia is dependent on mos expression. Histological examination of the tissue reveals a general involvement of the entire gland epithelium in hyperplastic growth, with no evidence of focal or malignant tumours. These observations show that in addition to neu, myc, ras and ret transgenes, mos, a member of the protein-serine/threonine kinase family of oncogenes, can induce Harderian gland hyperplasia, thus revealing an unusual response by this organ to various classes of oncogenes. Analysis of fos, jun, myc and ets oncogene RNA in mos-induced hyperplastic Harderian glands shows that there are no consistent changes in the level of expression of these oncogenes, suggesting that mos acts via a mechanism other than by increasing the expression of these genes.

Animals↗
PubMed1992

Pheochromocytomas and C-cell thyroid neoplasms in transgenic c-mos mice: a model for the human multiple endocrine neoplasia type 2 syndrome.

Transgenic mice carrying and expressing a mos protooncogene, linked to the Moloney murine sarcoma virus long terminal repeat, develop severe neurological defects and lens abnormalities. Here we report that after long latent periods, mice in three of four of these mos transgenic lines develop a high frequency of multicentric pheochromocytomas and/or medullary thyroid neoplasms. The pattern of tumor formation is remarkably similar to the human autosomal dominantly inherited neoplastic syndrome, multiple endocrine neoplasia type 2 (MEN 2), and tumors from these transgenic animals display the same neuroendocrine marker staining pattern as seen in MEN 2. The similarity between the tumor pathologies and presentation patterns of MEN 2 patients and mos transgenic mice suggests that they may arise through related pathways. The type of tumor presentation varies in a line-dependent manner indicating that there is interaction between the transgene and the genetic background. Moreover, when the non-tumor-bearing mos transgenic line is crossed to a different mouse background, the F1 offspring display the MEN 2 phenotype. These studies indicate that penetrance of the autosomal dominant mos transgenic phenotype is dependent on both integration site and background.

Adrenal Gland Neoplasms↗
PubMed1992

Ets-1 and Ets-2 protooncogene expression in theca cells of the adult mouse ovary.

We have investigated the mRNA expression of the Ets-1 and Ets-2 genes in murine gonads and found expression in adult ovaries. In situ hybridization experiments show that the Ets genes are predominantly expressed in theca cells and cells of ovarian interstitium. By gel retardation experiments we detected DNA binding proteins in ovaries that specifically bind to the ETS motif, suggesting the expression of Ets or Ets-related proteins. Our results raise the possibility of Ets-2 involvement in ovarian pathology seen in patients with Down's syndrome.

Animals↗
PubMed1992

Progressive hind limb paralysis in mice carrying a v-Mos transgene.

To study the function of the protooncogene Mos in mouse brain development we have created a transgenic mouse model system in which an activated form of the gene, the murine retroviral v-Mos gene, is highly overexpressed in the brain. Six transgenic founder animals and mice of one established transgenic line (line TG66) displayed a progressive hind limb paralysis with onset between 18 days and 9 months. The severity of the neurological phenotype correlated with pathological alterations and the degree of v-Mos expression in the brain which varied between individual animals of line TG66. The most striking feature of the brain pathology was the presence of large, abnormal astrocytes in the cerebellum, medulla, thalamus and in the dorsal horn of the spinal cord. These areas also contained shrunken and basophilic neurons whose cytoplasm was abnormally immunoreactive for phosphorylated epitopes of neurofilaments. In addition to neuropathologic changes, these mice also displayed aberrant eye lens differentiation and absence of hair cells in the inner ear. These results establish v-Mos transgenic mice as a model system to study progressive neurodegenerative disease and provide further evidence that the Mos protein-serine/threonine kinase has a function in brain development.

Animals↗
PubMed1992

Patterns of neoplasia in c-mos transgenic mice and their relevance to multiple endocrine neoplasia.

We have previously described a neurological phenotype for transgenic mice carrying the c-Mos proto-oncogene. Pheochromocytomas and C-cell thyroid neoplasms occur in these transgenic lines in patterns that are similar to those seen in multiple endocrine neoplasia type 2 (MEN 2). Characterization of the pathological lesions via immunohistochemistry underscores similarities between MEN 2 and these transgenic mice. When transgenic mice that do not display the MEN 2 phenotype are crossed to a different background, the progeny display the MEN 2 phenotype. Thus the interaction of the background with the transgene is such that it can suppress tumor information. This observation bears special relevance to the human syndrome in that this model system may be used to study the question of penetrance of phenotype.

Adrenal Gland Neoplasms↗
PubMed1990

Neuropathological changes in transgenic mice carrying copies of a transcriptionally activated Mos protooncogene.

Independent transgenic mouse lines carrying the mouse Mos protooncogene linked to a retroviral transcriptional control sequence display behavioral abnormalities including circling, head tilting, and head bobbing. This dominant phenotype shows various degrees of penetrance in different transgenic founder animals and lines. Neuronal and axonal degeneration, gliosis, and inflammatory infiltrates are found in all transgenic mouse lines in which behavioral traits are present. Recordings of auditory-evoked potentials in mice of one of these lines demonstrate that transgenic mice are deaf; in these mice spiral ganglia degenerate and most of the cochlear hair cells are absent. By using an S1 nuclease protection assay, we have detected RNA expression of the transgene in all tissues examined and, in particular, at high levels in brain. In situ hybridization experiments show that Mos expression can be detected in specific areas of the central nervous system. Lesions are present in areas with demonstrable overexpression of Mos.

Animals↗
PubMed1989

The Mos proto-oncogene maps near the centromere on mouse chromosome 4.

The Mos proto-oncogene, the cellular homolog of the transforming gene of Moloney murine sarcoma virus, was originally assigned to mouse chromosome 4 using independent panels of mouse/hamster somatic cell hybrids. By in situ hybridization to metaphase chromosomes and standard genetic backcrosses, we have confirmed this assignment and determined that Mos maps near the centromere in a region devoid of other markers. We have also identified a restriction fragment length polymorphism (RFLP) that defines two alleles of the Mos locus in selected inbred strains of laboratory mice. Using the RFLP, we determined the strain distribution pattern for the Mos gene in three sets of recombinant inbred strains and in five strains congenic for histocompatibility antigen genes localized on chromosome 4. These results establish Mos as a useful marker in a poorly characterized region of the mouse genome. In addition, these results will facilitate the genetic analysis of the Mos locus.

Alleles↗
PubMed1988

Chicken homolog of the mos proto-oncogene.

We compared the sequence and properties of the chicken mos homolog with the previously characterized mouse and human c-mos genes. Sequence analysis revealed one major open reading frame of 1,047 base pairs encoding a protein of 349 amino acids. Both the nucleotide sequence and the deduced amino acid sequence showed 62% overall homology to mouse and human c-mos, but regions of higher conservation (approximately 70%) occurred in the putative ATP-binding and kinase domains. We detected mos transcripts by Northern (RNA) analyses in RNA prepared from chicken and quail ovaries and testes. Evidence for low levels of mos RNA expression in adult chicken heart, kidney, and spleen and in the entire embryo was obtained by S1 nuclease protection experiments. In contrast to the low transforming efficiency of human c-mos when linked to a mouse retroviral long terminal repeat element, chicken c-mos transformed NIH 3T3 cells as efficiently as mouse c-mos did. We also show that chicken primary embryo fibroblasts were morphologically altered when infected with an avian retroviral vector containing the chicken c-mos coding region.

Amino Acid Sequence↗
PubMed1988

Genetic analysis and developmental regulation of testis-specific RNA expression of Mos, Abl, actin and Hox-1.4.

The pattern of Mos proto-oncogene RNA expression in the gonads of the sterile mouse mutants, dominant spotting (W), sex reversal (Sxr), testicular feminization (Tfm), hypogonadal (hpg), quaking (qk), two t-haplotypes, three X-autosomal translocations, and the YPOS strain, is consistent with its presence in haploid spermatids in the testes and in oocytes in the ovaries. In the male-sterile mouse mutants the pattern of expression of the testis-specific transcripts for Abl, actin, and the mouse homeobox Hox-1.4 genes is identical to that observed for Mos. However, during the postnatal onset of normal spermatogenesis we detected differences in the time of the appearance of the four transcripts. We detected Hox-1.4 transcripts at day 20, Mos at day 25, and Abl and actin at day 30, demonstrating a specific regulation of expression of each of these genes during haploid spermatid maturation in the mouse. Furthermore, comparison of Mos, Abl and actin RNA expression in mouse and rat testes revealed species-specific variations in the regulation of gene expression.

Actins↗
PubMed1988

Developmental regulation of ovarian-specific Mos expression.

To gain better insight into the physiologic role of the Mos proto-oncogene in mice we have been studying the cell type and developmental specificity of its expression. It was previously shown that in adult mice, Mos is transcribed predominantly in ovaries and in haploid spermatids of the testes. Using in situ hybridization techniques we now show that in the ovary, Mos is expressed in oocytes, but not in somatic cells. In these analyses Mos transcripts are not detected in primary resting oocytes, but accumulate soon after the oocyte enters the growth phase. High levels of Mos RNA are present throughout oocyte growth and maturation. Mos RNA is also abundant in ovulated eggs prior to fertilization. Following fertilization, however, there is a dramatic loss of Mos RNA, as evidenced by the failure to detect hybridization in late one-cell embryos. The narrow developmental window for Mos transcription defined by this study suggests a role for ovarian Mos in one or more of the processes of oocyte growth, meiotic maturation, ovulation, or fertilization.

Age Factors↗