Yeast as a Model to Understand Actin-Mediated Cellular Functions in Mammals-Illustrated with Four Actin Cytoskeleton Proteins.

The budding yeast Saccharomyces cerevisiae has an actin cytoskeleton that comprises a set of protein components analogous to those found in the actin cytoskeletons of higher eukaryotes. Furthermore, the actin cytoskeletons of S. cerevisiae and of higher eukaryotes have some similar physiological roles. The genetic tractability of budding yeast and the availability of a stable haploid cell type facilitates the application of molecular genetic approaches to assign functions to the various actin cytoskeleton components. This has provided information that is in general complementary to that provided by studies of the equivalent proteins of higher eukaryotes and hence has enabled a more complete view of the role of these proteins. Several human functional homologues of yeast actin effectors are implicated in diseases. A better understanding of the molecular mechanisms underpinning the functions of these proteins is critical to develop improved therapeutic strategies. In this article we chose as examples four evolutionarily conserved proteins that associate with the actin cytoskeleton: 1) yeast Hof1p/mammalian PSTPIP1, 2) yeast Rvs167p/mammalian BIN1, 3) yeast eEF1A/eEF1A1 and eEF1A2 and 4) yeast Yih1p/mammalian IMPACT. We compare the knowledge on the functions of these actin cytoskeleton-associated proteins that has arisen from studies of their homologues in yeast with information that has been obtained from in vivo studies using live animals or in vitro studies using cultured animal cell lines.

Bone substitution materials on the basis of BONITmatrix® up-regulate mRNA expression of IGF1 and Col1a1.

The aim of this study was to investigate the effects of BONITmatrix(®) and OSSA NOVA on the expression of growth factors and osteogenic differentiation. For this purpose, the mRNA expression of VEGF, IGF1, IGF2, collagen-1, collagen-2 and MMP8 was analysed in surgically created defects on the crania of adult male rats. Cranial samples were collected after implantation of BONITmatrix(®) or OSSA NOVA scaffolds for 4 weeks and determinations of gene expression were performed by quantitative RT-PCR. Real-time RT-PCR analyses showed a significantly higher expression of IGF1 in both groups treated with BONITmatrix(®) and OSSA NOVA compared to untreated controls, whereas type I collagen mRNA expression only increased in BONITmatrix(®) treated rats compared to controls. No changes in transcript expression of IGF2, VEGF, collagen-2 and MMP8 were detectable between the analysed groups. In conclusion, BONITmatrix(®) and OSSA NOVA stimulate the expression of growth factor IGF1, but only the granular dosage form is able to stimulate osteoblast differentiation.

Changes in condylar cartilage after anterior mandibular displacement in juvenile pigs.

UNLABELLED: Adaptive remodelling of the mandibular condyle in response to mandibular advancement is the mechanism exploited by orthodontic forward displacement devices. OBJECTIVE: This work investigated the expression of collagens, matrix metalloproteinases and vascular endothelial growth factor during this process. DESIGN: Twenty juvenile pigs were randomly divided into two experimental groups, where the treatment group was fitted with mandibular advancement splints, and the control group was not. Changes in the mRNA content of condylar cartilage tissue was then were measured by real-time PCR using specific primers after 4weeks of treatment. RESULTS: The temporal pattern of the expression of Col1 and MMP13 during condylar adaptation coincided with that during natural condylar growth. The amount of the expression of Col10 during condylar adaptation was significantly lower (p<0.05), whereas the expression of Col2, MMP8 and VEGF was significantly higher compared to natural growth (p<0.05). CONCLUSIONS: It is suggested that condylar adaptation in growing pigs triggered by mandibular forward positioning results not only from passive adaptation of cartilage, but also involves growth affected processes. Our results showed that mechanical strain produced by mandibular advancement induced remodelling and revascularization in the posteriocranial mandibular condyle. These results are mostly consistent with former published histological and histomorphometrical analyses.

Analysis of HIC-1 methylation and transcription in human ependymomas.

Ependymomas are among the most common brain tumors in children. They develop from ependymal cells lining the ventricular system of the CNS. Previous studies have demonstrated a significant rate of allelic loss at chromosome 17p13.3. The HIC-1 putative tumor-suppressor gene, which exhibits hypermethylation and loss of expression in various tumor entities including medulloblastomas and gliomas, maps to the affected region. In the present study, we analyzed HIC-1 in ependymomas. Therefore, we applied methylation-specific PCR of the 5'-untranslated region as well as of a central region of HIC-1 and bisulfite sequencing to determine the methylation status in 52 ependymomas of different histologic subtypes, grades and locations. In addition, we used a competitive RT-PCR approach for sensitive assessment of HIC-1 transcripts. Hypermethylation of at least one of the 2 analyzed regions was found in 43/52 (83%) cases. There was a significant correlation between hypermethylation of HIC-1 and nonspinal localization (p = 0.019) as well as age. Of 27 ependymomas, 22 (81%) showed absent or low expression of HIC-1. The elevated methylation of HIC-1 in nonspinal ependymomas supports the hypothesis that spinal and nonspinal ependymomas represent genetically distinct entities.