Biomedical subjects

Julia Asp

Publications and source records attributed to Julia Asp.

9 recordsLinked to original sources

PubMed2007

Differentiation of human mesenchymal stem cells and articular chondrocytes: analysis of chondrogenic potential and expression pattern of differentiation-related transcription factors.

Mesenchymal stem cells (MSCs) are a candidate for replacing chondrocytes in cell-based repair of cartilage lesions. However, it has not been clarified if these cells can acquire the hyaline phenotype, and whether chondrocytes and MSCs show the same expression patterns of critical control genes in development. In order to study this, articular chondrocytes and iliac crest derived MSCs were allowed to differentiate in pellet mass cultures. Gene expression of markers for the cartilage phenotype, helix-loop-helix (HLH) transcription factors, and chondrogenic transcription factors were analyzed by real-time PCR. Matrix production was assayed using biochemical analysis for hydroxyproline, glycosaminoglycans, and immunohistochemistry for collagen types I and II. Significantly decreased expression of collagen type I was accompanied by increased expression of collagen types IIA and IIB during differentiation of chondrocytes, indicating differentiation towards a hyaline phenotype. Chondrogenesis in MSCs on the other hand resulted in up-regulation of collagen types I, IIA, IIB, and X, demonstrating differentiation towards cartilage of a mixed phenotype. Expression of HES1 increased significantly during chondrogenesis in chondrocytes while expression in MSCs was maintained at a low level. The HLH gene HES5 on the other hand was only detected in chondrocytes. Expression of ID1 decreased significantly in chondrocytes while the opposite was seen in MSCs. These findings suggest that chondrocytes and MSCs differentiated and formed different subtypes of cartilage, the hyaline and a mixed cartilage phenotype, respectively. Differentially regulated HLH genes indicated the possibility for HLH proteins in regulating chondrogenic differentiation. This information is important to understand the potential use of MSCs in cartilage repair.

Adult↗

PubMed2006

Notch and HES5 are regulated during human cartilage differentiation.

The molecular mechanisms of cartilage differentiation are poorly understood. In a variety of tissues other than cartilage, members of the basic helix-loop-helix (bHLH) family of transcription factors have been demonstrated to play critical roles in differentiation. We have characterized the human bHLH gene HES5 and investigated its role during chondrogenesis. Blockage of the Notch signaling pathway with a gamma-secretase inhibitor has demonstrated that the human HES5 gene is a downstream marker of Notch signaling in articular chondrocytes. Markers for the Notch signaling pathway significantly decrease during cartilage differentiation in vitro. Cell proliferation assayed by using BrdU has revealed that blockage of Notch signaling is associated with significantly decreased proliferation. Northern blot and reverse transcription/polymerase chain reaction of a panel of various tissues have shown that HES5 is transcribed as a 5.4-kb mRNA that is ubiquitously expressed in diverse fetal and adult tissues. Articular cartilage from HES5(-/-) and wild-type mice has been analyzed by using various histological stains. No differences have been detected between the wild-type and HES5(-/-) mice. Our data thus indicate that the human HES5 gene is coupled to the Notch receptor family, that expression of Notch markers (including HES5) decreases during cartilage differentiation, and that the blockage of Notch signaling is associated with significantly decreased cell proliferation.

Adolescent↗

PubMed2006

Expression of genes involved in the regulation of p16 in psoriatic involved skin.

It has been suggested that the up-regulation of the tumour suppressor p16 gene and induction of senescence protect the phenotype of psoriatic involved skin from malignant transformation. On the other hand, Id1, which is inversely correlated with p16 has been shown to be up-regulated in psoriatic involved skin. To test the hypothesis that there may be an altered regulation of p16 in psoriatic involved skin, we have measured genes involved in the Igf-1 receptor signalling through the Ras/MAPK cascade. Igf-1R, IGFBP3, hRas, Ets2, JunB, Egr-1, Id1, MIDA1 and p16 gene expressions were measured using quantitative real-time PCR in total RNA isolated from punch biopsies from psoriatic involved (n = 9) and uninvolved skin (n = 9) and from cutaneous squamous cell cancer (SCC) involved (n = 8) and uninvolved skin (n = 8). The IGFBP3, hRas, JunB, Egr-1, Id1 and MIDA1 genes were up-regulated in psoriatic involved skin compared with uninvolved skin. The p16, JunB and MIDA1 genes were up-regulated in SCC involved skin compared with uninvolved skin. Our results indicate that there may be a balance between the proliferation and induction of senescence in psoriasis. This balance may vary and the psoriatic involved skin represented in this study appears to be in a proliferative state rather than senescence. Furthermore, we suggest that the noted up-regulation of JunB, which has been shown to up-regulate p16, in combination with the previously reported elevation of p16 expression in psoriatic involved skin, may indicate activation of a pathway by which JunB may protect the psoriatic plaque by inducing p16 in an event of malignant stress.

Biopsy↗

PubMed2006

Large-scale identification of genes implicated in kidney glomerulus development and function.

To advance our understanding of development, function and diseases in the kidney glomerulus, we have established and large-scale sequenced cDNA libraries from mouse glomeruli at different stages of development, resulting in a catalogue of 6053 different genes. The glomerular cDNA clones were arrayed and hybridized against a series of labeled targets from isolated glomeruli, non-glomerular kidney tissue, FACS-sorted podocytes and brain capillaries, which identified over 300 glomerular cell-enriched transcripts, some of which were further sublocalized to podocytes, mesangial cells and juxtaglomerular cells by in situ hybridization. For the earliest podocyte marker identified, Foxc2, knockout mice were used to analyze the role of this protein during glomerular development. We show that Foxc2 controls the expression of a distinct set of podocyte genes involved in podocyte differentiation and glomerular basement membrane maturation. The primary podocyte defects also cause abnormal differentiation and organization of the glomerular vascular cells. We surmise that studies on the other novel glomerulus-enriched transcripts identified in this study will provide new insight into glomerular development and pathomechanisms of disease.

Animals↗

PubMed2006

CHCHD7-PLAG1 and TCEA1-PLAG1 gene fusions resulting from cryptic, intrachromosomal 8q rearrangements in pleomorphic salivary gland adenomas.

Pleomorphic salivary gland adenomas are characterized by recurrent chromosome rearrangements of 8q12, leading to activation of the PLAG1 oncogene. Here we demonstrate that CHCHD7-PLAG1 is a novel and recurrent gene fusion generated by a cytogenetically cryptic rearrangement in pleomorphic adenomas. CHCHD7 is a newly identified member of a multifamily of proteins containing a conserved (coiled coil 1)-(helix 1)-(coiled coil 2)-(helix 2) domain. Northern blot analysis revealed that the gene is ubiquitously expressed. Its biological function is unknown and the gene has hitherto not been associated with neoplasia. CHCHD7 and PLAG1 are located head-to-head about 500 bp apart in 8q12. Molecular analyses of 27 tumors revealed CHCHD7-PLAG1 fusions in three tumors, two of which had t(6;8) and t(8;15) translocations as the sole anomalies and one a normal karyotype. FISH analyses of interphase nuclei and nuclear chromatin fibers of a fourth adenoma with a normal karyotype revealed that a second fusion partner gene, TCEA1, located about 2 Mb centromeric to PLAG1, also is fused to PLAG1 as a result of a cryptic 8q rearrangement. The breakpoints in both fusions occur in the 5'-noncoding regions of the genes, leading to activation of PLAG1 by promoter swapping/substitution. Western blot and immunohistochemical analyses demonstrated that the PLAG1 protein was overexpressed in epithelial, myoepithelial, and mesenchymal-like tumor cells in tumors with both fusions. Our findings further emphasize the significance of PLAG1 activation in pleomorphic adenomas and demonstrate that the gene is more frequently activated than previously anticipated.

Adenoma↗

PubMed2006

Nonradioactive in situ hybridization on frozen sections and whole mounts.

Nonradioactive in situ hybridization offers a unique opportunity to study gene expression on samples with preserved histological information. This method makes it possible to locate not only where in a tissue a particular gene is expressed, but in many cases also in which specific cell type it is active. Here, we describe our current protocols for in situ hybridization on frozen sections or whole mounts of mouse embryos. The protocols included describe synthesis of a digoxigenin-labeled probe, tissue handling, hybridization of the probe to the mRNA expressed in the sample and signal detection.

Animals↗

PubMed2005

Evaluation of p16 and Id1 status and endogenous reference genes in human chondrosarcoma by real-time PCR.

Both the tumour suppressor, p16, and the helix-loop-helix transcription factor, Id1, have been assigned roles in tumour growth in general and appear to be involved in chondrosarcoma. Id1 has further been found to repress the expression of p16. Therefore, the mRNA expression of these two genes was studied by real-time PCR in a search for prognostic markers in human chondrosarcoma. To get reliable quantitative data, however, the choice of endogenous reference gene for use in the assay is important. Therefore, eleven different endogenous reference genes were evaluated in chondrosarcoma cells and articular chondrocytes. 18S rRNA appeared to be the best choice to use as endogenous reference gene, since it was suitable for both kinds of cells. Several of the other reference genes tested showed variation between individuals or between normal chondrocytes and chondrosarcoma cells. This demonstrates the importance of using a correct endogenous reference gene to get reliable results from quantitative measurements. Both p16 and Id1 showed varied gene expression patterns among the samples and none of these genes could be significantly correlated to prognosis.

Bone Neoplasms↗

PubMed2004

Epigenetic loss of the familial tumor-suppressor gene exostosin-1 (EXT1) disrupts heparan sulfate synthesis in cancer cells.

Germline mutations in the Exostoses-1 gene (EXT1) are found in hereditary multiple exostoses syndrome, which is characterized by the formation of osteochondromas and an increased risk of chondrosarcomas and osteosarcomas. However, despite its putative tumor-suppressor function, little is known of the contribution of EXT1 to human sporadic malignancies. Here, we report that EXT1 function is abrogated in human cancer cells by transcriptional silencing associated with CpG island promoter hypermethylation. We also show that, at the biochemical and cellular levels, the epigenetic inactivation of EXT1, a glycosyltransferase, leads to the loss of heparan sulfate (HS) synthesis. Reduced HS production can be reversed by the use of a DNA demethylating agent. Furthermore, the re-introduction of EXT1 into cancer cell lines displaying methylation-dependent silencing of EXT1 induces tumor-suppressor-like features, e.g. reduced colony formation density and tumor growth in nude mouse xenograft models. Screening a large collection of human cancer cell lines (n=79) and primary tumors (n=454) from different cell types, we found that EXT1 CpG island hypermethylation was common in leukemia, especially acute promyelocytic leukemia and acute lymphoblastic leukemia, and non-melanoma skin cancer. These findings highlight the importance of EXT1 epigenetic inactivation, leading to an abrogation of HS biosynthesis, in the processes of tumor onset and progression.

Animals↗

PubMed2004

Hash4, a novel human achaete-scute homologue found in fetal skin.

To find additional members of the basic helix-loop-helix (bHLH) protein family in human, the bioinformatic tools provided by the National Center for Biotechnology Information was used for homology searches through databases. We report the identification and cloning of a new, fourth member in the achaete-scute complex family of genes, Hash4 or Ascl4, which maps to chromosome 12q24.1. The bHLH domain of the putative HASH4 protein shows most identity to HASH3/ASCL3. The expression of Hash4 and Hash3 was analyzed by reverse transcriptase polymerase chain reaction (PCR), in a panel of different human tissues and cells. Expression of Hash3 was detected in all samples tested, while the expression of Hash4 was restricted to skin. Quantification of the Hash4 expression by real-time PCR revealed a 7-fold higher expression in fetal skin compared to adult skin. Our results suggest HASH4 to be involved in skin development.

Amino Acid Sequence↗