Dorothea L. Schiller

Bio: Dorothea L. Schiller is an academic researcher from German Cancer Research Center. The author has contributed to research in topics: Cytokeratin & Cytoskeleton. The author has an hindex of 18, co-authored 18 publications receiving 8345 citations.

Patterns of Expression and Organization of Cytokeratin Intermediate Filaments

Abstract: Cytokeratins are a large multigene family comprising two polypeptide types, i.e. acidic (type I) and basic (type II) ones, which are distinguished on the basis of immunological, peptide mapping, mRNA hybridization, and primary amino acid sequence data. The acidic (type I) cytokeratins can be subdivided into at least two different subtypes on the basis of their carboxy-terminal sequences. Considerable interspecies conservation of sequences exists, even extending to the 3'-non-coding mRNA regions. Different pairs of type I and II cytokeratins show different resistance to dissociation in urea. Sequence differences of the type I cytokeratins containing functional domains may be an explanation of the observed preference of co-expression with certain type II cytokeratins. The distribution of the different type I and II cytokeratins in normal epithelia and in carcinomas is differentiation related and can be used for cell typing and identification. The cell type-specific expression of cytokeratin polypeptides is recognized at both the protein and the mRNA level. The building block of cytokeratin IFs is a heterotypic tetramer, consisting of two type I and two type II polypeptides arranged in pairs of laterally aligned coiled coils. This principle of tetrameric organization is thought to be generally applicable to IFs.

Molecular cloning and amino acid sequence of human plakoglobin, the common junctional plaque protein

Abstract: Plakoglobin is a major cytoplasmic protein that occurs in a soluble and a membrane-associated form and is the only known constituent common to the submembranous plaques of both kinds of adhering junctions, the desmosomes and the intermediate junctions. Using a partial cDNA clone for bovine plakoglobin, we isolated cDNAs encoding human plakoglobin, determined its nucleotide sequence, and deduced the complete amino acid sequence. The polypeptide encoded by the cDNA was synthesized by in vitro transcription and translation and identified by its comigration with authentic plakoglobin in two-dimensional gel electrophoresis. The identity was further confirmed by comparison of the deduced sequence with the directly determined amino acid sequence of two fragments from bovine plakoglobin. Analysis of the plakoglobin sequence showed the protein (744 amino acids; 81,750 Da) to be unrelated to any other known proteins, highly conserved between human and bovine tissues, and characterized by numerous changes between hydrophilic and hydrophobic sections. Only one kind of plakoglobin mRNA (3.4 kilobases) was found in most tissues, but an additional mRNA (3.7 kilobases) was detected in certain human tumor cell lines. This longer mRNA may be represented by a second type of plakoglobin cDNA, which contains an insertion of 297 nucleotides in the 3' non-coding region.

Normal keratinization in a spontaneously immortalized aneuploid human keratinocyte cell line.

Abstract: In contrast to mouse epidermal cells, human skin keratinocytes are rather resistant to transformation in vitro. Immortalization has been achieved by SV40 but has resulted in cell lines with altered differentiation. We have established a spontaneously transformed human epithelial cell line from adult skin, which maintains full epidermal differentiation capacity. This HaCaT cell line is obviously immortal (greater than 140 passages), has a transformed phenotype in vitro (clonogenic on plastic and in agar) but remains nontumorigenic. Despite the altered and unlimited growth potential, HaCaT cells, similar to normal keratinocytes, reform an orderly structured and differentiated epidermal tissue when transplanted onto nude mice. Differentiation-specific keratins (Nos. 1 and 10) and other markers (involucrin and filaggrin) are expressed and regularly located. Thus, HaCaT is the first permanent epithelial cell line from adult human skin that exhibits normal differentiation and provides a promising tool for studying regulation of keratinization in human cells. On karyotyping this line is aneuploid (initially hypodiploid) with unique stable marker chromosomes indicating monoclonal origin. The identity of the HaCaT line with the tissue of origin was proven by DNA fingerprinting using hypervariable minisatellite probes. This is the first demonstration that the DNA fingerprint pattern is unaffected by long-term cultivation, transformation, and multiple chromosomal alterations, thereby offering a unique possibility for unequivocal identification of human cell lines. The characteristics of the HaCaT cell line clearly document that spontaneous transformation of human adult keratinocytes can occur in vitro and is associated with sequential chromosomal alterations, though not obligatorily linked to major defects in differentiation.

Identification of FAP locus genes from chromosome 5q21

Abstract: Recent studies suggest that one or more genes on chromosome 5q21 are important for the development of colorectal cancers, particularly those associated with familial adenomatous polyposis (FAP). To facilitate the identification of genes from this locus, a portion of the region that is tightly linked to FAP was cloned. Six contiguous stretches of sequence (contigs) containing approximately 5.5 Mb of DNA were isolated. Subclones from these contigs were used to identify and position six genes, all of which were expressed in normal colonic mucosa. Two of these genes (APC and MCC) are likely to contribute to colorectal tumorigenesis. The MCC gene had previously been identified by virtue of its mutation in human colorectal tumors. The APC gene was identified in a contig initiated from the MCC gene and was found to encode an unusually large protein. These two closely spaced genes encode proteins predicted to contain coiled-coil regions. Both genes were also expressed in a wide variety of tissues. Further studies of MCC and APC and their potential interaction should prove useful for understanding colorectal neoplasia.