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Abstract

Cell shape is influenced by physical surface topography of the substrate to which cells are attached [23,8]. Most prominent is the polarization and elongation of cells along the direction of microfabricated grooves. Microstructured substrates are also known to affect intracellular processes such as apoptosis [8], gene expression [9] or protein production [6]. However, little is known about the mechanism of how surface topography exerts its effects, although several studies have focused on the role of cytoskeletal elements such as actin microfilaments [29], focal contacts [28],and microtubules [24] as all these structures are observed to align with topographic features such as grooves. Most of these experiments were performed with cultured fibroblasts where filament structures showed to align along microstructured lines. We examined cell shape alternations of human melanocyte cells cultured on micro-grooved polymeric substrates. These cells were derived from healthy persons and patients suffering on Neurofibromatosis 1 (NF1). NF1 is caused by a germline mutation in the NFI-gene a classical tumor suppressor gene. The majority of the NF1 mutations are null mutations resulting in reduction of the related protein product, neurofibromin, to about 50% [16,11]. Neurofibromin shows a Ras-GAP activity [14,21] and is involved in regulation of growthin vitro [1,20]. In addition, it is found to be associated with the cytoskeleton (Xu and Gutmann 1997) and NF1 deficient cells exhibit morphological changes, as demonstrated for Nfl-/- Schwann cells [20] or cells from Drosophila homozygous for null mutations of an NF1 homolog [27]. Neurofibromin reduction can also result in morphological changes in cultured human NF1 keratinocytes in which it is co-localized with intermediate filaments [22]. We demonstrated that the cellular consequence of haploinsufficiency