PubMed · 16354268
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Rosanna Pallotta, Anita Saponari. Hyperpigmented patch associated to heterochromia iridis.. https://doi.org/10.1111/j.1525-1470.2005.00144.x
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Bilateral segmental neurofibromatosis is a rare condition characterized by the occurrence of neurofibromas and/or café-au-lait spots limited to an area or segment of the body bilaterally. It is caused by a postzygotic mutation in the neurofibromatosis type I gene, resulting in a phenotype of genetic mosaicism. This report describes a case of bilateral segmental neurofibromatosis with multiple nodules sitting on a café-au-lait spot.
The neurofibromatosis type 1 (NF1) gene product, neurofibromin, is known to interact with Ras, thereby negatively regulating its growth-promoting function. Although this is a well-established interaction, the discovery of other neurofibromin interacting partners could reveal new functional properties of this large protein. Using yeast two-hybrid analysis against a brain cDNA library, we identified a novel interaction between the amyloid precursor protein and the GTPase activating protein-related domain of neurofibromin. This interaction was further analyzed in human melanocytes and confirmed by immunoprecipitation and colocalization studies. In addition, we observed a colocalization of amyloid precursor protein and neurofibromin with melanosomes. Amyloid precursor protein has been proposed to function as a vesicle cargo receptor for the motor protein kinesin-1 in neurons. This colocalization of amyloid precursor protein and neurofibromin with melanosomes was lost in melanocytes obtained from normal skin of a NF1 patient. We suggest that a complex between amyloid precursor protein, neurofibromin, and melanosomes might be important in melanosome transport, which could shed a new light on the etiopathogenesis of pigment-cell-related manifestations in NF1.
Neurofibromatosis type 1 (NF1) is a genetic disease caused by mutations in the NF1 gene, which encodes the protein neurofibromin. Patients exhibit characteristic hyperpigmented patches called café-au-lait patches. Melanocytes of NF1 patients differ from normal human melanocytes, but no differences account completely for lesional hyperpigmentation. An association between beta-amyloid precursor protein (APP) and neurofibromin, and their localization to the melanosome, may help explain the development of café-au-lait patches.