Spontaneous chromosomal aberrations in cell cultures from patients with neurofibromatosis 1

Pigment cell-related manifestations in neurofibromatosis type 1: an overview

Neurofibromatosis type 1 (NF1) is an autosomal dominant neurocutaneous disorder, affecting approximately 1 in 3500 individuals. The most commonly seen tumors in NF1 patients are the (sub)cutaneous neurofibromas. However, individuals with NF1 typically present in childhood with well-defined pigmentary defects, including cafe-au-lait macules (CALMs), intertriginous freckling and iris Lisch nodules. NF1 is considered a neurocristopathy, primarily affecting tissues derived from the neural crest. Since the pigment producing melanocyte originates in the neural crest, the presence of (hyper)pigmentary lesions in the NF1 phenotype because of changes in melanocyte cell growth and differentiation is to be expected. We want to discuss the pigmentary cutaneous manifestations of NF1 represented by CALMs and intertriginous freckles and the pigmentary non-cutaneous manifestations represented by iris Lisch nodules. Several hypotheses have been suggested in explaining the poorly understood etiopathogenesis of CALMs. Whether other pigmentary manifestations might share similar etiopathogenic mechanisms remains obscure. Additional attention will be drawn to a readily seen phenomenon in NF1: hyperpigmentation overlying (plexiform) neurofibromas, which could suggest common etiopathogenetic-environmental cues or mechanisms underlying CALMs and neurofibromas. Finally, we want to address the relationship between malignant melanoma and NF1.

Survival advantage of cultured human vascular endothelial cells that lost chromosome 13

We explored the nature of chromosome 13 loss in cultured human vascular endothelial cells (HUVECs). Chromosome 13 loss detected by metaphase and interphase analysis was noted in earlier passages of HUVEC strains with no relation to telomere length or replicative senescence. Ectopic expression of telomerase did not influence the loss of chromosome 13. HUVECs losing chromosome 13 demonstrated increased migratory potential and loss of heterozygosity. Collectively, these observations suggest that the loss of chromosome 13 gives cultured HUVECs a replicative advantage.

Genetics of Neurofibromatosis 1-Associated Peripheral Nerve Sheath Tumors

Neurofibromatosis 1, an inherited disorder that affects 1/3500 individuals worldwide, predisposes to the development of benign and malignant peripheral nerve sheath tumors. The disorder results from inactivation of one of the NFI genes. The second NFI gene is typically inactivated in Schwann cells during tumor formation. This article reviews the different types of genetic alterations in NFI in both constitutional and tumor tissues and genetic alterations of other genes that may affect tumorigenesis. These studies have provided insight into the genetic basis of both the variable expression of the disorder and of benign and malignant peripheral nerve sheath tumorigenesis.

Loss of chromosome 13 in cultured human vascular endothelial cells

In the vascular endothelium of human beings, telomere length is negatively related while the frequency of aneuploidy is positively related to donor age. Both in culture and in vivo the frequency of aneuploidy increases as telomere length is shortened. In this study we explored the relation between telomere length and aneuploidy in cultured human umbilical vein endothelial cells (HUVEC) by: (a) karyotype analysis and fluorescent in situ hybridization (FISH), (b) measurement of the terminal restriction fragments (TRF), and (c) assessment of replicative senescence by the expression of beta-galactosidase. Of 8 HUVEC strains, 7 cell strains lost chromosome 13, as shown by metaphase analysis and FISH of interphase cells. Five strains gained chromosome 11. In addition, five HUVEC strains became hypotetraploid shortly after the loss of chromosome 13. The loss of chromosome 13 was observed as early as PD 20, when mean TRF length was greater than 9 kb and the percentage of cells positive for beta-galactosidase was relatively low. The almost uniform loss of chromosome 13 suggests that this unique type of aneuploidy of HUVEC is the result of a progressive expression of clones with survival advantage.