A gene discovered by positional cloning has been identified as the von Hippel-Lindau (VHL) disease tumor suppressor gene. A restriction fragment encompassing the gene showed rearrangements in 28 of 221 VHL kindreds. Eighteen of these rearrangements were due to deletions in the candidate gene, including three large nonoverlapping deletions. Intragenic mutations were detected in cell lines derived from VHL patients and from sporadic renal cell carcinomas. The VHL gene is evolutionarily conserved and encodes two widely expressed transcripts of approximately 6 and 6.5 kilobases. The partial sequence of the inferred gene product shows no homology to other proteins, except for an acidic repeat domain found in the procyclic surface membrane glycoprotein of Trypanosoma brucei.

https://science.sciencemag.org/content/sci/260/5112/1317.full.pdf

Identification of the von Hippel-Lindau disease tumor suppressor gene.

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.

https://science.sciencemag.org/content/sci/253/5020/661.full.pdf

Identification of FAP locus genes from chromosome 5q21

https://www.cell.com/cell/pdf/0092-8674(93)90330-S.pdf

Mutations of a mutS homolog in hereditary nonpolyposis colorectal cancer

GTPases of the Ras superfamily regulate many aspects of cell growth, differentiation and action. Their functions depend on their ability to alternate between inactive and active forms, and on their cellular localization. Numerous proteins affecting the GTPase activity, nucleotide exchange rates and membrane localization of Ras superfamily members have now been identified. Many of these proteins are much larger and more complex than their targets, containing multiple domains capable of interacting with an intricate network of cellular enzymes and structures.

Proteins regulating Ras and its relatives.

From the pioneering work with acute transforming retroviruses to the current post-genomic era, RAS genes have always been at the leading edge of signal transduction and molecular oncology. Yet, a complete understanding of RAS function and dysfunction - mainly in human cancer - is still to come. The knowledge that has accumulated since their discovery 30 years ago has, however, been remarkable, and should pave the way for not only solving the outstanding issues regarding RAS biology, but also for developing efficacious drugs that could have a significant impact on cancer treatment.

RAS oncogenes: the first 30 years

Von Recklinghausen neurofibromatosis (NF1) is a common autosomal dominant disorder characterized by abnormalities in multiple tissues derived from the neural crest. No reliable cellular phenotypic marker has been identified, which has hampered direct efforts to identify the gene. The chromosome location of the NF1 gene has been previously mapped genetically to 17q11.2, and data from two NF1 patients with balanced translocations in this region have further narrowed the candidate interval. The use of chromosome jumping and yeast artificial chromosome technology has now led to the identification of a large (approximately 13 kilobases) ubiquitously expressed transcript (denoted NF1LT) from this region that is definitely interrupted by one and most likely by both translocations. Previously identified candidate genes, which failed to show abnormalities in NF1 patients, are apparently located within introns of NF1LT, on the antisense strand. A new mutation patient with NF1 has been identified with a de novo 0.5-kilobase insertion in the NF1LT gene. These observations, together with the high spontaneous mutation rate of NF1 (which is consistent with a large locus), suggest that NF1LT represents the elusive NF1 gene.

https://science.sciencemag.org/content/sci/249/4965/181.full.pdf

Type 1 neurofibromatosis gene: identification of a large transcript disrupted in three NF1 patients

cDNA cloning of the type 1 neurofibromatosis gene: Complete sequence of the NF1 gene product

The neurofibromatosis type 1 (NF1) gene was recently identified by positional cloning and found to encode a protein with structural and functional homology to mammalian and yeast GTPase-activating proteins (GAPs). Using antibodies directed against the NF1 gene product, a protein of approximately 250 kDa was identified and termed neurofibromin. Double-indirect immunofluorescent labeling with anti-neurofibromin and anti-tubulin antibodies demonstrates that neurofibromin associates with cytoplasmic microtubules. Immunoblotting of microtubule-enriched cytoplasmic fractions, using antibodies generated against neurofibromin, shows that neurofibromin copurifies with microtubules. When portions of neurofibromin are expressed in Sf9 insect cells they associate with polymerized microtubules; furthermore, the critical residues for this interaction reside within the GAP-related domain of neurofibromin. The unexpected association of neurofibromin with microtubules suggests that neurofibromin is involved in microtubule-mediated intracellular signal transduction pathways.

/pdf/neurofibromatosis-type-1-gene-product-neurofibromin-3cqt7yaxt8.pdf

Neurofibromatosis type 1 gene product (neurofibromin) associates with microtubules

N-terminal Sequences Contained in the Src Homology 2 and 3 Domains of p120 GTPase-activating Protein Are Required for Full Catalytic Activity Toward Ras

Anna L. Mitchell

Papers

Type 1 neurofibromatosis gene: identification of a large transcript disrupted in three NF1 patients

cDNA cloning of the type 1 neurofibromatosis gene: Complete sequence of the NF1 gene product

Neurofibromatosis type 1 gene product (neurofibromin) associates with microtubules

N-terminal Sequences Contained in the Src Homology 2 and 3 Domains of p120 GTPase-activating Protein Are Required for Full Catalytic Activity Toward Ras