Alternatively spliced transcript variants encoding different isoforms have also been described for this gene.In 1989, through linkage and cross over analyses, neurofibromin was localized to chromosome 17. It was localized to the long arm of chromosome 17 by chance when researchers discovered chromosome exchanges between chromosome 17 with chromosome 1 and 22. This exchange of genetic material presumably caused a mutation in the neurofibromin gene, leading to the NF1 phenotype. Two recurrent microdeletion types with microdeletion breakpoints located in paralogous regions flanking NF1 (proximal NF1-REP-a and distal NF1-REP-c for the 1.4 Mb type-1 microdeletion, and SUZ12 and SUZ12P for the 1.2 Mb type-2 microdeletion), are found in most cases. Structure
The neurofibromin gene was soon sequenced and found to be 350,000 base pairs in length. However, the protein is 2818 amino acids long leading to the concept of splice variants. For example, exon 9a, 23a and 48a are expressed in the neurons of the forebrain, muscle tissues and adult neurons respectively.Homology studies have shown that neurofibromin is 30% similar to proteins in the GTPase activating protein (GAP) family. This homologous sequence is in the central portion of neurofibromin and being similar to the GAP family is recognized as a negative regulator of the Ras kinase.Additionally, being such a large protein, more active domains of the protein have been identified. One such domain interacts with the protein adenylyl cyclase, and a second with collapsin response mediator protein.
Mepivacaine  is a local anesthetic of the amide type. Mepivacaine has a reasonably rapid onset (more rapid than that of procaine) and medium duration of action (shorter than that of procaine) and is marketed under various trade names including Carbocaine and Polocaine. Mepivacaine became available in the United States in the 1960s. Mepivacaine is used in any infiltration and local anesthesia. It is supplied as the hydrochloride salt of the racemate, which consists of R(-)-mepivacaine and S(+)-mepivacaine in equal proportions. These two enantiomers have markedly different pharmacokinetic properties.Mepivacaine was originally synthesized in Sweden at the laboratory of Bofors Nobelkrut in 1956. References
External links
Mepivacaine at RxList