 Neurofibromin localizes in the cytoplasm; however, some studies have found neurofibromin or fragments of it in the nucleus.Neurofibromin does contain a nuclear localization signal that is encoded by exon 43, but whether or not neurofibromin plays a role in the nucleus is currently unknown.Neurofibromin is ubiquitously expressed, but expression levels vary depending on the tissue type and developmental stage of the organism.