Vijaya Ramesh — Page 2

PubMed2003

A 34 bp deletion within TSC2 is a rare polymorphism, not a pathogenic mutation.

Tuberous sclerosis (TSC) is an autosomal dominant hamartoma syndrome due to mutations in either TSC1 or TSC2. Previous reports have identified a mutation consisting of a 34 bp deletion affecting portions of exon 38 and the adjacent intron 38 of TSC2. We found this genetic variation in 4 of 800 TSC patients screened for mutations in TSC1 and TSC2. In every case, the variant was present in one unaffected parent of the sporadically affected TSC child. By RT-PCR analysis of RNA samples from two additional families with this genetic variant, we demonstrate that the allele with the deletion generates about 50% normal RNA transcript, and 50% RNA transcript including intron 38. In addition, there is no correlation between the extent of splicing and clinical status of family members. We also excluded the possibility of mosaicism in the parents with this variant. We conclude that this deletion is a rare polymorphism that does not cause TSC, but may be a modifier of the TSC phenotype.

Base Sequence↗

PubMed2002

The TSC1 tumor suppressor hamartin interacts with neurofilament-L and possibly functions as a novel integrator of the neuronal cytoskeleton.

Tuberous sclerosis complex, an autosomal dominant disease caused by mutations in either TSC1 or TSC2, is characterized by the development of hamartomas in a variety of organs. The proteins encoded by TSC1 and TSC2, hamartin and tuberin, respectively, associate with each other forming a tight complex. Here we show that hamartin binds the neurofilament light chain and it is possible to recover the hamartin-tuberin complex over the neurofilament light chain rod domain spanning amino acids 93-156 by affinity precipitation. Homologous rod domains in other intermediate filaments such as neurofilament medium chain, alpha-internexin, vimentin, and desmin are not able to bind hamartin. In cultured cortical neurons, hamartin and tuberin co-localize with neurofilament light chain preferentially in the proximal to central growth cone region. Interestingly, in the distal part of the growth cone hamartin overlaps with the ezrin-radixin-moesin family of actin binding proteins, and we have validated the interaction of hamartin with moesin. These results demonstrate that hamartin may anchor neuronal intermediate filaments to the actin cytoskeleton, which may be critical for some of the CNS functions of the hamartin-tuberin complex, and abolishing this through mutations in TSC1 or TSC2 may lead to certain neurological manifestations associated with the disease.

Animals↗