Dataset Information

Biallelic TSC gene inactivation in tuberous sclerosis complex.

ABSTRACT:

Background

A pivotal developmental question is whether tubers in tuberous sclerosis complex (TSC) form by germline and somatic TSC1 or TSC2 gene mutations. Loss of TSC1 or TSC2 in vitro and in vivo leads to mTORC1 cascade activation and ribosomal protein S6 phosphorylation (P-S6). Giant cells (GCs) in tubers exhibit S6 phosphorylation, suggesting cell-specific loss of TSC gene function.

Methods

TSC1 and TSC2 gene mutations were investigated in DNA extracted from tuber sections (n = 6) and microdissected P-S6-labeled GCs by sequencing and loss of heterozygosity (LOH) analysis to define germline and somatic mutations.

Results

A germline TSC1 mutation was defined in 1 case and TSC2 mutations were defined in 5 cases. LOH was not detected in whole tuber sections or microdissected P-S6-labeled GCs. TSC1 and TSC2 were sequenced in microdissected P-S6-immunolabeled GCs. In 5 specimens, a somatic mutation was identified in single GCs that was not detected in whole tuber sections or leukocyte DNA. Four somatic mutations were novel variants (1 nonsense and 3 missense mutations) and 1 additional nonsense somatic mutation was previously reported as a germline mutation. In 1 case, no somatic mutation was identified. There was reduced expression of TSC1 or TSC2 transcripts in the TSC1 or TSC2 associated specimens. In the cases containing a nonsense mutation, no transcript mRNA was detected, suggesting nonsense-mediated degradation.

Conclusions

We provide evidence to support the hypothesis that tubers form by biallelic TSC1 or TSC2 gene inactivation reflecting a "2-hit" mechanism of germline and somatic mutational events. AML = angiomyolipoma; DN = dysplastic neuron; FFPE = formalin fixed, paraffin embedded; GC = giant cell; H-E = hematoxylin and eosin; LOH = loss of heterozygosity; TSC = tuberous sclerosis complex.

SUBMITTER: Crino PB

PROVIDER: S-EPMC2882213 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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Publications

Biallelic TSC gene inactivation in tuberous sclerosis complex.

Crino Peter B PB Aronica Eleonora E Baltuch Gordon G Nathanson Katherine L KL

Neurology 20100501 21

<h4>Background</h4>A pivotal developmental question is whether tubers in tuberous sclerosis complex (TSC) form by germline and somatic TSC1 or TSC2 gene mutations. Loss of TSC1 or TSC2 in vitro and in vivo leads to mTORC1 cascade activation and ribosomal protein S6 phosphorylation (P-S6). Giant cells (GCs) in tubers exhibit S6 phosphorylation, suggesting cell-specific loss of TSC gene function.<h4>Methods</h4>TSC1 and TSC2 gene mutations were investigated in DNA extracted from tuber sections (n ...[more]

PMID: 20498439

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Project description:Tuberous sclerosis complex (TSC) is a model disorder for understanding brain development because the genes that cause TSC are known, many downstream molecular pathways have been identified, and the resulting perturbations of cellular events are established. TSC, therefore, provides an intellectual framework to understand the molecular and biochemical pathways that orchestrate normal brain development. The TSC1 and TSC2 genes encode Hamartin and Tuberin which form a GTPase activating protein (GAP) complex. Inactivating mutations in TSC genes (TSC1/TSC2) cause sustained Ras homologue enriched in brain (RHEB) activation of the mammalian isoform of the target of rapamycin complex 1 (mTORC1). TOR is a protein kinase that regulates cell size in many organisms throughout nature. mTORC1 inhibits catabolic processes including autophagy and activates anabolic processes including mRNA translation. mTORC1 regulation is achieved through two main upstream mechanisms. The first mechanism is regulation by growth factor signaling. The second mechanism is regulation by amino acids. Gene mutations that cause too much or too little mTORC1 activity lead to a spectrum of neuroanatomical changes ranging from altered brain size (micro and macrocephaly) to cortical malformations to Type I neoplasias. Because somatic mutations often underlie these changes, the timing, and location of mutation results in focal brain malformations. These mutations, therefore, provide gain-of-function and loss-of-function changes that are a powerful tool to assess the events that have gone awry during development and to determine their functional physiological consequences. Knowledge about the TSC-mTORC1 pathway has allowed scientists to predict which upstream and downstream mutations should cause commensurate neuroanatomical changes. Indeed, many of these predictions have now been clinically validated. A description of clinical imaging and histochemical findings is provided in relation to laboratory models of TSC that will allow the reader to appreciate how human pathology can provide an understanding of the fundamental mechanisms of development.

Dataset Information

Biallelic TSC gene inactivation in tuberous sclerosis complex.

Background

Methods

Results

Conclusions

Publications

Biallelic TSC gene inactivation in tuberous sclerosis complex.

Similar Datasets

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