Transgenic expression of dominant negative tuberin through a strong constitutive promoter results in a tissue-specific tuberous sclerosis phenotype in the skin and brain.
Tuberous sclerosis (TS) is a common autosomal dominant disorder caused by loss or malfunction of hamartin (tsc1) or tuberin (tsc2). Many lesions in TS do not demonstrate loss of heterozygosity for these genes, implying that dominant negative forms of these genes may account for some hamartomas and neoplasms in TS. To test this hypothesis, we expressed a dominant negative allele of tuberin (DeltaRG) behind the cytomegalovirus promoter in NIH3T3 cells and transgenic mice. This allele binds hamartin but has a deletion in the C terminus of tuberin, leading to constitutive activation of rap1 and rab5/rabaptin. Expression of DeltaRG in NIH3T3 cells led to a strong induction of reactive oxygen species, induction of vascular endothelial growth factor, and malignant transformation in vivo. Expression of DeltaRG driven by the constitutive cytomegalovirus promoter led to high level expression in all murine tissues examined, including skin, kidney, liver, and brain. Surprisingly, mice expressing the DeltaRG transgene developed a fibrovascular collagenoma in the dermis, which closely resembles the Shagreen patch observed in human patients with TS. In addition, numerous small subpial collections of external granule cells in the cerebellum were observed, which may be the murine equivalent of subependymal giant cell astrocytomas or tubers commonly seen in TS patients. Thus, expression of a dominant negative tuberin in multiple tissues can lead to a tissue-specific phenotype resembling some of the findings in human TS. Our data are the first to demonstrate that specific signaling abnormalities underlie specific hamartomas in a model of a human genetic disorder.
Govindarajan
Baskaran
B
Department of Dermatology, Emory University School of Medicine, Atlanta, GA 30322, USA.
Brat
Daniel J
DJ
Csete
Marie
M
Martin
William D
WD
Murad
Emma
E
Litani
Karin
K
Cohen
Cynthia
C
Cerimele
Francesca
F
Nunnelley
Matthew
M
Lefkove
Benjamin
B
Yamamoto
Toshiyuki
T
Lee
Chunsik
C
Arbiser
Jack L
JL
D000483:Alleles; D000818:Animals; D017209:Apoptosis; D001932:Brain Neoplasms / Q000235:genetics / Q000473:pathology*; D018932:Chemokine CCL2 / Q000378:metabolism; D005799:Genes, Dominant / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D018485:Muscle Fibers, Skeletal; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D009928:Organ Specificity; D010641:Phenotype; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D054390:Receptors, CCR2; D019707:Receptors, Chemokine / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D019076:Transgenes / Q000235:genetics; D014402:Tuberous Sclerosis / Q000235:genetics* / Q000473:pathology; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
C515334:CCR2 protein, human; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D012097:Repressor Proteins; C000624653:TSC2 protein, human; C000624654:Tsc2 protein, mouse; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D019893:Ribosomal Protein S6 Kinases