Downregulation of Wnt-mediated ROS generation is causally implicated in leprechaunism.
Although mutations in the insulin receptor have been causally implicated with leprechaunism, the full pathophysiology of the syndrome cannot be accounted for by malfunction of this gene alone. We sought to characterize a connection between Wnt-mediated cell signaling and the production of reactive oxygen species (ROS) which revealed a novel mechanistic basis for understanding the pathogenesis of leprechaunism. To identify candidate genes involved in this process, a PCR-based subtractive hybridization was performed. Candidate genes were examined for interaction with the Wnt signaling pathway and ROS generation. We found that Dickkopf 1 (Dkk1), a Wnt inhibitor, is overexpressed in skin fibroblast cells derived from three leprechaunism patients and that the cells showed an impaired response to Wnt2 in terms of beta-catenin-Tcf activation. Knockdown of Dkk1 in the patient cell lines rescued Wnt2-mediated Tcf activation. Concerted action of Wnt2 and knockdown of Dkk1 resulted in enhanced Nox4 expression and PDGF-induced ROS generation compared to parental patient cells. Furthermore, we found that NFATc2 was activated in response to Wnt2 stimulation and directly activates Nox4 expression. These data show a crosstalk between Wnt and ROS pathways which in turn provides new mechanistic insights at the molecular level into the pathogenesis of leprechaunism.
Park
Ji Won
JW
Department of Life Sciences, Ewha Womans University, Seoul, 120-750, Korea.
Kuehn
Hye Sun
HS
Kim
So Youn
SY
Chung
Kyung Min
KM
Choi
Hyun
H
Kim
Mira
M
Kim
Jaesang
J
Lee
Soo Young
SY
Bae
Duk Soo
DS
Jin
Dong-Kyu
DK
Bae
Yun Soo
YS
D018929:Cell Culture Techniques; D002478:Cells, Cultured; D056731:Donohue Syndrome / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D020869:Gene Expression Profiling; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000096:biosynthesis / Q000235:genetics; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012867:Skin / Q000473:pathology; D051822:T Cell Transcription Factor 1 / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D051154:Wnt2 Protein / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism
C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D050778:NFATC Transcription Factors; C494006:NFATC2 protein, human; D010982:Platelet-Derived Growth Factor; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D051822:T Cell Transcription Factor 1; D051154:Wnt2 Protein; D051176:beta Catenin; C075278:platelet-derived growth factor A; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human