Birt-hogg-dubé syndrome is a novel ciliopathy

Luijten, Monique N.H. and Basten, Sander G. and Claessens, Tijs and Vernooij, Marigje and Scott, Claire L. and Janssen, Renske and Easton, Jennifer A. and Kamps, Miriam A.F. and Vreeburg, Maaike and Broers, Jos L.V. and Geel, Michel van and Menko, Fred H. and Harbottle, Richard P. and Nookala, Ravi K. and Tee, Andrew R. and Land, Stephen C. and Giles, Rachel H. and Coull, Barry J. and van Steensel, Maurice A.M. (2013) Birt-hogg-dubé syndrome is a novel ciliopathy. Human Molecular Genetics, 22 (21). pp. 4383-4397. ISSN 0964-6906

Abstract

Birt-Hogg-Dubé (BHD) syndromeis an autosomal dominant disorder where patients are predisposed to kidney cancer, lung and kidney cysts and benign skin tumors. BHD is caused by heterozygous mutations affecting folliculin (FLCN), a conserved protein that is considered a tumor suppressor. Previous research has uncovered multiple roles for FLCN in cellular physiology, yet it remains unclear how these translate to BHD lesions. Since BHD manifests hallmark characteristics of ciliopathies, we speculated that FLCN might also have a ciliary role. Our data indicate that FLCN localizes to motile and non-motile cilia, centrosomes and the mitotic spindle. Alteration of FLCN levels can cause changes to the onset of ciliogenesis, without abrogating it. In threedimensional culture, abnormal expression of FLCN disrupts polarized growth of kidney cells and deregulates canonical Wnt signalling. Our findings further suggest that BHD-causing FLCN mutants may retain partial functionality. Thus, several BHD symptoms may be due to abnormal levels of FLCN rather than its complete loss and accordingly, we show expression of mutant FLCN in a BHD-associated renal carcinoma. We propose that BHD is a novel ciliopathy, its symptoms at least partly due to abnormal ciliogenesis and canonical Wnt signalling.