The folliculin-FNIP1 pathway deleted in human Birt-Hogg-Dubé syndrome is required for murine B-cell development.
Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant disorder characterized by cutaneous fibrofolliculomas, pulmonary cysts, and kidney malignancies. Affected individuals carry germ line mutations in folliculin (FLCN), a tumor suppressor gene that becomes biallelically inactivated in kidney tumors by second-hit mutations. Similar to other factors implicated in kidney cancer, FLCN has been shown to modulate activation of mammalian target of rapamycin (mTOR). However, its precise in vivo function is largely unknown because germ line deletion of Flcn results in early embryonic lethality in animal models. Here, we describe mice deficient in the newly characterized folliculin-interacting protein 1 (Fnip1). In contrast to Flcn, Fnip1(-/-) mice develop normally, are not susceptible to kidney neoplasia, but display a striking pro-B cell block that is entirely independent of mTOR activity. We show that this developmental arrest results from rapid caspase-induced pre-B cell death, and that a Bcl2 transgene reconstitutes mature B-cell populations, respectively. We also demonstrate that conditional deletion of Flcn recapitulates the pro-B cell arrest of Fnip1(-/-) mice. Our studies thus demonstrate that the FLCN-FNIP complex deregulated in BHD syndrome is absolutely required for B-cell differentiation, and that it functions through both mTOR-dependent and independent pathways.
Urologic Oncology Branch, National Cancer Institute (NCI), National Institutes of Health (NIH), Bethesda, MD 20892, USA.
Masaya
M
Baba
Jonathan R
JR
Keller
Hong-Wei
HW
Sun
Wolfgang
W
Resch
Stefan
S
Kuchen
Hyung Chan
HC
Suh
Hisashi
H
Hasumi
Yukiko
Y
Hasumi
Kyong-Rim
KR
Kieffer-Kwon
Carme Gallego
CG
Gonzalez
Robert M
RM
Hughes
Mara E
ME
Klein
Hyoungbin F
HF
Oh
Paul
P
Bible
Eileen
E
Southon
Lino
L
Tessarollo
Laura S
LS
Schmidt
W Marston
WM
Linehan
Rafael
R
Casellas
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D058249:Birt-Hogg-Dube Syndrome / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics* / Q000276:immunology; D002478:Cells, Cultured; D017353:Gene Deletion; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013045:Species Specificity; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology
D002352:Carrier Proteins; C476078:FLCN protein, human; C516440:FNIP1 protein, human; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins