title: Filamin-interacting proteins, Cfm1 and Cfm2, are essential for the formation of cartilaginous skeletal elements.
abstract: Mutations of Filamin genes, which encode actin-binding proteins, cause a wide range of congenital developmental malformations in humans, mainly skeletal abnormalities. However, the molecular mechanisms underlying Filamin functions in skeletal system formation remain elusive. In our screen to identify skeletal development molecules, we found that Cfm (Fam101) genes, Cfm1 (Fam101b) and Cfm2 (Fam101a), are predominantly co-expressed in developing cartilage and intervertebral discs (IVDs). To investigate the functional role of Cfm genes in skeletal development, we generated single knockout mice for Cfm1 and Cfm2, as well as Cfm1/Cfm2 double-knockout (Cfm DKO) mice, by targeted gene disruption. Mice with loss of a single Cfm gene displayed no overt phenotype, whereas Cfm DKO mice showed skeletal malformations including spinal curvatures, vertebral fusions and impairment of bone growth, showing that the phenotypes of Cfm DKO mice resemble those of Filamin B (Flnb)-deficient mice. The number of cartilaginous cells in IVDs is remarkably reduced, and chondrocytes are moderately reduced in Cfm DKO mice. We observed increased apoptosis and decreased proliferation in Cfm DKO cartilaginous cells. In addition to direct interaction between Cfm and Filamin proteins in developing chondrocytes, we showed that Cfm is required for the interaction between Flnb and Smad3, which was reported to regulate Runx2 expression. Furthermore, we found that Cfm DKO primary chondrocytes showed decreased cellular size and fewer actin bundles compared with those of wild-type chondrocytes. These results suggest that Cfms are essential partner molecules of Flnb in regulating differentiation and proliferation of chondryocytes and actin dynamics.
authors.affiliation: Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Mizuhashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanamoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Moriishi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Muranishi
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Koji
authors.initials: K
authors.lastname: Terada
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Omori
authors.forename: Masako
authors.initials: M
authors.lastname: Ito
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Komori
authors.forename: Takahisa
authors.initials: T
authors.lastname: Furukawa
mesh_terms: D000818:Animals; D017209:Apoptosis; D002356:Cartilage / Q000002:abnormalities / Q000254:growth & development / Q000378:metabolism*; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D005097:Exostoses, Multiple Hereditary / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D064448:Filamins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D013131:Spine / Q000002:abnormalities / Q000254:growth & development / Q000378:metabolism*
chemical_list: C000594353:FAM101A protein, mouse; C000594354:FLNB protein, mouse; D064448:Filamins; C529499:FlnA protein, mouse; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; C502203:Rflnb protein, mouse