|Mutation Type||splice site|
|Coordinate||54,493,181 bp (GRCm38)|
|Base Change||T ⇒ A (forward strand)|
|Gene Name||folliculin interacting protein 1|
|Chromosomal Location||54,438,199-54,518,235 bp (+)|
FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] This gene encodes a member of the folliculin-interacting protein family. The encoded protein binds to the tumor suppressor folliculin and to AMP-activated protein kinase (AMPK) and be involved in cellular metabolism and nutrient sensing by regulating the AMPK-mechanistic target of rapamycin signaling pathway. A homologous binding partner of this protein, folliculin-interacting protein 2, has similar binding activities and may suggest functional redundancy within this protein family. Both folliculin-interacting proteins have also been shown to bind the molecular chaperone heat shock protein-90 (Hsp90) and they may function as a co-chaperones in the stabilization of tumor suppressor folliculin which is a target of Hsp90 chaperone activity. [provided by RefSeq, Sep 2016]
PHENOTYPE: Mice homozygous for an ENU-induced or targeted allele exhibit arrested B cell development at the pre-B cell stage with increased B cell apoptosis. [provided by MGI curators]
|Amino Acid Change|
|Institutional Source||Beutler Lab|
|Gene Model||predicted gene model for protein(s): [ENSMUSP00000049026] [ENSMUSP00000121399]|
|Predicted Effect||probably benign|
|Predicted Effect||probably benign|
|Meta Mutation Damage Score||0.0898|
|Is this an essential gene?||Possibly essential (E-score: 0.738)|
|Candidate Explorer Status||CE: potential candidate; Verification probability: 0.081; ML prob: 0.12; human score: 1.5|
Linkage Analysis Data
|Alleles Listed at MGI|
|Mode of Inheritance||Unknown|
|Last Updated||2019-09-04 9:31 PM by Anne Murray|
|Record Created||2019-01-22 11:22 AM by Bruce Beutler|
The Normandy phenotype was identified among G3 mice of the pedigree R0840, some of which showed reduced B200 expression on peripheral blood B cells (Figure 1).
|Nature of Mutation|
Whole exome HiSeq sequencing of the G1 grandsire identified 51 mutations. The reduced B220 MFI phenotype was linked by continuous variable mapping to mutations in two genes: Pisd (chromosome 5) and Fnip1 (chromosome 11). The mutation in Fnip1 was presumed causative as the B220 MFI phenotype in the Normandy mice mimics that of mice expressing another mutant Fnip1 allele (see hamel2). The Fnip1 mutation is a T to A transversion at base pair 54,493,181 (v38) on chromosome 11, or base pair 55,037 in the GenBank genomic region NC_000077 within intron 9, 12-base pairs from exon 10 (out of 18 total exons). Linkage was found with a dominant model of inheritance, wherein one variant homozygote and five heterozygous mice departed phenotypically from four homozygous reference mice with a P value of 0.000832 (Figure 2).
The effect of the mutation at the cDNA and protein levels has not been examined, but the mutation is predicted to not affect splicing. In case the mutation does affect splicing, the most likely aberrant splicing would result in skipping of the 202-base pair exon 10. The mutation would cause a frame-shifted protein product beginning after amino acid 305 of the protein, which is normally 1,165 amino acids in length, and termination after the inclusion of one aberrant amino acid.
The acceptor splice site of intron 9 indicated in blue lettering and the mutated nucleotide is indicated in red.
|Illustration of Mutations in
Gene & Protein
Fnip1 encodes the 1,165 amino acid folliculin (FLCN)-interacting protein 1 (FNIP1) protein. BLAST and SMART analysis revealed no known functional domains in FNIP1; however, there are five blocks of conserved amino acid sequence with at least 35% similarity between FNIP1 orthologs in Homo sapiens, Xenopus tropicalis, Danio rerio, Drosophila melanogaster, and Caenorhabditis elegans (Figure 3). Amino acids 300 to 1166 of FNIP1 (containing all but the first conserved block) are essential for binding to the C-terminus of FLCN; full-length FNIP1 is required for maximum binding (1). In addition to FLCN [and putatively FNIP2 (2;3)], FNIP1 interacts with HSP90, as well as with the alpha, beta, and gamma subunits of 5’-AMP-activated protein kinase (AMPK) (1).
The Normandy mutation may result in a frame-shifted protein product beginning after amino acid 305 of the protein and termination after the inclusion of one aberrant amino acid.
Please see the record hamel for more information about Fnip1.
The FLCN/FNIP complex negatively regulates AMPK, subsequently leading to alterations in AMPK-mTOR signaling (4). Modulation of the interaction between FLCN and FNIP1 by rapamycin and nutrient load suggests that FLCN and FNIP1 proteins are both involved in energy and/or nutrient sensing through AMPK and mTOR signaling pathways (1). mTOR signaling regulates the differentiation, activation, and function of several immune cell types including mast cells, neutrophils, natural killer cells, γδ T cells, macrophages, dendritic cells (DCs), T cells and B cells [(5-8); reviewed in (9)].
Fnip1 knockout (KO) mice are viable and fertile, but they display a marked reduction in spleen size as well as an almost complete lack of conventional splenic CD19+ cells, B220lowCD19high peritoneal B1 cells, and B cells in the bone marrow with a concomitant accumulation of B220lowCD43+CD25−pro-B cells (10). Thymus size, thymocyte numbers, and peripheral T cells as well as bone marrow monocyte, granulocyte, and erythrocyte lineages were normal in the Fnip1 KO animals. The reduced cell numbers were due to increased cell death of peripheral pro-B and pre-B cells in the KO; overexpression of antiapoptoic protein Bcl2 in the B cell compartment led to increased B220+IgM+ B cells in the bone marrow. Taken together, these results show that FNIP1 is essential for the survival of B-cells in the bone marrow. The defect in pro-B cell development was not caused by changes in V(D)J recombination or the failure to express a functional B cell receptor.
An ENU-induced Fnip1 mutant with a 32 bp deletion in exon 9, which resulted in coding of a premature stop codon at amino acid 293 exhibited changes in skeletal muscle, hypertrophic cardiomyopathy, and increased liver glycogen content (11). The Fnip1 mutant mice also showed a block at the pre-B cell stage in the bone marrow. Mature B cells were not detected in the bone marrow or the spleen and B1 B lymphocytes were not found in the peritoneal and pleural cavities. This study determined that FNIP1 mediates B cell development at the large pre-B to small pre-B cell transition; no changes to the signals from the pre-BCR and IL-7 receptor were detected in the Fnip1 mutant animals. Reduced Fnip1 expression also led to metabolic imbalance, which triggered apoptosis in response to pre-BCR stimulation, nutrient deprivation, or oncogene activation. FNIP1 was proposed to act as a molecular switch that permits pre-B cell differentiation and survival and FNIP1 ensures that maturing B cells have adequate metabolic capacity to finish maturing (11).
The phenotype observed in the Normandy mice indicates loss of FNIP1-associated function.
1) 94°C 2:00
The following sequence of 734 nucleotides is amplified (chromosome 11, + strand):
1 ttttcatgac tcaggctggg cagcttgctc agcctcaaga ttttcttcct ttagcttttg
Primer binding sites are underlined and the sequencing primers are highlighted; the mutated nucleotide is shown in red.
1. Baba, M., Hong, S. B., Sharma, N., Warren, M. B., Nickerson, M. L., Iwamatsu, A., Esposito, D., Gillette, W. K., Hopkins, R. F.,3rd, Hartley, J. L., Furihata, M., Oishi, S., Zhen, W., Burke, T. R.,Jr, Linehan, W. M., Schmidt, L. S., and Zbar, B. (2006) Folliculin Encoded by the BHD Gene Interacts with a Binding Protein, FNIP1, and AMPK, and is Involved in AMPK and mTOR Signaling. Proc Natl Acad Sci U S A. 103, 15552-15557.
2. Hasumi, H., Baba, M., Hong, S. B., Hasumi, Y., Huang, Y., Yao, M., Valera, V. A., Linehan, W. M., and Schmidt, L. S. (2008) Identification and Characterization of a Novel Folliculin-Interacting Protein FNIP2. Gene. 415, 60-67.
3. Takagi, Y., Kobayashi, T., Shiono, M., Wang, L., Piao, X., Sun, G., Zhang, D., Abe, M., Hagiwara, Y., Takahashi, K., and Hino, O. (2008) Interaction of Folliculin (Birt-Hogg-Dube Gene Product) with a Novel Fnip1-Like (FnipL/Fnip2) Protein. Oncogene. 27, 5339-5347.
4. Siggs, O. M., Stockenhuber, A., Deobagkar-Lele, M., Bull, K. R., Crockford, T. L., Kingston, B. L., Crawford, G., Anzilotti, C., Steeples, V., Ghaffari, S., Czibik, G., Bellahcene, M., Watkins, H., Ashrafian, H., Davies, B., Woods, A., Carling, D., Yavari, A., Beutler, B., and Cornall, R. J. (2016) Mutation of Fnip1 is Associated with B-Cell Deficiency, Cardiomyopathy, and Elevated AMPK Activity. Proc Natl Acad Sci U S A. 113, E3706-15.
5. Mills, R. E., and Jameson, J. M. (2009) T Cell Dependence on mTOR Signaling. Cell Cycle. 8, 545-548.
6. Weichhart, T., and Saemann, M. D. (2009) The Multiple Facets of mTOR in Immunity. Trends Immunol. 30, 218-226.
7. Delgoffe, G. M., and Powell, J. D. (2009) MTOR: Taking Cues from the Immune Microenvironment. Immunology. 127, 459-465.
8. Thomson, A. W., Turnquist, H. R., and Raimondi, G. (2009) Immunoregulatory Functions of mTOR Inhibition. Nat Rev Immunol. 9, 324-337.
9. Powell, J. D., Pollizzi, K. N., Heikamp, E. B., and Horton, M. R. (2011) Regulation of Immune Responses by mTOR. Annu Rev Immunol. .
10. Baba, M., Keller, J. R., Sun, H. W., Resch, W., Kuchen, S., Suh, H. C., Hasumi, H., Hasumi, Y., Kieffer-Kwon, K. R., Gonzalez, C. G., Hughes, R. M., Klein, M. E., Oh, H. F., Bible, P., Southon, E., Tessarollo, L., Schmidt, L. S., Linehan, W. M., and Casellas, R. (2012) The Folliculin-FNIP1 Pathway Deleted in Human Birt-Hogg-Dube Syndrome is Required for Murine B-Cell Development. Blood. 120, 1254-1261.
|Science Writers||Anne Murray|
|Illustrators||Diantha La Vine|
|Authors||Jin Huk Choi, Xue Zhong, and Bruce Beutler|