|Coordinate||60,779,870 bp (GRCm38)|
|Base Change||C ⇒ T (forward strand)|
|Gene Name||Smith-Magenis syndrome chromosome region, candidate 8 homolog (human)|
|Chromosomal Location||60,777,524-60,788,287 bp (+)|
|MGI Phenotype||PHENOTYPE: Mouse embryonic fibroblasts homozygous for a knock-out allele show impaired autophagy induction, a reduced autophagic flux, and abnormal expression of lysosomal enzymes. [provided by MGI curators]|
|Amino Acid Change||Glutamine changed to Stop codon|
|Institutional Source||Beutler Lab|
|Gene Model||predicted gene model for protein(s): [ENSMUSP00000055926] [ENSMUSP00000099728]|
AA Change: Q615*
|Predicted Effect||probably null|
AA Change: Q615*
|Predicted Effect||probably null|
|Meta Mutation Damage Score||0.578|
|Is this an essential gene?||Non Essential (E-score: 0.000)|
|Candidate Explorer Status||CE: excellent candidate; human score: 2.5; ML prob: 0.886|
Linkage Analysis Data
|Alleles Listed at MGI|
|Mode of Inheritance||Autosomal Recessive|
|Last Updated||2019-09-04 9:40 PM by Anne Murray|
|Record Created||2017-05-31 4:45 PM|
The patriot3 phenotype was identified among N-ethyl-N-nitrosourea (ENU)-mutagenized G3 mice of the pedigree R5108, some of which showed susceptibility to dextran sodium sulfate (DSS)-induced colitis at 7 (Figure 1) and 10 days (Figure 2) after DSS exposure.
|Nature of Mutation|
Whole exome HiSeq sequencing of the G1 grandsire identified 74 mutations. The DSS susceptibility phenotype was linked by continuous variable mapping to a mutation in Smcr8: a C to T transition at base pair 60,779,870 (v38) on chromosome 11, or base pair 2,346 in the GenBank genomic region NC_000077 encoding Smcr8. The strongest association was found with a recessive model of inheritance to the DSS susceptibility phenotype at day 10, wherein six variant homozygotes departed phenotypically from 18 homozygous reference mice and 41 heterozygous mice with a P value of 3.043 x 10-6 (Figure 3).
The mutation corresponds to residue 2,346 in the mRNA sequence NM_001085440 within exon 1 of 2 total exons.
The mutated nucleotide is indicated in red. The mutation results in substitution of glutamine 615 for a premature stop codon (Q615*) in the SMCR8 protein.
Smcr8 encodes SMCR8 (Smith-Magenis syndrome chromosome region, candidate 8). SMCR8 is a homolog of the DENN module, which is GDP-GTP exchange factor for Rab GTPases (1). The DENN module and SMCR8 both have an N-terminal longin (alternatively, u-DENN) domain, a DENN domain, and a d-DENN domain (Figure 4). The longin domain mediates interaction with GTPases (2) and has a PAS domain-like fold similar to ligand-binding domains (3).
The patriot3 mutation results in substitution of glutamine 615 for a premature stop codon (Q615*); Q615 is within the central DENN domain.
Please see the record patriot for more information about Smcr8.
SMCR8 interacts with C9ORF72 and WDR41 (see the record for gogi) to form the SWC (SMCR8-WDR41-C9ORF72) tripartite complex (4). The SWC complex functions as a GDP-GTP exchange factor for the small GTPases RAB8A and RAB39B, which function in vesicle trafficking and autophagy (5-9). After TBK1-mediated phosphorylation of SMCR8, the SWC complex interacts with the autophagy initiation complex ULK1/FIP200/autophagy-related protein 13 (ATG13)/ATG101 via C9ORF72 binding (5;6;8). The interaction between the SWC complex and the ULK1 complex regulates the expression and activity of ULK1 (8;9). Knockout of SMCR8 or C9ORF72 resulted in enlarged lysosome vesicles, while SMCR8 knockout alone showed accumulation of lysosomes and lysosomal enzymes as well as impaired autophagy induction (5-8;10). Mouse embryonic fibroblasts from Smcr8-deficient (Smcr8-/-) mice exhibited abnormal autophagy as well as a block in lysosomal degradation (MGI; accessed August 17, 2017).
Smcr8-/- and SMCR8-mutant (Smcr8I2T/I2T) showed increased TNF production in response to the TLR9 ligand CpG (11). The Smcr8-/- and Smcr8I2T/I2T mice also showed increased TNF responses and IL-6 production in response to stimulation with TLR7 and TLR3 ligands; TNF production was normal in response to TLR2 or TLR4 stimulation. Taken together, loss of SMCR8 function results in aberrant activation of endosomal TLRs. The defects in TLR9-associated signaling is proposed to be caused by defects in the SWC complex due to loss of SMCR8-assocated function (11). Loss of SWC complex function causes defects in lysosome and phagosome maturation, resulting in protracted TLR stimulation. Smcr8-/- and Smcr8I2T/I2T mice also showed splenomegaly and lymphadenopathy at 9 and 12 months of age (11). The mice showed normal numbers of macrophages, monocytes, neutrophils, B cells, and T cells in the peripheral blood; however, the percentages of naïve CD4+ and CD8+ T cells was reduced and the percentages of activated CD4+ and CD8+ T cells was increased (11). The mice also showed increased plasma levels of the cytokine IL-12p40 compared to wild-type mice (11). Smcr8-/- macrophages showed an accumulation of putative lysosomes. Similar to the patriot mice the Smcr8-/- and Smcr8I2T/I2T mice showed susceptibility to DSS treatment. Smcr8-/- mice also exhibited autoimmunity and increased lysosomal exocytosis in macrophages (4).
The colitis phenotype observed in the patriot3 mice is putatively caused by defects in endosomal TLR signaling; the endosomal TLRs are required for protection in colitis.
1) 94°C 2:00
The following sequence of 401 nucleotides is amplified (chromosome 11, + strand):
1 cctatgcgga taatgagggg gccatccatt tccaggcaag tgccggctca ccagaaccgg
Primer binding sites are underlined and the sequencing primers are highlighted; the mutated nucleotide is shown in red.
1. Zhang, D., Iyer, L. M., He, F., and Aravind, L. (2012) Discovery of Novel DENN Proteins: Implications for the Evolution of Eukaryotic Intracellular Membrane Structures and Human Disease. Front Genet. 3, 283.
2. Schlenker, O., Hendricks, A., Sinning, I., and Wild, K. (2006) The Structure of the Mammalian Signal Recognition Particle (SRP) Receptor as Prototype for the Interaction of Small GTPases with Longin Domains. J Biol Chem. 281, 8898-8906.
3. Aravind, L., Mazumder, R., Vasudevan, S., and Koonin, E. V. (2002) Trends in Protein Evolution Inferred from Sequence and Structure Analysis. Curr Opin Struct Biol. 12, 392-399.
4. Zhang, Y., Burberry, A., Wang, J. Y., Sandoe, J., Ghosh, S., Udeshi, N. D., Svinkina, T., Mordes, D. A., Mok, J., Charlton, M., Li, Q. Z., Carr, S. A., and Eggan, K. (2018) The C9orf72-Interacting Protein Smcr8 is a Negative Regulator of Autoimmunity and Lysosomal Exocytosis. Genes Dev. 32, 929-943.
5. Sellier, C., Campanari, M. L., Julie Corbier, C., Gaucherot, A., Kolb-Cheynel, I., Oulad-Abdelghani, M., Ruffenach, F., Page, A., Ciura, S., Kabashi, E., and Charlet-Berguerand, N. (2016) Loss of C9ORF72 Impairs Autophagy and Synergizes with polyQ Ataxin-2 to Induce Motor Neuron Dysfunction and Cell Death. EMBO J. 35, 1276-1297.
6. Sullivan, P. M., Zhou, X., Robins, A. M., Paushter, D. H., Kim, D., Smolka, M. B., and Hu, F. (2016) The ALS/FTLD Associated Protein C9orf72 Associates with SMCR8 and WDR41 to Regulate the Autophagy-Lysosome Pathway. Acta Neuropathol Commun. 4, 51-016-0324-5.
7. Amick, J., Roczniak-Ferguson, A., and Ferguson, S. M. (2016) C9orf72 Binds SMCR8, Localizes to Lysosomes, and Regulates mTORC1 Signaling. Mol Biol Cell. 27, 3040-3051.
8. Yang, M., Liang, C., Swaminathan, K., Herrlinger, S., Lai, F., Shiekhattar, R., and Chen, J. F. (2016) A C9ORF72/SMCR8-Containing Complex Regulates ULK1 and Plays a Dual Role in Autophagy. Sci Adv. 2, e1601167.
9. Jung, J., Nayak, A., Schaeffer, V., Starzetz, T., Kirsch, A. K., Muller, S., Dikic, I., Mittelbronn, M., and Behrends, C. (2017) Multiplex Image-Based Autophagy RNAi Screening Identifies SMCR8 as ULK1 Kinase Activity and Gene Expression Regulator. Elife. 6, 10.7554/eLife.23063.
10. Ugolino, J., Ji, Y. J., Conchina, K., Chu, J., Nirujogi, R. S., Pandey, A., Brady, N. R., Hamacher-Brady, A., and Wang, J. (2016) Loss of C9orf72 Enhances Autophagic Activity Via Deregulated mTOR and TFEB Signaling. PLoS Genet. 12, e1006443.
11. McAlpine, W., Sun, L., Wang, K. W., Liu, A., Jain, R., San Miguel, M., Wang, J., Zhang, Z., Hayse, B., McAlpine, S. G., Choi, J. H., Zhong, X., Ludwig, S., Russell, J., Zhan, X., Choi, M., Li, X., Tang, M., Moresco, E. M. Y., Beutler, B., and Turer, E. (2018) Excessive Endosomal TLR Signaling Causes Inflammatory Disease in Mice with Defective SMCR8-WDR41-C9ORF72 Complex Function. Proc Natl Acad Sci U S A. 115, E11523-E11531.
|Science Writers||Anne Murray|
|Illustrators||Diantha La Vine|
|Authors||William McAlpine, Braden Hayse, Emre Turer, and Bruce Beutler|