Phenotypic Mutation 'gasder' (pdf version)
Allelegasder
Mutation Type missense
Chromosome15
Coordinate75,864,357 bp (GRCm38)
Base Change T ⇒ C (forward strand)
Gene Gsdmd
Gene Name gasdermin D
Synonym(s) M2-4, Dfna5l, DF5L, 1810036L03Rik, Gsdmdc1
Chromosomal Location 75,862,327-75,867,408 bp (+)
MGI Phenotype FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] Gasdermin D is a member of the gasdermin family. Members of this family appear to play a role in regulation of epithelial proliferation. Gasdermin D has been suggested to act as a tumor suppressor. Alternatively spliced transcript variants have been described. [provided by RefSeq, Oct 2009]
PHENOTYPE: Mice homozygous for a knock-out allele are viable and grossly normal with no apparent defects in the development and maintenance of the intestinal epithelium. Mice homozygous for another null allele exhibit impaired induced pyroptosis and Il1b secretion. [provided by MGI curators]
Accession Number

NCBI RefSeq: NM_026960; MGI:1916396

Mapped Yes 
Amino Acid Change Serine changed to Proline
Institutional SourceBeutler Lab
Gene Model predicted gene model for protein(s): [ENSMUSP00000023238] [ENSMUSP00000155802] [ENSMUSP00000155766]
SMART Domains Protein: ENSMUSP00000023238
Gene: ENSMUSG00000022575
AA Change: S112P

DomainStartEndE-ValueType
Pfam:Gasdermin 4 461 8.3e-175 PFAM
low complexity region 470 482 N/A INTRINSIC
Predicted Effect probably damaging

PolyPhen 2 Score 1.000 (Sensitivity: 0.00; Specificity: 1.00)
(Using ENSMUST00000023238)
Predicted Effect probably damaging

PolyPhen 2 Score 0.999 (Sensitivity: 0.14; Specificity: 0.99)
(Using ENSMUST00000229331)
Predicted Effect probably benign
Phenotypic Category
Phenotypequestion? Literature verified References
Nlrc4 inflammasome: low response 26375003
Penetrance  
Alleles Listed at MGI

All Mutations and Alleles(19) : Chemically induced (other)(3) Endonuclease-mediated(3) Gene trapped(6) Radiation induced(2) Targeted(5)

Lab Alleles
AlleleSourceChrCoordTypePredicted EffectPPH Score
IGL01351:Gsdmd APN 15 75864337 missense probably damaging 1.00
IGL01528:Gsdmd APN 15 75863505 missense possibly damaging 0.62
IGL03005:Gsdmd APN 15 75867166 missense possibly damaging 0.85
R0788:Gsdmd UTSW 15 75864254 nonsense probably null
R1301:Gsdmd UTSW 15 75867059 synonymous probably null
R3725:Gsdmd UTSW 15 75866090 missense probably benign 0.05
R4585:Gsdmd UTSW 15 75865751 splice site probably null
R4917:Gsdmd UTSW 15 75864392 missense probably benign 0.01
R4918:Gsdmd UTSW 15 75864392 missense probably benign 0.01
R4920:Gsdmd UTSW 15 75864357 missense probably damaging 1.00
R5593:Gsdmd UTSW 15 75867007 missense probably damaging 0.99
X0052:Gsdmd UTSW 15 75866128 missense possibly damaging 0.68
Z1088:Gsdmd UTSW 15 75863474 missense probably benign 0.00
Mode of Inheritance Autosomal Recessive
Local Stock
Repository
Last Updated 2018-11-16 1:49 PM by Anne Murray
Record Created 2016-11-17 1:15 PM by Hexin Shi
Record Posted 2018-11-16
Phenotypic Description
Figure 1. Gasder mice exhibited decreased IL-1β secretion in response to priming with lipopolysaccharide (LPS) followed by nigericin treatment. IL-1β levels were determined by ELISA. Normalized data are shown. Abbreviations: WT, wild-type; REF, homozygous reference mice; HET, heterozygous variant mice; VAR, homozygous variant mice. Mean (μ) and standard deviation (σ) are indicated.
Figure 2. Gasder mice exhibited decreased IL-1β secretion in response to priming with lipopolysaccharide (LPS) followed by flagellin treatment. IL-1β levels were determined by ELISA. Normalized data are shown. Abbreviations: WT, wild-type; REF, homozygous reference mice; HET, heterozygous variant mice; VAR, homozygous variant mice. Mean (μ) and standard deviation (σ) are indicated.

The gasder phenotype was identified among N-ethyl-N-nitrosourea (ENU)-mutagenized G3 mice of the pedigree R4920, some of which showed reduced inflammatory responses related to reduced secretion of the proinflammatory cytokine interleukin (IL)-1β in response to priming with lipopolysaccharide (LPS) followed by flagellin treatment (NLRC4 inflammasome; Figure 1) and to priming with lipopolysaccharide (LPS) followed by nigericin treatment (NLRP3 inflammasome; Figure 2).

Nature of Mutation
Figure 3. Linkage mapping of the reduced IL-1β secretion after flagellin stimulation using a recessive model of inheritance. Manhattan plot shows -log10 P values (Y-axis) plotted against the chromosome positions of 45 mutations (X-axis) identified in the G1 male of pedigree R4920. Normalized phenotype data are shown for single locus linkage analysis without consideration of G2 dam identity. Horizontal pink and red lines represent thresholds of P = 0.05, and the threshold for P = 0.05 after applying Bonferroni correction, respectively.

Whole exome HiSeq sequencing of the G1 grandsire identified 45 mutations. Both of the above phenotypes were linked by continuous variable mapping to two genes on chromosome 15: Dendd3 and Gsdmd. The mutation in Gsdmd was presumed causative, and is a T to C transition at base pair 75,864,357 (v38) on chromosome 15, or base pair 2,217 in the GenBank genomic region NC_000081 encoding Gsdmd. The strongest association was found with a recessive model of inheritance to the NLRC4 inflammasome phenotype, wherein seven variant homozygotes departed phenotypically from 13 homozygous reference mice and 10 heterozygous mice with a P value of 1.391 x 10-9 (Figure 3).  

 

The mutation corresponds to residue 483 in the NM_026960 mRNA sequence in exon 3 of 11 total exons. 

 

466 GGTGGGGCTGCAGTGTCTGACAGTTCCAGTGCC
107 -G--G--A--A--V--S--D--S--S--S--A-

 

The mutated nucleotide is indicated in red. The mutation results in a serine (S) to proline (P) substitution at residue 112 (S112P) in the GSDMD protein, and is strongly predicted by PolyPhen-2 to be damaging (score = 1.000).

Protein Prediction
Figure 4. Domain organization of GSDMD. The location of the gasder mutation is indicated. Abbreviations: LH, linker helix; HR, helix repeat; β, intermediated β-strand insertion. Domain information is from SMART and UniProt.
Figure 5. Crystal structure of mouse GSDMA3. Subdomains of GSDMA-C are colored as GSDMD-C in Figure 4. UCSF Chimera model is based on PDB 5B5R, Ding, et al. Nature. 535, 111-116 (2016). Click on the 3D structure to view it rotate.

Gsdmd encodes gasdermin D (GSDMD; alternatively, DFNA5L), a member of the gasdermin (GSDM) protein family that also includes GSDMA, GSDMB, GSDMC, GSDME (alternatively, DFNA5), and DFNB59 (alternatively, pejvakin). Mice lack GSDMB, but have three GSDMA (GSDMA1–3; see the record Michelin for information about GSDMA3) and four GSDMC (GSDMC1–4) proteins. The GSDM proteins share approximately 45 percent overall sequence homology, and mouse GSDMD shares approximately 70 percent homology with GSDMA3.

 

The GSDM proteins contain a novel, roughly conserved region known as the DFNA5-GSDM domain, which includes most of the protein sequence, excluding the very N-terminus and approximately 25 amino acids at the C-terminus (1-3). Additionally, all GSDM proteins contain four conserved leucine-rich motifs at the N-terminus and five at the C-terminus with the last motif being the most highly conserved. The GSDM proteins have two putative leucine zippers at the C-terminus, indicating that they may participate in DNA binding.

 

GSDMD is cleaved by caspases (i.e., caspase-1, caspase-4, caspase-5, or caspase-11) after Asp276 (in mouse) to form a 31-kDa N-terminal fragment (GSDMD-N) and a 22-kDa C-terminal fragment (GSDMD-C) (Figure 4) (4-6). The C-terminus has an autoinhibitory effect on the intrinsic activity of the N-terminus [(7); reviewed in (8)]. The first loop of the C-terminus inserts into the N-terminal domain to help stabilize the conformation of full-length GSDMD; cleavage releases the GSDMD-N autoinhibition by GSDMD-C (7). GSDMD-N can form arc- and split-shaped oligomers that form dynamic structures, which transform into larger thermodynamically stable ring‐shaped oligomers (9;10). GSDMD-N exhibits intrinsic pyroptosis-inducing activity after inflammasome activation (6;11); the function of GSDMD-N is discussed in more detail in the “Background” section. The structure of GSDMD-N is unknown, but the highly homologous GSDMA3-N contains an extended twisted β-sheet formed by nine tandem β-strands (β3 to β11) [Figure 5; PDB:5B5R; (12)]. GSDMD-C forms a compact globular fold comprising 10 α-helices and two β-strands [PDB:5B5R, (12); PDB:5WQT, (7); and PDB:6AO4, (13)]. The GSDMD-C fragment has four subdomains: the linker helix, the helix repeat-I bundle (α2 to α5), the helix repeat repeat-II bundle (α6, α7, α9, and α10), and the intermediate β-strand insertion (α8) (7). The two helix repeats are composed of similar four-helix bundles, and the linker helix contacts the two helix repeats. A flexible loop (amino acids 276 to 287) located between the N-terminal domain and the linker helix, stretches out to the N-terminal pocket.

 

The gasder mutation results in a serine (S) to proline (P) substitution at residue 112 (S112P) in the GSDMD protein; amino acid 112 is within GSDMD-N.

Expression/Localization

GSDMD is widely expressed, with high expression in gastrointestinal tissue, skin, placenta, esophagus, and stomach as well as in human B- and T-lymphocyte lines, in various tumor tissues, and cancer cell lines (14;15).

 

GSDMD localizes to the cytosol (10). Upon inflammasome activation, GSDMD (namely GSDMD-N) translocates to the plasma membrane and GSDMD-C remains cytoplasmic.

Background
Figure 6. Caspases induce pyroptosis by generating GSDMD pores on the plasma membrane. The NLRP3 inflammasome is shown. NLRP3 is present in the cytosol in an inactive conformation state due to its association with the SGT1/HSP90 chaperone complex. The NLRP3 inflammasome is activated by a wide variety of agents. Several activators have been shown to generate pore formation by a pannexin hemichannel that may allow extracellular molecules access to the cytoplasm and contact with NLRP3. Extracellular ATP mediates inflammasome activation through the P2X7 ATP-gated ion channel, triggering rapid K+ efflux from the cell (decreased potassium (K+) concentration may favor inflammasome assembly). Rupture of lysosomes containing certain particulates releases Cathepsin B into the cytoplasm, activating the inflammasome. NLRP3 activators may also trigger inflammasome assembly by generating reactive oxygen species (ROS), often produced under situations of cellular stress. The inactive state of caspase-1 contains a CARD-containing prodomain. Oligomerization of NLRP3 and the recruitment of caspase-1, ASC, and CARDINAL leads to the autoproteolytic maturation of caspase-1. Caspase-1 is capable of cleaving pro-1L-1β, pro-IL-18, and pro-IL-33. These mature cytokines mediate a variety of biological effects by activating key processes such as the nuclear factor κB and mitogen-activated protein kinase (MAPK) pathways.   

Members of the NLR family, including NLRC4 (see the record for inwood), NLRP1b, and NLRP3 (see the record for ND1), oligomerize and assemble into large caspase-1-activating multiprotein complexes termed inflammasomes upon the detection of pathogenic or other danger signals (e.g., lipopolysaccharide, peptidoglycan, pathogenic bacteria, DNA, single-stranded (ss) RNA, double-stranded (ds) RNA, environmental irritants, and endogenous danger signals) in the cytoplasm (Figure 6). Activated caspase-1 is able to cleave a variety of substrates, most notably the proinflammatory cytokines IL-1β, IL-18, and IL-33 to generate biologically active proteins. In turn, these cytokines mediate a wide variety of biological effects associated with infection, inflammation, and autoimmune processes by activating key processes such as the nuclear factor κB (NF-κB; see the record for panr2) and mitogen-activated protein kinase (MAPK) pathways. Activation of caspase-1 also leads to pyroptosis, which is a form of programmed necrosis that involves pore formation, membrane rupture, and leakage of cytosolic contents.

 

GSDMD is a mediator of inflammasome-activated caspase 1-induced pyroptosis as well as IL-1β and IL-18 secretion (6;11;16-18). GSDMD-N binds to phosphatidylinositol phosphates (i.e., PtdIns3P, PtdIns4P, PtdIns5P, PtdIns(3,4)P2, PtdIns(3,5)P2, and PtdIns(3,4,5)P3) and phosphatidylserine found in the inner leaflet of cell membranes as well as to cardolipin found in inner and outer leaflets of bacterial membranes (12;19). Binding of GSDMD to the membrane facilitates plasma membrane pore formation, allowing the release of IL-1β (19-21); GSDMD-associated IL-1β secretion is independent of pyroptosis (17;18;22). After recognition of viral/bacterial dsDNA, the AIM2 inflammasome causes GSDMD-mediated potassium efflux. The potassium efflux subsequently inhibits the dsDNA sensor cGAS-STING and prevents interferon production (23).

 

GSDMD also functions in the formation of neutrophil extracellular traps (NETs) during NETosis (24;25). NETosis is a form of neutrophil cell death that releases chromatin structures (i.e., the NETs) to the extracellular space, providing host defense against extracellular pathogens. The NETs capture microorganisms, activate myeloid cells, and promote coagulation (26). GSDMD is proteolytically activated by cleavage at Cys268 by neutrophil proteases (e.g., neutrophil elastase; see the record for Elane) during NETosis, which subsequently affects protease activation and nuclear expansion (27;28).

Putative Mechanism
Figure 7. Activation of the NLRC4 inflammasome. Infection of macrophages with various gram-negative bacteria activates caspase-1 via NLRC4. A critical step is the cytosolic delivery of flagellin or proteins through the bacterial T3SS or T4SS. Flagellin is recognized by Naip5 or Naip6,  whereas rod proteins are recognized by Naip2. S. flexneri activates the NLRC4 inflammasome independently of flagellin through IpaB. Activation of caspase-1 via NLRC4 leads to the processing and release of IL-1β and IL-18, the processing of caspase-7, and pyroptosis. This image is interactive. Other mutations associated with the NLRC4 inflammasome pathway are noted in red. Click on each mutation for more information.

The NLRC4 inflammasome stimulates caspase-1 activation and subsequent IL-1β secretion from macrophages after exposure to lipopolysaccharide, peptidoglycan, and pathogenic bacteria (e.g., Aeromonas veronii, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enterica serovar typhimurium (S. typhimurium), and Yersinia species) (29) (Figure 7).  In contrast to NLRP3-associated caspase-1 activation, which predominantly results in the processing and secretion of IL-1β and IL-18 without necessarily resulting in cell death, NLRC4-mediated activation of caspase-1 often results in cell death [reviewed in (30)]. For more information about the NLRC4-associated inflammasome, please see the record for inwood.

 

Gsdmd-deficient mouse bone marrow-derived macrophages exhibited resistance to LPS- and inflammasome-induced pyroptosis induction as well as reduced release of IL-1β (6;9). The phenotype of the gasder mice mimics that of the Gsdmd-deficient mouse, indicating loss of GSDMD-associated function.

Primers PCR Primer
gasder(F):5'- AGTCCTTTAAAGGTCCCATCAC -3'
gasder(R):5'- CCCTCATTCAGTGCTGAGAG -3'

Sequencing Primer
gasder_seq(F):5'- TTTAAAGGTCCCATCACTACAGAGG -3'
gasder_seq(R):5'- CATTCAGTGCTGAGAGATACTGCC -3'
References
Science Writers Anne Murray
Illustrators Diantha La Vine
AuthorsHexin Shi and Bruce Beutler