Phenotypic Mutation 'Ernie2' (pdf version)
Mutation Type splice site
Coordinate122,180,862 bp (GRCm38)
Base Change A ⇒ G (forward strand)
Gene Ern2
Gene Name endoplasmic reticulum (ER) to nucleus signalling 2
Synonym(s) Ire1b
Chromosomal Location 122,169,893-122,186,207 bp (-)
MGI Phenotype PHENOTYPE: Mice homozygous for disruption of this gene are generally normal but display an increased susceptibility to intestinal inflammation. [provided by MGI curators]
Accession Number

NCBI RefSeq: NM_012016, NM_001316689; MGI:1349436

Mapped Yes 
Amino Acid Change
Institutional SourceBeutler Lab
Gene Model predicted gene model for protein(s): [ENSMUSP00000033153] [ENSMUSP00000145716]
SMART Domains Protein: ENSMUSP00000033153
Gene: ENSMUSG00000030866

low complexity region 14 28 N/A INTRINSIC
PQQ 33 64 5.5e-8 SMART
PQQ 115 147 4.7e-4 SMART
PQQ 148 180 6.1e-2 SMART
PQQ 192 223 6.2e-3 SMART
low complexity region 449 461 N/A INTRINSIC
S_TKc 508 768 2.5e-11 SMART
PUG 831 888 9e-24 SMART
Predicted Effect probably benign
Predicted Effect probably benign
Meta Mutation Damage Score 0.0898 question?
Is this an essential gene? Probably nonessential (E-score: 0.116) question?
Phenotypic Category
Phenotypequestion? Literature verified References
DSS: sensitive day 10 11238559
DSS: sensitive day 7 11238559
Candidate Explorer Status CE: excellent candidate; Verification probability: 0.412; ML prob: 0.428; human score: 3.5
Single pedigree
Linkage Analysis Data
Alleles Listed at MGI

All Mutations and Alleles(2) : Chemically induced (ENU)(1) Targeted(1)

Lab Alleles
AlleleSourceChrCoordTypePredicted EffectPPH Score
IGL01060:Ern2 APN 7 122170092 missense probably damaging 0.99
IGL01324:Ern2 APN 7 122183190 missense possibly damaging 0.88
IGL02185:Ern2 APN 7 122173375 splice site probably benign
IGL02738:Ern2 APN 7 122182899 missense probably damaging 0.99
IGL02750:Ern2 APN 7 122181406 splice site probably benign
IGL03247:Ern2 APN 7 122171671 missense probably benign 0.02
ernie UTSW 7 122171661 critical splice donor site probably null
ernie3 UTSW 7 122173819 critical splice acceptor site probably null
R0165:Ern2 UTSW 7 122179779 missense probably benign 0.02
R0785:Ern2 UTSW 7 122171661 critical splice donor site probably null
R0801:Ern2 UTSW 7 122180862 splice site probably benign
R1345:Ern2 UTSW 7 122177770 missense probably damaging 1.00
R1649:Ern2 UTSW 7 122177400 missense probably damaging 1.00
R1747:Ern2 UTSW 7 122173819 critical splice acceptor site probably null
R1747:Ern2 UTSW 7 122173820 critical splice acceptor site probably null
R1846:Ern2 UTSW 7 122176536 missense probably benign 0.32
R1899:Ern2 UTSW 7 122183842 splice site probably benign
R1986:Ern2 UTSW 7 122171529 missense probably benign 0.06
R2055:Ern2 UTSW 7 122183945 missense possibly damaging 0.84
R2329:Ern2 UTSW 7 122173487 missense possibly damaging 0.82
R2351:Ern2 UTSW 7 122171508 missense probably damaging 0.97
R2894:Ern2 UTSW 7 122181587 missense possibly damaging 0.94
R3176:Ern2 UTSW 7 122180964 missense possibly damaging 0.89
R3276:Ern2 UTSW 7 122180964 missense possibly damaging 0.89
R3945:Ern2 UTSW 7 122176530 missense probably benign 0.10
R4303:Ern2 UTSW 7 122177846 critical splice acceptor site probably null
R4874:Ern2 UTSW 7 122176587 missense probably benign 0.28
R4943:Ern2 UTSW 7 122173258 missense possibly damaging 0.95
R5184:Ern2 UTSW 7 122179959 missense probably benign 0.03
R5629:Ern2 UTSW 7 122170166 missense probably damaging 1.00
R5770:Ern2 UTSW 7 122179907 missense possibly damaging 0.92
R6255:Ern2 UTSW 7 122173272 missense probably damaging 1.00
R6272:Ern2 UTSW 7 122176646 missense probably benign 0.05
R6277:Ern2 UTSW 7 122186107 missense probably benign
R6624:Ern2 UTSW 7 122177783 missense probably benign 0.00
R6940:Ern2 UTSW 7 122186146 missense probably benign 0.01
R7491:Ern2 UTSW 7 122170533 missense probably damaging 1.00
R7544:Ern2 UTSW 7 122173199 missense probably benign 0.06
R7555:Ern2 UTSW 7 122170241 missense probably damaging 1.00
R7843:Ern2 UTSW 7 122173708 missense probably damaging 1.00
R8281:Ern2 UTSW 7 122170260 missense probably damaging 1.00
R8321:Ern2 UTSW 7 122173208 missense probably damaging 1.00
R8377:Ern2 UTSW 7 122181292 nonsense probably null
R8548:Ern2 UTSW 7 122177839 missense probably damaging 1.00
Mode of Inheritance Autosomal Semidominant
Local Stock
Last Updated 2019-09-04 9:44 PM by Anne Murray
Record Created 2015-12-07 3:26 PM by Emre Turer
Record Posted 2016-05-02
Phenotypic Description

Figure 1. Ernie2 mice exhibited weight loss on day 10 after DSS treatment. 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 Ernie2 phenotype was identified among G3 mice of the pedigree R0801, some of which showed weight loss at day 10 after treatment with dextran sulfate sodium (DSS)-containing water, indicating susceptibility to DSS-induced colitis (Figure 1).

Nature of Mutation

Figure 2. Linkage mapping of the DSS-induced weight loss at day 10 after DSS treatment using a semidominant model of inheritance. Manhattan plot shows -log10 P values (Y-axis) plotted against the chromosome positions of 44 mutations (X-axis) identified in the G1 male of pedigree R0801. 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 44 mutations. The increased susceptibility to DSS-induced colitis was linked by continuous variable mapping to a mutation in Ern2: a T to C transition at base pair 122,180,862 (v38) on chromosome 7, or base pair 5,365 in the GenBank genomic region NC_000073 within the donor splice site of intron 7. Linkage was found with an additive model of inheritance (P = 1.30 x 10-4) wherein two variant homozygotes departed phenotypically from seven homozygous reference mice and 11 heterozygous mice (Figure 2).  The effect of the mutation at the cDNA and protein level have not examined, but the mutation is predicted to not result in disruption of the splice donor site; native splicing sites might be used. In the event that the mutation affects splicing, the most likely aberrant splicing result will be skipping of the 102-base pair exon 7 (out of 22 total exons (shown below), resulting in an in-frame deletion of 34 amino acids beginning after amino acid 161 of the protein.


              <--exon 6          <--exon 7 intron 7-->              exon 8-->         <--exon 22

157  ……-F--I--G--R--T-- ……-G--S--P--G--K--                          Y--M--S--H-…… ……-T--K--S--*-

           correct            deleted                                         correct


Genomic numbering corresponds to NC_000073. The donor splice site of intron 7, which is affected by the Ernie2 mutation, is indicated in blue lettering and the mutated nucleotide is indicated in red. 

Protein Prediction

Figure 3. Domains of IRE1β. IRE1β is a type I transmembrane receptor in the endoplasmic reticulum. See the text for more details. Abbreviations: SP, signal peptide; PQQ, pyrrolo-quinoline quinone beta-propeller repeat; TM, transmembrane domain; KEN, kinase-extension-nuclease domain. The Ernie2 mutation within intron 7 is indicated in red.

Ern2 encodes inositol-requiring enzyme 1β (IRE1β), a type I transmembrane receptor paralog of IRE1α. IRE1β and IRE1α have an N-terminal sensory domain that faces the endoplasmic reticulum (ER) lumen (amino acids 35-426), a transmembrane domain (amino acid 427-447), and a cytoplasmic effector domain at the C-terminus (amino acid 448-911) [Figure 3; (1;2)]. Amino acids 1-33 comprise a signal peptide. The luminal domain (LD) of IRE1β has four pyrrolo-quinoline quinone (PQQ) beta-propeller repeats (amino acids 33-64, 115-147, 148-180, and 192-223; SMART) (3). The cytoplasmic domain of IRE1β has both a protein kinase domain (amino acids 508-768) and a kinase-extension-nuclease domain (KEN domain; alternatively, RNAse domain; amino acids 771-899) (3).


The Ernie2 mutation may cause aberrant splicing and subsequent deletion of exon 7, which encodes amino acids 162-196 within the third PQQ beta-propeller repeat of the N-terminal sensory domain.


For more information about Ern2, please see the record for ernie.

Putative Mechanism

IRE1β is expressed in the gastrointestinal epithelial cells and mucus cells in bronchial epithelia. During the unfolded protein response (UPR), both IRE1α and IRE1β can catalyze the processing of Xbp1 (4-6), although IRE1β is less efficient than IRE1α (1). IRE1α and IRE1β both activate c-Jun NH2-terminal kinase (JNK) in response to ER stress (7). IRE1β is unique from IRE1α in that IRE1β directly interacts with unfolded proteins rather than with GRP78 during conditions of ER stress (8).


IRE1β posttranscriptionally degrades Mtp (9), which is induced during enterocyte differentiation. Mtp encodes an ER chaperone required for lipid mobilization via apolipoprotein B (apoB) lipoproteins (9). MTP and apoB are also required for chylomicron assembly in the ER of enterocytes (10-12). Chylomicrons are vesicles synthesized by the intestine and function to transport large quantities of dietary fat and fat-soluble vitamins (12-14).


Ern2 knockout (Ern2-/-) mice are viable and healthy. However, when challenged with DSS, the Ern2-/- mice (in both the 129svev and C57BL/6 genetic backgrounds) developed colitis 3-5 days earlier than wild-type and heterozygous mice. In addition, the Ern2-/- mice exhibited mortality approximately 5 days earlier than wild-type or heterozygous mice.  Further studies determined that loss of IRE1β expression promotes ER stress specifically in immature goblet cells (15). Examination of goblet cells from Ern2-/- mice determined that the ER was distended in the cells. Within the distended ER of the immature goblet cells, aberrant mucin accumulation was observed. Tsuru et al. proposed that the susceptibility to colitis may indicate a qualitative defect in mucins secreted by the goblet cells in the Ern2-/- mice (15). Similar to the Ern2-/- mice, the Ernie2 mice exhibit susceptibility to DSS-induced colitis indicating loss of function in IRE1β.

Primers PCR Primer

Sequencing Primer

PCR program

1) 94°C 2:00
2) 94°C 0:30
3) 55°C 0:30
4) 72°C 1:00
5) repeat steps (2-4) 40x
6) 72°C 10:00
7) 4°C hold

The following sequence of 453 nucleotides is amplified (chromosome 7, - strand):

1   tgggtttggg aaggaccaca tgaccattct cctggtagct ttgcttgtga cacacagagt
61  acacagtctc catgcatgac ctacggaccc cagccctgcg gtggaacaca acctatcgcc
121 gctactcagc acccctcctg aatggctcac ccgggaaatg tgagtcctcc ccttttgcag
181 cgttaccttg gaacaaagtc cccaacctgg gaagccccgg gtgacatcag gaccaaatac
241 tagcaaatac tgatccactg atccactgtc ccctcacatg atgaatgaca gcctgacaga
301 tgacctgggt tgactctgat gatcacatag cctgagcaat acatccgaac ttctccatac
361 tccaaatgac cccagccagg tagcctgagg tgaccccttg catcttaagg gacccccaag
421 caacctccct aatgccctgc tcaatcctgt cag

Primer binding sites are underlined and the sequencing primers are highlighted; the mutated nucleotide is shown in red.

Science Writers Anne Murray
Illustrators Peter Jurek
AuthorsEmre Turer and Bruce Beutler