Phenotypic Mutation 'split_pea' (pdf version)
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Allelesplit_pea
Mutation Type nonsense
Chromosome2
Coordinate121,228,606 bp (GRCm38)
Base Change T ⇒ A (forward strand)
Gene Trp53bp1
Gene Name transformation related protein 53 binding protein 1
Synonym(s) 53BP1, p53BP1
Chromosomal Location 121,193,281-121,271,407 bp (-)
MGI Phenotype PHENOTYPE: Homozygous mutations in this gene result in growth retardation, immunodeficiency, thymic hypoplasia, and increased incidence of thymic lymphomas. [provided by MGI curators]
Accession Number

NCBI RefSeq: NM_013735NM_001290830; MGI:1351320

Mapped Yes 
Amino Acid Change Arginine changed to Stop codon
Institutional SourceBeutler Lab
Gene Model predicted gene model for protein(s): [ENSMUSP00000106277] [ENSMUSP00000106278] [ENSMUSP00000114457]
SMART Domains Protein: ENSMUSP00000106277
Gene: ENSMUSG00000043909
AA Change: R925*

DomainStartEndE-ValueType
low complexity region 136 149 N/A INTRINSIC
low complexity region 158 169 N/A INTRINSIC
low complexity region 647 661 N/A INTRINSIC
low complexity region 1031 1042 N/A INTRINSIC
low complexity region 1099 1112 N/A INTRINSIC
low complexity region 1260 1272 N/A INTRINSIC
low complexity region 1290 1332 N/A INTRINSIC
Pfam:53-BP1_Tudor 1430 1551 2.5e-80 PFAM
low complexity region 1581 1601 N/A INTRINSIC
BRCT 1673 1785 7.13e-1 SMART
BRCT 1813 1901 1.03e-6 SMART
Predicted Effect probably null
SMART Domains Protein: ENSMUSP00000106278
Gene: ENSMUSG00000043909
AA Change: R925*

DomainStartEndE-ValueType
low complexity region 136 149 N/A INTRINSIC
low complexity region 158 169 N/A INTRINSIC
low complexity region 647 661 N/A INTRINSIC
low complexity region 1031 1042 N/A INTRINSIC
low complexity region 1099 1112 N/A INTRINSIC
low complexity region 1260 1272 N/A INTRINSIC
low complexity region 1290 1332 N/A INTRINSIC
low complexity region 1389 1409 N/A INTRINSIC
Pfam:53-BP1_Tudor 1480 1601 1.5e-80 PFAM
low complexity region 1631 1651 N/A INTRINSIC
BRCT 1723 1835 7.13e-1 SMART
BRCT 1863 1951 1.03e-6 SMART
Predicted Effect probably null
SMART Domains Protein: ENSMUSP00000114457
Gene: ENSMUSG00000043909

DomainStartEndE-ValueType
low complexity region 136 149 N/A INTRINSIC
low complexity region 158 169 N/A INTRINSIC
low complexity region 647 661 N/A INTRINSIC
low complexity region 991 1002 N/A INTRINSIC
Predicted Effect probably benign
Predicted Effect probably null
Predicted Effect probably null
Phenotypic Category
Phenotypequestion? Literature verified References
FACS IgD MFI - decreased 28137874
Penetrance  
Alleles Listed at MGI

All Mutations and Alleles(36) : Chemically induced (ENU)(5) Chemically induced (other)(1) Gene trapped(26) Radiation induced(1) Targeted(3)

Lab Alleles
AlleleSourceChrCoordTypePredicted EffectPPH Score
IGL00336:Trp53bp1 APN 2 121256579 missense possibly damaging 0.69
IGL00690:Trp53bp1 APN 2 121235995 missense probably damaging 1.00
IGL00922:Trp53bp1 APN 2 121208482 missense probably damaging 0.96
IGL01475:Trp53bp1 APN 2 121270319 splice site probably null
IGL01639:Trp53bp1 APN 2 121202692 missense possibly damaging 0.51
IGL01662:Trp53bp1 APN 2 121236025 missense probably damaging 1.00
IGL01757:Trp53bp1 APN 2 121211304 missense probably damaging 0.99
IGL01829:Trp53bp1 APN 2 121215896 missense probably benign 0.39
IGL02247:Trp53bp1 APN 2 121236589 missense probably damaging 1.00
IGL02349:Trp53bp1 APN 2 121199074 missense probably damaging 1.00
IGL02391:Trp53bp1 APN 2 121202710 missense possibly damaging 0.67
chives UTSW 2 121251868 missense probably null 0.13
concur UTSW 2 121270319 splice site probably null
lentil UTSW 2 121251868 missense probably null 0.13
lentil2 UTSW 2 121207887 missense probably damaging 1.00
verily UTSW 2 121211313 missense probably damaging 1.00
PIT1430001:Trp53bp1 UTSW 2 121271275 missense probably damaging 1.00
R0045:Trp53bp1 UTSW 2 121204497 missense probably benign
R0060:Trp53bp1 UTSW 2 121204525 missense probably damaging 1.00
R0060:Trp53bp1 UTSW 2 121204525 missense probably damaging 1.00
R0103:Trp53bp1 UTSW 2 121236759 missense possibly damaging 0.92
R0103:Trp53bp1 UTSW 2 121236759 missense possibly damaging 0.92
R0281:Trp53bp1 UTSW 2 121270237 missense probably damaging 1.00
R0386:Trp53bp1 UTSW 2 121204943 missense probably damaging 1.00
R0427:Trp53bp1 UTSW 2 121236017 missense probably damaging 1.00
R0505:Trp53bp1 UTSW 2 121269969 missense probably damaging 0.99
R0522:Trp53bp1 UTSW 2 121251868 missense probably null 0.13
R0523:Trp53bp1 UTSW 2 121251868 missense probably null 0.13
R0525:Trp53bp1 UTSW 2 121251868 missense probably null 0.13
R0543:Trp53bp1 UTSW 2 121251868 missense probably null 0.13
R0559:Trp53bp1 UTSW 2 121227801 missense probably damaging 1.00
R0573:Trp53bp1 UTSW 2 121228172 splice site probably benign
R0593:Trp53bp1 UTSW 2 121270528 missense possibly damaging 0.95
R0648:Trp53bp1 UTSW 2 121235707 missense probably benign 0.20
R0680:Trp53bp1 UTSW 2 121251868 missense probably null 0.13
R0732:Trp53bp1 UTSW 2 121248264 missense probably null 0.96
R0905:Trp53bp1 UTSW 2 121204318 splice site probably benign
R1377:Trp53bp1 UTSW 2 121270642 missense probably damaging 1.00
R1415:Trp53bp1 UTSW 2 121236184 missense probably damaging 1.00
R1725:Trp53bp1 UTSW 2 121252000 missense possibly damaging 0.46
R1971:Trp53bp1 UTSW 2 121205036 missense probably damaging 1.00
R2045:Trp53bp1 UTSW 2 121204483 missense probably benign
R2143:Trp53bp1 UTSW 2 121216064 missense probably benign 0.00
R2282:Trp53bp1 UTSW 2 121270273 nonsense probably null
R2296:Trp53bp1 UTSW 2 121209247 missense possibly damaging 0.96
R3106:Trp53bp1 UTSW 2 121236652 missense probably damaging 1.00
R3792:Trp53bp1 UTSW 2 121200329 missense probably damaging 1.00
R3793:Trp53bp1 UTSW 2 121200329 missense probably damaging 1.00
R3946:Trp53bp1 UTSW 2 121228626 missense probably damaging 0.99
R4001:Trp53bp1 UTSW 2 121205085 missense probably damaging 1.00
R4327:Trp53bp1 UTSW 2 121256650 missense probably damaging 1.00
R4585:Trp53bp1 UTSW 2 121207951 missense probably damaging 1.00
R4630:Trp53bp1 UTSW 2 121207887 missense probably damaging 1.00
R4744:Trp53bp1 UTSW 2 121211313 missense probably damaging 1.00
R4751:Trp53bp1 UTSW 2 121227809 missense probably damaging 1.00
R4754:Trp53bp1 UTSW 2 121207879 missense probably damaging 1.00
R4755:Trp53bp1 UTSW 2 121228606 nonsense probably null
R4850:Trp53bp1 UTSW 2 121205113 critical splice acceptor site probably null
R4870:Trp53bp1 UTSW 2 121256641 missense probably damaging 1.00
R4879:Trp53bp1 UTSW 2 121202603 missense probably damaging 0.99
R4924:Trp53bp1 UTSW 2 121221220 nonsense probably null
R4962:Trp53bp1 UTSW 2 121270546 missense probably benign 0.12
R5019:Trp53bp1 UTSW 2 121270319 splice site probably null
R5111:Trp53bp1 UTSW 2 121211387 missense probably damaging 0.99
R5149:Trp53bp1 UTSW 2 121216117 missense probably benign 0.00
R5252:Trp53bp1 UTSW 2 121243983 missense probably benign 0.40
R5533:Trp53bp1 UTSW 2 121207746 missense probably damaging 1.00
R5642:Trp53bp1 UTSW 2 121236662 missense probably benign 0.00
R5773:Trp53bp1 UTSW 2 121243914 missense probably damaging 1.00
R5819:Trp53bp1 UTSW 2 121208392 nonsense probably null
R5886:Trp53bp1 UTSW 2 121205021 missense probably damaging 1.00
R5908:Trp53bp1 UTSW 2 121236823 missense probably benign 0.06
R6012:Trp53bp1 UTSW 2 121256602 missense probably benign 0.07
R6351:Trp53bp1 UTSW 2 121269945 missense probably damaging 1.00
R6406:Trp53bp1 UTSW 2 121270612 missense probably damaging 0.99
R6575:Trp53bp1 UTSW 2 121228603 missense probably damaging 1.00
R6619:Trp53bp1 UTSW 2 121247499 critical splice donor site probably null
R6626:Trp53bp1 UTSW 2 121207803 missense probably damaging 1.00
R6754:Trp53bp1 UTSW 2 121270576 missense possibly damaging 0.83
R6765:Trp53bp1 UTSW 2 121209309 missense probably damaging 1.00
R6806:Trp53bp1 UTSW 2 121228666 missense probably damaging 0.99
R6860:Trp53bp1 UTSW 2 121199113 missense probably damaging 1.00
Z1088:Trp53bp1 UTSW 2 121253645 missense probably benign 0.04
Mode of Inheritance Unknown
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Repository
Last Updated 2019-02-14 3:19 PM by Anne Murray
Record Created 2019-01-23 10:32 AM by Bruce Beutler
Record Posted 2019-02-14
Phenotypic Description
Figure 1. Split_pea mice exhibit reduced IgD mean fluorescence intensity (MFI). Flow cytometric analysis of peripheral blood was utilized to determine the IgD MFI. 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 split_pea phenotype was identified among N-ethyl-N-nitrosourea (ENU)-mutagenized G3 mice of the pedigree R4755, some of which showed reduced IgD expression on B cells compared to wild-type littermates (Figure 1).

Nature of Mutation
Figure 2. Linkage mapping of reduced IgD MFI using a recessive model of inheritance. Manhattan plot shows -log10 P values (Y-axis) plotted againts the chromosome positions of 66 mutations (X-axis) identified in the G1 male of pedigree R4755.  Normalized phenotypic data are shown for single locus linkage analysis with 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 66 mutations. The IgD phenotype was linked by continuous variable mapping to a mutation in Trp53bp1: an A to T transversion at base pair 121,228,606 (v38) on chromosome 2, or base pair 61,720 in the GenBank genomic region NC_000068 encoding Trp53bp1. Linkage was found with a recessive model of inheritance, wherein one variant homozygote departed phenotypically from six homozygous reference mice and 11 heterozygous mice with a P value of 5.707 x 10-5 (Figure 2). The mutation in Trp53bp1 was presumed causative as the phenotype of the split_pea mice mimics that of other Trp53bp1 alleles (see lentil).

 

The mutation corresponds to residue 2,902 in the mRNA sequence NM_013735 within exon 13 of 28 total exons.

 

2887 AAATTGGAGCCCAAGAGACATAGTACTCCTATT

920  -K--L--E--P--K--R--H--S--T--P--I-

 

The mutated nucleotide is indicated in red. The mutation results in substitution of arginine 925 for a stop codon (R925*) in the 53BP1 protein.

Protein Prediction
Figure 3. Domain structure of 53BP1. The split_pea mutation (R925*) is indicated in red. This image is interactive. Click on each allele for more information. See the text for more details on the domains of 53BP1. Click on the other mutations to view more information about those alleles. Abbreviations: KBD, kinetochore-binding domain; OLIGO, oligomerization domain; GAR, glycine/arginine-rich region; UDR, ubiquitin-dependent recruitment motif; NLS, nuclear localization signal; BRCT, BRCA1 C-terminus. The phosphoinositide 3-kinase-like kinase (PIKK) S/TQ phosphorylation sites are labeled (Ser6, Ser25, Ser29, Ser166, Ser176/Ser178, Thr302, Ser452, Ser831, and Ser1219) as well as the site of ubiquitination (Lys1523).

Trp53bp1 (transformation related protein 53 binding protein 1) encodes 53BP1. 53BP1 has two tandem Tudor domains at amino acids 1475-1575 (1) (alternatively, amino acids 1469-1574 (2) or amino acids 1480-1601, SMART) [Figure 3(3;4)]. Amino acids 1220-1601 of 53BP1 comprise a kinetochore-binding domain (KBD) (1;5). A nuclear localization signal (NLS; amino acids 1645-1703) and the KBD are sufficient to target 53BP1 to IR-induced foci (IRIF) (2). Within the KBD, amino acids 1231–1270 are required for homo-oligomerization (6). 53BP1 has two tandem breast cancer 1 early-onset (BRCA1) C-terminus (BRCT) domains at amino acids 1708-1969 (alternatively, amino acids 1723-1951, SMART(7). 53BP1 has a highly conserved glycine/arginine-rich region (GAR; RGRGRRGR; amino acids 1380-1386) (1;2).

 

The split_pea mutation results in substitution of arginine 925 for a stop codon (R925*). Residue 925 is in an undefined region preceding the KBD.

 

For more information about Trp53bp1, please see the record for lentil and (8).

Putative Mechanism

53BP1 has several functions including facilitating DNA damage signaling, telomere fusions, NHEJ of DNA double strand break (DSBs) in CSR, transducing ATM-dependent cell cycle checkpoints (intra-S and G2/M), accumulation of p53, phosphorylation of several ATM substrates (e.g., Chk2 and BRCA1) in response to IR, and tumor suppression (9-16).

 

Dysregulation of TRP53BP1 expression is associated with several human conditions. TRP53BP1 expression in BRCA1-associated breast cancers (17;18), lymphomas, and solid tumors is reduced (17;19-21). Low levels of TRP53BP1 are correlated with an aggressive form of the disease, correlating with increased metastases and decreased survival [reviewed in (22)]. 53BP1 deficiency and the deregulation of AID, leads to increased DSB formation, resulting in B cell lymphoma (23). Patients with RIDDLE syndrome (OMIM: #611943) lack the ability to recruit 53BP1 to the sites of DNA DSBs (24).

 

MEFs from both Trp53bp1-/- and m53BP1tr/tr embryos exhibited reduced proliferation compared to controls (25). Both models are viable, but exhibit growth retardation and increased cellular sensitivity to IR (25;26). The m53BP1tr/tr mice were fertile, but produced smaller litters than wild-type animals (26). After IR, Trp53bp1-/- cells arrested in G2 and exhibited a delayed exit from the G2/M phase; the percentage of mitotic cells 24 hours after IR was lower than wild-type cells (25). The Trp53bp1 mouse models exhibit immune deficiencies including defects in T cell maturation (25;26). The levels of CD4 T cells, γ–δ T cells, and B cells were all reduced in the Trp53bp1-/- mice with a concomitant increase in the percentage of CD4-CD8progenitors and apoptosis (25;27). In addition, the Trp53bp1-/- thymocytes exhibited an increased number of aberrant cells (either lost Cα (2 TCRVα, 1 TCRCα signal) or both Vα and Cα from one allele (1 TCRVα, 1 TCRCα)) (27). Bone marrow pro-B, pre-B, myeloid, and erthyroid progenitor populations were normal in the m53BP1tr/tr mice (16;26). However, the spleens from the m53BP1tr/tr mice were deficient in mature B cells (IgMloIgDhi(26). IgM levels in the Trp53bp1-/- mice were similar to those in wild-type mice, indicating that B cell activation to mediate IgM secretion is not affected upon loss of 53BP1, however, the levels of all IgG subclasses and IgA were decreased (16). CD4 and CD8 T cell populations were similar between m53BP1tr/tr and wild-type mice, but the progression out of the DNIII stage in development, when β-gene rearrangement occurs, was impaired in the m53BP1tr/tr mice (26). Thymus size in the m53BP1tr/tr mice was smaller and had fewer cells than wild-type mice; the lymphoid organ architecture was normal (26). The phenotype exhibited by the split_pea mice indicates loss of 53BP1-associated function.

Primers PCR Primer
split_pea(F):5'- AGTGAGGTCAAACCCTGCTG -3'
split_pea(R):5'- GGCTGTGAAGCTGATAGGAC -3'

Sequencing Primer
split_pea_seq(F):5'- GTCAAACCCTGCTGCTCCAC -3'
split_pea_seq(R):5'- GAAGGTGATATTATCCCACCA -3'
References
Science Writers Anne Murray
Illustrators Diantha La Vine
AuthorsJin Huk Choi, Xue Zhong, and Bruce Beutler
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