Phenotypic Mutation 'charbon' (pdf version)
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Allelecharbon
Mutation Type missense
Chromosome7
Coordinate56,316,405 bp (GRCm38)
Base Change A ⇒ G (forward strand)
Gene Oca2
Gene Name oculocutaneous albinism II
Synonym(s) D7H15S12, p, D7H15S12
Chromosomal Location 56,239,760-56,536,517 bp (+)
MGI Phenotype Mutations generally result in varying degrees of coat and eye pigment dilution. Specific alleles produce cleft palate, reproductive, endocrine or neurological disorders, and/or lethality.
Accession Number
NCBI RefSeq: NM_021879; MGI: 97454
Mapped Yes 
Amino Acid Change Threonine changed to Alanine
Institutional SourceBeutler Lab
Ref Sequences
T382A in Ensembl: ENSMUSP00000032633 (fasta)
Gene Model not available
SMART Domains

DomainStartEndE-ValueType
transmembrane domain 171 193 N/A INTRINSIC
Pfam:ArsB 325 554 4.5e-5 PFAM
Pfam:CitMHS 333 754 3.8e-69 PFAM
Pfam:ArsB 564 826 4.6e-2 PFAM
Pfam:Na_sulph_symp 573 832 2.4e-7 PFAM
Pfam:CitMHS 717 829 1.2e-6 PFAM
Predicted Effect probably damaging

PolyPhen 2 Score 0.997 (Sensitivity: 0.40; Specificity: 0.98)
(Using Ensembl: ENSMUSP00000032633)
Phenotypic Category pigmentation, skin/coat/nails
Penetrance 100% 
Alleles Listed at MGI
All alleles(66) : Gene trapped(1) Spontaneous(19) Chemically induced(7) Radiation induced(39)
Lab Alleles
AlleleSourceChrCoordTypePredicted EffectPPH Score
IGL00509:Oca2 APN 7 56280846 missense possibly damaging 0.46
IGL01022:Oca2 APN 7 56324756 missense probably damaging 1.00
IGL01666:Oca2 APN 7 56314811 splice site 0.00
IGL02157:Oca2 APN 7 56324797 splice site 0.00
IGL02213:Oca2 APN 7 56321484 splice site 0.00
IGL02314:Oca2 APN 7 56357151 missense probably damaging 0.99
IGL03083:Oca2 APN 7 56295484 missense probably benign 0.00
IGL03356:Oca2 APN 7 56535968 missense probably benign 0.25
cotton UTSW 7 56535968 missense probably benign 0.00
Dirk UTSW 7 56535968 missense
draco1 UTSW 7 56423352 missense probably benign 0.00
faded UTSW 7 56324661 missense
hardy UTSW 7 56295460 missense probably damaging 1.00
narwhal UTSW 7 56295498 nonsense probably null
quicksilver UTSW 7 56324661 missense probably damaging 0.98
renesmee UTSW 7 56535968 missense probably benign 0.00
snowflake UTSW 7 56324680 missense probably damaging 1.00
whitemouse UTSW 7 56414431 missense probably damaging 1.00
R0440:Oca2 UTSW 7 56423352 missense probably benign 0.00
R1067:Oca2 UTSW 7 56316393 missense probably damaging 1.00
R1349:Oca2 UTSW 7 56535968 missense probably benign 0.00
R1372:Oca2 UTSW 7 56535968 missense probably benign 0.00
R1457:Oca2 UTSW 7 56321521 missense probably damaging 1.00
R1737:Oca2 UTSW 7 56328785 missense probably damaging 1.00
R1802:Oca2 UTSW 7 56254980 missense probably benign 0.00
R1957:Oca2 UTSW 7 56321498 missense possibly damaging 0.82
R1966:Oca2 UTSW 7 56414467 missense probably damaging 0.99
R2082:Oca2 UTSW 7 56297137 missense probably benign 0.01
R2229:Oca2 UTSW 7 56357155 missense probably benign 0.11
R4120:Oca2 UTSW 7 56254882 missense probably damaging 1.00
R4192:Oca2 UTSW 7 56297249 missense probably damaging 1.00
R4405:Oca2 UTSW 7 56414434 missense possibly damaging 0.63
R4654:Oca2 UTSW 7 56328812 missense probably benign 0.44
R4701:Oca2 UTSW 7 56255002 missense probably benign 0.00
R4782:Oca2 UTSW 7 56279521 nonsense probably null
R4887:Oca2 UTSW 7 56330358 nonsense probably null
R4983:Oca2 UTSW 7 56321505 missense noncoding transcript
R5053:Oca2 UTSW 7 56323580 nonsense probably null
R5215:Oca2 UTSW 7 56295498 nonsense probably null
R5430:Oca2 UTSW 7 56295460 missense probably damaging 1.00
R5677:Oca2 UTSW 7 56414462 missense probably damaging 1.00
X0026:Oca2 UTSW 7 56332080 splice donor site probably benign
Z1088:Oca2 UTSW 7 56330375 unclassified probably null 0.83
Mode of Inheritance Autosomal Recessive
Local Stock Sperm, gDNA
Repository

none

Last Updated 01/05/2017 2:02 PM by Katherine Timer
Record Created unknown
Record Posted 04/10/2008
Phenotypic Description
The charbon mutation was induced by an N-ethyl-N-nitrosourea (ENU)-mutagenesis on a C57BL/6J (black) background. Charbon is a strictly recessive phenotype with hypopigmented fur and ocular albinism, similar to the phenotype created by mutations at the Oca2 or p (pink-eyed dilution) locus.  Mutations at Oca2 are known to cause a reduction of eumelanin (black-brown) pigment and altered morphology of black pigment granules (eumelanosomes), but have little effect on pheomelanin (yellow-red) pigment (1;2).
 
Immune system function is largely normal in charbon mutants.  Charbon mice, like allelic quicksilver and snowflake mice, display normal resistance to murine cytomegalovirus (MCMV) (MCMV Susceptibility and Resistance Screen).  Charbon mutants are slightly susceptible to infection by Listeria monocytogenes, showing a 75% survival rate compared with 100% survival in wild type controls.  However, they produce normal amounts of cytokines in response to Listeria infection and clear infection from the liver as well as wild type mice.  In vitro, NK cells from charbon mice degranulate normally upon stimulation of Ly49H or NKp46 receptors, PMA ionomycin treatment, or upon exposure to YAC-1 cells.  IFN-γ production after PMA ionomycin stimulation is also normal. The pigmentation phenotype for charbon mice is very similar to quicksilver mutants.

 

Nature of Mutation
The charbon mutation mapped to Chromosome 7, and corresponds to an A to G transition at position 1274 of the Oca2 transcript, in exon 11 of 24 total exons.
 
1259 TGGATTGATTTCGAGACTCTGGCCCTGCTGTTT
377  -W--I--D--F--E--T--L--A--L--L--F-
 
The mutated nucleotide is indicated in red lettering and results in a threonine to alanine change at amino acid 382 in the OCA2 protein.
Protein Prediction

 

The charbon mutation occurs in the fourth transmembrane domain of the OCA2 protein (Figure 1).  It is unknown whether normal levels of the altered OCA2 protein exist in charbon mice or whether the protein is localized appropriately.
 
Please see the record for quicksilver for information about Oca2.
Putative Mechanism
The charbon mutation results in a T382A change in the fourth transmembrane region of the OCA2 protein.  This region is well-conserved between the mouse and human proteins as well as in related bacterial transporters.  The change from polar threonine to nonpolar alanine may disrupt the structure of this transmembrane domain, but the effect on the structure of the protein is unknown.  Threonine can undergo post-translational modifications such as phosphorylation and O-linked glycosylation, but whether this occurs at T382 in the OCA2 protein has not been tested.  Human mutations in the same region cause oculocutaneous albinism.
 
For a further explanation of the charbon mutant phenotype, please refer to the record for quicksilver.
Primers Primers cannot be located by automatic search.
Genotyping
Charbon genotyping is performed by amplifying the region containing the mutation using PCR, followed by sequencing of the amplified region to detect the single nucleotide change.
 
Primers for PCR amplification
Char(F): 5’-GGCTGGAGTGAGATTGCCTCTGATA-3’
Char(R): 5’-TGCCAACTTTTGGAAATAATGATGCCAC-3’
 
PCR program
1) 94°C             2:00
2) 94°C             0:30
3) 56°C             0:30
4) 72°C             1:00
5) repeat steps (2-4) 29X
6) 72°C             7:00
7) 4°C               ∞
 
Primers for sequencing
Char_seq(F): 5’- CAGGCAATAATTCTTCCTGGAGC-3’
Char_seq(R): 5’- GCCACTTCATTGTTCAAAAGC-3’
 
The following sequence of 1309 nucleotides (from Genbank genomic region NC_000073 for linear DNA sequence of Oca2) is amplified:
 
75599                                                                gg
75601 ctggagtgag attgcctctg atatatttta taaagctaat ggtatgtttc atacagagga
75661 gtatggtgtg gagggatgga ggacctcagc aggcccaggt tgaggcatct ctcccctgag
75721 gtatcagcca tactaagggt ctagtataga atagagttag ttaggggatg ggaaggggag
75781 ttgagaaggg agtagaggca gagaaagaga gggatcagag gacagagaga gatagagaaa
75841 ggagaaagaa gaggctggct gggaacacat gagggaggag agaaagggaa agagaggaga
75901 gagagagaga gagagagaga gagagagaga gagagagaga gagagagaga gaagagtcag
75961 agtgacaaaa gggtcagaga gaggaaagag aagccaaaca gtccctttta tagacagtca
76021 ggcctatctg ctattgctaa gtaactttgg cagagcctag aaggaatgct aacacgctaa
76081 cagcctccga gtctctgagt catgcacttg ttctcatgag tatggttcac ataatgtttc
76141 atttggaaaa ttgctcttat ggcatatagt aggcacatgc atcaagaagc ccccagggta
76201 ctcagtgaac tgccctttcc gaggcaggct cggttctggc agtccctcac ttcacacttt
76261 gttctagtgg cacttggaga gtagaataga gagtgtcaat catgccaccc cactgaggaa
76321 gaccaaacca gcagtccagg caataattct tcctggagct tccaggatta gatcccctcc
76381 cttttgttca tgaatacttt ggatgtgaca gattcactgg gtcatgagtg taattcagca
76441 gtgtgataga attcaacttc aaaggcaagt ggatgcagtg tttccagctt tggcccaatg
76501 tctgcgcttg cagtaagggc agcccatttt tagagctttg ctcagtaggt tgatgcacag
76561 gattaattgg caaatttgtg ctttgattac agagacccag cctgacccac gtggtggagt
76621 ggattgattt cgagactctg gccctgctgt ttggcatggt aattacagtc ttcccagcag
76681 gatatggctc caagtctggg tccttcacta tcccacagtt gctgatccta tcattatagt
76741 caagatggca tatctcttga cagttagggc tttattgaga agtgttaata caggtctagt
76801 tattttctca gggaggaggg actggctggt gctggtttgt taactaaaga cttcatctct
76861 aaggcttttg aacaatgaag tggcatcatt atttccaaaa gttggca
 
PCR primer binding sites are underlined; sequencing primer binding sites are highlighted in gray; the mutated A is shown in red text.
References
Science Writers Nora G. Smart
Illustrators Diantha La Vine
AuthorsCeline Eidenschenk, Sophie Rutschmann, Bruce Beutler
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