Phenotypic Mutation 'charbon' (pdf version)
Allelecharbon
Mutation Type missense
Chromosome7
Coordinate55,966,153 bp (GRCm39)
Base Change A ⇒ G (forward strand)
Gene Oca2
Gene Name oculocutaneous albinism II
Synonym(s) p, D7H15S12, D7H15S12
Chromosomal Location 55,889,508-56,186,266 bp (+) (GRCm39)
MGI Phenotype FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] This gene encodes the human homolog of the mouse p (pink-eyed dilution) gene. The encoded protein is believed to be an integral membrane protein involved in small molecule transport, specifically tyrosine, which is a precursor to melanin synthesis. It is involved in mammalian pigmentation, where it may control skin color variation and act as a determinant of brown or blue eye color. Mutations in this gene result in type 2 oculocutaneous albinism. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jul 2014]
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. [provided by MGI curators]
Accession Number
NCBI RefSeq: NM_021879; MGI: 97454
MappedYes 
Amino Acid Change Threonine changed to Alanine
Institutional SourceBeutler Lab
Gene Model not available
AlphaFold Q62052
SMART Domains Protein: ENSMUSP00000032633
Gene: ENSMUSG00000030450
AA Change: T382A

DomainStartEndE-ValueType
transmembrane domain 171 193 N/A INTRINSIC
Pfam:ArsB 319 558 2e-10 PFAM
Pfam:CitMHS 337 770 2e-49 PFAM
Pfam:ArsB 562 827 8.9e-9 PFAM
Pfam:Na_sulph_symp 573 832 6e-13 PFAM
Predicted Effect probably damaging

PolyPhen 2 Score 1.000 (Sensitivity: 0.00; Specificity: 1.00)
(Using ENSMUST00000032633)
Predicted Effect probably benign
SMART Domains Protein: ENSMUSP00000119099
Gene: ENSMUSG00000030450

DomainStartEndE-ValueType
transmembrane domain 171 193 N/A INTRINSIC
Predicted Effect probably benign
Meta Mutation Damage Score Not available question?
Is this an essential gene? Probably nonessential (E-score: 0.106) question?
Phenotypic Category Autosomal Recessive
Candidate Explorer Status loading ...
Single pedigree
Linkage Analysis Data
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 55930594 missense probably damaging 0.99
IGL01022:Oca2 APN 7 55974504 missense probably damaging 1.00
IGL01666:Oca2 APN 7 55964559 splice site probably null
IGL02157:Oca2 APN 7 55974545 splice site probably null
IGL02213:Oca2 APN 7 55971232 splice site probably benign
IGL02314:Oca2 APN 7 56006899 missense probably benign 0.00
IGL03083:Oca2 APN 7 55945232 missense probably benign 0.28
IGL03356:Oca2 APN 7 56185716 missense probably benign 0.01
cotton UTSW 7 56185716 missense probably benign 0.00
cutworm UTSW 7 55966168 missense probably damaging 1.00
Dirk UTSW 7 56185716 missense probably benign 0.00
draco1 UTSW 7 56073100 missense probably benign 0.00
faded UTSW 7 55974409 missense probably benign 0.19
hardy UTSW 7 55945208 missense probably damaging 1.00
narwhal UTSW 7 55945246 nonsense probably null
quicksilver UTSW 7 55974409 missense probably benign 0.19
renesmee UTSW 7 56185716 missense probably benign 0.00
slush UTSW 7 55927189 critical splice donor site probably null
snowflake UTSW 7 55974428 missense probably damaging 1.00
whitemouse UTSW 7 56064179 missense probably damaging 1.00
R0440:Oca2 UTSW 7 56073100 missense probably benign 0.00
R1067:Oca2 UTSW 7 55966141 missense probably damaging 1.00
R1349:Oca2 UTSW 7 56185716 missense probably benign 0.00
R1372:Oca2 UTSW 7 56185716 missense probably benign 0.00
R1457:Oca2 UTSW 7 55971269 missense probably damaging 1.00
R1737:Oca2 UTSW 7 55978533 missense probably damaging 1.00
R1802:Oca2 UTSW 7 55904728 missense possibly damaging 0.96
R1957:Oca2 UTSW 7 55971246 missense possibly damaging 0.82
R1966:Oca2 UTSW 7 56064215 missense probably damaging 0.99
R2082:Oca2 UTSW 7 55946885 missense probably benign 0.01
R2229:Oca2 UTSW 7 56006903 missense probably benign 0.11
R4120:Oca2 UTSW 7 55904630 missense probably damaging 1.00
R4192:Oca2 UTSW 7 55946997 missense probably damaging 1.00
R4405:Oca2 UTSW 7 56064182 missense possibly damaging 0.63
R4654:Oca2 UTSW 7 55978560 missense probably benign 0.44
R4701:Oca2 UTSW 7 55904750 missense probably benign 0.00
R4887:Oca2 UTSW 7 55980106 nonsense probably null
R5053:Oca2 UTSW 7 55973328 missense probably benign 0.02
R5215:Oca2 UTSW 7 55945246 nonsense probably null
R5430:Oca2 UTSW 7 55945208 missense probably damaging 1.00
R5677:Oca2 UTSW 7 56064210 missense probably damaging 1.00
R6416:Oca2 UTSW 7 55978515 missense probably benign 0.44
R6645:Oca2 UTSW 7 55964522 missense probably benign 0.21
R7257:Oca2 UTSW 7 55929286 intron probably benign
R7409:Oca2 UTSW 7 56064145 missense probably benign 0.00
R7530:Oca2 UTSW 7 55981720 missense probably damaging 0.99
R7820:Oca2 UTSW 7 55981713 missense probably damaging 1.00
R9043:Oca2 UTSW 7 55927189 critical splice donor site probably null
R9153:Oca2 UTSW 7 55943586 missense probably benign 0.00
R9205:Oca2 UTSW 7 55966168 missense probably damaging 1.00
R9681:Oca2 UTSW 7 55943623 missense probably null 1.00
Z1088:Oca2 UTSW 7 55980123 missense probably null 0.83
Mode of Inheritance Autosomal Recessive
Local Stock Sperm, gDNA
Repository

none

Last Updated 2018-01-12 4:36 PM by Diantha La Vine
Record Created unknown
Record Posted 2008-04-10
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.
Illustration of Mutations in
Gene & Protein
Protein Prediction
Figure 1. Domain organization and function of the OCA2 protein. A, Topography. B, Domain structure. The charbon mutation results in a threonine to alanine change at amino acid 382 in the OCA2 protein. Other mutations found in OCA2  are noted in red. This image is interactive. Click on the mutations for more specific information.

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
Edit History
2011-01-07 8:57 AM (current)
2010-10-01 10:28 AM
2010-10-01 10:27 AM
2010-02-03 8:10 AM