Phenotypic Mutation 'Draco2' (pdf version)
AlleleDraco2
Mutation Type start codon destroyed
Chromosome15
Coordinate11,000,903 bp (GRCm39)
Base Change A ⇒ T (forward strand)
Gene Slc45a2
Gene Name solute carrier family 45, member 2
Synonym(s) Aim1, Dbr, blanc-sale, dominant brown, Aim-1, Matp, bls, Oca4
Chromosomal Location 11,000,807-11,029,319 bp (+) (GRCm39)
MGI Phenotype FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] This gene encodes a transporter protein that mediates melanin synthesis. The protein is expressed in a high percentage of melanoma cell lines. Mutations in this gene are a cause of oculocutaneous albinism type 4, and polymorphisms in this gene are associated with variations in skin and hair color. Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Mar 2009]
PHENOTYPE: Homozygotes for spontaneous mutations exhibit varied degrees of hypopigmentation of the eyes, skin, and hair, especially the underfur. Eyes are very light at birth but darken with age. [provided by MGI curators]
Accession Number

NCBI RefSeq: NM_053077; MGI:2153040

MappedYes 
Amino Acid Change Methionine changed to Leucine
Institutional SourceBeutler Lab
Gene Model predicted gene model for protein(s): [ENSMUSP00000112408]
AlphaFold P58355
SMART Domains Protein: ENSMUSP00000022851
Gene: ENSMUSG00000022243
AA Change: M1L

DomainStartEndE-ValueType
Pfam:MFS_2 34 262 2.4e-17 PFAM
Pfam:MFS_1 36 363 3e-13 PFAM
transmembrane domain 365 387 N/A INTRINSIC
transmembrane domain 394 416 N/A INTRINSIC
transmembrane domain 421 443 N/A INTRINSIC
transmembrane domain 477 499 N/A INTRINSIC
transmembrane domain 504 526 N/A INTRINSIC
Predicted Effect probably benign

PolyPhen 2 Score 0.053 (Sensitivity: 0.94; Specificity: 0.84)
(Using ENSMUST00000022851)
SMART Domains Protein: ENSMUSP00000112408
Gene: ENSMUSG00000022243
AA Change: M1L

DomainStartEndE-ValueType
Pfam:MFS_2 1 457 2e-22 PFAM
Pfam:MFS_1 2 292 2.6e-12 PFAM
Predicted Effect probably benign

PolyPhen 2 Score 0.053 (Sensitivity: 0.94; Specificity: 0.84)
(Using ENSMUST00000117100)
Meta Mutation Damage Score 0.8707 question?
Is this an essential gene? Probably nonessential (E-score: 0.094) question?
Phenotypic Category Autosomal Recessive
Candidate Explorer Status loading ...
Single pedigree
Linkage Analysis Data
Penetrance  
Alleles Listed at MGI

All mutations/alleles(21) : Chemically induced (ENU)(11) Spontaneous(7) Targeted(3)

Lab Alleles
AlleleSourceChrCoordTypePredicted EffectPPH Score
IGL02074:Slc45a2 APN 15 11000903 start codon destroyed probably null 0.80
IGL02283:Slc45a2 APN 15 11001268 missense probably damaging 1.00
IGL02634:Slc45a2 APN 15 11023440 missense probably benign 0.21
IGL03039:Slc45a2 APN 15 11012773 missense probably benign
IGL03123:Slc45a2 APN 15 11012741 missense probably benign 0.01
IGL03226:Slc45a2 APN 15 11022278 missense probably damaging 1.00
cardigan UTSW 15 11022257 synonymous probably benign
cheng UTSW 15 11025954 missense probably damaging 0.99
galak UTSW 15 11012752 missense probably benign
goku UTSW 15 11000941 nonsense probably null
grey_goose UTSW 15 11003067 missense probably damaging 1.00
june_gloom UTSW 15 11023529 missense possibly damaging 0.94
nilla UTSW 15 splice donor site
Olaf UTSW 15 unclassified
sweater UTSW 15 11012696 missense probably damaging 1.00
voldemort UTSW 15 unclassified
yuki UTSW 15 11001178 missense probably damaging 1.00
zuckerkuss UTSW 15 11026020 critical splice donor site probably benign
R0148:Slc45a2 UTSW 15 11025954 missense probably damaging 0.99
R0433:Slc45a2 UTSW 15 11025831 missense probably benign 0.17
R0440:Slc45a2 UTSW 15 11000903 start codon destroyed probably benign 0.05
R0675:Slc45a2 UTSW 15 11025864 missense probably damaging 1.00
R1384:Slc45a2 UTSW 15 11025832 missense probably benign 0.04
R1616:Slc45a2 UTSW 15 11022214 missense probably null 0.01
R1824:Slc45a2 UTSW 15 11022172 missense probably damaging 0.99
R2244:Slc45a2 UTSW 15 11003087 missense probably benign 0.21
R3761:Slc45a2 UTSW 15 11012800 missense probably benign 0.07
R4631:Slc45a2 UTSW 15 11012662 missense probably benign 0.13
R4756:Slc45a2 UTSW 15 11028016 nonsense probably null
R4990:Slc45a2 UTSW 15 11001236 missense probably benign 0.00
R5066:Slc45a2 UTSW 15 11012693 missense probably benign 0.31
R5209:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5210:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5211:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5212:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5213:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5259:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5261:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5390:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5394:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5395:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5422:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5496:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5498:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5499:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5500:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5501:Slc45a2 UTSW 15 11027871 missense probably damaging 0.98
R5649:Slc45a2 UTSW 15 11012693 missense probably benign 0.00
R5662:Slc45a2 UTSW 15 11022169 missense probably benign 0.31
R5696:Slc45a2 UTSW 15 11001219 missense probably damaging 1.00
R5896:Slc45a2 UTSW 15 11000941 nonsense probably null
R6236:Slc45a2 UTSW 15 11022158 missense probably benign 0.00
R6709:Slc45a2 UTSW 15 11001216 missense possibly damaging 0.46
R7243:Slc45a2 UTSW 15 11023436 missense possibly damaging 0.94
R7839:Slc45a2 UTSW 15 11027835 missense probably benign
R8221:Slc45a2 UTSW 15 11001233 missense probably benign 0.02
R8404:Slc45a2 UTSW 15 11027958 missense possibly damaging 0.62
R8502:Slc45a2 UTSW 15 11027958 missense possibly damaging 0.62
R8680:Slc45a2 UTSW 15 11000972 missense probably benign 0.00
R8724:Slc45a2 UTSW 15 11012610 missense probably benign 0.00
R8966:Slc45a2 UTSW 15 11001122 missense probably damaging 1.00
R9431:Slc45a2 UTSW 15 11026005 missense possibly damaging 0.94
Mode of Inheritance Autosomal Recessive
Local Stock Sperm
MMRRC Submission 038244-MU
Last Updated 2018-08-01 4:30 PM by Diantha La Vine
Record Created 2013-09-13 11:25 PM by Tiana Purrington
Record Posted 2015-01-27
Phenotypic Description
Figure 1. Draco2 is a hypopigmentation mutant. The draco2 mice have gray coats and black eyes.

The draco2 phenotype was initially identified among N-ethyl-N-nitrosourea (ENU)-induced G3 animals. The draco2 homozygous mice have a light gray/“dirty white” coat and black eyes (Figure 1). 

Nature of Mutation

The draco2 phenotype is presumed to result from an Slc45a2 mutation identified in the G1 grandsire (R0440) of affected G3 mice because the draco2 phenotype is similar to that caused by Slc45a2 mutations [see the records for june gloom, yuki, and zuckerkuss as well as Slc45a2uw-6J (MGI:5448550) and Slc45a2uw-7J (MGI:5448551)]. The mutation is an A to T transversion at base pair 11000817 (v38) on chromosome 15 in the GenBank genomic region NC_000081 encoding Slc45a2. The mutation corresponds to residue 97 in the NM_053077 mRNA sequence in exon 1 of 7 total exons. The effect of the mutation on the cDNA and protein level is unknown. One possibility, shown below, is that loss of the start codon (M) in the protein encoded by Slc45a2draco2 would result in deletion of the first 36 amino acids; the next methionine (i.e., putative start site) is at amino acid 37. 

97 ATGAGTGGAAGCAATGGG……  205 ……ATGCACAGCATGGCCATG……

1  -M--S--G--S--N--G-……  37    -M--H--S--M--A--M-……

        deleted

The mutated nucleotide is indicated in red. The mutation results in a methionine (M) to leucine (L) substitution at residue 1 in the SLC45A2 protein. 

Illustration of Mutations in
Gene & Protein
Protein Prediction
Figure 2. Protein topology and domain structure of SLC45A2. SLC45A2 is a 55kD protein with 12 membrane-spanning (TM) domains, an elongated N-terminus, and enlarged cytoplasmic loop between transmembrane domains six and seven. The sucrose-transporter signature sequence, R-W-G-R-R is noted. The draco2 mutation methionine (M) to leucine (L) substitution at residue 1 in the SLC45A2 protein. This image is interactive. Click on the mutations for more specific information. 

The draco2 mutation occurs at the N-terminal methionine of the SLC45A2 protein (Figure 2). The function of the N-terminus is unknown. The cytoplasmic N-terminus of SLC45A2 (amino acids 1-45) does not contain any defined domains (UniProt) or post-translational modifications. However, SMART defines a Major Facilitator Superfamily (MFS)_1 Pfam domain, a domain shared by carriers that transport small solutes, consisting of amino acids 36-364. 

Please see the record cardigan for information about Slc45a2.

Putative Mechanism

Homozygous mice with Slc45a2 mutations exhibit varied degrees of hypopigmentation of the eyes, skin, and fur (1). In addition, mutations in SLC45A2 can cause oculocutaneous albinism, type IV (OCA4; OMIM: #606574). Mutations at or near the cytoplasmic N-terminus have not been documented in either mouse or human. Although draco2 exhibits hypopigmentation, it is not as severe as the proposed null mutant cardigan, indicating that a truncated SLC45A2 is expressed, although this has not been confirmed. 

Primers PCR Primer
Draco2_pcr_F: CACCGTAACTTGTGATCTTGGAGGC
Draco2_pcr_R: TGCGATCCACTTACCTGATACGACC

Genotyping

Draco2 genotyping is performed by amplifying the region containing the mutation using PCR, followed by sequencing of the amplified region to detect the single nucleotide transition.

PCR Primers

Draco2(F): 5’- CACCGTAACTTGTGATCTTGGAGGC- 3’

Draco2(R): 5’- TGCGATCCACTTACCTGATACGACC- 3’

Sequencing Primer

Draco2_seq(F): 5’- GGCATGAAAGAATTTCAGCCC -3’


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               ∞

The following sequence of 550 nucleotides (from NT_039618.8 Mus musculus strain C57BL/6J chromosome 15 genomic contig, GRCm38.p1 C57BL/6J MMCHR15_CTG2) is amplified:

  1 caccgtaact tgtgatcttg gaggcatgaa agaatttcag cccctcctcc agcctgacca

 61 tctctgttgg ttgctctgac aggctccatg tcagacccgg tttggagcac aaatctgagg

121 accacgcaag aaggctattt tctccgtggt catgagtgga agcaatgggc cgactgacac

181 ccatacctat caatccttag ccgaggattg cccctttggc tctgtggagc aacccaagag

241 atccacaggg agacttgtca tgcacagcat ggccatgttt ggccgagagt tttgctatgc

301 ggtggaggca gcttatgtga ctccagttct gctcagcgtg ggcctgccta agagcctgta

361 cagcatggtg tggctcctaa gccccatctt gggattcctg ctccagcctg tggtgggatc

421 agccagtgat cactgcaggg cccgttgggg tcgccggaga ccatacatcc tgactctggc

481 cattatgatg ctcttgggaa tggctctgta cctcaatgga gatgcggtcg tatcaggtaa

541 gtggatcgca

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

References
Science Writers Anne Murray
Illustrators Peter Jurek
AuthorsTiana Purrington