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|Coordinate||87,493,221 bp (GRCm38)|
|Base Change||T ⇒ C (forward strand)|
|Chromosomal Location||87,424,771-87,493,512 bp (-)|
FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] The enzyme encoded by this gene catalyzes the first 2 steps, and at least 1 subsequent step, in the conversion of tyrosine to melanin. The enzyme has both tyrosine hydroxylase and dopa oxidase catalytic activities, and requires copper for function. Mutations in this gene result in oculocutaneous albinism, and nonpathologic polymorphisms result in skin pigmentation variation. The human genome contains a pseudogene similar to the 3' half of this gene. [provided by RefSeq, Oct 2008]
PHENOTYPE: Numerous mutations at this locus result in albinism or hypopigmentation. Albinism is associated with reduced number of optic nerve fibers and mutants can have impaired vision. Some alleles are lethal. [provided by MGI curators]
|Amino Acid Change||Serine changed to Glycine|
|Institutional Source||Beutler Lab|
|Gene Model||predicted gene model for protein(s): [ENSMUSP00000004770] [ENSMUSP00000146757]|
AA Change: S44G
|Predicted Effect||possibly damaging
PolyPhen 2 Score 0.938 (Sensitivity: 0.80; Specificity: 0.94)
|Alleles Listed at MGI|
|Mode of Inheritance||Autosomal Recessive|
|Local Stock||Live Mice|
|Last Updated||2016-07-13 2:46 PM by Anne Murray|
|Record Created||2013-05-08 2:48 PM by Jennifer Weatherly|
The waffle mutation was induced by N-ethyl-N-nitrosourea (ENU) mutagenesis on the C57BL/6J (black) background, and was discovered in G3 animals. Homozygous waffle mice exhibit a light tan/yellow coat color and black eyes (Figure 1).
|Nature of Mutation|
Whole exome HiSeq sequencing of the G1 grandsire identified 99 mutations. Three affected G3 mice from the waffle pedigree were genotyped at 99 mutation sites and all three mice were homozygous for a mutation in Tyr on chromosome 7. Subsequent analysis of an additional waffle mouse (homozygous for the Tyr mutation) and six unaffected mice (all heterozygous or wild-type for the Tyr locus) supported the Tyr mutation as causative for the waffle phenotype (LOD=5.107).
The waffle mutation is an A to G transition at base pair 87493221 (v38) on chromosome 7, or base pair 191 in the GenBank genomic region NC_000073 encoding Tyr. The mutation corresponds to residue 191 in the NM_011661.4 mRNA sequence in exon 1 of 5 total exons.
The mutated nucleotide is indicated in red. The mutation results in a serine (S) to glycine (G) substitution at residue 44 in the Tyr protein.
The residue altered by the waffle mutation (Ser44) occurs N-terminal to the epidermal growth factor (EGF)-like laminin domain in the Tyr protein; Ser44 has no known function (Figure 2).
Please see the record ghost for information about Tyr.
The waffle mutation causes a weak form of albinism, similar to the spontaneous Tyrc-e allele (extreme dilution; MGI:1855978). Homozygous Tyrc-e mice have pigmented eyes with an off-white/yellow coat that darkens to a brownish shade with age (1). Because waffle mice are not completely white, it is likely that the mutation is hypomorphic and Tyrwaffle retains residual activity sufficient for some pheomelanin but not eumelanin production to occur (2).
During melanosome biogenesis and maturation, transport vesicles traffic melanosomal proteins (e.g., Tyr, Tyrp1 (Tyr-related protein 1; see the record for chi), lysosome-associated membrane protein (Lamp), and gp100 (Pmel17) from the trans-Golgi network (TGN) to the melanosomal compartment (3). Regulation of trafficking may be distinct for eumelanosomes, to which Tyr, Tyrp1, and DCT (dopachrome tautomerase) are transported from the TGN, versus pheomelanosomes, to which only Tyr is transported from stage I melanosomes to stage II melanosomes. Thus, an alternative mechanism for the waffle mutation may be to impair the ability of the mutant Tyr to traffic to eumelanosomes but not pheomelanosomes.
The waffle mouse may be a model for oculocutaneous albinism (OCA1) as a Ser44Gly mutation has been identified in a human patient with OCA1 (4). OCA1 can be subdivided into two phenotypes: OCA1A (OMIM: #203100) and OCA1B (OMIM: #606952). Type 1A is characterized by a complete lack of Tyr activity and melanin synthesis resulting in white hair, skin, and blue eyes. Type IB is characterized by reduced Tyr activity; patients have yellow or blond hair (with age). Since waffle mice appear to retain some pigmentation, they may represent a model of OCA1B. The subtype of OCA1 that the Ser44Gly patient presented with was not discussed.
waffle(F):5'- TGTGGGGATGACATAGACTGAGCTG -3'
waffle(R):5'- TCACTCCAGGGGTTGCTGGAAAAG -3'
waffle_seq(F):5'- TTACAGTTTCCGCAGTTGAAACC -3'
waffle_seq(R):5'- GAAGTCTGTGACACTCATTAACC -3'
Waffle 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.
Waffle(F): 5’- TGTGGGGATGACATAGACTGAGCTG -3’
Waffle(R): 5’- TCACTCCAGGGGTTGCTGGAAAAG-3’
Waffle_seq(F): 5’- TTACAGTTTCCGCAGTTGAAACC-3’
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 540 nucleotides is amplified (Chr. 7: 87492892-87493431, GRCm38):
tgtggggatg acatagactg agctgatagt atgttttgct aaagtgaggt aagaaaagaa
cttattcttt tcggagacac tcaaatcaaa aatgtttctt ctaatcaaga ctcgcttctc
tgtacaattt gggcccccaa atccaaactt acagtttccg cagttgaaac ccatgaagtt
gcctgagcac tggcaggtcc tattataaaa cacagagggc caggactcac ggtcatccac
ccctttgaag gggaactgag gtccagatgg tgcactggac agaaggatat cctggcagga
acctctgcct gaaagctggc cgcagggact cccatcaccc atccatggtg ggcagcattc
ttttgccaac aagttcttag aggaggcaca ggctcgagga aaatggccat cagagatctg
gaaactccac agaaggcaat acaaaacagc caagaacatt ttctccttta gatcatacaa
aatctgcacc aataggttaa tgagtgtcac agacttcttt tccagcaacc cctggagtga
Primer binding sites are underlined and the sequencing primer is highlighted; the mutated nucleotide is shown in red text (T>C, Chr. + strand; A>G, sense strand).
1. Detlefsen, J. A. (1921) A New Mutation in the House Mouse. Amer Nat. 55, 469-473.
2. Kobayashi, T., Vieira, W. D., Potterf, B., Sakai, C., Imokawa, G., and Hearing, V. J. (1995) Modulation of Melanogenic Protein Expression during the Switch from Eu- to Pheomelanogenesis. J Cell Sci. 108 ( Pt 6), 2301-2309.
3. Jimbow, K., Hua, C., Gomez, P. F., Hirosaki, K., Shinoda, K., Salopek, T. G., Matsusaka, H., Jin, H. Y., and Yamashita, T. (2000) Intracellular Vesicular Trafficking of Tyrosinase Gene Family Protein in Eu- and Pheomelanosome Biogenesis. Pigment Cell Res. 13 Suppl 8, 110-117.
|Science Writers||Anne Murray|
|Illustrators||Diantha La Vine, Peter Jurek|
|Authors||Jennifer Weatherly Tiana Purrington|
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