Disease relevance of Gpr143

• Hypopigmentation of the RPE in Oa1-/- mice is due to a reduced number of melanosomes [1].
• RESULTS: Differently from other albinism models, Tyr activity was not impaired in Oa1-/- eyes [1].
• Expression pattern of the ocular albinism type 1 (Oa1) gene in the murine retinal pigment epithelium [2].
• To this end, a small fragment of the Oa1 promoter was cloned in front of a reporter gene in an adeno-associated virus [3].
• Two Moa1 isoforms were isolated from a melanoma cDNA library and predicted to encode proteins of 405 and 249 amino acids with six and two transmembrane-spanning regions, respectively [4].

High impact information on Gpr143

• We demonstrated that Oa1 is a target of Mitf and that this regulatory mechanism is conserved in the human gene [3].
• We performed an analysis of the regulatory region of Oa1, the murine homolog of the gene that is mutated in the X-linked form of ocular albinism, as Oa1's function affects melanosome biogenesis [3].
• Like its human counterpart, the expression pattern of Oa1, apart from the eye, is restricted to the epidermal melanocyte lineage [5].
• Karyotype analysis showed that there were several marker chromosomes including deletion of chromosome 3p shared by these three cell lines, supporting the belief that MOA1 and MOA2 originated from SCLC-MO [6].
• When transplanted into nude mice, both SCLC-MO and MOA1 showed intermediate cell type histology, while MOA2 showed a picture of large cell carcinoma as non-SCLC [6].

Biological context of Gpr143

• The localization of Oa1 mRNA was studied and compared with the expression of other genes involved in melanosomal biogenesis [2].
• The mouse homologues, Oa1 and Apxl, have recently been shown to lie proximal to their expected locations on the mouse X chromosome, but their positions with respect to critical gene loci in the vicinity have not been defined [7].
• By analyzing recombination events from (Mus musculus x Mus spretus) x M. musculus backcrosses, we have constructed a detailed mouse genetic map that encompasses Oa1, five other genes, and 13 microsatellite loci [7].
• Mutation at amino acid 106 that eliminated glycosylation did not affect the endo/lysosomal distribution of the Oa1 protein in either COS cells or cultured murine melanocytes [8].
• Based upon sequence homology, it has been predicted that Oa1 belongs to the G protein coupled receptor (GPCR) superfamily [9].

Anatomical context of Gpr143

• Acting at early maturation stages, Oa1 controls the abundance of melanosomes in RPE cells [1].
• At later stages, expression of Oa1, TYR:, and p expanded to the entire RPE and ciliary body [2].
• This suggests that lack of Oa1 in the RPE impacts on photoreceptor activity [10].
• The Oa1(-/-) mouse also displays some of the retinal developmental abnormalities observed in albino patients such as misrouting of the optic tracts [10].
• Sucrose gradient and immunofluorescence studies revealed that when expressed in yeast, Oa1 localizes to the prevacuolar compartment, the functional equivalent of the mammalian late endosome [9].

Associations of Gpr143 with chemical compounds

• These results indicate that Oa1 is a melanocyte-specific integral membrane glycoprotein localized to late endosomes/lysosomes but not mature melanosomes [11].

Physical interactions of Gpr143

• Tissue-specific control of Oa1 transcription lies within a region of 617 bp that contains the E-box bound by Mitf [3].

Co-localisations of Gpr143

• Upon density gradient centrifugation of organelles of melan-a cells, Oa1 protein colocalized with the late endosomal/lysosomal marker Lamp1, but only partial overlap was observed with melanosomal proteins in the high density region of the gradient [11].

Other interactions of Gpr143

• In contrast, colocalization of Oa1 and Oa1-green fluorescent protein fusion product with Lamp1 was extensive throughout the cell [11].
• Interspecific backcross mapping yielded a map order and distances (cM) of cen-Moa1-3.1 +/- 1.8-Piga-2.1 +/- 1.5-Amel, indicating that Moa1 is located much farther away from the pseudoautosomal region than its human homolog [4].

Analytical, diagnostic and therapeutic context of Gpr143

• METHODS: Enzyme activity and protein localization were analyzed by immunohistochemistry of tyrosinase (Tyr) in Oa1-null mice [1].
• RESULTS: RT-PCR revealed that Oa1 expression began at embryonic day (E)10.5 and was maintained until adulthood [2].
• By in situ hybridization analysis Oa1 transcripts were detected in the retinal pigment epithelium (RPE) beginning at E10.5 in the dorsal part of the eyecup and in the same area where transcripts of other genes involved in pigmentation are found [2].
• In this study, we have generated and characterized Oa1-deficient mice by gene targeting (KO) [12].
• To examine whether N-glycosylation plays a role in the post-translational trafficking of the Oa1 protein, we constructed a series of mutant mouse Oa1 cDNAs encoding an Oa1-green fluorescent protein fusion in which some or all of the potential glycosylation sites were eliminated by site-directed mutagenesis [8].

References