Rescue From Oculocutaneous Albinism Type 4 Using Medaka slc45a2 cDNA Driven by Its Own Promoter

Shoji Fukamachi^*^,^,1, Masato Kinoshita, Taro Tsujimura^*, Atsuko Shimada, Shoji Oda^*, Akihiro Shima, Axel Meyer, Shoji Kawamura^* and Hiroshi Mitani^*

^* Department of Integrated Biosciences, University of Tokyo, Kashiwa-no-ha, Kashiwa-shi, Chiba 277-8562, Japan, Department of Biology, University of Konstanz, D-78457 Konstanz, Germany, Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan and Department of Biological Sciences, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

^¹ Corresponding author: Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, D-78457 Konstanz, Germany.
E-mail: shoji.fukamachi{at}uni-konstanz.de

Patients and vertebrate mutants with oculocutaneous albinismtype 4 (OCA4) have mutations in the solute carrier family 45member 2 (slc45a2) gene. However, there is no empirical evidencefor this gene–phenotype relationship. There is a uniqueOCA4 mutant in medaka (b) that exhibits albinism only in theskin, but the mechanism underlying this phenotype is also unknown.In this study, we rescued medaka OCA4 phenotypes, in both theeyes and the skin, by micro-injection of an slc45a2-containinggenomic fragment or slc45a2 cDNA driven by its own 0.9-kb promoter.We also identified a spontaneous nucleotide change of 339 bpin the promoter as the b mutation. There are multiple transcriptionstart sites in medaka slc45a2, as in its human ortholog, andonly the shortest and eye-specific mRNA is transcribed withthe b mutation. Interestingly, we further revealed a conservedpyrimidine (Py)-rich sequence of $~$ 10 bp in the promoter by medaka–pufferfishcomparative genomics and verified that it plays an indispensablerole for expression of slc45a2 in the skin. Further studiesof the 0.9-kb promoter identified in this study should provideinsights into the cis/trans-regulatory mechanisms underlyingthe ocular and cutaneous expression of slc45a2.