The Role of Potassium Channels in Stripe Pattern Formation

Shigeru Kondo1,Masafumi Inaba1, Ken-ichiro Ida2, Koichi Kawakami3

1)Osaka University, Suita, Japan, 2)Nagoya University, Nagoya, Japan,3)Institute of Genetics, Mishima, Japan

 Understanding the mechanisms that generate complex patterns seen in animals is one of the goals of developmental biology. To address this issue at the molecular level, we have analyzed stripe pattern mutant of zebrafish. Our previous study about jaguar/obelix mutant revealed that dysfunction of inwardly rectifying potassium channel 7.1 (Kir7.1) caused the change of stripe width resulting in broad stripes on fish body. The role of Kir7.1 channel in stripe pattern formation remains unclear, because (1) little is known about the physiological functions of this channel; (2) molecular functions of the channel differ from those of other Kir subfamilies. Here, we used transgenic approaches to examine how Kir7.1 channels form the stripe pattern on zebrafish. We first generated transgenic jaguar fish that expresses WT-kir7.1 only in melanophores. The transgenic mutant fish showed normal stripe pattern like wild-type fish, suggesting that expression of kir7.1 only in melanophores is enough for stripe pattern formation. We then generated transgenic jaguar fish that expresses kir4.1, kir2.1 (Kir subfamilies) or kv1.2 (voltage gated potassium channel) only in melanophores instead of kir7.1. As a result, both kir4.1 and kir2.1 could rescue the jaguar phenotype, whereas kv1.2 failed to rescue. These results suggest that common features of Kir channels are required for stripe pattern formation, rather than some unique properties of kir7.1. Taken together, our results suggest that resting membrane potential (Eres) of melanophores is a key factor in stripe pattern formation, because all of Kir channels we tested play a role in maintenance of Eres, whereas Kv1.2 does not. We are currently using voltage sensitive dye to investigate the Eres of melanophores, and the results will be discussed in this meeting.