Role of the Connexin C-terminus in skin pattern formation of Zebrafish.

BACKGROUND

Zebrafish display a striped skin pattern on their body; two types of connexins, namely, Connexin39.4 (Cx39.4) and Connexin41.8 (Cx41.8), are involved in stripe pattern formation. Herein, we investigated the role of the C-terminal (CT) domains of Cx39.4 and Cx41.8 and .

METHODS

To investigate the role of CT domains , we established transgenic zebrafish lines expressing the CT-domain-modified connexin series in pigmented cells and observed skin patterns in fish. To investigate the role of the CT domains , we expressed the CT-domain modified connexin series in Neuro-2a (N2a) cells and calculated the plaque formation frequency.

RESULTS

The overexpression of Cx39.4 lacking a CT domain produced skin patterns similar to that produced by full-length Cx39.4 in the mutant and in and double-knockout mutant zebrafish. Fluorescence-protein-fused CT-domain-modified Cx39.4 formed gap junction plaques between N2a cells. The overexpression of CT-truncated Cx41.8 rescued the mutant phenotype in the mutant but did not function in the double knockout zebrafish. Fluorescence-protein-fused CT-truncated Cx41.8 hardly formed plaques between N2a cells without Cx39.4 but formed gap junction plaques when co-expressed with Cx39.4.

CONCLUSIONS

The CT domain of Cx39.4 is not required for protein function, at least in the pigment cells of zebrafish. However, the need for the CT domain of Cx41.8 depends on Cx39.4 expression.

GENERAL SIGNIFICANCE

These results provide evidence for the interactions between Cx39.4 and Cx41.8 in pigment cells of zebrafish and suggest that at least one connexin must have a CT domain.