Shunichi Yoshikawa

G2R Cre reporter transgenic zebrafish

The Cre/loxP site‐specific recombination system has been widely used to manipulate DNA in vivo and to study gene function in the mouse by inducible transgenic and conditional gene targeting. To fully use this powerful genetic tool in a relatively new animal model, zebrafish, we generated reporter transgenic lines for easy detection of Cre recombinase activity in vivo. The transgenic fish lines, designated G2R, express two fluorescent protein genes, GFP and RFP, under the control of the ubiquitous promoter of the Xenopus EF1 alpha gene. The G2R animals change their color from green to red (G2R) after Cre‐mediated recombination and are useful for development of cell type specific Cre transgenic lines and for cell lineage and fate mapping studies in zebrafish. Developmental Dynamics 237:2460–2465, 2008.

Transgenic Analysis of the Anterior Eye- Specific Enhancers of the Zebrafish gelsolin- like 1 (gsnl1) Gene

The anterior segment of the eye includes such structures as the cornea, lens, iris, and ciliary body and is essential for many visual and physiological functions of the eye. The zebrafish gelsolin‐like 1 (gsnl1) gene encodes an actin regulatory protein and is expressed in the anterior segment of the eye. We report the transgenic analyses of the gsnl1 promoter and enhancer that are required for expression in the anterior segment of the eye. A 6.4‐kb genomic fragment upstream from the translation initiation site (ATG) was capable of driving green fluorescent protein (GFP) expression in transient transgenic embryos and stable transgenic adult fish, which mimics the endogenous gsnl1 expression. The GFP expression was localized in the corneal epithelium (CE) and the annular ligament (AL) at the iridocorneal angle. A unique enhancer for each of these two tissues was identified at 3.7‐kb upstream from the ATG. The 60‐bp AL and 25‐bp CE enhancers were separated by 100‐bp and functioned independently from each other. Deletion analysis indicated that the proximal promoter was located 1.6‐kb upstream from the ATG. Stable GFP transgenic lines were established for future studies of genetic regulation in the anterior segment of the fish eye. Developmental Dynamics 236:1929–1938, 2007.