A Gal4/UAS system for conditional transgene expression in rhombomere 4 of the zebrafish hindbrain

Background: The zebrafish is well established as a model organism for the study of vertebrate embryogenesis, but transgenic lines enabling restricted gene expression are still lacking for many tissues. Results: We first generated the hoxb1a(beta-globin):eGFPum8 line that expresses eGFP in hindbrain rhombomere 4 (r4), as well as in facial motor neurons migrating caudally from r4. Second, we generated the hoxb1a(beta-globin) Gal4VP16um60 line to express the exogenous Gal4VP16 transcription factor in r4. Lastly, we prepared the UAS(beta-actin):hoxa3aum61 line where the hoxa3a gene, which is normally expressed in r5 and r6, is under control of Gal4-regulated UAS elements. Crossing the hoxb1a(beta-globin):Gal4VP16um60 line to the UAS(beta-actin):hoxa3aum61 line drives robust hoxa3a expression in r4. We find that transgenic expression of hoxa3a in r4 does not affect hoxb1a expression, but has variable effects on migration of facial motorneurons and formation of Mauthner neurons. While cases of somatic transgene silencing have been reported in zebrafish, we have not observed such silencing to date, possibly because of our efforts to minimize repetitive sequences in the transgenic constructs. Conclusion: We have generated three transgenic lines that will be useful for future studies by permitting the labeling of r4-derived cells, as well as by enabling r4-specific expression of various transgenes. Developmental Dynamics 241:11251132, 2012. (c) 2012 Wiley Periodicals, Inc.