b'39The bright blue light (chemiluminescence) seen in these developing zebrafish is emitted by the NanoLuc protein in LipoGlo. The glowing enzyme is tagged to bad-cholesterol particles so researchers can visualize how much cholesterol is present in each fish and where it is located. The top image shows a 24-hour-old zebrafish embryo, with many cholesterol particlesJohns Hopkins graduate student James Thierer (left) was lead shown glowing from its large spherical yolk. Subsequent imagesauthor on the study. He performed the work with Steve Farber were taken every 24 hours, indicating that cholesterol levels peak(right) and team. Thierer recently received his Ph.D.between three and four days of age. Image courtesy John RawlsImage courtesy James Thierer and Ed Hirschmugl, Carnegie Institution for Science Furthermore, the larval zebrafish is the only animalPLA2G12B, has a huge impact on both the size model conducive to high-throughput screening.and number of ApoB-containing lipoproteins. It is One lab can breed thousands of zebrafish larvaeunclear how exactly this gene works, but intensive each week, to potentially conduct thousands ofongoing studies by the team point to its central experiments, such as screening collections of drugsrole in packing lipids into lipoproteins before they to identify new potential treatments. are secreted into the bloodstream. Understanding the cell biology of this system may point to new Using their system, Thierer and Farber alsostrategies for treating heart disease. discovered that a mysterious gene, called'