Lipoprotein kinetics are a crucial factor in understanding lipoprotein metabolism because a prolonged time in circulation can contribute to the atherogenic character of B-lps (ApoB-containing lipoprot Show more
Lipoprotein kinetics are a crucial factor in understanding lipoprotein metabolism because a prolonged time in circulation can contribute to the atherogenic character of B-lps (ApoB-containing lipoproteins). We developed a genetically encoded B-Lp reporter, LipoTimer, in which the zebrafish endogenous By quantifying the red population of ApoB-Dendra2 over time, we found that B-lp turnover in wild-type larvae becomes faster as development proceeds. Mutants with impaired B-lp uptake or lipolysis present with increased B-lp levels and half-life. In contrast, mutants with impaired B-lp triglyceride loading display slightly fewer and smaller B-lps, which have a significantly shorter B-lp half-life. Furthermore, we showed that chronic high-cholesterol feeding is associated with a longer B-lp half-life in wild-type juveniles but does not lead to changes in B-lp half-life in lipolysis-deficient In conclusion, the new LipoTimer reporter allows for direct in vivo examination of B-lp kinetics, which can be used to better understand the role of lipoprotein modifier genes and environmental factors (eg, diet) on B-lp lifetime. Show less
Forward genetic screening is a powerful approach to assign functions to genes and can be used to elucidate the many genes whose functions remain unknown. A key step in forward genetic screening is map Show more
Forward genetic screening is a powerful approach to assign functions to genes and can be used to elucidate the many genes whose functions remain unknown. A key step in forward genetic screening is mapping: identification of the gene causing the phenotype. Existing mapping methods use a bioinformatic mapping-by-sequencing approach based on allelic frequency calculations that often identify large genomic regions which contain an intractable number of candidate genes for testing. Here, we describe WheresWalker, a modern mapping-by-sequencing algorithm that identifies a mutation-containing interval and then supports positional cloning to shrink the interval, which drastically reduces the number of potential candidates, allowing for extremely rapid mutation identification. We validated this method using mutants from a forward genetic mutagenesis screen in zebrafish for modifiers of ApoB-lipoprotein metabolism. WheresWalker correctly mapped and identified novel zebrafish mutations in mttp, apobb.1, and mia2 genes, as well as a previously published mutation in maize. Further, we used WheresWalker to identify a previously unappreciated ApoB-lipoprotein metabolism-modifying locus, slc3a2a. Show less