Genomic interval engineering of mice identifies a novel modulator of triglyceride production

Abstract

To accelerate the biological annotation of novel genes discovered in sequenced regions of mammalian genomes, we are creating large deletions in the mouse genome targeted to include clusters of such genes. Here we describe the targeted deletion of a 450-kb region on mouse chromosome 11, which, based on computational analysis of the deleted murine sequences and human 5q orthologous sequences, codes for nine putative genes. Mice homozygous for the deletion had a variety of abnormalities, including severe hypertriglyceridemia, hepatic and cardiac enlargement, growth retardation, and premature mortality. Analysis of triglyceride metabolism in these animals demonstrated a several-fold increase in hepatic very-low density lipoprotein triglyceride secretion, the most prevalent mechanism responsible for hypertriglyceridemia in humans. A series of mouse BAC and human YAC transgenes covering different intervals of the 450-kb deleted region were assessed for their ability to complement the deletion induced abnormalities. These studies revealed that OCTN2, a gene recently shown to play a role in carnitine transport, was able to correct the triglyceride abnormalities. The discovery of this previously unappreciated relationship between OCTN2, carnitine, and hepatic triglyceride production is of particular importance because of the clinical consequence of hypertriglyceridemia and the paucity of genes known to modulate triglyceride secretion.

Discovery of Genes Essential for Heme Biosynthesis through Large-Scale Gene Expression Analysis

“…One of these is the mitochondrial solute carrier SLC22A4 . This gene is highly homologous to the carnitine transporter SLC22A5 ( OCTN2 ), but has low affinity for carnitine and does not rescue carnitine deficiency in mice (Zhu et al, 2000). SLC22A4 has been suggested to protect red blood cells from oxidative stress (Grundemann et al, 2005), and a previous study found that terminal differentiation of MEL cells is disrupted upon SLC22A4 depletion, although the cause of this is unclear (Nakamura et al, 2007).…”

Engineering chromosomal rearrangements in mice

“…Variations of the aforementioned strategy have been reported by other groups 24,[30][31][32] . Besides pOG231, several other cre-expression vectors, such as pBS185…”

Use ofin vitrotransporter assays to understand hepatic and renal disposition of new drug candidates

“…There are interspecies differences in the hepatic and renal transporters, and all results should be extrapolated with caution [10,207,212,220]. Other available in vivo models are the transgenic or knockout animals (e.g., the mdr1a/1b [221], mrp1 [222], mrp2 [223], bcrp [224], oct1, oct2, oct3 [225], pept2 [226] and octn2 [227] knockout/transgenic mice). These models can further help clarify specific transporter involvement in an in vivo setting.…”