Knockout of lipoprotein lipase with CRISPR/Cas9 causes severe developmental defects and affects lipid deposition in Japanese medaka (Oryzias latipes)

Abstract

In mammals, lipoprotein lipase (LPL) has been found to play an important role in lipid mentalism and deposition. LPL deficiency in humans (Homo sapiens) and mice (Mus musculus) tends to cause hypertriglyceridemia. The lpl gene is not expressed in adult mammalian liver, but is in adult fish liver. The functions provided by the lpl gene are diverse in vertebrates. Here, we knocked out the lpl gene in Japanese medaka (Oryzias latipes) with the CRISPR/Cas9 system. The lpl-knockout (KO) homozygous individuals showed severe developmental defects with an extremely emaciated and deformed body and only accounted for about 5% of the F2 fish. This is consistent with the findings in mice but disaccords with the results for zebrafish (Danio rerio). Compared with wild-type (WT) madaka, the mRNA level of lpl in lpl-KO heterozygous mutant was significantly higher in the muscle, showed no significant difference in the liver, and was significantly lower in the heart. Under lpl heterozygous deficiency, the relative area of Oil Red O and triglycerides (TG) level in the liver, heart and muscle tissue covaried with levels of lpl mRNA in medaka. The lpl heterozygous deficiency did not affect the levels of TG, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and total cholesterol (TC) in the plasma of medaka, which is inconsistent with the findings in mammals. In general, the lpl gene plays an important role in the growth and development and is closely related to lipid deposition of medaka.