Apolipoprotein E gene expression correlates with endogenous lipid nutrition and yolk syncytial layer lipoprotein synthesis during fish development

Abstract

During embryogenesis of teleost fish, the formation of a yolk syncytial layer (YSL) enables the resorption of the yolk reserves and development up to the larval stage. We have examined the changes of the yolk cell structure in relation to yolk and oil-globule lipid utilization during development of the turbot (Scophthalmus maximus). After encapsulation by the YSL, resorption of the single, large oil globule occurred predominantly after yolk resorption and was slower in fasting larvae. The YSL was in contact with an enlarged perisyncytial space, but no vascular network or red blood cells were present within the walls of the yolk sac. Intrasyncytial channels infiltrated by pigmented lining cells were observed in the YSL surrounding the oil globule. Apolipoprotein E (apoE) has a prominent role in lipid metabolism because of its ability to interact with lipoprotein receptors. We performed molecular cloning of the putative low-density lipoprotein-receptor binding domain of turbot apoE. In situ hybridization analysis revealed a very high level of apoE transcripts in the YSL, while no expression could be detected in the intestine. YSL apoE expression was correlated with the synthesis of very low density lipoprotein (VLDL) particles. An extraordinarily high number of VLDL particles were poured into the perisyncytial space, and intrasyncytial channels enabled the transfer of yolk- and oil globule-derived lipids to the developing embryo or larva. The pattern of apoE mRNA distribution in relation to YSL lipoprotein synthesis indicates that apoE expression is a suitable molecular marker for monitoring endogenous lipid nutrition during the endoexotrophic period of teleost fish development.

BMP and RA signaling cooperate to regulate Apolipoprotein C1 expression during embryonic development

“…1B, arrow), similar to other apolipoproteins that have been reported in fish (Babin et al, 1997;Poupard et al, 2000;Xia et al, 2008). YSL is a layer consisting of a membrane-enclosed group of nuclei on top of the yolk cells and beneath the blastoderm cells.…”

Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

“…Apo E expression correlated with endogenous lipid nutrition and lipoprotein synthesis during development of turbot (Poupard et al, 2000).…”

Molecular cloning and expression characterization of ApoC-I in the orange-spotted grouper

“…During the period from fertilization to mouth opening, the embryos and prefeeding larvae use endogenous yolk nutrients previously stored in the yolk globules, hyaloplasm, and oil globules (Poupard et al 2000). In the past decade, many attempts have been undertaken on the biochemical composition of egg yolk components and their digestion, synthesis and transformation during embryonic development of teleosts (Henderson and Tocher 1987;Heming and Buddington 1988;Rønnestad and Fyhn 1993;Wiegand 1996;Poupard et al 2000).…”

“…In the past decade, many attempts have been undertaken on the biochemical composition of egg yolk components and their digestion, synthesis and transformation during embryonic development of teleosts (Henderson and Tocher 1987;Heming and Buddington 1988;Rønnestad and Fyhn 1993;Wiegand 1996;Poupard et al 2000). A large amount of data revealed that the formation of a YSL (yolk syncytial layer), a structure unique to teleosts, enables the resorption of the yolk reserves and development to the larval stage (Manfredi Romanini et al 1969;Walzer and Schönenberger 1979a;Shimizu and Yamada 1980;Cousin et al 1987;Sire et al 1994;Mani-Ponset et al 1996;Babin et al 1997;Poupard et al 2000). However, the developmental behavior of genes that control the utilization of yolk reserves is virtually unknown (Poupard et al 2000).…”

“…A large amount of data revealed that the formation of a YSL (yolk syncytial layer), a structure unique to teleosts, enables the resorption of the yolk reserves and development to the larval stage (Manfredi Romanini et al 1969;Walzer and Schönenberger 1979a;Shimizu and Yamada 1980;Cousin et al 1987;Sire et al 1994;Mani-Ponset et al 1996;Babin et al 1997;Poupard et al 2000). However, the developmental behavior of genes that control the utilization of yolk reserves is virtually unknown (Poupard et al 2000). Lipids are prominent components of fish egg yolk.…”