The patatin-like lipase family in Gallus gallus

Jani Saarela,Marcela Hermann,Gerlinde Jung,Wolfgang J Schneider,Johannes Nimpf

doi:10.1186/1471-2164-9-281

Abstract

BackgroundIn oviparous species, genes encoding proteins with functions in lipid remodeling, such as specialized lipases, may have evolved to facilitate the assembly and utilization of yolk lipids by the embryo. The mammalian gene family of patatin-like phospholipases (PNPLAs) has received significant attention, but studies in other vertebrates are lacking; thus, we have begun investigations of PNPLA genes in the chicken (Gallus gallus).ResultsWe scanned the draft chicken genome using human PNPLA sequences, and performed PCR to amplify and sequence orthologous cDNAs. Full-length cDNA sequences of galline PNPLA2/ATGL, PNPLA4, -7, -8, -9, and the activator protein CGI-58, as well as partial cDNA sequences of avian PNPLA1, -3, and -6 were obtained. The high degree of sequence identities (~50 to 80%) between the avian and human orthologs suggests conservation of important enzymatic functions. Quantitation by qPCR of the transcript levels of PNPLAs and CGI-58 in 21 tissues indicates that expression patterns and levels diverge greatly between species. A particularly interesting tissue in which certain PNPLAs may contribute to physiological specialization is the extraembryonic yolk sac.ConclusionKnowledge about the exact in-vivo functions of PNPLAs in any system is still sparse. Thus, studies about the temporal expression patterns and functions of the enzymes identified here, and of other already known extracellular lipases and co-factors, in the yolk sac and embryonic tissues during embryogenesis are called for. Based on the information obtained, further studies are anticipated to provide important insights of the roles of PNPLAs in the yolk sac and embryo development.

Highlights

In oviparous species, genes encoding proteins with functions in lipid remodeling, such as specialized lipases, may have evolved to facilitate the assembly and utilization of yolk lipids by the embryo
The laying hen's lipid metabolism is a remarkable paradigm for hormonal control, as estrogen directly regulates the hepatic expression of genes for yolk precursor synthesis [3,4], but likely is involved in the modulation of lipolytic activities and lipid transfer processes important in deposition of yolk into oocytes and subsequent embryonic yolk utilization [5]
The resulting DNA fragments were cloned and sequenced. By this approach we obtained the full-length cDNA clones from the chicken genes corresponding to PNPLA2/adiposome TG-lipase (ATGL), PNPLA4, PNPLA8, PNPLA9, PNPLA7, and Comparative gene identification 58 (CGI-58)

Summary

Introduction

Genes encoding proteins with functions in lipid remodeling, such as specialized lipases, may have evolved to facilitate the assembly and utilization of yolk lipids by the embryo. BMC Genomics 2008, 9:281 http://www.biomedcentral.com/1471-2164/9/281 embryo growth likewise depends on efficient nutrient transfer, i.e., mainly of lipid components, from the yolk into the embryonic circulation. These mobilization processes are maintained through concerted regulation of lipoprotein metabolism involving genes for lipases, lipid transfer proteins, lipoprotein receptors, and others. The laying hen's lipid metabolism is a remarkable paradigm for hormonal control, as estrogen directly regulates the hepatic expression of genes for yolk precursor synthesis (e.g., vitellogenin and very low density lipoproteins, VLDL) [3,4], but likely is involved in the modulation of lipolytic activities and lipid transfer processes important in deposition of yolk into oocytes and subsequent embryonic yolk utilization [5]. To mediate the mobilization of lipids from yolk, lipolytic enzymes resistant to apoVLDLII must exist which allow the developing embryo to efficiently access the lipid moiety of yolk lipoproteins

Methods

Results

Discussion

Conclusion