Differential gene expression of Caenorhabditis elegans grown on unmethylated sterols or 4α-methylsterols

Merris Mark,Wang Tongsheng,Soteropoulos Patricia,Lenard John

doi:10.1194/jlr.m600552-jlr200

Abstract

Transcriptional profiles of Caenorhabditis elegans grown on unmethylated sterols (desMSs) or on 4alpha-methylsterols (4MSs) were compared using microarrays. Thirty-four genes were upregulated and 2 were downregulated>2-fold by growth on 4MSs, including 13 cuticle collagen (col) genes, 1 cuticulin gene (cut-1), 2 groundhog-like (grl) genes, and 1 groundhog gene (grd-4); col-36 and grl-20 were increased 12- and 19-fold, respectively. Fifteen of these 17 genes have been assigned to metabolic mountain 17, suggesting coordinate 4MS-mediated regulation of expression. Quantitative RT-PCR was performed on 27-51 h old animals grown on cholesterol (a desMS) or lophenol (a 4MS). col-36 and grl-20 showed similar cyclic peaks of expression in cholesterol and similar alterations in lophenol, suggesting coregulation. Of six additional grl genes, only grl-3 was upregulated on lophenol; the rest were downregulated. Cyclicity of expression was lost or altered in all six. Nuclear receptor genes nhr-23, nhr-25, nhr-41, and daf-12 all showed cyclic expression in cholesterol and significant downregulation in lophenol by RT-PCR. Expression of the insulin-like receptor daf-2 was lower in lophenol, whereas that of its major downstream target daf-16 was higher. Thus, major changes in gene expression accompany growth on 4MSs, but with surprisingly little effect on normal growth and development.

Highlights

Transcriptional profiles of Caenorhabditis elegans grown on unmethylated sterols or on 4a-methylsterols (4MSs) were compared using microarrays
1) Minute amounts of sterols, insufficient to modify plasma membrane properties globally, are required [3]. 2) Sterols accumulate in a few specific cells rather than being distributed uniformly in cellular plasma membranes [3, 7]. 3) The enantiomer of cholesterol does not substitute for cholesterol in supporting growth, sterol-lipid interactions in bilayers are generally not enantiospecific [8]. 4) The sterol requirement can be met by 4a-methylsterols (4MSs) containing 1% or less unmethylated sterols [3, 6], even though 4MSs are inferior to desMSs in their ability to modify membrane bilayers
RNA from animals at all stages of development was isolated for microarray analysis from unsynchronized populations grown in four different sterol conditions: 1 mg/ml cholesterol, lathosterol, lophenol, or D8(14) sterol (Fig. 1)

Summary

Introduction

Transcriptional profiles of Caenorhabditis elegans grown on unmethylated sterols (desMSs) or on 4a-methylsterols (4MSs) were compared using microarrays. Thirty-four genes were upregulated and 2 were downregulated .2-fold by growth on 4MSs, including 13 cuticle collagen (col ) genes, 1 cuticulin gene (cut-1), 2 groundhog-like (grl ) genes, and 1 groundhog gene (grd-4 ); col-36 and grl-20 were increased 12- and 19-fold, respectively. Fifteen of these 17 genes have been assigned to metabolic mountain 17, suggesting coordinate 4MS-mediated regulation of expression. Nuclear receptor genes nhr-23, nhr-25, nhr-41, and daf-12 all showed cyclic expression in cholesterol and significant downregulation in lophenol by RT-PCR. Differential gene expression of Caenorhabditis elegans grown on unmethylated sterols or 4a-methylsterols. Are 4MSs synthesized by C. elegans, but they are present in significant amounts at all stages of growth and development, suggesting a continuing role [10]

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Results

Conclusion