Elsevier

Gene Expression Patterns

Volume 10, Issue 6, September 2010, Pages 227-236
Gene Expression Patterns

Diversification of fasting regulated transcription in a cluster of duplicated nuclear hormone receptors in C. elegans

https://doi.org/10.1016/j.gep.2010.05.001Get rights and content

Abstract

The genome of Caenorhabditis elegans encodes more than 280 nuclear hormone receptors (NHRs) in contrast to the 48 NHRs in humans and 18 NHRs in Drosophila. The majority of the C. elegans NHRs are categorized as supplementary nuclear receptors (supnrs) that evolved by successive duplications of a single ancestral gene. The evolutionary pressures that lead to the expansion of NHRs in nematodes, as well as the function of the majority of supnrs, are not known. Here, we have studied the expression of seven genes organized in a cluster on chromosome V: nhr-206, nhr-208, nhr-207, nhr-209, nhr-154, nhr-153 and nhr-136. Reverse transcription-quantitative PCR and analyses using transgenic lines carrying GFP fusion genes with their putative promoters revealed that all seven genes of this cluster are expressed and five have partially overlapping expression patterns including in the pharynx, intestine, certain neurons, the anal sphincter muscle, and male specific cells. Four genes in this cluster are conserved between C. elegans and Caenorhabditis briggsae whereas three genes are present only in C. elegans, the apparent result of a relatively recent expansion. Interestingly, we find that a subset of the conserved and non-conserved genes in this cluster respond transcriptionally to fasting in tissue-specific patterns. Our results reveal the diversification of the temporal, spatial, and metabolic gene expression patterns coupled with evolutionary drift within supnr family members.

Section snippets

Rhabditidae genomes encode far more NHRs than insects or mammals

While the Drosophila genome contains only 18 nhr genes and the human genome contains 48 such genes, sequence homology identifies more that 284 nhrs in the Caenorhabditis elegans genome (Antebi, 2006, Haerty et al., 2008, King-Jones and Thummel, 2005, Sluder et al., 1999), 232 in Caenorhabditis briggsae (reported by Haerty et al. (2008)) and 256 in Caenorhabditis remanei (Haerty et al., 2008). Of the 284 nhr genes in C. elegans, only 13 (Robinson-Rechavi et al., 2003, Robinson-Rechavi et al.,

Worm cultures and lines

Caenorhabditis elegans and C. briggsae worms were obtained from C. elegans Stock Center and cultures were maintained as described (Brenner, 1974). Stock cultures were frozen in liquid nitrogen and fresh cultures were started from frozen stocks when necessary. Larvae were grown on nematode growth medium (NGM) plates or on 2% agarose-capped plates and fed the OP50 bacterial strain of E. coli (Brenner, 1974).

Transgenic lines were prepared as described (Mello and Fire, 1995) from N2 wild type

Acknowledgments

We thank Dr. A. Fire for vectors pPD95.67, L4440 and HT115 cells host. The work was supported by Grant 304/08/0970, Grant 304/07/0529 from the Czech Science Foundation and by Grant 0021620806 from the Ministry of Education, Youth and Sports of the Czech Republic. M.W.K. was supported by the Intramural Research Program of the National Institutes of Health, USA.

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