Biology subjects

Lefebvre, P.

Publications and source records attributed to Lefebvre, P..

3 recordsLinked to original sources

bioRxiv2024

The Chlamydomonas reinhardtii CLiP2 mutant collection expands genome coverage with high-confidence disrupting alleles

Chlamydomonas reinhardtii (Chlamydomonas hereafter) is a powerful model organism for studies of photosynthesis, ciliary motility, and other cellular processes [1-4]. The CLiP library of mapped nuclear random insertion mutants [5,6] has accelerated progress for hundreds of laboratories in these fields by providing mutants in genes of interest. However, its value was limited by its modest coverage of the genome with high-confidence disruption alleles (46% of nuclear protein-coding genes with 1+ high-confidence allele in exons/introns; 12% of genes with 3+ alleles in exons/introns). Here we introduce the CLiP2 (Chlamydomonas Library Project 2) library, which greatly expands the number of available mapped high-confidence insertional mutants. The CLiP2 library includes 71,700 strains, covering 79% of nuclear protein-coding genes with 1+ high-confidence allele in exons/introns and 49% of genes with 3+ alleles in exons/introns. The mutants are available to the community via the Chlamydomonas Resource Center.

plant biology↗

bioRxiv2024

Mutation of negative regulatory gene CEHC1 encoding an FBXO3 protein results in normoxic expression of HYDA genes in Chlamydomonas reinhardtii

Oxygen is known to prevent hydrogen production in Chlamydomonas, both by inhibiting the hydrogenase enzyme and by preventing the accumulation of HYDA-encoding transcripts. We developed a screen for mutants showing constitutive accumulation of HYDA1 transcripts in the presence of oxygen. A reporter gene required for ciliary motility, placed under the control of the HYDA1 promoter, conferred motility only in hypoxic conditions. By selecting for mutants able to swim even in the presence of oxygen we obtained strains that express the reporter gene constitutively. One mutant identified a gene encoding an F-box only protein 3 (FBXO3), known to participate in ubiquitylation and proteasomal degradation pathways in other eukaryotes. Transcriptome profiles revealed that the mutation, termed cehc1-1, leads to constitutive expression of HYDA1 and other genes regulated by hypoxia, and of many genes known to be targets of CRR1, a transcription factor in the nutritional copper signaling pathway. CRR1 was required for the constitutive expression of the HYDA1 reporter gene in cehc1-1 mutants. The CRR1 protein, which is normally degraded in Cu-supplemented cells, was stabilized in cehc1-1 cells, supporting the conclusion that CEHC1 acts to facilitate the degradation of CRR1. Our results reveal a novel negative regulator in the CRR1 pathway and possibly other pathways leading to complex metabolic changes associated with response to hypoxia.

plant biology↗

bioRxiv2023

A time- and space-resolved nuclear receptor atlas in mouse liver

The unique functional versatility of the liver is paramount for organismal homeostasis. Both liver development and adult functions are controlled by tightly regulated transcription factor networks, within which nuclear receptors regulate essential functions of parenchymal and non-parenchymal cells. Acting as transcription factors sensitive to extracellular cues such as steroidal hormones, lipid metabolites, xenobiotics... and modulated by intracellular signaling pathways, nuclear receptors orchestrate many aspects of hepatic physiology. While liver functional zonation and adaptability to fluctuating conditions are known to rely on a sophisticated cellular architecture, a comprehensive knowledge of nuclear receptor functions in the different liver cell types is still lacking. As a first step toward the accurate mapping of nuclear receptor functions in mouse liver, we characterized their levels of expression in whole liver as a function of time and diet, and explored nuclear receptor isoform expression in hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells and liver sinusoidal cells. In addition, we leveraged liver single cell RNAseq studies to provide here an up-to-date compendium of nuclear receptor expression in mouse liver in space and time.

molecular biology↗