Research Projects

Our earlier work revealed that the C. elegans gene plp-1 (Pur alpha Like Protein-1) functions in the germline gene-silencing (GGS) process. PLP-1 belongs to the conserved PURA family of proteins (also known as Pur alpha or Pur α; Pur stands for purine-rich element binding) present in both prokaryotes and eukaryotes including human. PURA binds single-stranded DNA and RNA, and certain proteins as well. Studies have shown that PURA is present on RNA granules such as the neuronal transport granules and stress granules. PURA’s RNA granule association appears conserved as we and another group found PLP-1 to be localized on the germ cell-specific RNA granules called the P granules. Two independent groups generated PURA knockout mice which displayed abnormalities in postnatal neurodevelopment. Possibly, PURA has an important role in RNA granules which are crucial for mRNA transport in neurons and gene silencing and translational control in germ cells. Intriguingly, our ongoing work identified a significant overlap between the lists of transcripts upregulated by DAF-16—the key FOXO transcription factor negatively regulated by the insulin/insulin-like growth factor-1 (IGF-1) signalling (IIS) pathway—and upregulated in plp-1(-) [potentially downregulated by PLP-1]. Normally, signalling via IGF-1 receptor DAF-2 suppresses DAF-16 activity. In daf-2(-) mutants, the transcript levels of DAF-16 target genes increase over wildtype levels, which enables the daf-2(-) mutant to live twice as long as the wildtype. Strikingly, in daf-2(-); plp-1(-) double mutants, the levels of some transcripts common to DAF-2 and PLP-1 lists mentioned above rise further by several folds over their levels in daf-2(-). Surprisingly, the daf-2(-); plp-1(-) double mutants die earlier than the wildtype, which tempts us to speculate that the hyper elevation of these transcripts is detrimental. We hypothesize that PLP-1 moderates DAF-16’s effect on the expression of at least some of its target genes and that this moderation is crucial for normal lifespan. Here, we plan to test this hypothesis. Experts in the field have long been curious about the effects of enhancing the expression of DAF-16 target genes over that observed in daf-2(-) mutants. Now we have a unique double mutant [daf-2(-); plp-1(-)] to address this curiosity. We believe that our findings will have a significant impact on investigations focused on PURA as well as those focused on lifespan regulation by the IIS pathway. We have three objectives: 1. Determine the genetic relationship between plp-1 and the IIS pathway components: In this objective, we plan to test if the daf-2; plp-1 double mutant phenotype is dependent on the misregulation of IIS, or an unknown activity of DAF-2 that is not connected to its role in the IIS cascade. 2. Determine the role of PLP-1 on the expression of DAF-16 target genes: Our metanalyses suggest a common set of target genes for DAF-16 and PLP-1. In our preliminary experiments, the transcript levels of a few of these genes were enhanced several folds in daf-2(-); plp-1(-) worms when compared to daf-2(-) single mutants. We plan to confirm these results and systematically analyze the effect of PLP-1 on the expression of DAF-16 targets. 3. Determine the tissue(s) in which PLP-1 expression is crucial for lifespan regulation: The PLP-1 protein is present in many cell types including germ cells, intestine, neurons and hypodermis. We plan to express PLP-1 in specific tissues in daf-2(-); plp-1(-) worms to determine the tissue(s) in which PLP-1 is crucial for the normal lifespan as well as the extended lifespan of daf-2(-). Results of these experiments, given the molecular and functional conservation of PLP-1 and the IIS pathway, will inform investigations on their mammalian counterparts. The potential connection between PLP-1 and the IIS pathway, if established, will be a new link of significant importance in the gene regulatory network.