The Ashrafi paper focuses on the gene knockouts that produced 2 outcomes: decreased fat droplet size and increased fat droplet size. The third outcome they mentioned was RNAi inactivation of another 261 genes that caused reduced fat but also was accompanied by developmental problems. One of such problems was sterility of the organism. What connection do you think exists between reproduction activity and fat storage that could explain the proteins necessary for both processes?
In this paper, the authors mention the role of serotonin in the regulation of body fat in passing. This stuck out to me because I researching depression for my project. I am interested in learning more about the role of serotonin in fat regulation. Do any papers cite this Ashrafi et al paper giving insight into the role of serotonin in fat regulation? If not, what is your hypothesis for its role? The paper mentions it could affect food intake behavior or metabolism. I suspect it is the first option.
In the article "Genome-wide RNAi analysis of Caenorhabditis elegans fat regulatory genes," by Ashrafi, et al., they mentioned a group of RNAi-inactivated genes that cause reduced fat, but also larval arrest, lethality, or sterility. They go on to say that it would be difficult to tease apart the roles of these genes in fat storage and in other processes. Do you think it would be possible to study these roles separately through the use of an interaction screen or another method?
The article "Genome-wide RNAi analysis of C. elegans fat regulatory genes" stated that mice that are deficient in either Tubby or in HTR2C are obese. Are all of the mice that are deficient in one of these obese and are there any mice that did not have either of these deficiencies but were still obese? The article expanded on statements concerning body fat but I did not see any direct elaboration on this obesity comment, which seemed like a pretty strong statement.
In the Ashrafi, et al. paper they note that the RNAi library only includes about 12% of genes that function in the nervous system and that RNAi clones may only result in partial inactivation in neurons. Do you think this is an important hole in their research since the nervous system is likely involved in feeding and food storage behaviors that could lead to obesity?
In the Ashrafi et al paper, they mentioned that some of the RNAi knockouts distorted the pattern of fat droplet deposition. Do you know if there are "categories" of RNAi's that alter the deposition in a similar manner? If so, what implications could that have for homologous mechanisms in larger organisms?
I'm wondering about the functional significance of a screen like the one presented in the Ashrafi, et al. paper. From everything that we've learned (since reading a few obesity-related papers) it seems like the development of obesity is an incredibly complex process. It would seem to me like research would be better focused on making connections between these widespread influencers of obesity in order to draw more causal connections. Is there evidence that I'm missing that might implicate a central molecule or pathway in the development of obesity? Do you think the most efficient way to decode the process of obesity development really to tackle each gene one by one?
In the primary research paper, the authors cited numerous points of missing information--many genes could not be observed due to severe phenotypic results with RNAi and only about 86% of genes are included in the RNAi library. Knowing this, how reliable or useful is this study? Is it just a starting point for the use of RNAi in C. elegans to study fat regulation or do you see its results as being more meaningful than that?
In the Ashrafi et. al. they tested 305 RNAi clones of fat regulatory genes on three mutant C. elegans strains which caused increased fat, to determine which clones resulted in a reduction in fat. Out of the 305 tested only 32 lead to a significant reduction in fats. After they came to discover this, the paper mentioned that many other C. elegans genes that regulate fat production have yet to be identified, and that their list of fat regulatory genes identified with 150 of the 30,000 mammalian genes. Given the variation in the genes from C. elegans to mammals, and the environments that each specifically endure, do you think that these 150 genes that identified with mammals from C. elegans is worth pursuing?
How is using RNAi different from creating a knockout form of an organism? Is RNAi as simple to use in a model organism such as a mouse? I have worked with C. elegans an RNAi in the past and I know how simple it is to have them ingesting the double stranded RNA, but I am curious as to how this would be done in a more complex organism. Another question I have is how successful is RNAi generally? Does the concentration of double stranded RNA that the C. elegans ingest affect how efficiently gene expression is blocked?
In the paper by Ashrafi, et al, it's mentioned that RNAi inactivation of certain genes caused not justs reduction of body fat but also larval arrest, sterility, and lethality. Can you speculate about the link between the two phenotypes? Without viable worms is this data even good enough to make a thorough conclusion?
In the review paper "High-throughput RNAi in Caenorhabditis elegans: genome-wide screens and functional genomics”, the author says that by using RNAi techniques, functional genomic RNAi analyses and high-throughput RNAi can be done easily. However, even though RNAi techniques are widely used, i wonder whether there is any drawback of RNAi techniques or not.
In the paper by Ashrafi et al., they mention that it is much more difficult to effectively use RNAi with genes in the nervous system than in the rest of the organism. Why do you think this is, and how might it affect the results they got on neuronal regulators of feeding and metabolism?
In the Ashrafi et al. paper, they discuss the important findings in worms to further research on treatments for obesity and diabetes in humans. However, the paper states that an identifiable leptin sequence has not been discovered in c. elegans. Do you think that this would cause difficulties in finding new treatments, since many of the market drugs targeting obesity now have some effect on leptin signaling?
The review by Sugimoto talks about how C. elegans and some other small invertebrates have systematic RNAi while more complex animals have RNAi responses that do not spread throughout the body. Why might this difference exist? Is there an evolutionary reason for this difference?
In the paper the authors reference gene inactivations that alter fat content but have no affect on viability or fertility of the organisms. The statement included no reference, but I found no further mention of viability testing of these organisms. How was this viability and fertility testing determined?
In the genome-wide RNAi paper, the authors screened the entire C.elegans genome for genes implicated in the fat biosynthesis pathway. They make no mention of the time commitment that this technique required. Are large scale RNAi screens like this a viable way of identifying genes in higher organisms with more genes?