The National Institutes of Health this month awarded three RNAi-related grants: two funding research into the role of microRNAs in hair follicle development and mental disorders, and one supporting the early-stage development of a targeted nanoparticle that acts as both an siRNA delivery vehicle and an imaging agent.
The first grant, which was awarded to University of Pennsylvania researcher Sarah Millar by the National Institute of Arthritis and Musculoskeletal and Skin Diseases, is designed to “define the global roles of miRNAs in skin homeostasis and to begin to identify specific miRNAs and their targets genes that are critical for normal skin function,” according to its abstract.
“We’re aiming at a fundamental understanding” of miRNAs, Millar told RNAi News this week. “This is obviously a whole new level of gene regulation, and … we want to know how [miRNAs] contribute to normal skin biology and development.”
The NIH-funded effort builds on earlier work conducted by Millar and her colleagues in which they found that Dicer was essential for the development and maintenance of hair follicles in mice lacking the pre-miRNA-processing enzyme in their skin.
“Basically what we saw in the first paper was that there was a failure of normal hair follicle development [in the mouse models] — the hair follicles started developing but then they degenerated,” she explained. “So one of the questions we want to ask was whether Dicer is required only during development, or if it is also required in post-natal life in order to maintain hair follicles and skin.”
Additionally, Millar is aiming to determine whether this phenotype is actually due to the loss of function of certain miRNAs, and if so, which ones.
To address this question, the researchers will inducibly delete epidermal Dicer in post-natal mice using floxed Dicer mice generated by collaborator Greg Hannon at Cold Spring Harbor Laboratory, as well as inducible Cre mice created by several other groups, Millar said.
Additionally, the team plans to delete Dicer specifically within hair follicle stem cells; determine whether epidermal deletion of Drosha, another essential miRNA processing enzyme, replicates the effects of epidermal Dicer deletion; and characterize miRNAs expressing in different skin compartments with the goal of identifying their target mRNAs.
Millar said that while she expects her work to contribute to the overall understanding of miRNAs, it could also have a more clinically relevant impact given the increasing evidence that miRNAs play a role in tumorigenesis.
“There is the feeling that [skin-specific miRNAs] might play a role in skin cancers,” she noted.
Millar’s grant runs from July 12 through June 30, 2012, and is worth approximately $215,000 each year.
The second grant was awarded to the University of Chicago’s Chun-Yu Liu by the National Institute of Mental Health to fund an examination of the role of miRNAs in bipolar disorder and schizophrenia.
“To date there has been little study of genomic variation in miRNA genes, the relationship between miRNA variants and psychiatric disorders, or [on] miRNA variants correlated with variations in gene expression in the brain,” the grant’s abstract states. “To promote such knowledge, we propose to use deep re-sequencing to exhaustively identify variants in all known miRNAs.”
With these data, Liu and colleagues will then study the correlation between the variants and gene expression in the brain, as well as the association of the variants with schizophrenia and bipolar disorder.
The team will re-sequence all 462 known human miRNA genomic DNA sequences in 310 Caucasian individuals, including ones with schizophrenia and bipolar disorder, the abstract notes. The researchers will then test association of disease with genotypes of these variants in a “large collection” of case-control bipolar and schizophrenia samples.
Additionally, the researchers will look for correlations between sequence variants in miRNAs and gene expression data in brain and lymphoblastoid cell samples.
“The idea is to combine imaging and delivery. These nanoparticles are a contrast agent in that … their distribution to the tumor can be visualized non-invasively by magnetic resonance imaging.”
Liu told RNAi News this week that it is not clear what technology will be used to conduct the sequencing experiments, but that this is expected to be worked out at an upcoming meeting with academic collaborators.
“These findings will potentially enhance our understanding of the miRNA genes and their potential roles” in bipolar disorder and schizophrenia, while opening the door for possible new diagnostics and therapeutics for the conditions, the abstract states.
Liu’s grant is set to run from July 1 to June 30, 2011, and is worth roughly $2.4 million in total costs.
The last grant was awarded to Massachusetts General Hospital’s Zdravka Medarova by the National Cancer Institute to support her effort to further develop dual-purpose nanoparticle probes “for in vivo transfer of synthetic siRNAs to tumors and the simultaneous imaging of [their] accumulation in target tissues,” according to its abstract.
“The idea is to combine imaging and delivery,” Medarova told RNAi News this week. “These nanoparticles are a contrast agent in that … their distribution to the tumor can be visualized non-invasively by magnetic resonance imaging.
“Because they also carry small interfering RNAs, we can track the delivery of [the RNAi payload] to the tumor in a semi-quantitative way … [and] then correlate that to a therapeutic effect mediated by these small interfering RNAs,” she added.
The probes consist of cross-linked superparamagnetic iron oxide nanoparticles labeled with a near-infrared dye and a peptide that targets the underglycosylated mucin-1 tumor-specific antigen, according to Medarova. She added that uMUC-1 is expressed by an estimated 50 percent of all human cancers, primarily adenocarcinomas.
“We did not develop these nanoparticles — they have been around for a while for magnetic resonance imaging,” she said. “The novelty of our idea was to conjugate them to siRNA molecules.”
Earlier this year, Medarova and her colleagues published data showing that the probes could be covalently linked to siRNAs and delivered into tumor models.
With funding from the NCI, she proposes to advance these early data into mouse models.
According to the grant’s abstract, Medarova and her colleagues will refine the synthesis and functionality of the probes, then examine their efficacy in animals. Specifically, they will test the probes’ therapeutic potential alone and in combination with chemotherapy.
“These studies represent an early step towards exploring the potential of siRNA for tumor therapy,” the abstract states. “In addition, our planned studies combine imaging and therapeutic agent delivery in a single nanoparticle, which is essential for cancer therapeutic … development and optimization.
Medarova’s project will run from July 13 to June 30, 2012. She said it is worth in excess of $1 million in total costs.