Alexander R Stanton

Background: 

    Diabetes is a disease caused by an aberrant metabolic pathway. Glucose, the primary sugar used for energy by the body, is absorbed into liver, muscle, and fat cells from the blood as a result of insulin signaling. Insulin is produced by specialized pancreatic cells called beta-cells. When beta cells have significantly down-regulated insulin production or the body loses insulin sensitivity, the organism is in a diabetic state. In this condition, the organism cannot metabolize glucose at an adequate rate - resulting in decreased energy levels. Sensing the high blood glucose content, the beta-cells attempt to compensate by increasing efforts to produce insulin. This effort exhausts the beta-cells, resulting in apoptosis. This phenomenon is one variation of  glucotoxicity and can cause life threatening problems with nerves, the heart, and other areas of the body.

     Insulin secretion is moderated by myriad factors. One of these regulatory factors is microRNA-375 (miR-375), known to repress insulin secretion. MicroRNAs bind to argonaute proteins in an RNA-induced silencing complex (RISC). Then, the short RNA sequence binds to the target DNA sequence, destabilizing or degrading the template. One of the targets of miR-375 is the gene for myotrophin, an important protein involved in insulin secretion - thereby decreasing glucose metabolism.
     In the pursuit of understanding the intricacies behind miR-375 regulation, the promoter region upstream of the gene has been characterized to an extent. The transcript contains four regions upstream of the gene that are highly conserved between species, designated block 1, 2, 3, and 4. The TATA box resides in block 2, and a possible enhancer site - including binding sites for Pdx1 and NeuroD1 - exists in blocks 1 and 2. In regards to repression, clone variants including blocks 3 and 4 express significantly less luciferase protein - suggesting a repressor site in one or both blocks. Previous research has not completely narrowed down this useful domain of the miR-375 promoter.
     The cAMP pathway has been implicated as a causal factor in the repression of miR-375 production. Increased cAMP levels have been shown to correlate to decreased levels of miR-375. This result indicates that the protein negatively regulating miR-375 is cAMP dependent - either by direct mediation or upstream pathway modulation. A likely protein family are the cAMP-response element modulators (CREMs). These proteins couple with cAMP and bind to regions called cAMP-response elements (CREs), and isoforms have been implicated in activation and repression.
     Regulation of insulin expression yields possibilities in the treatment of diabetic patients. Before this is feasible, a richer understanding of insulin production must be attained. By learning how miR-375 is repressed, interactions can be manipulated to improve insulin secretion.

 

Project:

     I'm investigating the involvement of HDAC1-mediated epigenetic repression in cAMP-regulated miR-375 expression. Additionally, I'm interrogating the conserved promoter regions, furthering its characterization.

 

Developing Project:

     Developing a gene curcuit that senses and moderates miR-375 in periods of physiologically high expression - thereby restoring insulin secretion and increased uptake of glucose.