Investigation of the Function of Mammalian Trisomy 21 Gene Dyrk1A on Neuromuscular Signaling and the Restorative Effects of Polyphenol EGCG in C. elegans

Down syndrome (DS), or trisomy 21, is often characterized in humans by motor dysfunctions, muscle weakness, and abnormal movement patterns, in addition to cognitive defects. While the specific proteins and processes involved in DS abnormalities are largely unknown, it has been observed that the serine-threonine kinase Dyrk1A, present on chromosome 21 in humans, chemically modifies neuronal proteins and is overexpressed at 1.5 times normal levels in DS patients. Recent work found that Dyrk1A also functions at the neuromuscular junction (NMJ). Transgenic mice overexpressing Dyrk1A display neuromuscular defects such as hyperactivity, delayed neurological development, and altered learning. NMJ involvement, including altered neurotransmission and abnormal presynaptic protein localization and function, also was observed. To further characterize the role of Dyrk1a at the NMJ and to develop a model for screening chemical treatments for neuromuscular DS phenotypes, we are using Caenorhabditis elegans roundworms as a model due to their simple nervous systems and easily characterized behaviors. We hypothesize Dyrk1a acts in motor neurons to control NMJ signaling and predict that neuronal overexpression of Dyrk1A will cause defects in neuromuscular signaling, which we will assess using assays for muscle contraction. Pending an observed difference in behavior, we will apply the green tea catechin EGCG to attempt to rescue NMJ function in the transgenic animals. ECGC is a selective inhibitor of Dyrk1A that decreased the severity of changes in brain weight and long term memory impairment in transgenic mice over expressing Dyrk1A. Currently, Dryk1a overexpression constructs have been made, and generation of transgenics is underway