February 20, 2015

Patrick Popa

Major and Classification

Biology, Psychology

Faculty Mentors

  • Professor Albert A. Herrera


  • Biological Sciences, Neurobiology

McNair Project

“An Assessment of Synapse Elimination in Xenopus laevis”

Using various stages of Xenopus laevis frog tadpoles as reference specimens, this research seeks to answer how synapse elimination occurs (i.e. the underlying mechanisms behind mononeuronal innervation) and the possible role of synapse activity (synaptic efficacy) in this process during embryonic development. Data will be collected using cholinesterase stained pectoral muscle fibers from stage 56-66 tadpoles. In adults, the number of neuromuscular junctions and motor inputs (axons) per muscle fiber is fixed. However, during embryonic development the number of neuromuscular junctions and motor inputs vary but then finalize as embryonic development terminates. Initially, there is excessive synapse formation which is followed by synapse elimination. This synapse elimination results in a reduction in polyneuronal innervation, separation of motor units, and establishment of the adult pattern of mononeuronal innervation. There is also evidence that suggests that synapse elimination is feasible in adults. The splicing of motor axons in adults causes regeneration to occur; this process establishes polyneuronal innervation akin to what is seen in early embryonic development. However, mononeuronal innervation occurs shortly thereafter, again similar to what is seen in embryonic development (McArdle). This finding has very important implications. It may elucidate the mechanism behind responses to neural injury. Therefore this preliminary research’s task is to determine at what tadpole stages do significant changes in the number of NMJs per fiber occur, and to examine the possible concurrent elimination of inputs into each NMJ as a function of synchronous activity in order to understand the process of synapse elimination.