Presenter: Tyler Ramos – Human Physiology
Faculty Mentor(s): Chundi Xu
Session: (In-Person) Oral Panel—Daily Dose of Proteins
How we perceive and integrate our experiences is the result of an intricate network of diverse neuron types, each with specific connectivity. To generate different neurons, signals in precursors give each neuron its unique neuronal fate. Subsequently, a combination of proteins called homeodomain transcription factors (TFs) grant neurons proper synaptic connectivity. The processes of fate selection and synapse assembly are sequential actions that have been characterized separately but are deeply connected. It is unknown if a common regulator exists between these two developmental steps. Our purpose is to test if a homeodomain TF can function as a regulator of both neuronal fate and synaptic connectivity. To pursue this, we use the lamina neurons (L1-L5) of the fruit fly, Drosophila melanogaster. We show that homeodomain TF Brain-specific homeobox (Bsh) is expressed in lamina precursor cells, which suggests it may play a role in establishing lamina neuron fate. Using cell- specific knockdown and tracing methods, we found removing Bsh generates L1 and L3 neurons at the expense of L5 and L4 neurons, respectively. In L4 neurons, Bsh activates another protein, Apterous (Ap). Knockdown of Bsh and Ap in L4 neurons resulted in the loss of a synapse recognition molecule and altered synaptic connectivity. We propose that the homeodomain TF Bsh functions as a regulator of both neuronal fate and synaptic connectivity, which may be a conserved developmental mechanism across organisms.