Irene Lee Ava C. Knickerbocker Charlotte R. Depew Elizabeth Martin Jocelyn Dicent Gary W. Miller Meghan L. Bucher ^*

• Columbia University, New York City, New York, United States

Introduction: The nematode, Caenorhabditis elegans (C. elegans), is an advantageous model for studying developmental toxicology due to its well-defined developmental stages and homology to humans. It has been established that across species, dopaminergic neurons are highly vulnerable to neurotoxicant exposure, resulting in developmental neuronal dysfunction and age-induced degeneration. C. elegans with genetic perturbations in dopamine system proteins can provide insight into the mechanisms of dopaminergic neurotoxicants. Here, we present a comprehensive analysis on the effect of gene mutations in dopamine-related proteins on body size, development, and behavior in C. elegans. Methods: We analyzed C. elegans that lack the ability to sequester dopamine (OK411), that overproduce dopamine (UA57), and a novel strain (MBIA) generated by genetic crossing of OK411 and UA57, which both lacks the ability to sequester dopamine into vesicles and additionally endogenously overproduces dopamine. The MBIA strain was generated to address the hypothesis that an endogenous increase in production of dopamine can rescue deficits caused by a lack of vesicular dopamine sequestration. These strains were analyzed utilizing multiple methods for body size, developmental stage, reproduction, egg laying, motor behaviors, and neuronal health. Results: Our results further implicate proper dopamine synthesis and sequestration in the regulation of C. elegans body size, development through larval stages into gravid adulthood, and motor functioning. Furthermore, our analyses demonstrate that body size in terms of length is distinct from developmental stage as fully developed gravid adult C. elegans with disruptions in the dopamine system have shorter body lengths. Thus, body size should not be used as proxy for developmental stage when designing experiments. Discussion: Our results provide additional evidence that the dopamine system impacts development, growth, and reproduction in C. elegans. Furthermore, our data suggest that endogenously increasing the production of dopamine mitigates deficits in C. elegans lacking the ability to package dopamine into synaptic vesicles. The novel strain, MBIA, and novel analyses of development and reproduction presented here can be utilized in developmental neurotoxicity experiments.