Effect of Bisphenol A (BPA) on Locomotor System Development in Zebrafish Embryos

Bisphenol A (BPA) is a chemical commonly found in plastics and can be toxic. Previous research has revealed exposure to BPA affects locomotor system development. In studies using zebrafish, results showed less spontaneous movement, swimming speed, touch response, and total distance swam after being exposed to BPA during development. Results from a study completed by a previous student of Dr. Lewis showed embryos exposed to BPA later in development had a more significant impact on their locomotor system compared to embryos exposed earlier. My project is a follow-up study to further investigate how the timing and concentration of BPA exposure affect locomotor system development. Embryos were treated at two different times in development, with two different groups included at each point. One group was exposed to 30 ?m BPA and the other to 50 ?m BPA, a control group was also included and was not exposed to any BPA. After completing a touch-evoked swimming assay, embryos exposed to BPA at both time periods had significantly fewer positive responses compared to the control. A response was considered positive if the embryo moved as a result of being touched. Embryos treated with BPA swam slower and had shorter total distances swam compared to the control. There were no significant differences between the embryos treated at the different time periods or the concentrations used. Results indicate BPA does negatively affect locomotor system development; however, the timing and concentration of exposure did not affect development differently.

Slide 1:

Hello, my name is Alyssa Lyon and my project further investigated the effect of bisphenol A (BPA) on locomotor system development in zebrafish embryos. My mentor is Dr. Lewis, in the Interdisciplinary Program in Neuroscience (IPN).

Slide 2:

BPA is a chemical commonly found in plastics. It can also result from municipal waste, causing it to be found in bodies of water. BPA is a toxic chemical; exposure to it can be from diet, air, or having it come into contact with the skin.

Slide 3:

Previous research has provided evidence BPA negatively impacts locomotor system development in zebrafish. Exposure to BPA led to a less spontaneous movement, touch-response, swimming speed, & total distance swam. Some evidence suggests the timing of exposure affects the impact BPA has on development differently. A previous student of Dr. Lewis’ completed a study where results showed embryos treated later in development had more locomotor deficits compared to the ones treated early on. My project was a follow-up to this study to further investigate how the timing and concentration of BPA exposure affect locomotor system development in zebrafish embryos.

Slide 4:

The research question for this project included “During which developmental period and at what concentration, does BPA affect locomotor system development the most?” It was hypothesized the embryos were treated later in development and at a higher concentration, then they would have the most developmental deficits.

Slide 5:

The George Mason University Institutional Animal Care and Use Committee approved all animal studies. *AB wild-type embryos were used. The treatment groups included embryos treated between 0-24 hours post fertilization (hpf) and ones treated between 24-48 hpf. At both time periods, 30 ?M & 50 ?m BPA was tested. A control group was included and was not exposed to any BPA. At 48 hpf, all groups were analyzed. A touch-evoked swimming assay was used to evaluate their locomotor response. The embryos were touched on the back of the head with a dissecting needle, if they moved it was considered a positive response. Videos were recorded and processed using FIJI to calculate the velocity and displacement of the embryos.

Slides 6-11:

A representative video of the locomotor response from each group is shown. The control had normal movement, while the experimental groups had impaired locomotor ability. There is also a difference in body shape between the control and experimental embryos.

Slide 12:

A touch-evoked swimming assay was used to analyze the embryos’ locomotor response. The embryos were touched on the back of the head with a dissecting needle. If they moved as a result of being touched, it was considered a positive response. BPA-treated embryos had significantly fewer positive responses compared to the control. There were no differences between treatment groups or the different concentrations.

Slide 13:

Displacement was found using video analysis of the touch-evoked swimming assay. The embryos exposed to BPA had a significantly shorter displacement than the control, meaning their total distance swam was much smaller. There again was no difference between when the groups were treated or at what concentration of BPA.

Slide 14:

Velocity was found using video analysis of the touch-evoked swimming assay. Embryos treated with BPA had a significantly slower velocity compared to the controls., indicating they were moving slower. There was no significant difference in velocity between treatment groups or the different concentrations. This suggests the timing of exposure did not impact locomotor development differently. There were also no significant differences between the concentrations used.

Slide 15:

Results show BPA negatively affects locomotor system development. BPA-treated embryos had significantly fewer positive responses, shorter displacement, and slower velocity compared to the control. There were no significant differences between the treatment groups, suggesting the timing of exposure does not change the effect BPA has on development. There was also no difference between the two concentrations used, indicating BPA has the same effect despite how much is present.

Overall, these results provide evidence that BPA exposure during development leads to locomotor system deficits. Treatment groups had significant differences in velocity, displacement, and locomotor responses compared to the control. The timing and concentration of BPA exposure did not have significant differences, suggesting they do not change the effect of BPA.

Future work should include immunofluorescent imaging, exposing embryos at other times in development to narrow down when the locomotor system is the most susceptible to BPA, investigating molecular mechanisms of BPA, and determining which type of motor neurons are the most affected by BPA.

Slide 16:

Thank you to Dr. Lewis for being my mentor this semester and helping me with this project. Thank you to OSCAR for funding my project and giving me this opportunity.