Presenter Information

Sushmita AdhikariFollow

Advisor Information

Dr. William Tapprich

Location

Dr. C.C. and Mabel L. Criss Library

Presentation Type

Poster

Start Date

2-3-2018 10:45 AM

End Date

2-3-2018 12:00 PM

Abstract

Introduction and Methods: Fear is a basic, conserved emotion that is essential for survival, yet little is known about how fear responses evolved. This research combined gene expression and behavioral analyses to study the evolution of the neuronal network that regulates fear behaviors. Using in situ hybridization, we examined the expression patterns of three genes, protein kinase C δ (prkcd), gastrin-releasing peptide (grp), and glypican 3 (gpc3), that are implicated in fear behaviors in Danio rerio (zebrafish), Xenopus tropicalis, and Gallus gallus domesticus. Additionally, anxiety behaviors were examined in young zebrafish that lacked genes for grp, grp receptor (grpr), and gpc3. We measured how often the fish were located on the edge vs. center of a well, and how often they were located in the upper vs. lower halves of the well in the presence of a still or moving ball, respectively. Our working hypothesis is that homologs of genes that mediate fear behaviors in mammals are expressed in amygdalar-like areas in all vertebrate animals and can be used to identify the functional roles of these genes in the neuronal network that underlies conserved fear behaviors.

Results: In situ hybridization studies revealed that the grp, gpc3, and prkcd genes are expressed in homologous regions in the forebrains of fish, amphibians and chicks, as compared to mammals. The grp -/- zebrafish spent less time near the edge (p < 0.0072) in presence of the moving ball, but showed no difference in upper vs. lower preference, compared to heterozygous and wildtype fish. This is either a consequence of network remodeling in the absence of grp during development, or due to the small sample size. Neither the grpr -/- nor gpc3 -/- fish showed a change in edge preference compared to het and wt fish. Wt, het, and mutant fish avoided the moving ball (p < 0.005) and preferred the stationary field. However, grpr -/- avoided the moving ball to a greater extent, as compared to wt and het fish (p = 0.125), and significance may be resolved with a greater sample size. We expect that with a larger sample size, the wt, het, and mutant fish will all display a significant preference for the side of the well without the moving ball.

Conclusions: The comparable patterns of grp, gpc3, and prkcd expression support our hypothesis that despite embryological differences in forebrain development among diverse vertebrates, the neurons that regulate fear are organized in similar networks within amgydalar-like regions. This patterning suggests that the neural network for fear regulation has been evolutionarily conserved amongst vertebrates. Furthermore, the fear and anxiety behaviors in young grp, grpr, and gpc3 (-/-) mutant zebrafish support our hypothesis that homologs of these genes have conserved roles in regulating fear behaviors in divergent vertebrates including mammals and fish.

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COinS
 
Mar 2nd, 10:45 AM Mar 2nd, 12:00 PM

Comparison of Amygdalar Neuronal Networks that Regulate Fear Behaviors among Vertebrates

Dr. C.C. and Mabel L. Criss Library

Introduction and Methods: Fear is a basic, conserved emotion that is essential for survival, yet little is known about how fear responses evolved. This research combined gene expression and behavioral analyses to study the evolution of the neuronal network that regulates fear behaviors. Using in situ hybridization, we examined the expression patterns of three genes, protein kinase C δ (prkcd), gastrin-releasing peptide (grp), and glypican 3 (gpc3), that are implicated in fear behaviors in Danio rerio (zebrafish), Xenopus tropicalis, and Gallus gallus domesticus. Additionally, anxiety behaviors were examined in young zebrafish that lacked genes for grp, grp receptor (grpr), and gpc3. We measured how often the fish were located on the edge vs. center of a well, and how often they were located in the upper vs. lower halves of the well in the presence of a still or moving ball, respectively. Our working hypothesis is that homologs of genes that mediate fear behaviors in mammals are expressed in amygdalar-like areas in all vertebrate animals and can be used to identify the functional roles of these genes in the neuronal network that underlies conserved fear behaviors.

Results: In situ hybridization studies revealed that the grp, gpc3, and prkcd genes are expressed in homologous regions in the forebrains of fish, amphibians and chicks, as compared to mammals. The grp -/- zebrafish spent less time near the edge (p < 0.0072) in presence of the moving ball, but showed no difference in upper vs. lower preference, compared to heterozygous and wildtype fish. This is either a consequence of network remodeling in the absence of grp during development, or due to the small sample size. Neither the grpr -/- nor gpc3 -/- fish showed a change in edge preference compared to het and wt fish. Wt, het, and mutant fish avoided the moving ball (p < 0.005) and preferred the stationary field. However, grpr -/- avoided the moving ball to a greater extent, as compared to wt and het fish (p = 0.125), and significance may be resolved with a greater sample size. We expect that with a larger sample size, the wt, het, and mutant fish will all display a significant preference for the side of the well without the moving ball.

Conclusions: The comparable patterns of grp, gpc3, and prkcd expression support our hypothesis that despite embryological differences in forebrain development among diverse vertebrates, the neurons that regulate fear are organized in similar networks within amgydalar-like regions. This patterning suggests that the neural network for fear regulation has been evolutionarily conserved amongst vertebrates. Furthermore, the fear and anxiety behaviors in young grp, grpr, and gpc3 (-/-) mutant zebrafish support our hypothesis that homologs of these genes have conserved roles in regulating fear behaviors in divergent vertebrates including mammals and fish.