GABAA α subunit control of hyperactive behavior in developing zebrafish

Abstract

GABAA receptors mediate rapid responses to the neurotransmitter GABA and are robust regulators of the brain and spinal cord neural networks that control locomotor behaviors, such as walking and swimming. In developing zebrafish, gross pharmacological blockade of these receptors causes hyperactive swimming, which is also a feature of many zebrafish epilepsy models. Although GABAA receptors are important to control locomotor behavior, the large number of subunits and homeostatic compensatory mechanisms have challenged efforts to determine subunit-selective roles. To address this issue, we mutated each of the eight zebrafish GABAA α subunit genes individually and in pairs using a CRISPR-Cas9 somatic inactivation approach, then we examined the swimming behavior of the mutants at two developmental stages, 48 and 96 hours post fertilization (hpf). We found that disrupting the expression of specific pairs of subunits resulted in different abnormalities in swimming behavior at 48 hpf. Mutation of α4 and α5 selectively resulted in longer duration swimming episodes, mutations in α3 and α4 selectively caused excess, large-amplitude body flexions (C-bends), and mutation of α3 and α5 resulted in increases in both of these measures of hyperactivity. At 96 hpf, hyperactive phenotypes were nearly absent, suggesting that homeostatic compensation was able to overcome the disruption of even multiple subunits. Taken together, our results identify subunit-selective roles for GABAA α3, α4, and α5 in regulating locomotion. Given that these subunits exhibit spatially restricted expression patterns, these results provide a foundation to identify neurons and GABAergic networks that control discrete aspects of locomotor behavior.

Amyotrophic Lateral Sclerosis-Associated Persistent Organic Pollutant cis-Chlordane Causes GABAA-Independent Toxicity to Motor Neurons, Providing Evidence toward an Environmental Component of Sporadic Amyotrophic Lateral Sclerosis

“…The cischlordane-induced behavior is also distinct from both the picrotoxin-treated zebrafish here and recent work in which the expression of individual and different combinations of GABA A subunits were mutated in zebrafish, again confirming that cischlordane disrupts different or additional mechanisms than GABA A receptors. 38 While the zebrafish still develop during our test period, intact NMJs are formed before the treatment began, thus leading us to hypothesize that these observations are not driven by developmental defects. The lack of observed muscle fiber organization abnormalities also supports this.…”

“…Additionally, cis- chlordane induced a unique larval zebrafish touch-evoked behavioral response culminating in decreased swimming efficiency, further illustrating the degeneration of the motor system. The cis -chlordane-induced behavior is also distinct from both the picrotoxin-treated zebrafish here and recent work in which the expression of individual and different combinations of GABA A subunits were mutated in zebrafish, again confirming that cis- chlordane disrupts different or additional mechanisms than GABA A receptors . While the zebrafish still develop during our test period, intact NMJs are formed before the treatment began, thus leading us to hypothesize that these observations are not driven by developmental defects.…”

Sulindac selectively induces autophagic apoptosis of GABAergic neurons and alters motor behaviour in zebrafish

“…They are involved in the regulation of multiple neural circuits, especially in regulating autonomic and motor behaviours 60 . Recently, it was reported that disrupting the normal development of GABAergic neurons during the early developmental stage of zebrafish leads to hyperactive motor behaviours 61 , 62 . Similarly, a study conducted on mice has demonstrated that dysfunction of ventral tegmental area GABA neurons can cause hyperactivity and manic-like behaviour 63 .…”

In Search of a Target Gene for a Desirable Phenotype in Aquaculture: Genome Editing of Cyprinidae and Salmonidae Species

“…Cleft lip and cleft palate mutants also have been tested [ 92 ]. Edited zebrafish are used to study feeding behavior [ 93 ], social behavior [ 94 , 95 ], hyperactivity [ 96 ], domestication patterns [ 97 ], and circadian rhythms [ 98 ]. These models are used to study the genetic basis of disease development and drug testing.…”