The Impact of Gabrb3 Expression Variation On Autism Spectrum Disorder Related Phenotypes in Mouse

Background: Several lines of evidence support a link between GABRB3, a GABA receptor subunit, and autism spectrum disorders. Total or conditional loss of this gene results in frequent post-natal lethality in mouse, with survivors exhibiting seizures and behavioral disorders. In contrast, haploinsufficiency results in variable gene expression and mild phenotypes that are gender, age and deletion parent-of-origin dependent. 

Objectives: To determine the phenotypic consequences of intermediate levels of Gabrb3 expression.

Methods: ShRNA-mediated Gabrb3-knockdown animals were generated on a C57Bl/6 background. Behavioral phenotypes were assessed in these, heterozygous gene knockout and wild-type control animals using standard protocols, including activity (wheel-running), anxiety (open field), exploratory (place preference & T-maze), socialization (interest, preference & memory: tethered & free interactions) and perseveration (radial maze).  

Results: As expected, both Gabrb3-knockdown (KD) and heterozygous knockout  (+/-) animals show behavioral differences from wild-type C57Bl/6 animals, with Gabrb3-KD animals exhibiting a phenotypic spectrum intermediate between Gabrb3^+/- and total-knockout (KO) animals. Post-natal lethality or gender imbalance in KD animals is not evident, but cannot be ruled out in the founder generation due to small numbers. Unlike Gabrb3^+/- animals, Gabrb3-KD animals exhibit hyperactivity reminiscent of surviving KO animals, but they do not exhibit the severe seizures seen in KO animals.

Conclusions: Phenotypic analyses of sh-mediated Gabrb3 knockdown animals complement studies using knockout and haploinsufficiency models, while avoiding early lethality and parent-of-origin dependent complications.