ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.

ZFIN is incorporating published figure images and captions as part of an ongoing project. Figures from some publications have not yet been curated, or are not available for display because of copyright restrictions.

Calcium imaging reveals broad neuronal activity triggered by light in gabrg2^−/−larvae. (A) Tg(neurod:GCaMP6f)^+/− and gabrg2^+/− were intercrossed, and neuronal activity was monitored under a confocal microscope (2.5 Hz) at 5 dpf. After a period of >30 min in complete darkness, switching on the laser induced a broad neuronal activity in both optic tecta in gabrg2^−/− (n=8) compared to gabrg2^+/+ siblings (n=7). ot, optic tectum; cb, cerebellum. (B) Fluorescence quantification in the optic tecta before and after laser exposure shows a significant increase of fluorescence in gabrg2^−/− larvae compared to wild-type siblings. Each point corresponds to the relative quantification of fluorescence from a frame with 400-ms exposure. (****P<0.0001, ***P<0.001, **P<0.01, *P<0.05, two-way ANOVA). (C) Single-plane light-sheet microscopy revealed marked hyperexcitability in the tectum in gabrg2^−/− fish. The left shows a maximum intensity projection of representative knock-out and wild-type larval fish recordings. The optic tectum shows a marked bilateral increase in fluorescence in the KO, with a much smaller response in the wild-type fish. The right shows ΔF/F normalized fluorescence intensity for 10 s after switching on visible light, with an early difference in the average amplitude of wild-type and KO tectal fluorescence. Inset shows area under the curve (a.u.c.) of the fluorescence traces from onset to 10 s. (D) A non-negative matrix factorization of regionally averaged fluorescence traces. The factor weights show distinct response patterns for bilateral tectum, bilateral cerebellum/rostral hindbrain and bilateral hindbrain regions (left), with distinct temporal profiles of the loading of these three factors (middle plot). In three-dimensional factorized state-space, there is a clear separation of wild-type and gabrg2^−/− responses early after being exposed to visible light.

Valproic acid (VPA) treatment alleviates the movement phenotype and neuronal hyperexcitability of gabrg2^−/−larvae. (A) Quantification of the maximum acceleration upon light stimulus before and after an acute VPA treatment of 200 µM for 2 h, showing the alleviating effect of VPA. (****P<0.0001, unpaired t-test.) (B) Representative swimming tracks (15 s following photic stimulus) showing that VPA exposure prevent the whirlpool behavior of gabrg2^−/− (5 dpf). (C,D) Calcium imaging and fluorescence quantification from gabrg2-KO Tg(neurod:GCaMP6f) larvae (5 dpf), showing that the neuronal hyperexcitability is relieved after VPA treatment (200 µM for 2 h). ot, optic tectum; cb, cerebellum. (****P<0.0001, ***P<0.001, **P<0.01, *P<0.05, two-way ANOVA).

The photic reflex seizures of gabrg2^−/−fish are transient during the early larval stage. (A) Quantification of the maximum acceleration upon light stimulus of gabrg2^−/− and gabrg2^+/+ siblings at different ages (from 3 to 11 dpf). A significant difference is observed at 3, 4, 5 and 6 dpf only. (****P<0.0001, ***P<0.001, unpaired t-test.) (B) Representative swimming tracks (15 s following photic stimulus) of gabrg2^+/+ versus gabrg2^−/− larvae at different ages, showing that the stereotypical whirlpool behavior is not observable from 8 dpf. Of note is that the phenotype is the strongest and the most penetrant at 5 dpf. (C) RT-PCR for gabra1 and gabrg2 transcripts over wild-type zebrafish development. The polr2d gene is used as a house-keeping gene. (D) Whole-mount in situ hybridization on whole-mount embryos using an anti-sense probe against gabra1 or gabrg2 transcripts. Both genes are strongly expressed in the brain and their expression is largely overlapping. (A sense probe is shown as a negative control.)