Reduced Bmal1 expression results in decreased levels of clock proteins, including Per1, Per2, Cry 1, and Clock but increased mTOR activities in the brain Bmal1 knockout mice exhibited aberrant ultrasonic vocalizations during maternal separation, deficits in sociability and social novelty, excessive repetitive behaviors, impairments in motor coordination, as well as increased anxiety-like behavior. The novel object recognition memory remained intact.
References
Type
Title
Author, Year
Primary
Autistic-like behavior and cerebellar dysfunction in Bmal1 mutant mice ameliorated by mTORC1 inhibition
Haploinsufficiency of a Circadian Clock Gene Bmal1 ( Arntl or Mop3) Causes Brain-Wide mTOR Hyperactivation and Autism-like Behavioral Phenotypes in Mice
Model Type:
Genetic
Model Genotype:
Heterozygous
Mutation:
The helix-loop-helix domain within exon 4 and all of exon 5 were replaced with a neomycin resistance gene cassette.
Allele Type: Knockout
Strain of Origin: 129/Sv
Genetic Background: C57BL/6J
ES Cell Line: GS1
Mutant ES Cell Line: Model Source: Jackson Laboratory
Model Type:
Genetic
Model Genotype:
Homozygous
Mutation:
Conditional knockout mice have Bmal1 specifically deleted in cerebellar Purkinje cells, by expressing Cre transgene inserted into exon 4 of a Pcp2 gene (L7-Cre)
Allele Type: Conditional Knockout
Strain of Origin: 129S4/SvJae; (129X1/SvJ x 129S1/Sv)F1-Kitl+
Genetic Background: C57BL/6J
ES Cell Line: J1; R1
Mutant ES Cell Line: Model Source: Jackson Laboratory
Model Type:
Genetic
Model Genotype:
Homozygous
Mutation:
The helix-loop-helix domain within exon 4 and all of exon 5 were replaced with a neomycin resistance gene cassette.
Allele Type: Knockout
Strain of Origin: 129/Sv
Genetic Background: C57BL/6J
ES Cell Line: GS1
Mutant ES Cell Line: Model Source: Jackson Laboratory
Description: The levels of clock proteins, including Per1, Per2 Clock, and Cry 1, were decreased by ~50% in the forebrains of Bmal1 heterozygous mutant mice.
Description: There was no difference in the numbers of pretraining trials between Bmal1 heterozygous mutant mice and wildtype mice. Further, the motor performance was significantly improved in both wildtype and Bmal1 heterozygous mutant mice over eight trials. However, Bmal1 heterozygous mutant mice showed a significantly lower latency to fall and fell at significantly slower rotating speeds in Trials 1, 6, 7, and 8 compared to wildtype mice.
Description: Bmal1 knockout mice displayed markedly shorter latencies to fall and fell at slower rotating speeds compared with the wildtype mice. In contrast to the wildtype mice, the knockout performance was not improved by training.
Description: There was a significant decrease of cerebellar interneurons in the molecular layer of the Bmal1 knockout mice, but no difference in the number of cerebellar granule cells between wildtype and Bmal1 knockout mice.
Exp Paradigm: Fox2, NeuN
Description: The fraction of immature dendritic spines (filopodial or branched) was increased, whereas the fraction of mature dendritic spines (stubby or mushroom shaped) was decreased in the Purkinje cells of Bmal1 knockout mice.
Description: There was a significant increase of Purkinje cell soma length in the cerebellum of Bmal1 knockout mice compared with the wildtype mice.
Exp Paradigm: Calbindin-D
Description: There was a significant increase of Purkinje cell density in the cerebellum of Bmal1 knockout mice compared with the wildtype mice.
Exp Paradigm: Calbindin-D
Description: There was no difference in the thickness of the molecular layer of Bmal1 knockout mice, but a moderate decrease in the thickness of the granular layer compared with the wildtype mice.
Exp Paradigm: Hematoxylin and eosin staining
Description: Inhibitory postsynaptic currents (IPSCs) elicited by parallel fiber stimulation gradually increased in response to increasing stimulus intensity in wildtype and knockout mice. The amplitude of IPSCs was about two-fold higher in the Bmal1 knockout mice compared with the wildtype mice.
Description: For excitatory postsynaptic currents (EPSCs) elicited by parallel fiber stimulation, there was a two-fold increase in EPSC amplitudes in Bmal1 knockout mice compared with the wildtype mice. For EPSCs elicited by climbing fiber stimulation, there was a three-fold increase in EPSC amplitudes in Bmal1 knockout mice compared with the wildtype mice.
Exp Paradigm: Parallel fiber stimulation; Climbing fiber stimulation
Description: Bmal1 knockout mice show a remarkable reduction (~40%) of spontaneous firing rates in the Purkinje cells compared with wildtype mice. When both excitatory and inhibitory transmission were blocked, the spontaneous firing rates were not significantly affected by the blockers and the rate was also markedly reduced (~30%) in the knockout mice compared with the wildtype mice.
Description: Bmal1 knockout mice exhibited a significantly increased number of spontaneous grooming bouts, but there was no difference in overall time spent grooming.
Description: The number of bouts and duration of route tracing, as well as the percentage of time spent route tracing were increased in the knockout mice compared with the wildtype mice.
Description: Bmal1 heterozygous mutant mice spent significantly more time in the chamber containing the familiar mouse than in the chamber containing the novel mouse, and a similar time sniffing in both cages. No difference was detected in the number of entries to the familiar mouse and the novel mouse chambers in either the wildtype or Bmal1 heterozygous mice.
Description: Bmal1 knockout mice spent less time engaging in social interactions including anogenital sniffing, push-crawl, and following, compared with the wildtype mice. However, the time spent nose-nose sniffing was not different between the wildtype and the knockout mice.
Description: Bmal1 knockout mice spent similar time in both the empty chamber and the chamber containing the stranger mouse and in sniffing the two cages.
Description: Bmal1 heterozygous mutant mice spent similar time in the chamber containing the stranger mouse as the chamber containing the empty cage, and similar times sniffing the both cages, whereas wildtype spent a longer time in the chamber containing the stranger mouse than the empty cage chamber. No difference was detected in the number of entries to the stranger mouse and the empty cage chambers in either the wildtype or Bmal1 heterozygous mice.
Description: Wildtype mice exhibited a trend of decreasing in the number of calls, developing from P7 to P14, but no such trend was found in the Bmal1 heterozygous mutant mice; The number of calls was increased in both the Bmal1 mutant pups as compared to the wildtype mice at P14; Bmal1 heterozygous mutant mice exhibited a longer call duration compared to wildtype pups at P7.
Description: Bmal1 heterozygous mutant mice spent less time in the center zone, but more time in the outside zone during the open field test compared to wildtype mice.
Description: The level of Bmal1 was decreased by ~50% in the cerebellum and ~75% in the forebrain of the Bmal1 heterozygous mutant mice compared to wildtype mice.
Description: p-S6 labeling was colocalized with Calbindin-D (28k) labeling, indicating that mTORC1 activities are enriched in cerebellar Purkinje neurons; There was a pervasive upregulation of p-S6 levels in all cerebellar lobules in the Bmal1 heterozygous mutant mice compared to wildtype mice.
Description: Bmal1 deletion in the cerebellum led to an altered translational landscape with 304 differentially translated genes (DTGs); Among the DTGs, 6 upregulated and 6 downregulated genes appear in the SFARI database.
Description: A total of 444 differentially expressed genes (DEGs) were identified in the knockout cerebellum, comprising 264 upregulated and 180 downregulated genes compared with the wildtype cerebellum.
Description: Interestingly, double labeling for phospho-S6 and Calbindin-D (28k) revealed cellular colocalization of the two proteins in the PC soma, indicating enriched mTORC1 activities in Purkinje cells; Pervasive upregulation of phospho-S6 was found in all lobules in the knockout mice as compared with the wildtype mice.
Description: Hyperactivation of the mTORC1/S6K1 pathway was detected, as demonstrated by increased levels of phospho-S6K1(Thr389) and phospho-S6 (Ser240/244).
Description: p-S6 levels were increased by ~50% in the cerebellum and the forebrain of Bmal1 heterozygous mutant mice compared to the levels in the wildtype mice; The levels of p-mTOR and p-S6K1, but not the level of p-4E-BP, were increased by about 50% in the forebrain of Bmal1 heterozygous mutant mice.
Description: Conditional knockout mice displayed markedly shorter latencies to fall and fell at slower rotating speeds compared with Bmal1^flox/flox littermates.
Description: The fraction of immature dendritic spines was increased but the fraction of mature dendritic spines was decreased in the Purkinje cells of conditional knockout mice.
Description: There was a two-fold increase in the amplitudes of IPSCs elicited by parallel fiber stimulation in the conditional knockout mice compared with Bmal1^flox/flox littermates.
Description: There was a two-fold increase in the amplitudes of EPSCs elicited by parallel fiber stimulation in the conditional knockout mice compared with Bmal1^flox/flox littermates. Responses elicited by climbing fiber stimulation were not significantly different between genotypes.
Description: There was a significant reduction (~30%) of firing rates in the Purkinje cells of the conditional knockout mice compared with Bmal1^flox/flox littermates with or without blocking synaptic inputs into Purkinje cells.
Description: Conditional knockout mice exhibited a significantly increased water puff-induced grooming time and number of bouts compared to Bmal1^flox/flox littermates.
Description: Conditional knockout mice spent similar time in the chamber of and interacting with the novel mouse and familiar mouse, whereas Bmal1^flox/flox littermates spent significantly more time in the chamber with the novel mouse than in the chamber with the familiar mouse; The numbers of entries to the two side chambers were not different between genotypes.
Description: Bmal1 expression was diminished in the PCL but not changed in the GL, confirming specific abolition of Bmal1 expression in cerebellar Purkinje cells in the conditional knockout mice.
Description: Wildtype mice exhibited a trend of decreasing in the number of calls (p = 0.1181), developing from P7 to P14, but no such trend was found in the Bmal1 homozygous mutant mice. The number of calls was increased in the Bmal1 homozygous pups at P7 and increased in both the Bmal1 mutant pups compared to the wildtype mice at P14. Bmal1 homozygous mutant mice exhibited a longer call duration compared to both Bmal1 heterozygous and wildtype pups at P14.
