Deleting the Arntl clock gene in the granular layer of the mouse cerebellum: impact on the molecular circadian clockwork

Abstract

The suprachiasmatic nucleus houses the central circadian clock and is characterized by the timely regulated expression of clock genes. However, neurons of the cerebellar cortex also contain a circadian oscillator with circadian expression of clock genes being controlled by the suprachiasmatic nucleus. It has been suggested that the cerebellar circadian oscillator is involved in food anticipation, but direct molecular evidence of the role of the circadian oscillator of the cerebellar cortex is currently unavailable. To investigate the hypothesis that the circadian oscillator of the cerebellum is involved in circadian physiology and food anticipation, we therefore by use of Cre-LoxP technology generated a conditional knockout mouse with the core clock gene Arntl deleted specifically in granule cells of the cerebellum, since expression of clock genes in the cerebellar cortex is mainly located in this cell type. We here report that deletion of Arntl heavily influences the molecular clock of the cerebellar cortex with significantly altered and arrhythmic expression of other central clock and clock-controlled genes. On the other hand, daily expression of clock genes in the suprachiasmatic nucleus was unaffected. Telemetric registrations in different light regimes did not detect significant differences in circadian rhythms of running activity and body temperature between Arntl conditional knockout mice and controls. Furthermore, food anticipatory behavior did not differ between genotypes. These data suggest that Arntl is an essential part of the cerebellar oscillator; however, the oscillator of the granular layer of the cerebellar cortex does not control traditional circadian parameters or food anticipation.

Circadian regulation of membrane physiology in neural oscillators throughout the brain

“…In primates, however, PER1/2‐ir is expressed in the Purkinje cell layer (the primary output of the cerebellum), but not the granule or molecular cell layers, with higher expression during the day (ZT 10) compared to the night (ZT 19; Guissoni Campos et al., ). Bmal1 deletion specifically in granule cells renders expression of the majority of clock genes arrhythmic; however, circadian locomotor behavior is not significantly changed (Bering, Carstensen, & Rath, ). Although the cerebellum has >2,000 rhythmic transcripts (detected in animals housed in DD for two cycles; (Pizarro, Hayer, Lahens, & Hogenesch, ), it is surprising that we know very little about the function of the molecular clock in this important area of the brain.…”

The Mysterious Food-Entrainable Oscillator: Insights from Mutant and Engineered Mouse Models

“…The first study of FAA in Bmal1 −/− mice showed that these mice had no FAA but that FAA was rescued by injecting virus expressing Bmal1 into the dorsomedial nucleus of the hypothalamus (Fuller et al, 2008). However, several independent laboratories have since demonstrated that Bmal1 −/− mice had FAA (Mistlberger et al, 2008; Pendergast et al, 2009; Storch and Weitz, 2009; Mieda and Sakurai, 2011; Takasu et al, 2012; Izumo et al, 2014, Bering et al, 2017). The discrepancy in results could be attributed, in part, to the fact that Bmal1 −/− mice may have been ill during restricted feeding in the Fuller et al study because food availability was not gradually reduced (for further discussion of FAA in Bmal1 −/− mice, see Fuller et al, 2009; Mistlberger et al, 2009b; Mistlberger et al, 2009a).…”

“…The discrepancy in results could be attributed, in part, to the fact that Bmal1 −/− mice may have been ill during restricted feeding in the Fuller et al study because food availability was not gradually reduced (for further discussion of FAA in Bmal1 −/− mice, see Fuller et al, 2009; Mistlberger et al, 2009b; Mistlberger et al, 2009a). Mice lacking functional BMAL1 in the nervous system, forebrain, or cerebellar granule cells also had intact FAA (Mieda and Sakurai, 2011; Izumo et al, 2014; Bering et al, 2017). In sum, numerous studies performed in different laboratories have demonstrated that BMAL1 is not necessary for FAA.…”

Rhythmic Release of Corticosterone Induces Circadian Clock Gene Expression in the Cerebellum

“…However, circadian oscillators characterized by circadian rhythms in clock gene expression are also present in extra-hypothalamic structures, including both peripheral tissues and various parts of the central nervous system [3,4]. All known clock genes are expressed in the granular and Purkinje cell layers of the cerebellar cortex [5][6][7][8][9][10][11].…”