Conditional gene targeting using UCP1-Cre mice directly targets the central nervous system beyond thermogenic adipose tissues

Abstract

Objective Uncoupling protein 1 (UCP1) is a mitochondrial protein critical for adaptive thermogenesis in adipose tissues, and it is typically believed to be restricted to thermogenic adipose tissues. UCP1-Cre transgenic mice are utilized in numerous studies to provide “brown adipose-specific” conditional gene targeting. Here, we examined the distribution of Cre and UCP1 throughout the body in UCP1-Cre reporter mice. Methods UCP1-Cre mice crossed to Ai14-tdTomato and Ai9-tdTomato reporter mice were used to explore the tissue distribution of Cre recombinase and Ucp1 mRNA in various tissues. UCP1-Cre mice were independently infected with either a Cre-dependent PHP.eB-tdTomato virus or a Cre-dependent AAV-tdTomato virus to determine whether and where UCP1 is actively expressed in the adult central nervous system. In situ analysis of the deposited single cell RNA sequencing data was used to evaluate Ucp1 expression in the hypothalamus. Results As expected, Ucp1 expression was detected in both brown and inguinal adipose tissues. Ucp1 expression was also detected in the kidney, adrenal glands, thymus, and hypothalamus. Consistent with detectable Ucp1 expression, tdTomato expression was also observed in brown adipose tissue, inguinal white adipose tissue, kidney, adrenal glands, and hypothalamus of both male and female UCP1-Cre; Ai14-tdTomato and UCP1-Cre; Ai9-tdTomato mice by fluorescent imaging and qPCR. Critically, expression of tdTomato, and thus UCP1, within the central nervous system was observed in regions of the brain critical for the regulation of energy homeostasis, including the ventromedial hypothalamus (VMH). Conclusions TdTomato expression in UCP1-Cre; tdTomato mice is not restricted to thermogenic adipose tissues. TdTomato was also expressed in the kidneys, adrenal glands, and throughout the brain, including brain regions and cell types that are critical for multiple aspects of central regulation of energy homeostasis. Collectively, these data have important implications for the utility of UCP1-Cre mice as genetic tools to investigate gene function specifically in brown adipose tissue.

Uncoupling Protein-1 Modulates Anxiety-Like Behavior in a Temperature-Dependent Manner

“…While previously the presence of other members of the UCP family of proteins in the brain has been affirmed and a role in neuronal function been demonstrated (for review, see Andrews et al, 2005 ), UCP-1 expression in the mouse brain ( Lengacher et al, 2004 ; Wang et al, 2019 ) has remained contradictory. However, a recent study using UCP1-cre reporter mice convincingly delineated the active expression of UCP1 in the mouse brain, with abundant levels of UCP-1 in the VMH and the amygdala ( Claflin et al, 2022 ). Indeed, in the present study we also confirmed UCP-1 expression in the hypothalamus of WT mice.…”

“…Also UCP-1, which originally was thought to be restricted to adipose tissues, is found in the brain, with significant expression in the ventromedial hypothalamus (VMH) and the amygdala ( Claflin et al, 2022 ), regions involved in both temperature and emotional control processes ( Charmandari et al, 2005 ; Morrison, 2016 ; Soto et al, 2019 ).…”

Central FGF21 production regulates memory but not peripheral metabolism

“…An augmented DISCO protocol was utilized to clear whole brain tissue of Fgf21 -P2A-CRE; Ai14-tdTomato and CRE negative control mice as previously described ( Claflin et al, 2022 ). Mice were anesthetized and transcardially perfused with pH 9.5 saline followed by pH 9.5 4% PFA.…”

“…The average of fEPSP slopes from the first 20 min of baseline recording was used to normalize the data and ''n'' refers to slices. Tissue clearing, imaging, and processing An augmented DISCO protocol was utilized to clear whole brain tissue of Fgf21-P2A-CRE; Ai14-tdTomato and CRE negative control mice as previously described (Claflin et al, 2022). Mice were anesthetized and transcardially perfused with pH 9.5 saline followed by pH 9.5 4% PFA.…”

Mitochondrial Phosphatidylethanolamine Directly Regulates UCP1 to Promote Brown Adipose Thermogenesis

“…A recent report suggests that constitutive UCP1-Cre mice have leaky Cre expression in other key metabolic tissues such as the hypothalamus and kidney resulting in nonspecific genetic recombination (Claflin et al, 2022). We examined whether the tamoxifen-inducible UCP1-Cre (UCP1 Cre-ERT2) we used resulted in PSD knockout in other tissues.…”