Circadian clocks in adipose tissue are known to regulate adipocyte biology. Although circadian dysregulation is associated with development of obesity, the underlying mechanism has not been established. Here we report that disruption of the clock gene, brain and muscle Arnt‐like 1 (Bmal1), in mice led to increased adipogenesis, adipocyte hypertrophy, and obesity, compared to wild‐type (WT) mice. This is due to its cell‐autonomous effect, as Bmal1 deficiency in embryonic fibroblasts, as well as stable shRNA knockdown (KD) in 3T3‐L1 preadipocyte and C3H10T1/2 mesenchymal stem cells, promoted adipogenic differentiation. We demonstrate that attenuation of Bmal1 function resulted in down‐regulation of genes in the canonical Wnt pathway, known to suppress adipogenesis. Promoters of these genes (Wnt10a, β‐catenin, Dishevelled2, TCF3) displayed Bmal1 occupancy, indicating direct circadian regulation by Bmal1. As a result, Wnt signaling activity was attenuated by Bmal1 KD and augmented by its overexpression. Furthermore, stabilizing β‐catenin through Wnt ligand or GSK‐3β inhibition achieved partial restoration of blunted Wnt activity and suppression of increased adipogenesis induced by Bmal1 KD. Taken together, our study demonstrates that Bmal1 is a critical negative regulator of adipocyte development through transcriptional control of components of the canonical Wnt signaling cascade, and provides a mechanistic link between circadian disruption and obesity.—Guo, B., Chatterjee, S., Li, L., Kim, J. M., Lee, J., Yechoor, V. K., Minze, L. J., Hsueh, W., Ma, K. The clock gene, brain and muscle Arnt‐like 1, regulates adipogenesis via Wnt signaling pathway. FASEB J. 26, 3453–3463 (2012). www.fasebj.org

A brain tumour is a mass or cluster of abnormal cells in the brain, which has the possibility of becoming life-threatening because of its ability to invade neighbouring tissues and also form metastases. An accurate diagnosis is essential for successful treatment planning, and magnetic resonance imaging is the principal imaging modality for diagnosing brain tumours and their extent. Deep Learning methods in computer vision applications have shown significant improvement in recent years, most of which can be credited to the fact that a sizeable amount of data is available to train models, and the improvements in the model architectures yield better approximations in a supervised setting. Classifying tumours using such deep learning methods has made significant progress with the availability of open datasets with reliable annotations. Typically those methods are either 3D models, which use 3D volumetric MRIs or even 2D models considering each slice separately. However, by treating one spatial dimension separately or by considering the slices as a sequence of images over time, spatiotemporal models can be employed as “spatiospatial” models for this task. These models have the capabilities of learning specific spatial and temporal relationships while reducing computational costs. This paper uses two spatiotemporal models, ResNet (2+1)D and ResNet Mixed Convolution, to classify different types of brain tumours. It was observed that both these models performed superior to the pure 3D convolutional model, ResNet18. Furthermore, it was also observed that pre-training the models on a different, even unrelated dataset before training them for the task of tumour classification improves the performance. Finally, Pre-trained ResNet Mixed Convolution was observed to be the best model in these experiments, achieving a macro F1-score of 0.9345 and a test accuracy of 96.98%, while at the same time being the model with the least computational cost.

Summary The circadian clock network is an evolutionarily conserved mechanism that imparts temporal regulation to diverse biological processes. Brain and muscle Arnt-like 1 (Bmal1), an essential transcriptional activator of the clock, is highly expressed in skeletal muscle. However, whether this key clock component impacts myogenesis, a temporally regulated event that requires the sequential activation of myogenic regulatory factors, is not known. Here we report a novel function of Bmal1 in controlling myogenic differentiation through direct transcriptional activation of components of the canonical Wnt signaling cascade, a major inductive signal for embryonic and postnatal muscle growth. Genetic loss of Bmal1 in mice leads to reduced total muscle mass and Bmal1-deficient primary myoblasts exhibit significantly impaired myogenic differentiation accompanied by markedly blunted expression of key myogenic regulatory factors. Conversely, forced expression of Bmal1 enhances differentiation of C2C12 myoblasts. This cell-autonomous effect of Bmal1 is mediated by Wnt signaling as both expression and activity of Wnt components are markedly attenuated by inhibition of Bmal1, and activation of the Wnt pathway partially rescues the myogenic defect in Bmal1-deficient myoblasts. We further reveal direct association of Bmal1 with promoters of canonical Wnt pathway genes, and as a result of this transcriptional regulation, Wnt signaling components exhibit intrinsic circadian oscillation. Collectively, our study demonstrates that the core clock gene, Bmal1, is a positive regulator of myogenesis, which may represent a temporal regulatory mechanism to fine-tune myocyte differentiation.

The molecular clock is intimately linked to metabolic regulation, and brown adipose tissue plays a key role in energy homeostasis. However, whether the cell‐intrinsic clock machinery participates in brown adipocyte development is unknown. Here, we show that Bmal1 (also known as ARNTL), the essential clock transcription activator, inhibits brown adipogenesis to adversely affect brown fat formation and thermogenic capacity. Global ablation of Bmal1 in mice increases brown fat mass and cold tolerance, and adipocyte‐selective inactivation of Bmal1 recapitulates these effects and demonstrates its cell‐autonomous role in brown adipocyte formation. Further loss‐ and gain‐of‐function studies in mesenchymal precursors and committed brown progenitors reveal that Bmal1 inhibits brown adipocyte lineage commitment and terminal differentiation. Mechanistically, Bmal1 inhibits brown adipogenesis through direct transcriptional control of key components of the TGF‐β pathway together with reciprocally altered BMP signaling; activation of TGF‐β or blockade of BMP pathways suppresses enhanced differentiation in Bmal1‐deficient brown adipocytes. Collectively, our study demonstrates a novel temporal regulatory mechanism in fine‐tuning brown adipocyte lineage progression to affect brown fat formation and thermogenic regulation, which could be targeted therapeutically to combat obesity.