Adipocyte differentiation is regulated by various mechanisms, of which mitotic clonal expansion (MCE) is a key step. Although this process is known to be regulated by cell cycle modulators, the precise mechanism remains unclear. N⁶-Methyladenosine (m⁶A) posttranscriptional RNA modification, whose methylation and demethylation are performed by respective enzyme molecules, has recently been suggested to be involved in the regulation of adipogenesis. Here, we show that an RNA N⁶-adenosine methyltransferase complex consisting of Wilms9 tumor 1-associating protein (WTAP), methyltransferase like 3 (METTL3), and METTL14 positively controls adipogenesis by promoting cell cycle transition in MCE during adipogenesis. WTAP, coupled with METTL3 and METTL14, is increased and distributed in nucleus by the induction of adipogenesis dependently on RNA in vitro. Knockdown of each of these three proteins leads to cell cycle arrest and impaired adipogenesis associated with suppression of cyclin A2 upregulation during MCE, whose knockdown also impairs adipogenesis. Consistent with this, Wtap heterozygous knockout mice are protected from diet-induced obesity with smaller size and number of adipocytes, leading to improved insulin sensitivity. These data provide a mechanism for adipogenesis through the WTAP-METTL3-METTL14 complex and a potential strategy for treatment of obesity and associated disorders.

The transcription factor nuclear factor I-A (NFIA) is a regulator of brown adipocyte differentiation. Here we show that the C-terminal 17 amino acid residues of NFIA (which we call pro#3 domain) are required for the transcriptional activity of NFIA. Full-length NFIA—but not deletion mutant lacking pro#3 domain—rescued impaired expression of PPARγ, the master transcriptional regulator of adipogenesis and impaired adipocyte differentiation in NFIA-knockout cells. Mechanistically, the ability of NFIA to penetrate chromatin and bind to the crucial Pparg enhancer is mediated through pro#3 domain. However, the deletion mutant still binds to Myod1 enhancer to repress expression of MyoD, the master transcriptional regulator of myogenesis as well as proximally transcribed non-coding RNA called ^DRReRNA, via competition with KLF5 in terms of enhancer binding, leading to suppression of myogenic gene program. Therefore, the negative effect of NFIA on the myogenic gene program is, at least partly, independent of the positive effect on PPARγ expression and its downstream adipogenic gene program. These results uncover multiple ways of action of NFIA to ensure optimal regulation of brown and beige adipocyte differentiation. Obesity and its complications including type 2 diabetes are growing concerns worldwide. While white adipocytes generally store energy in the form of lipid, classical brown and cold- or β-adrenergic stimulation-induced beige adipocytes dissipate chemical energy in the form of heat through uncoupling protein-1 (Ucp1). Since the re-discovery of human brown and beige adipocytes, it has been considered a promising target for the treatment of obesity. During mesenchymal development, not only activation of brown/beige adipocyte gene program but also repression of muscle gene program is required to achieve thermogenic adipocyte differentiation. Previously, we identified the transcription factor nuclear factor I-A (NFIA) as a regulator of brown adipocyte differentiation. Here we show that the C-terminal 17 amino acid residues of NFIA, which we call pro#3 domain, is required for activation of adipocyte differentiation. However, the deletion mutant which lacks this domain is still able to suppress muscle gene program by repressing the expression of Myod1, which encode the master transcriptional regulator of myogenesis, MyoD. We demonstrate that NFIA activates adipogenesis and also “actively” suppresses myogenesis through distinct molecular pathways to ensure brown and beige adipocyte differentiation.

The physiological actions of a gut hormone, glucagon-like peptide-1 (GLP-1), in Alzheimer's disease (AD) brain remain poorly understood, although GLP-1 receptor (GLP-1R) expression in this organ has been shown in several experimental studies. Therefore, we explored whether the GLP-1R signaling promotes the clearance of amyloid β (Aβ) (1-42) which is a core pathological hallmark of AD, focusing on the water channel protein aquaporin 4 (AQP4) localized to astrocyte endfeet perivascular membranes in intact brain. First, we confirmed that Glp1r mRNA is predominantly expressed at perivascular site of astrocytes in normal mouse cerebral cortex through in situ hybridization analysis. Next, we observed that 20-week subcutaneous administration of a GLP-1R agonist (GLP-1RA) liraglutide significantly reduced Aβ (1-42) accumulation in the cerebral cortex and improved spatial working memory in an AD mouse model, App^{NL-G-F/NL-G-F} mice. Furthermore, our current data revealed that the 4-week liraglutide treatment relocalized subcellular AQP4 in morphologically injured reactive astrocytes of App^{NL-G-F/NL-G-F} mice to the cell surface perivascular site through PKA-mediated AQP4 phosphorylation. Such translocation of phosphorylated AQP4 to astrocyte cell surface following incubation with liraglutide was observed also in the present in vitro study using the cell line in which AQP4 cDNA was introduced into immortalized human astrocyte. These results suggest that enhanced intracerebral GLP-1R signaling following peripheral administration of GLP-1RA restores AQP4 subcellular polarization in reactive astrocytes and would promote Aβ excretion possibly through increasing AQP4-mediated intracerebral water flux in the brain in AD.

White adipose tissue (WAT) is essential for lipid storage and systemic energy homeostasis. Understanding adipocyte formation and stability is key to developing therapies for obesity and metabolic disorders. Through a high-throughput cDNA screen, we identified PATZ1, a POZ/BTB and AT-Hook Containing Zinc Finger 1 protein, as an important adipogenic transcription factor. PATZ1 is expressed in human and mouse adipocyte precursor cells (APCs) and adipocytes. In cellular models, PATZ1 promotes adipogenesis via protein-protein interactions and DNA binding. PATZ1 ablation in mouse adipocytes and APCs leads to a reduced APC pool, decreased fat mass, and hypertrophied adipocytes. ChIP-Seq and RNA-seq analyses show that PATZ1 supports adipogenesis by interacting with transcriptional machinery at the promoter regions of key early adipogenic factors. Mass-spec results show that PATZ1 associates with GTF2I, with GTF2I modulating PATZ1’s function during differentiation. These findings underscore PATZ1’s regulatory role in adipocyte differentiation and adiposity, offering insights into adipose tissue development.

CDK5 Regulatory Subunit-Associated Protein 1-like 1 (CDKAL1) was identified as a susceptibility gene for type 2 diabetes and body mass index in genome-wide association studies. Although it was reported that CDKAL1 is a methylthiotransferase essential for tRNA^Lys(UUU) and faithful translation of proinsulin generated in pancreatic β cells, the role of CDKAL1 in adipocytes has not been understood well. In this study, we found that CDKAL1 is expressed in adipose tissue and its expression is increased during differentiation. Stable overexpression of CDKAL1, however, inhibited adipocyte differentiation of 3T3-L1 cells, whereas knockdown of CDKAL1 promoted differentiation. CDKAL1 increased protein levels of β-catenin and its active unphosphorylated form in the nucleus, thereby promoting Wnt target gene expression, suggesting that CDKAL1 activated the Wnt/β-catenin pathway—a well-characterized inhibitory regulator of adipocyte differentiation. Mutant experiments show that conserved cysteine residues of Fe-S clusters of CDKAL1 are essential for its anti-adipogenic action. Our results identify CDKAL1 as novel negative regulator of adipocyte differentiation and provide insights into the link between CDKAL1 and metabolic diseases such as type 2 diabetes and obesity.