The transcription factor CUX1 exerts opposing roles in human and mouse adipocyte differentiation.

OBJECTIVE: Adipocyte differentiation is critical for the metabolically protective expansion of adipose tissue. Impaired differentiation drives lipodystrophy and pathologic tissue remodeling, major contributors to cardiometabolic diseases. The differentiation process is governed by master transcription factors, including the pioneer factor C/EBPβ, which initiates the adipogenic program. Here, we sought to identify novel C/EBPβ-associated factors that regulate human adipocyte differentiation. METHODS: We used chromatin immunoprecipitation followed by selective isolation of chromatin-associated proteins (ChIP-SICAP) to identify proteins that interact with C/EBPβ on chromatin during human adipocyte differentiation. Candidate factors were assessed for their effects on differentiation, through conducting a CRISPR/Cas9-based knockout screen in human adipocyte precursor cells (hAPCs). The transcription factor CUX1 emerged as a top candidate. We performed gain- and loss-of-function studies in primary human and mouse adipocyte differentiation models, coupled with RNA-seq and ChIP-seq, to define CUX1-regulated genes and pathways. In vivo relevance was tested using adipocyte precursor-selective Cux1 knockout and lineage reporter mice. RESULTS: Loss of CUX1 impaired, whereas its overexpression enhanced, adipocyte differentiation in hAPCs. RNA-seq and ChIP-seq analyses revealed that CUX1 promotes the expression of key adipogenic genes, including PPARG in hAPCs. By contrast, CUX1 exerted the opposite effect in mouse adipocyte differentiation. Cux1 deletion enhanced, while CUX1 overexpression suppressed, differentiation in mouse APCs (mAPCs). CUX1 exhibited distinct chromatin-binding patterns and motif enrichment profiles in mouse versus human cells. In vivo, Cux1 deletion in APCs of mice increased de novo adipocyte formation during early stages of obesity development. CONCLUSIONS: The transcription factor CUX1 regulates adipocyte differentiation in opposite directions in humans and mice, emphasizing the need for species-specific models in metabolic disease research.