Targeting leptin-positive adipocytes by expressing the Cre recombinase transgene under the endogenous leptin gene

Adipose tissue plays an important role in metabolic physiology through energy storage and endocrine functions. Spatial transcriptomics is revealing the complexity of cell types and their interaction in the adipose tissue with regards to development, homeostasis and disease. Emerging evidence suggests the existence of different subtypes of mature adipocytes that may have distinct functions, the markers of which include leptin (LEP), adiponectin (ADIPOQ), perilipin-1/4 (PLIN), and serum amyloid A (SAA), marking different adipocyte subtypes. Currently, Adipoq-Cre is widely used to study adipocyte biology, however, there is no Cre line that specifically targets LEP⁺ adipocytes. Here, we report the construction and validation of a Lep-Cre mouse line, which has the endogenous Lep gene edited by the CRISPR-Cas9 technology to generate the Lep-peptide 2A (P2A)-Cre fusion gene. P2A induces an auto-hydrolysis of the fusion protein, leading to expression of the Cre recombinase by the Lep gene activity. The activity of Lep-Cre in different depots of adipose tissues and non-adipose tissues was visualized by the immunofluorescence microscopy in the Lep-Cre Rosa26-loxP-Stop-loxP-tdTomato mice. We showed that Lep-Cre marked white/beige adipose depots extensively, followed by brown adipose depots. Leaky activity was observed in varying degrees among peripheral organs but not in the paraventricular nucleus of the hypothalamus. In summary, we have constructed a new adipocyte-targeting Cre mouse line that would be useful to study the development and physiology of LEP⁺ adipocytes.