Bone marrow adipocyte (BMAd)-specific deletion of Pnpla2 reveals local roles for lipolysis to fuel cells of bone and the marrow niche

Purpose: To determine mechanisms by which BMAd-Pnpla2 deficiency-causes bone loss in calorie restricted (CR) mice, we profiled global gene expression in bone marrow plugs from distal tibiae, a location highly enriched with bone marrow adipose tissue. Methods: Male control and BMAd-Pnpla2-/- mice at 24 weeks of age were either fed AL or underwent 30% CR for 6 weeks. Distal tibial cBMAT was flushed and cBMAT from two mice was pooled as one sample for RNAseq analyses (n of 3 or 4 per treatment). Results: Using an optimized data analysis workflow, we mapped about 20 million sequence reads per sample to the mouse genome (UCSC mm10) and identified 23,441 transcripts in the bone marrow adipose tissue of WT and Pnpla2 deficiency mice using STAR with default parameters. PCA plots show that RNA profiles from CR groups are distinct from their Ad libitum (AL) controls. Whereas Pnpla2 deficiency in mice fed AL does not cause gene expression to diverge substantially, loss of Pnpla2 interacts with CR resulting in a well-segregated pattern of gene expression Conclusion: Caloric restriction induces dramatic elevations in extracellular matrix organization and skeletal development genes, and energy from BMAd is required for these adaptations. Overall design: Gene profiling of bone marrow adipose tissue from WT and BMAd-Pnpla2-/- mice fed an ad libitum or a caloric restricted diet for 6 weeks.