Pluto Bioinformatics

GSE112694: RNA-seq analysis of osteogenic differentiating mouse wild type (WT) and Zfp384 (Nmp4) knockout mesenchymal stem/progenitor cells (MSPCs)

Bulk RNA sequencing

A goal of osteoporosis therapy is to restore lost bone with structurally sound tissue. Mice lacking the transcription factor Nmp4 respond to several classes of osteoporosis drugs with enhanced bone formation compared to wild type (WT) animals. To address how loss of Nmp4 maximizes anabolic output we used RNA-seq and network analyses, along with biochemical and bone mechanical measurements to define this anti-anabolic axis. Several independent preparations of expanded mesenchymal stem/progenitor cells (MSPCs) were derived from individual Nmp4-/- and WT mice. The Nmp4-/- cells exhibited accelerated and enhanced mineralization. Loss of Nmp4 significantly altered the expression of over 5,000 genes. While Nmp4 status did not alter the mRNA expression of Runx2 and Sp7, key regulators of osteoblast differentiation, Nmp4-depletion enhanced expression of genes that drive osteogenesis and conversion to aerobic glycolysis, a key step in bone anabolism. Functional studies confirmed that Nmp4-/- MSPCs exhibited an enhanced capacity for glycolytic conversion. Several canonical pathways sensitive to Nmp4 status controlled protein production and delivery and as predicted the Nmp4-/- cells showed elevated collagen translation and secretion. Expression of matrix genes that contribute to bone material-level mechanical properties were elevated in Nmp4-/- cells. Mechanical analysis of femurs from Nmp4-/- mice treated with osteoporosis therapies resulted in enhanced bone material properties compared to WT mice. In conclusion, disabling Nmp4 converts the osteoblast into a super-secretor by metabolically reprogramming the cell to support the concomitant elevated matrix production and expansion of the cells delivery capacity. Resolving this pathway will guide advances in osteoporosis therapy. SOURCE: Joseph Bidwell (jbidwell@iupui.edu) - MS1030 Indiana University School of Medicine