LRRC15 and arthritic joint disease: Cluster 5 contains the bulk of the mouse S2d(Dkk3/Lrrc15+) SLSFs and M5 is linked to human cells in both clusters 5 and 6, suggesting that both human clusters (H5 and 6) likely acquire the “intermediate” arthritis-specific profile previously identified in hTNFtg SF states (Fig. 7B, Additional file 1: Fig. S13A, D).