A model of a “multi-component PC niche” has recently been proposed whereby CXCL12+ BM SCs provide scaffolding and basic survival factors for the PCs and a second support cell type in the niche further contributes to the longevity of PCs through additional soluble factors.[22] Thus, we next attempted to define the role of Eos in a more complex MM cell niche that includes BM SCs. This evidence concerns the gene CXCL12 and Miyoshi myopathy.