In contrast to Axin1 cKO mice, deletion of Axin1 in Sox9-, Col2a1-, and Sp7-expressing cells does not affect fibular development (Figure 2K, Figure 2—source data 1), suggesting that FH disease is caused by defects in the specific cell population, limb mesenchymal cells. Here, COL2A1 is linked to familial hyperaldosteronism.