SOX9 and cyclic hematopoiesis: The control of the CH phenotype assessed by the expression profile of COL1, COL2, and COL3 is located at the interplay between (i) SF regulation and SOX9 expression and phosphorylation, as both regulate COL2 expression as detailed below; and (ii) MRTF cytoplasmic vs. nuclear localization, which regulates COL1 expression.