Fig. 11.

Migrating entheses develop through template replacement. (A-B) Schematic of the developmental sequence of migratory and stationary entheses. During embryogenesis, Sox9 lineage cells form an enthesis template. (A) In migrating entheses, Sox9 lineage cells are replaced by a second population of Gli1 lineage cells, which eventually form the mature enthesis. Specification of Gli1 lineage is regulated by SHH, whereas maintenance of this population is regulated by IHH. (B) In stationary entheses, embryonic Sox9 lineage cells proliferate and differentiate and, eventually, populate the postnatal enthesis structure. During late embryonic development, some Sox9 lineage cells start expressing Gli1.