Chemokines, such as Stromal Derived Factor 1 (SDF-1 or CXCL12) and their G protein coupled receptors (GPCRs) are well known regulators of the development and functions of numerous tissues. CXCL12 has two receptors: CXCR4 and CXCR7 or atypical chemokine receptor 3 (ACKR3). CXCR7 has been described as an atypical “biased”...