Figure 5

STAT5 is required for differentiation of luminal progenitor cells into alveolar cells. STAT5 activation mediates alveolar cell fate commitment and proliferation that leads to lactational differentiation. Mammary stem cells give rise to progenitor cells that differentiate into ductal or luminal progenitor cells. ELF5 induces differentiation of luminal progenitor cells into alveolar cells downstream of prolactin signaling. Cell types illustrated in pink exhibit STAT5 activation. ELF5, E74-like factor 5 (ets domain transcription factor); PRL, prolactin; STAT5, signal transducer and activator of transcription 5.