Gene expression in mammary glands of lactating wild-type or Th-POK-deficient mice.

The Th-inducing POK (Th-POK, also known as cKrox or ZBTB7B) transcription factor is a key regulator of lineage commitment of immature T cell precursors. It is yet unclear the physiological functions of Th-POK besides helper T cell differentiation. We found that Th-POK is restrictedly expressed in the luminal epithelial cells in the mammary glands. Th-POK is not required for mammary gland development in puberty and alveologenesis in pregnancy. Th-POK-deficient mice are defective in secretory activation upon parturition with large cellular lipid droplets retained within alveolar epithelial cells. We compared microarray gene expression in mammary glands of lactating wild-type or Th-POK-deficient mice. We show that Th-POK directly regulates expression of insulin receptor substrate-1 (IRS-1) and insulin-induced Akt-mTOR-SREBP signaling. Th-POK deficiency compromises IRS-1 expression and Akt-mTOR-SREBP signaling in the mammary glands. Thus, Th-POK function as an important regulator of insulin signaling in mammary gland lactation. No. 4 mammary glands were harvested and snap frozen from quadruplicate wild-type or Th-POK-deficient dams at lactation day 1. Total RNA was extracted from the mammary glands for microarray analyses (Agilent Whole Mouse Genome Microarray 4x44K array, Design ID: 014868) at the Shanghai Biotech Corp., following the manufacturer's recommendation.