TGF-β Inducible Early Gene 1 Regulates Osteoclast Differentiation and Survival by Mediating the NFATc1, AKT, and MEK/ERK Signaling Pathways

TGF-β Inducible Early Gene-1 (TIEG1) is a Krüppel-like transcription factor (KLF10) that was originally cloned from human osteoblasts as an early response gene to TGF-β treatment. As reported previously, TIEG1−/− mice have decreased cortical bone thickness and vertebral bone volume and have increased spacing between the trabeculae in the femoral head relative to wildtype controls. Here, we have investigated the role of TIEG1 in osteoclasts to further determine their potential role in mediating this phenotype. We have found that TIEG1−/− osteoclast precursors differentiated more slowly compared to wildtype precursors in vitro and high RANKL doses are able to overcome this defect. We also discovered that TIEG1−/− precursors exhibit defective RANKL-induced phosphorylation and accumulation of NFATc1 and the NFATc1 target gene DC-STAMP. Higher RANKL concentrations reversed defective NFATc1 signaling and restored differentiation. After differentiation, wildtype osteoclasts underwent apoptosis more quickly than TIEG1−/− osteoclasts. We observed increased AKT and MEK/ERK signaling pathway activation in TIEG1−/− osteoclasts, consistent with the roles of these kinases in promoting osteoclast survival. Adenoviral delivery of TIEG1 (AdTIEG1) to TIEG1−/− cells reversed the RANKL-induced NFATc1 signaling defect in TIEG1−/− precursors and eliminated the differentiation and apoptosis defects. Suppression of TIEG1 with siRNA in wildtype cells reduced differentiation and NFATc1 activation. Together, these data provide evidence that TIEG1 controls osteoclast differentiation by reducing NFATc1 pathway activation and reduces osteoclast survival by suppressing AKT and MEK/ERK signaling

TIEG1 Inhibits Breast Cancer Invasion and Metastasis by Inhibition of Epidermal Growth Factor Receptor (EGFR) Transcription and the EGFR Signaling Pathway

TIEG1 can induce apoptosis of cancer cells, but its role in inhibiting invasion and metastasis has not been reported and is unclear. In this study, we find that decreased TIEG1 expression is associated with increased human epidermal growth factor receptor (EGFR) expression in breast cancer tissues and cell lines. TIEG1 plays an important role in suppressing transcription of EGFR by directly binding to the EGFR promoter. While overexpression of TIEG1 attenuates EGFR expression, knockdown of TIEG1 stimulates EGFR expression. Furthermore, TIEG1 and HDAC1 form a complex, which binds to Sp1 sites on the EGFR promoter and inhibits its transcription by suppressing histone acetylation. TIEG1 significantly inhibits breast cancer cell invasion, suppresses mammary tumorigenesis in xenografts in mice, and decreases lung metastasis by inhibition of EGFR gene transcription and the EGFR signaling pathway. Therefore, TIEG1 is an antimetastasis gene product; regulation of EGFR expression by TIEG1 may be part of an integral signaling pathway that determines and explains breast cancer invasion and metastasis

Normal Development of Brain Circuits

Spanning functions from the simplest reflex arc to complex cognitive processes, neural circuits have diverse functional roles. In the cerebral cortex, functional domains such as visual processing, attention, memory, and cognitive control rely on the development of distinct yet interconnected sets of anatomically distributed cortical and subcortical regions. The developmental organization of these circuits is a remarkably complex process that is influenced by genetic predispositions, environmental events, and neuroplastic responses to experiential demand that modulates connectivity and communication among neurons, within individual brain regions and circuits, and across neural pathways. Recent advances in neuroimaging and computational neurobiology, together with traditional investigational approaches such as histological studies and cellular and molecular biology, have been invaluable in improving our understanding of these developmental processes in humans in both health and illness. To contextualize the developmental origins of a wide array of neuropsychiatric illnesses, this review describes the development and maturation of neural circuits from the first synapse through critical periods of vulnerability and opportunity to the emergent capacity for cognitive and behavioral regulation, and finally the dynamic interplay across levels of circuit organization and developmental epochs