Postnatal Notch1 activation induces T‑cell malignancy in conditional and inducible mouse models

Area of Science:

• Hematology
• Molecular Biology
• Developmental Biology

Background:

• The Notch1 signaling pathway is crucial for hematopoietic development.
• The impact of postnatal Notch1 signaling activation on the hematopoietic system remains unclear.

Purpose of the Study:

• To investigate the effects of inducible, postnatal activation of Notch1 signaling on adult hematopoiesis and T-cell development.
• To elucidate the role of Notch1 in T-cell malignancy and its potential impact on the ARF-p53 pathway.

Main Methods:

• Generation of ZEG-IC-Notch1 transgenic mice with a conditional intracellular Notch1 (IC-Notch1) domain.
• Utilizing a tetracycline-regulated Cre system for inducible, postnatal expression of IC-Notch1 in hematopoietic cells.
• Analysis of hematopoietic system, organ infiltration, and T-cell malignancy in triple transgenic mice after tetracycline withdrawal.

Main Results:

• Embryonic expression of IC-Notch1 caused vascular defects but not hematopoietic issues.
• Postnatal induction of IC-Notch1 in adult mice resulted in widespread T-cell infiltration and lymph node T-cell malignancy.
• Protein levels of p53 and ARF were reduced in neoplasms, while mRNA levels remained unchanged, indicating post-transcriptional repression.

Conclusions:

• Constitutive Notch1 signaling activation after embryonic development significantly alters adult hematopoiesis.
• Postnatal Notch1 activation can induce T-cell malignancy, potentially through post-transcriptional regulation of the ARF-p53 pathway.