Asxl1 exerts an antiproliferative effect on mouse lung maturation via epigenetic repression of the E2f1-Nmyc axis

Area of Science:

• Developmental Biology
• Epigenetics
• Respiratory Medicine

Background:

• The role of Additional sex combs-like 1 (ASXL1) in organ development remains largely uncharacterized, despite its known involvement in hematologic malignancies.
• Understanding ASXL1's function is crucial for deciphering developmental processes and potential disease mechanisms.
• Previous research has primarily focused on ASXL1's role in cancer, leaving its broader biological functions unexplored.

Purpose of the Study:

• To investigate the molecular role of ASXL1 in organ development, specifically focusing on its impact on lung maturation.
• To elucidate the mechanisms by which ASXL1 regulates lung epithelial cell proliferation and gene expression.
• To identify key target genes and pathways influenced by ASXL1 during lung development.

Main Methods:

• Generated Asxl1-ablated mice to study its in vivo function.
• Utilized microarray analysis to identify ASXL1-regulated genes, including E2F1-responsive genes.
• Performed molecular assays to examine the interaction between ASXL1, HCF-1, and the Nmyc promoter, including ChIP-qPCR for histone modifications (H3K27me3, H3K9me3).

Main Results:

• Asxl1 ablation in mice led to postnatal lethality, characterized by cyanosis and respiratory failure due to defective lung maturation.
• Microarray analysis revealed that ASXL1 represses E2F1-responsive genes, notably Nmyc, and this repression is impaired in Asxl1-deficient lungs.
• ASXL1, along with HCF-1 and E2F1, is recruited to the Nmyc promoter, where ASXL1 promotes H3K27me3 enrichment, indicating epigenetic repression of Nmyc.

Conclusions:

• ASXL1 plays a critical role in mouse lung development by epigenetically repressing Nmyc expression, thereby modulating lung epithelial cell proliferation.
• Deficiency in ASXL1 leads to Nmyc dysregulation, resulting in lung hyperplasia and respiratory failure.
• These findings highlight ASXL1 as a key regulator of lung development and suggest its dysfunction can lead to severe respiratory defects.