ASCL1 is a MYCN- and LMO1-dependent member of the adrenergic neuroblastoma core regulatory circuitry

Lu Wang,Jo Lynne Rokita,A Thomas Look,Tze King Tan,John M Maris,Koshi Akahane,Mark W Zimmerman,Richard A Young,Adam D Durbin,Nina Weichert-Leahey,Takaomi Sanda,Shi Hao Tan,Brian J Abraham,Lee N Lawton,Phuong Cao Thi Ngoc

doi:10.1038/s41467-019-13515-5

Abstract

A heritable polymorphism within regulatory sequences of the LMO1 gene is associated with its elevated expression and increased susceptibility to develop neuroblastoma, but the oncogenic pathways downstream of the LMO1 transcriptional co-regulatory protein are unknown. Our ChIP-seq and RNA-seq analyses reveal that a key gene directly regulated by LMO1 and MYCN is ASCL1, which encodes a basic helix-loop-helix transcription factor. Regulatory elements controlling ASCL1 expression are bound by LMO1, MYCN and the transcription factors GATA3, HAND2, PHOX2B, TBX2 and ISL1—all members of the adrenergic (ADRN) neuroblastoma core regulatory circuitry (CRC). ASCL1 is required for neuroblastoma cell growth and arrest of differentiation. ASCL1 and LMO1 directly regulate the expression of CRC genes, indicating that ASCL1 is a member and LMO1 is a coregulator of the ADRN neuroblastoma CRC.

Highlights

A heritable polymorphism within regulatory sequences of the LMO1 gene is associated with its elevated expression and increased susceptibility to develop neuroblastoma, but the oncogenic pathways downstream of the LMO1 transcriptional co-regulatory protein are unknown
A large-scale neuroblastoma genome-wide association study (GWAS) study demonstrated that a polymorphism within the LMO1 gene locus is strongly associated with the susceptibility of children to develop neuroblastoma[8]
GATA3 participates with other CRC transcription factors to generate a potent enhancer that activates LMO1 gene expression

Summary

Introduction

A heritable polymorphism within regulatory sequences of the LMO1 gene is associated with its elevated expression and increased susceptibility to develop neuroblastoma, but the oncogenic pathways downstream of the LMO1 transcriptional co-regulatory protein are unknown. G>T, which is the most highly associated variant, creates a GATA motif, and GATA3 binds at this locus[9] This GATA3 binding is essential for the creation of a super-enhancer that drives high levels of LMO1 expression and increases the proliferative fraction of sympathetic neuroblasts[9]. Subsequent studies showed that LMO1 overexpression significantly accelerates the latency, penetrance, and metastatic potential of MYCN-induced neuroblastomas in a zebrafish transgenic model[10]. These findings implicate LMO1 as an oncogene that collaborates with MYCN in neuroblastoma pathogenesis, causing arrest of neuroblast differentiation into chromaffin cells or sympathetic ganglia within the adrenal medulla, and driving rapid neuroblast proliferation[10]. Molecular mechanisms by which LMO1 alters transcription to drive cellular proliferation and differentiation block remain to be identified

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