HLXB9 gene expression, and nuclear location during in vitro neuronal differentiation in the SK-N-BE neuroblastoma cell line

PLoS One. 2014 Aug 19;9(8):e105481. doi: 10.1371/journal.pone.0105481. eCollection 2014.

Abstract

Different parts of the genome occupy specific compartments of the cell nucleus based on the gene content and the transcriptional activity. An example of this is the altered nuclear positioning of the HLXB9 gene in leukaemia cells observed in association with its over-expression. This phenomenon was attributed to the presence of a chromosomal translocation with breakpoint proximal to the HLXB9 gene. Before becoming an interesting gene in cancer biology, HLXB9 was studied as a developmental gene. This homeobox gene is also known as MNX1 (motor neuron and pancreas homeobox 1) and it is relevant for both motor neuronal and pancreatic beta cells development. A spectrum of mutations in this gene are causative of sacral agenesis and more broadly, of what is known as the Currarino Syndrome, a constitutional autosomal dominant disorder. Experimental work on animal models has shown that HLXB9 has an essential role in motor neuronal differentiation. Here we present data to show that, upon treatment with retinoic acid, the HLXB9 gene becomes over-expressed during the early stages of neuronal differentiation and that this corresponds to a reposition of the gene in the nucleus. More precisely, we used the SK-N-BE human neuroblastoma cell line as an in vitro model and we demonstrated a transient transcription of HLXB9 at the 4th and 5th days of differentiation that corresponded to the presence, predominantly in the cell nuclei, of the encoded protein HB9. The nuclear positioning of the HLXB9 gene was monitored at different stages: a peripheral location was noted in the proliferating cells whereas a more internal position was noted during differentiation, that is while HLXB9 was transcriptionally active. Our findings suggest that HLXB9 can be considered a marker of early neuronal differentiation, possibly involving chromatin remodeling pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Differentiation / drug effects
  • Cell Differentiation / genetics
  • Cell Line, Tumor
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism*
  • Cell Proliferation / drug effects
  • Cell Proliferation / genetics
  • Gene Expression / drug effects
  • Gene Expression / genetics*
  • Genes, Homeobox / genetics
  • Hep G2 Cells
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism*
  • Humans
  • Neuroblastoma / genetics*
  • Neuroblastoma / metabolism*
  • Neurons / drug effects
  • Neurons / metabolism
  • Trans-Activators / genetics
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism*
  • Transcription, Genetic / drug effects
  • Transcription, Genetic / genetics
  • Tretinoin / pharmacology

Substances

  • Homeodomain Proteins
  • MNX1 protein, human
  • Trans-Activators
  • Transcription Factors
  • Tretinoin

Grants and funding

The work was supported by PRA from the University of Catania to SS. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.