We have cloned a basic helix-loop-helix (bHLH) factor gene, Bh1hb4, from a mouse β-cell line. Fluorescence in situ hybridization (FISH) and genetic mapping place Bh1hb4 at the telomeric end of mouse chromosome 2 (H3-H4), syntenic to human chromosome 20q13. Based on phylogenetic analysis, BHLHB4 belongs to a new subgroup of bHLH factors including at least four previously identified mouse bHLH factors: BHLHB5, MIST1, OLIG1, OLIG2, and OLIG3. In the developing nervous system, Bh1hb4 was found to mark the dimesencephalic boundary, suggesting that Bh1hb4 may have a role in diencephalic regionalization. In the pancreas, Bh1hb4 is expressed in a transient fashion that suggests a role in the pancreatic endocrine cell lineage. Transfection experiments show that BHLHB4 can repress transcriptional activation mediated through the pancreatic β-cell specific insulin promoter enhancer RIPE3. Together, these data suggest that BHLHB4 may modulate the expression of genes required for the differentiation and/or maintenance of pancreatic and neuronal cell types.
- Basic helix-loop-helix protein
- Pancreatic β-cells
- Physical chromosome mapping
- Transcription factor
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