Basic Helix Loop Helix Family, Member e22 (BHLHE22)

BHLHE22 belongs to the basic helix-loop-helix (bHLH) family of transcription factors that regulate cell fate determination, proliferation, and differentiation. These proteins function as dimers and bind to an E-box DNA sequence (CANNTG). BHLHE22 is expressed exclusively in the central nervous system and retina. The deduced 381-amino acid protein has a calculated molecular mass of 37 kD and shares 94% identity with the 355-amino acid mouse protein. BHLHB5 has an N-terminal proline-rich domain, followed by a glycine-rich domain, a polyglycine-serine region, a bHLH domain, and a C-terminal alanine-rich region. The polyglycine-serine region of human BHLHB5 has a serine stretch encoded by a 27-bp trinucleotide repeat (CAG)9 that is absent in mouse and hamster Bhlhb5.