Table 3

Functional classes of bHLH proteins

Phylogenetic class

bHLH family

Example mammalian protein

Function

A

MyoD

Myf4

Myogenic: initiates myogenic programme in many cell types

NeuroD

Neurogenic differentiation factor NDF2

Neurogenic: involved in terminal neurone differentiation

SCL

Tal1

Hematopoietic: essential for primitive hematopoiesis and invokes enhanced proliferation and differentiation during erythroid development

Hand

dHand

Cardiogenic: regulates the morphogenetic events of asymmetric heart development

B

Myc

c-Myc

Cell proliferation and differentiation; oncogenic

Mad

Mad1

Regulation of cell proliferation

SREBP

SREBP-2

Cholesterol metabolism

C

Sim

Single-minded 1 (Sim1)

Neurogenic: regulation of midline cell lineage in the central nervous system

D

Emc

Id1

Myogenic and neurogenic: negative inhibition of DNA binding

E

Hairy

Hes1

Neurogenic: restricts differentiation of neurons from neural precursor cells

F

Coe

Early B-cell factor (EBF1)

Hematopoietic: essential for B-cell development

Examples of mammalian proteins and their diverse functions are shown for each phylogenetic group of bHLH proteins. The phylogenetic groups are those indicated in Table 1 and discussed in the text.

Jones Genome Biology 2004 5:226   doi:10.1186/gb-2004-5-6-226