Expression of the winged helix genes fkh-4 and fkh-5 defines domains in the central nervous system.

The 'winged helix' or 'forkhead' transcription factor gene family is defined by a common 100 amino acid DNA binding domain which is a variant of the helix-turn-helix motif. Here we describe the structure and expression of the mouse fkh-4 and fkh-5 genes. The two genes encode proteins of 427 and 324 amino acids, respectively, with highly similar winged helix domains. Both genes are expressed in adjacent domains in the developing diencephalon from the headfold stage onward. Linkage analysis localised fkh-5 to chromosome 9 at 34.5 centiMorgans (cM) and fkh-4 to chromosome 19 at 10.5 cM. The potential relationship of the two genes to the mouse mutations staggerer and small thymus (for fkh-5) and muscle deficient (for fkh-4) is discussed.