The homeobox genes Lhx7 and Gbx1 are expressed in the basal forebrain cholinergic system.

The specific combination of homeobox genes is proposed to be decisive in the terminal differentiation of neuronal systems. In order to identify combined expression of homeobox genes in the ventral forebrain, a reverse transcriptase-polymerase chain reaction strategy using degenerated primers was employed. We identified, amongst others, Lhx7 and Gbx1, displaying a marked overlapping expression in septal and pallidal areas. Gbx1 and Lhx7 were both expressed in those adult brain nuclei that collectively form the basal forebrain cholinergic system, a prime target of neurodegeneration in Alzheimer's disease. Indeed, we detected Lhx7 within cholinergic neurons, whereas the related Lhx6 gene was found in adjacent neurons. From these data we suggest that combined expression of Lhx7 and Gbx1 plays a role in the development of the cholinergic system of the basal forebrain. It is speculated that both genes remain participating in molecular processes in the adult cholinergic neurons, and can be employed to study regulation and survival of these neurons under normal and pathological conditions.