Int. J. Dev. Biol. 45: S75 - S76 (2001)

Vol 45, Issue S1

Pax6 and Msx1, two homeobox genes involved in the development of the subcommissural organ

Published: 1 June 2001

G Estivill-Torrus, MF Lopez-Aranda, JM Grondona, A Bach, B Robert, T Vitalis, DJ Price, C Ramos, E Soriano, P Fernandez-Llebrez

Univ Malaga, Fac Ciencias, Dept Biol Anim, Lab Fisiol Anim, E-29071 Malaga, Spain; Univ Edinburgh, Sch Med, Dept Biomed Sci, Dev Biol Lab, Edinburgh, Midlothian, Scotland; Inst Pasteur, Unite Genet Mol Morphogenese, Paris, France; Inst Pasteur, CNRS, URA

Abstract

During mouse central nervous system (CNS) development, the homeobox -containing genes Pax6 and Msx1, have a spatial and temporal restricted expression in the CNS and craniofacial skeleton. Both genes are highly expressed in the glial secretory cells that forms the subcommissural organ (SCO), a circumventricular organ located at the forebrain-midbrain boundary, in the pretectal dorsal midline neuroepithelium beneath the posterior commissure. Pax6 (Small eye, Sey/Sey) and Msx1 (-/-) null mutants homozygous fall to develop the SCO and a normal posterior commissure. Pineal gland is also absent in Small eye mice. Analysis of Small eye heterozygotes demonstrated specific Pax6 defects in the developing SCO, with an important reduction in the secretory basal cell processes, in accordance with the dosage effect of Pax6. Also for Msx1, a gene-dosage effect was found since heterozygous showed a reduced (about one half) SCO. In both mutants, homozygotes and sometimes heterozygotes develop hydrocephalus. This suggests a causal relationship between the development of the SCO and of the posterior commissure, and between the absence of a normal SCO and the development of hydrocephalus.

Keywords

Sco-spondin