Heterozygous deletion of the linked genes ZIC1 and ZIC4 is involved in Dandy-Walker malformation

Dandy-Walker malformation (DWM; OMIM #220200) is a common but poorly understood congenital cerebellar malformation in humans. Through physical mapping of 3q2 interstitial deletions in several individuals with DWM, we defined the first critical region associated with DWM, encompassing two adjacent Zinc finger in cerebellum genes, ZIC1 and ZIC4. Mice with a heterozygous deletion of these two linked genes have a phenotype that closely resembles DWM, providing a mouse model for this malformation.     

The mouse Dreher gene Lmx1a controls formation of the roof plate in the vertebrate CNS

In the vertebrate central nervous system (CNS), a cascade of signals that originates in the ectoderm adjacent to the neural tube is propagated by the roof plate to dorsalize the neural tube. Here we report that the phenotype of the spontaneous neurological mutant mouse dreher (dr) results from a failure of the roof plate to develop. Dorsalization of the neural tube is consequently affected: dorsal interneurons in the spinal cord and granule neurons in the cerebellar cortex are lost, and the dorsal vertebral neural arches fail to form. Positional cloning of dreher indicates that the LIM homeodomain protein, Lmx1a, is affected in three different alleles of dreher. Lmx1a is expressed in the roof plate along the neuraxis during development of the CNS. Thus, Lmx1a is required for development of the roof plate and, in turn, for specification of dorsal cell fates in the CNS and developing vertebrae.