ZIC1 function in normal cerebellar development and human developmental pathology

Abstract

Zic genes are strongly expressed in the cerebellum. This feature leads to their initial identification and their name “zic,” as the abbreviation of “zinc finger protein of the cerebellum.” Zic gene function in cerebellar development has been investigated mainly in mice. However, association of heterozygous loss of ZIC1 and ZIC4 with Dandy-Walker malformation, a structural birth defect of the human cerebellum, highlights the clinical relevance of these studies. Two proposed mechanisms for Zic-mediated cerebellar developmental control have been documented: regulation of neuronal progenitor proliferation-differentiation and the patterning of the cerebellar primordium. Clinical studies have also revealed that ZIC1 gain of function mutations contribute to coronal craniosynostosis, a rare skull malformation. The molecular pathways contributing to these phenotypes are not fully explored; however, embryonic interactions with sonic hedgehog signaling, retinoic acid signaling, and TGFβ signaling have been described during mouse cerebellar development. Further, Zic1/2 target a multitude of genes associated with cerebellar granule cell maturation during postnatal mouse cerebellar development.