Overall Management > Genetics

Meeting Abstract

Boncinelli E

Scientific Institute San Raffaele, Milan and SISSA, Trieste, Italy

Four vertebrate homeobox genes have been isolated and characterized that play a role in the development and regionalization of the head. 
These four genes are Emx1 and Emx2, related to a fruit fly gene termed ems, and Otx1 and Otx2, related to a fruit fly gene termed otd. 
The four vertebrate genes are expressed in extended regions of the developing rostral brain of mouse embryos, including the presumptive cerebral cortex and olfactory bulbs. 
At day 10 of development their expression domains are continuous regions contained within each other in the sequence Emx1<Emx2<Otx1<Otx2.
Otx2 appears to play an early role in gastrulation and first specification of anterior head and rostral brain in mouse, frog, chick and zebrafish embryos and the two Emx genes play some role in the developing cerebral cortex. 
It is interesting to consider the temporal pattern of expression of these two genes in the various zones of the forming cerebral cortex. 
Here, at least three major zones can be defined: the germinal neuroepithelium or ventricular zone, where cortical neurons proliferate, a transitional field, and finally the forming cortical plate from which the cortical gray matter will subsequently develop. 
In mouse embryos of all stages Emx2 expression coincides with cells of the germinal neuroepithelium. 
It is conceivable that Emx2 plays a role in the control of proliferation parameters of cortical neuroblasts or in the regulation of their subsequent migration process. 
Conversely, Emx1 is expressed in most cortical neurons, whether proliferating, migrating, differentiating, fully differentiated and organized in a mature cerebral cortex.
Mutations in the human Emx2 gene, EMX2, have been reported in sporadic cases of schizencephaly. 
This rare developmental disorder is characterized by a full -thickness cleft within the cerebral hemispheres.
Large portions of the cerebral hemispheres may be absent and replaced by cerebro -spinal fluid. 
In severe schizencephaly there is a large defect consisting in a holohemispheric cleft in the cerebral cortex filled with fluid and lined by polymicrogyric gray matter. 
Usually there is mental retardation, seizures,