FINE STRUCTURE OF THE CEREBELLUM OF ldquo;STAGGERERhyphen;REELERcomma;rdquo; A DOUBLE MUTANT OF MICE AFFECTED BY STAGGERER AND REELER CONDITIONSIperiod; THE PREMATURE DISAPPEARANCE OF THE EXTERNAL GRANULAR LAYER AND ENSUING CEREBELLAR DISORGANIZATION

摘要

It was reasoned that cerebella of mice carrying both staggerer and reeler conditions, called double mutant, might accentuate some of the anomalies observed in single mutants, thus revealing further details otherwise undetectable. As expected, the cerebellar hypoplasia, the paucity of fissures, granule cells and interneurons of the molecular layer, and the external granular layer hypoplasia, common in both staggerer and reeler, were much more pronounced in double mutant. However, the most striking feature of the double mutant cerebellum was the premature disappearance of the external granular layer.The external granular layer is smaller both in staggerer and reeler as compared to the normal but it persists beyoned the normal time (around day 15). In double mutant, however, the external granular layer disappeared by day 7 or 8, reducing the density of granule cells even further. This observation was interpreted as indicating that both the staggerer and reeler genes effect the premature disappearance of the external granular layer. Most of the gross cerebellar anomalies in double mutant such as cerebellar hypoplasia, paucity of fissures and Purkinje and Golgi epithelial cell disalignment could be explained as the result of this premature disappearance of the external granular layer.On the other hand, anomalies of Purkinje cells and Bergmann fibers, which are also present both in staggerer and reeler, did not follow the same additive change.