Interaction of cerebellar mutant genes. II. Mice doubly affected by 'reeler' and 'weaver' conditions

An an extension of a study of the mode of ineraction of mutant genes that affect motor activities and cerebellar cytoarchitectonics, mice doubly affected by both the 'reeler' and 'weaver' conditions were produced. The cerebellum of the double mutant showed both reeler and weaver characteristics. Anomalies present in both mutants were greatly accentuated in the double mutant. In addition to the paucity of fissures and general cerebellar disorganization observed in reeler and the extreme scarcity of granule cells seen in weaver, double mutants showed an additional decrease in the cerebellar size and the molecular layer, and a further loss of external granule cells. These observations were interpreted as indicating that the effects of the reeler and weaver genes upon altering the cytoarchitectonics of the cerebellum were additive.