A biometrical-genetic analysis of granule cell number in the area dentata of house mice.

Considerable variability in the number of granule cells in the area dentata has been found among inbred strains of mice. In this report a simplified triple-test cross breeding design was employed to identify and discriminate between heritable and non-heritable sources of this variability. Granule cell numbers were estimated in two previously identified extreme strains of mice and in their reciprocal F1 hybrids with 3 strains of mice known to be intermediate between the 2 extremes. Analytical techniques of biometrical genetics applied to the neuron number estimates indicated that genetic transmission of this trait involves genes located upon autosomes. Transmission does not involve cytoplasmic factors within the female egg, or maternally-mediated differences in nutrition. Of the total variability in dentate granule cell number, 86% is estimated to be determined by an additive genetic component. A dorsal-to-ventral increase in the size of granule cell nuclei was found for all genotypes; some possible bases for this increase are discussed.