Deficiency of the Corpus Callosum: Incomplete Penetrance and Substrain Differentiation in BALB/c Mice

Abstract

In a foundation population of BALB/c mice used to establish a colony at Waterloo in 1977, about 11% of adults showed either total absence or gross deficiency of the corpus callosum. Comparisons between parents and offspring, between progenies of different males, and between 13 separate lines established by full-sib inbreeding showed that variation in the adult corpus callosum reflected a genuine incomplete penetrance in a genetically uniform population. However, after seven generations of inbreeding, a spontaneous change occurred in one line (BALB/cWahl), resulting in more than 50% of adults with deficient corpus callosum, among which about 20% have complete absence of callosal axons traversing the hemispheres.

Key Words:

• Inbred strain
• incomplete penetrance
• corpus callosum
• hippocampal commissure
• anterior commissure
• brain weight
• sex difference
• spontaneous mutation

Additional information

Notes on contributors

Douglas Wahlsten

Joyce Laing works in the Department of Child and Family Psychiatry, Playfield House, Cupar, Fife, and is a Consultant Art Therapist to Psychiatric Hospitals and Prisons and Chairwoman of the Scottish Society of Art and Psychology.