Project 1: The Mouse Brain Library Project 2: Internet Microscopy (iScope) Project 3: Neurocartographer and Segmentation of the MBL Project 4: The Neurogenetics Tool Box
















Principal Investigator/Program Director Williams, Robert W.


Selectivity of QTLs.

 Before mapping QTLs, we need to consider the issue of specificity of gene action. The brain weight data in the MBL were not corrected for the significant differences in the mean body weights of these strains. Because brain weight may simply be a function of body size, there is a risk of mapping body weight QTLs instead of QTLs that have specific effects on brain weight or cell number. To ensure that brain weight and not some other factor was mapped, variation in brain weight predictable from variation in body weight must be factored out. A crude way of doing this is to take the ratio of brain to body weight as the variable, but a computationally and conceptually better approach uses regression analysis to remove predictable variance associated with body size . Williams and colleagues used multiple regression to remove variance in cell number that was actually associated with total brain weight. This same logic applies in mapping QTLs that affect particular CNS cell populations.

The lesson to be taken from this discussion is that whatever types of QTLs we are trying to map, we need to carefully consider the higher-order structures and make sure that we have taken variation in these structures into account.





Mapping Brain Weight QTLs