Evaluating Ctbp2 as a candidate QTL for App
This is the Ctbp2 cis QTL, but is detected only in the Rosen striatum data set.
This is the App QTL in the INIA data set.
This slide illustrates one reason why Ctbp2 should be considered a high priority positional candidate gene that may modulate the expression level of App.  Ctbp2 is a strong cis QTL in some brain regions (here the data are taken from the striatum).  If Ctbp2 contains variants that modulate its own expression then these expression differences may produce many downstream effects. Of course, we now want to know much more about the known biology of Ctbp2. What kind of gene is it? To begin to answer that question we can use a number of resources listed in the LINKS page.

Notes:
1. The App QTL is bimodal. Perhaps there are actually two causal factors in this region--one close to 123 Mb and the other close to 127 Mb.
2. The precision of QTL mapping depends on several factors, including the effect size and interactions among QTLs modulating a trait, the number of genetic individuals that are studied, and the distribution of recombinations in the study population.  In the case above, the QTL(s) are likely to be confined to the interval from 120 to 132 Mb. The bootstrap test (yellow bars shown in some of the previous slides) can be usual for estimating the consistency of QTL peaks.