It is hard to interpret gene lists. But before we would even get into the statistical properties of annotation term enrichment, or whether network models are appropriate, or anything like that, we have the simpler problem of how to talk, colloquially, about genes connected with a biological process. In particular, there is a weak way to describe gene function one ought to avoid.

What is, for example, an immune-related gene? Why, it’s a gene that is important to immune function, of course! Is beta-catenin an immune-related gene? Wnt signalling is certainly important to immune cell differentiation (Chae & Bothwell 2018), and beta-catenin is certainly important to Wnt signalling function.

Similarly, Paris is a city in France. Therefore, all cities in France are Paris-related.

The thing is, any indirect mechanism can be a mechanism of genuine genetic causation, and this one isn’t even very roundabout. I couldn’t find a known Mendelian disorder with a mechanism that fit the above story, but I don’t think it’s out of the question. At the same time, labeling everything Wnt ”immune-related” would be a little silly, because those genes also do all sorts of other things. If the omnigenenic hypothesis of near-universal pleiotropy is correct, we should expect a lot of genetic causation to be like that: indirect, based on common pathways that do many kinds of different work in different parts of the organism.

That leaves X-related genes a vague notion that can contract or expand at will. From now on, I will think twice before using it.