I suppose this has a related change in core-api?

In any case, we already have an interface for returning the gene (among other things), which we've used in the other types. It's the `BiomarkerRow` (or something like that). `RegionRowImpl` should implement that in addition to `Region` (I (reading  `Region`'s description, I don't think it's entirely appropriate `Region` should extend that `BiomarkerRow`). This won't allow you to give back the gene id, but no one cares about it.