Hi Jing,
Thanks for diving deep into the gene identification issue.
I think it's fine to use symbols as long as the mapping is reversible to standardized identifiers. For example, if there is a file that contains a (one-to-one) Symbol–ID mapping, we can easily convert the dataset without fear of corruption.
If I understand correctly: Currently there is no file that will allow us to map `HiSeqV2` from symbols to IDs. We can always use a third-party mapping, but should expect some information loss due to symbol ambiguity and version differences. In the future, Xena plans to modify its data wrangling to become more aware of gene IDs and will be able to provide a symbol-to-ID map?