Assume I have found the top 0.01% most frequent genes from a [gene expression file](https://bioinformatics.stackexchange.com/questions/559/how-to-read-and-interpret-a-gene-expression-quantification-file). 

Let's say, these are 10 genes and I want to study the [protein protein interactions](https://en.wikipedia.org/wiki/Protein%E2%80%93protein_interaction), the protein network and pathway.

I thought to use [string-db](https://string-db.org) or [interactome](http://interactome.dfci.harvard.edu), but I am not sure what would be a plausible way to approach this problem and to build the protein network etc. Are there other more suitable databases?

How can I build a mathematical graph or network for these data?