Trim Seurat object to contain expression info only for selected genes I'm working with some large Seurat objects (MOCA, MCA, Tabula Muris) studying gene coexpression, and I'm running into memory issues. 

Is it possible to remove all genes in a Seurat object that are not in a specified gene array? Ideally I'd like to be working with a small R matrix with say, 250k rows (cells) and 10-50 columns (gene expression data) which will enable fast processing and comprehensive analysis using other packages.
A different approach if you are using Seurat3, is DietSeurat(). It allows you to diet the object by removing the components that you don't need. For example you can keep the normalised/scaled matrix and remove the raw counts. This approach could reduce space and memory usage, while keeping all your genes in place.