Example of how to get all mouse gene coordinates using biomaRt:

library(biomaRt)

mouse <- useMart("ensembl", dataset="mmusculus_gene_ensembl")

# check out what's available
ma <- listAttributes(mouse)

loci <- getBM(attribute=c("ensembl_gene_id", "chromosome_name", "start_position", "end_position", "strand"), mart=mouse)

library(biomaRt)

# what marts are available?
listMarts()

bm <- useMart("ensembl")

# what data sets are available?
listDatasets(bm)

bm <- useDataset("dmelanogaster_gene_ensembl", mart=bm)