Gene name converter: Human to Mouse / Mouse to Human / Gene name to Ensembl ID

convert_human_to_mouse <- function(gene_list) {
    output = c()
    mouse_human_genes = read.csv("https://www.informatics.jax.org/downloads/reports/HOM_MouseHumanSequence.rpt",sep="\t")
    for(gene in gene_list) {
          class_key = (mouse_human_genes %>% filter(Symbol == gene & Common.Organism.Name == "human"))[['DB.Class.Key']]
          if( !identical(class_key, integer(0)) ) {
            human_genes = (mouse_human_genes %>% filter(DB.Class.Key == class_key[1] & Common.Organism.Name=="mouse, laboratory"))[,"Symbol"]
            for(human_gene in human_genes) {
                output = rbind(c(gene, human_gene), output)
            }}}
     return (output)}


convert_mouse_to_human <- function(gene_list) {
    output = c()
    mouse_human_genes = read.csv("https://www.informatics.jax.org/downloads/reports/HOM_MouseHumanSequence.rpt",sep="\t")
    for(gene in gene_list) {
          class_key = (mouse_human_genes %>% filter(Symbol == gene & Common.Organism.Name == "mouse, laboratory"))[['DB.Class.Key']]
          if( !identical(class_key, integer(0)) ) {
            human_genes = (mouse_human_genes %>% filter(DB.Class.Key == class_key[1] & Common.Organism.Name=="human"))[,"Symbol"]
            for(human_gene in human_genes) {
                output = rbind(c(human_gene, gene), output)
            }}}
     return (output)}

human_mart <- useMart("ensembl", dataset = "hsapiens_gene_ensembl")
ensg_conversion <- getBM(attributes = c("external_gene_name", "ensembl_gene_id"),
                         filters = "external_gene_name",
                         values = c("CLEC4E", DEGNet_overlap_H),
                         mart = human_mart)
DEGNet_overlap_H_ensg <- ensg_conversion$ensembl_gene_id