ETV5 and brain neoplasm: brain tumor (brat) and erm function in the immature INP to promote INP identity specification in the type II neuroblast lineage, and the defective specification of an INP identity leads to the formation of supernumerary type II neuroblasts in the brat or erm mutant brain (Xiao et al., 2012; Eroglu et al., 2014; Janssens et al., 2014; Koe et al., 2014; Komori et al., 2014).