Mash1 and Ngn2 GOF experiment. (a) Mouse embryos at 10.5 days of development were electroporated in the telencephalic vesicle with Mash1 or Ngn2 expression vectors together with LacZ reporter constructs specific for either Ngn2 (0.27 kb DeltaN LacZ) or Mash1 (0.16 kb DeltaM LacZ) [12,79]. The two regulatory sequences used in these reporter transgenes are located within the 0.8 kb distal promoter region of the Dll1 gene . Embryos were orientated during the electroporation to target the cortex (Ngn2 vector and 0.27 kb DeltaN LacZ reporter) or the basal ganglia (Mash1 vector and 0.16 kb DeltaM LacZ reporter). Ngn2 and Mash1 overexpression enhances the activity of the LacZ reporter, assessed by β-galactosidase staining, compared with endogenous proneural proteins (empty expressing vector: Ctrl). Efficiency of electroporation was assessed using a GFP expression vector and was similar in all electroporated embryos (not shown). (b) Fold changes of selected potential targets of Ngn2, Mash1, or both factors in Ngn2 GOF and Mash1 GOF experiments and in Mash1 mutant and Mash1;Ngn2 double mutant embryos, based on normalized microarray data. A * indicates known direct targets of Mash1 or Ngn2. (c) Putative targets of Mash1 and Ngn2 were identified through fusion of Ngn2 and Mash1 LOF and GOF microarray datasets. Common targets were identified as transcripts that were decreased in Mash1 LOF and Mash1;Ngn2 LOF experiments and increased in Ngn2 and Mash1 GOF experiments. Mash1 targets are those transcripts that were only decreased in Mash1 LOF and increased in Mash1 GOF. Ngn2 targets are those transcripts that were only decreased in Ngn2/Mash1 LOF and increased in Ngn2 GOF. A cut-off of 1.3-fold was used as described in more detail in Methods. A full list of predicted targets categorized by GO is available in Additional file 3.