In vivo screen of genomic regions sufficient for Rab3A endogenous expression. (a) Physical map of Rab3A locus on mouse chromosome 8, adapted from the UCSC Genome Browser. The top panel describes the 15 kb genomic region of the Rab3A locus. The middle track shows a measure of evolutionary conservation of the Rab3A locus in 17 vertebrates. Pairwise alignments of each species to the mouse genome are displayed as a grayscale density plot in which darker scale indicates higher conservation. The arrows on the bottom indicate the positions of multiple-species conserved elements (MCE1 to 5) around the Rab3A gene. (b) Schematic drawing of the EGFP reporter constructs used to generate transgenic mice. The two constructs (15 kb and 5.5 kb) were derived from the modified BAC clone RP23-433N2 containing an EGFP reporter (green block) in the position of Rab3A exon 1 (blue block). (c) Sagittal view of wild-type mouse embryos at 14.5 dpc stained with Rab3A antibody. A strong signal in the central nervous system (brain and spinal cord) was observed. (d, e) Sagittal view of transgenic embryos at 14.5 dpc stained with EGFP antibody. A strong signal in the central nervous system was observed in transgenic positive individuals, either carrying the 15 kb or 5.5 kb construct. TG-, transgenic negative; TG+, transgenic positive.