Scanning a large genomic region for Gdf6 regulatory elements using overlapping BAC clones. (a) Map of the mouse Gdf6 locus. The second exon of Gdf6 is shaded blue to denote the relative position of the IRES-βgeo cassette in each BAC construct. The structure of the Uqcrb and Gapdh pseudogenes (see text) is indicated, with the Gapdh homology region shown below the map to indicate its opposite orientation relative to Gdf6. SalI (S) and NotI (N) sites used for mapping are indicated. The colored bars represent the five regions marked by BAC ends that contain Gdf6 regulatory elements. Representative examples are shown of reproducibly observed transgenic X-gal staining patterns that require one of the five regions: (b) Cleared 15.5-dpc forelimb stained in the humeroulnar joint of the elbow, (c) cryosection through mammary gland of 12.5-dpc embryo showing punctate expression, (d) medial view of an embryo head bisected sagittally to show expression at base of the sphenoid bone (arrowhead), (e) expression in dorsal neural tube (arrowheads), (f) close-up of whole-mount embryonic eye bisected sagittally, showing dorsal retina expression, (g) ectodermal staining at tip of genital tubercle, (h) cryosection through larynx with expression in vocal folds and near thyroid cartilage, (i) bisected embryo with expression in gut mesentery (arrowhead), (j) distal digit tips of forelimb, (k) whisker buds, and (l) bisected embryo showing incisor bud expression.
