Gad1 expression in developing limbs. (A-H) Gad1 expression in the limb buds from E9.5 to E11.5. (A,B) Expression in the forelimb bud (arrow) at E9.5. (C-E) Gad1 transcripts in the developing limbs at E10.5. (C) Lateral view of E10.5 embryo indicating the forelimb (black arrow) and hindlimb (white arrow). Expression is seen in the proximal forelimb. (D) Higher magnification view of expression in the proximal forelimb (white arrow) and AER (black arrow). (E) Gad1 expression in the hindlimb AER (arrow). (F-H) E11.5 embryos. (F) Fading Gad1 expression in the forelimb AER (black arrow) and crecent-shaped expression in the proximal hindlimb (white arrow). (G) Higher magnification view of declining expression in the AER (black arrow) and strong expression in mesenchyme and ectoderm (white arrow). (H) Higher magnification view of the crescent-shaped expression pattern in the hindlimb (arrow). Scale bar: A, C 1 mm; B, D, E, G, H 500 μm; F 1.5 mm.