Shh signaling in limb bud ectoderm: potential role in teratogen-induced postaxial ectrodactyly.
A variety of teratogens induce the loss of postaxial forelimb structures when administered during mid-gestation to the mouse. Previous studies demonstrated that teratogen exposure is associated with a reduction in zone of polarizing activity (ZPA) -related polarizing activity without a noticeable loss of Shh expression. Herein, we quantitatively confirm that expression of Shh, Ptch1, and Gli3 are unaltered by teratogen exposure and demonstrate that sonic hedgehog (Shh) translation is unaffected. Examination of the polarizing response of host chick wings to teratogen-exposed ZPA tissue revealed an induced growth response and ectopic induction of Fgf4, Bmp2, Ptch1, and Gli1 expression similar to control ZPA tissue. Control ZPA tissue altered the fate of cells destined to die in the anterior necrotic zone, whereas cell death ensued in hosts receiving teratogen-exposed grafts. Immunohistochemical studies localized Shh protein in the mouse limb to the posterior mesoderm and overlying ectoderm. We postulate that teratogen exposure alters the ability of Shh to signal to the ectoderm and present microarray and reverse transcriptase-polymerase chain reaction data, indicating that Shh signaling could occur in the limb bud ectoderm.
Bell
Sheila M
SM
Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA. sheila.belle@cchmc.org
Schreiner
Claire M
CM
Goetz
John A
JA
Robbins
David J
DJ
Scott
William J
WJ
D000818:Animals; D016923:Cell Death; D018076:DNA, Complementary / Q000235:genetics; D004475:Ectoderm / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D053823:Hedgehog Proteins; D018878:Limb Buds / Q000166:cytology / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D017880:Limb Deformities, Congenital / Q000139:chemically induced* / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D008648:Mesoderm / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D015398:Signal Transduction / Q000187:drug effects*; D013723:Teratogens / Q000494:pharmacology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014921:Wings, Animal / Q000187:drug effects / Q000196:embryology / Q000378:metabolism
D018076:DNA, Complementary; D053823:Hedgehog Proteins; C465570:Shh protein, mouse; D013723:Teratogens; D015534:Trans-Activators