title: Elevated rate of DNA synthesis and its correlation to cAMP-phosphodiesterase activity during induction of polydactyly in mouse embryos heterozygous for Hemimelia-extra toe (Hmx).
abstract: The induction of polydactyly in mouse embryos heterozygous for Hemimelia-extra toe (Hmx) is associated with aberrant outgrowth of the developing autopod on day 12 of gestation. We have quantitated the rate of DNA synthesis and the activity of cAMP-phosphodiesterase (PDE) that is characteristic of the prospective polydactylous region. Mid-stage 18 hind-limb buds were labeled with [3H]dThd either in situ using whole embryo culture, or as isolated preaxial autopod fragments cultured on a membrane substratum. The mean specific activities of incorporation were compared for normal (+/+) and mutant (Hmx/+) genotypes. A significant (P less than or equal to 0.01) 19% increase, peculiar to the prospective polydactylous region, was measured after 4 hours in embryo culture. The same increment was detected after 4 hours in organ culture, but was amplified linearly to 55% when incubation was extended to 20 hours. During this period, continuous exposure to 1.0 mM IBMX (3-isobutyl-1-methyl xanthine), an inhibitor of cAMP-PDE activity, "slowed down" the rate of DNA synthesis to untreated +/+ proportions. When cAMP-PDE activity was assayed in uncultured autopods, a significant (P less than or equal to 0.01) 18% increase was detected within the prospective polydactylous region specifically on stage 18 of gestation. This is the developmental phase during which polydactylous outgrowth is induced in situ. Thus, uncontrolled cAMP-PDE activity may, in part, provoke the enhanced rate of cell proliferation.
authors.forename: T B
authors.initials: TB
authors.lastname: Knudsen
authors.forename: W A
authors.initials: WA
authors.lastname: Elmer
authors.forename: D M
authors.initials: DM
authors.lastname: Kochhar
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis*; D004622:Embryo, Mammalian / Q000201:enzymology / Q000378:metabolism*; D005532:Foot Deformities, Congenital; D006614:Hindlimb / Q000196:embryology / Q000378:metabolism; D051379:Mice / Q000235:genetics*; D009924:Organ Culture Techniques; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*
chemical_list: D004247:DNA; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D015056:1-Methyl-3-isobutylxanthine