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We have assessed the efficacy of the recently developed CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated) system for genome modification in the amphibian Xenopus tropicalis. As a model experiment, targeted mutations of the tyrosinase gene were verified, showing the expected albinism phenotype in injected embryos. We(More)
By using a photoactivatable analog of 11-cis-retinal in rhodopsin, we have previously identified the amino acids Phe-115, Ala-117, Glu-122, Trp-126, Ser-127, and Trp-265 as major sites of cross-linking to the chromophore. To further investigate the amino acids that interact with retinal, we have now used site-directed mutagenesis to replace a variety of(More)
A photoactivatable analog of 11-cis-retinal has been used to probe the orientation of retinal in bovine rhodopsin. The analog binds to the opsin to regenerate a chromophore with lambda max at 458 nm. The linkage site of the analog to the opsin was confirmed to be Lys-296 as in 11-cis-retinal rhodopsin. The analog-reconstituted rhodopsin activated transducin(More)
ProBMP4 is initially cleaved at a site adjacent to the mature ligand (the S1 site) allowing for subsequent cleavage at an upstream (S2) site. Mature BMP4 synthesized from a precursor in which the S2 site cannot be cleaved remains in a complex with the prodomain that is targeted for lysosomal degradation, and is thus less active when overexpressed in(More)
Smad6 and Smad7 comprise a subclass of vertebrate Smads that antagonize, rather than transduce, TGF-beta family signaling. These Anti-Smads can block BMP signaling, as evidenced by their ability to induce a secondary dorsal axis when misexpressed ventrally in Xenopus embryos. Smad7 inhibits additional TGF-beta related pathways, and causes spina bifida when(More)
To explore the origins and consequences of tetraploidy in the African clawed frog, we sequenced the Xenopus laevis genome and compared it to the related diploid X. tropicalis genome. We characterize the allotetraploid origin of X. laevis by partitioning its genome into two homoeologous subgenomes, marked by distinct families of 'fossil' transposable(More)
Cyclophilins are ubiquitous and abundant proteins that exhibit peptidyl prolyl cis-trans isomerization (PPlase) activity in vitro. Their functions in vivo, however, are not well understood. Two new retinal cyclophilin isoforms, types I and II, are highly expressed in cone photoreceptors of the vertebrate retina. Type-II cyclophilin is identical to RanBP2, a(More)
Mutations in the Pax6 gene cause ocular defects in both vertebrate and invertebrate animal species, and the disease aniridia in humans. Despite extensive experimentation on this gene in multiple species, including humans, we still do not understand the earliest effects on development mediated by this gene. This prompted us to develop pax6 mutant lines in(More)
In order to prepare a completely light-stable rhodopsin, we have synthesized an analog, II, of 11-cis retinal in which isomerization at the C11-C12 cis-double bond is blocked by formation of a cyclohexene ring from the C10 to C13-methyl. We used this analog to generate a rhodopsin-like pigment from opsin expressed in COS-1 cells and opsin from rod outer(More)
We describe a novel recessive and nonlethal pigmentation mutant in Xenopus tropicalis. The mutant phenotype can be initially observed in tadpoles after stage 39/40, when mutant embryos display markedly reduced pigmentation in the retina and the trunk. By tadpole stage 50 almost all pigmented melanophores have disappeared. Most interestingly, those embryos(More)