Kif2a depletion generates chromosome segregation and pole coalescence defects in animal caps and inhibits gastrulation of the Xenopus embryo.

Kif2a is a member of the kinesin-13 microtubule depolymerases, which tightly regulate microtubule dynamics for many cellular processes. We characterized Kif2a depletion in Xenopus animal caps and embryos. Kif2a depletion generates defects in blastopore closure.

Pituitary melanotrope cells of Xenopus laevis are of neural ridge origin and do not require induction by the infundibulum.

Classical studies in amphibians have concluded that the endocrine pituitary and pars intermedia are derived from epithelial buccal epidermis and do not require the infundibulum for their induction. These studies also assumed that the pituitary is not subsequently determined by infundibular induction. Our extirpation, auto-transplantation and immunohistochemical studies with Xenopus laevis were initiated to investigate early presumptive pituitary development.

Origin and segregation of cranial placodes in Xenopus laevis.

Cranial placodes are local thickenings of the vertebrate head ectoderm that contribute to the paired sense organs (olfactory epithelium, lens, inner ear, lateral line), cranial ganglia and the adenohypophysis. Here we use tissue grafting and dye injections to generated fate maps of the dorsal cranial part of the non-neural ectoderm for Xenopus embryos between neural plate and early tailbud stages. We show that all placodes arise from a crescent-shaped area located around the anterior neural plate, the pre-placodal ectoderm.

A developmental analysis of periodic albinism in the amphibian Xenopus laevis.

The periodic albino of Xenopus laevis displays a transitory presence of black melanin pigment in the embryo but looses this during tadpole development. This mutation, involving a recessive allele, affects melanogenesis in dermal melanophore pigment cells. It has been suggested that the mutation is intrinsic to the melanophore cell itself or, alternatively, reflects malfunction in the neuroendocrine system that regulates melanophore cell function.

Stage-specific effects of retinoic acid on gene expression during forebrain development.

Treatment of early gastrula- and neurula-staged Xenopus embryos with all-trans retinoic acid (RA) results in truncation of the anterior structures of the forebrain and head. The extent of truncation is dependent upon both the stage of immersion and the RA concentration used. As a method to investigate genes important during early forebrain regionalization, late gastrula and neurula embryos were immersed for 2h within low (1x10(-9)M to 5x10(-8)M) concentrations of RA.

The role of the anterior neural ridge and Fgf-8 in early forebrain patterning and regionalization in Xenopus laevis.

The tissue, cellular and molecular mechanisms that regulate early regional specification of the vertebrate forebrain are largely unknown. We studied the expression patterns of Xbf-1, an anterior (and telencephalon) neural-specific winged helix transcription factor and Fgf-8, an early-secreted factor. This study looked at Xbf-1 and Fgf-8 expression in combination with embryonic grafting experiments and also used beads containing the recombinant Fgf-8 protein to determine these factors' effects upon forebrain patterning events.