Differential and overlapping expression patterns of X-dll3 and Pax-6 genes suggest distinct roles in olfactory system development of the African clawed frog Xenopus laevis.

In Xenopus laevis, the formation of the adult olfactory epithelium involves embryonic, larval and metamorphic phases. The olfactory epithelium in the principal cavity (PC) develops during embryogenesis from the olfactory placode and is thought to respond to water-borne odorants throughout larval life. During metamorphosis, the PC undergoes major transformations and is exposed to air-borne odorants. Also during metamorphosis, the middle cavity (MC) develops de novo. The olfactory epithelium in the MC has the same characteristics as that in the larval PC and is thought to respond to water-borne odorants. Using in situ hybridization, we analyzed the expression pattern of the homeobox genes X-dll3 and Pax-6 within the developing olfactory system. Early in development, X-dll3 is expressed in both the neuronal and non-neuronal ectoderm of the sense plate and in all cell layers of the olfactory placode and larval PC. Expression becomes restricted to the neurons and basal cells of the PC by mid-metamorphosis. During metamorphosis, X-dll3 is also expressed throughout the developing MC epithelium and becomes restricted to neurons and basal cells at metamorphic climax. This expression pattern suggests that X-dll3 is first involved in the patterning and genesis of all cells forming the olfactory tissue and is then involved in neurogenesis or neuronal maturation in putative water- and air-sensing epithelia. In contrast, Pax-6 expression is restricted to the olfactory placode, larval PC and metamorphic MC, suggesting that Pax-6 is specifically involved in the formation of water-sensing epithelium. The expression patterns suggest that X-dll3 and Pax-6 are both involved in establishing the olfactory placode during embryonic development, but subtle differences in cellular and temporal expression patterns suggest that these genes have distinct functions.

Developmental eye and neural tube defects in the eye blebs mouse.

In the mouse, eye blebs (eb) is a spontaneous mutation that presents a useful model for the study of abnormal eye development. Since its initial description three decades ago, little information has been generated regarding the developmental course of eb eyes. Although the gene for eb has not been identified, much can be learned from the developmental defects present in the eb mouse. First detected in the eye at embryonic day 11.5 (E11.5), the eb defect is observed as an increased vascularization throughout the developing eye and head region. As development proceeds, the embryonic eye fills with blood, and the resulting hematoma distorts the shape of the iris. The eyelids fail to close, and animals are born with open eyes. Lens degeneration and retinal folding are characteristic of eb, as are microphthalmia and thick, disorganized irises. A second presentation of the eb defect is disruption of neural tube closure in the anterior and hindbrain neuropores. These eb animals are born with open neural tubes but with apparently normal eyes.

Embryonic stem cell lines derived from human blastocysts.

Human blastocyst-derived, pluripotent cell lines are described that have normal karyotypes, express high levels of telomerase activity, and express cell surface markers that characterize primate embryonic stem cells but do not characterize other early lineages. After undifferentiated proliferation in vitro for 4 to 5 months, these cells still maintained the developmental potential to form trophoblast and derivatives of all three embryonic germ layers, including gut epithelium (endoderm); cartilage, bone, smooth muscle, and striated muscle (mesoderm); and neural epithelium, embryonic ganglia, and stratified squamous epithelium (ectoderm). These cell lines should be useful in human developmental biology, drug discovery, and transplantation medicine.

Characterization of proliferin-related protein.

Proliferin-related protein (mPRP) is a member of the PRL/GH family in the mouse. We have generated an antiserum against mPRP expressed as a bacterial fusion protein; this antiserum detects mPRP in the conditioned media of placental tissue cultures as a heterogeneous population of glycoproteins. We have also expressed mPRP in mammalian tissue culture cells and purified the secreted protein. N-terminal sequence analysis of the purified protein reveals that it is secreted as a 214 amino acid protein after removal of a 30 amino acid signal polypeptide. An antiserum raised against the purified protein detects high levels of mPRP in maternal serum during gestation. The site of synthesis of this protein has been localized by in situ hybridization to the basal zone of the day-10 mouse placenta, which is distinct from the site of synthesis of other placental proteins in this family.