Faculty Bibliography

Differential adhesion between migrating neurons and transient radial glial fibers enables the deployment of neurons into appropriate layers in the developing cerebral cortex. The identity of radial glial signals that regulate the termination of migration remains unclear. Here, we identified a radial glial surface antigen, SPARC (secreted protein acidic and rich in cysteine)-like 1, distributed predominantly in radial glial fibers passing through the upper strata of the cortical plate (CP) where neurons end their migration. Neuronal migration and adhesion assays indicate that SPARC-like 1 functions to terminate neuronal migration by reducing the adhesivity of neurons at the top of the CP. Cortical neurons fail to achieve appropriate positions in the absence of SPARC-like 1 function in vivo. Together, these data suggest that antiadhesive signaling via SPARC-like 1 on radial glial cell surfaces may enable neurons to recognize the end of migration in the developing cerebral cortex.

The genes that control development of embryonic melanocytes are poorly defined. Although transcription factor Ap-2alpha is expressed in neural crest (NC) cells, its role in development of embryonic melanocytes and other neural crest derivatives is unclear because mouse Ap-2alpha mutants die before melanogenesis. We show that zebrafish embryos injected with morpholino antisense oligonucleotides complementary to ap-2alpha (ap-2alpha MO) complete early morphogenesis normally and have neural crest cells. Expression of c-kit, which encodes the receptor for the Steel ligand, is reduced in these embryos, and, similar to zebrafish c-kit mutant embryos, embryonic melanophores are reduced in number and migration. The effects of ap-2alpha MO injected into heterozygous and homozygous c-kit mutants support the notion that Ap-2alpha works through C-kit and additional target genes to mediate melanophore cell number and migration. In contrast to c-kit mutant embryos, in ap-2alpha MO-injected embryos, melanophores are small and under-pigmented, and unexpectedly, analysis of mosaic embryos suggests Ap-2alpha regulates melanophore differentiation through cell non-autonomous targets. In addition to melanophore phenotypes, we document reduction of other neural crest derivatives in ap-2alpha MO-injected embryos, including jaw cartilage, enteric neurons, and sympathetic neurons. These results reveal that Ap-2alpha regulates multiple steps of melanophore development, and is required for development of other neuronal and non-neuronal neural crest derivatives

Epithelial-mesenchymal transformation (EMT), the process by which epithelial cells are converted into motile, invasive mesenchymal cells, is critical to valvulogenesis. Transforming growth factor-beta3 (TGF-beta3), an established mediator of avian atrioventricular (AV) canal EMT, is secreted as a latent complex. In vitro, plasmin-mediated proteolysis has been shown to release active TGF-betas from the latent complex. Annexin II, a co-receptor for tissue plasminogen activator (tPA) and plasminogen, promotes cell-surface generation of the serine protease plasmin. Here, we show that annexin II-mediated plasmin activity regulates release of active TGF-beta3 during chick AV canal EMT. Primary embryonic endocardial-derived cells express annexin II which promotes plasminogen activation in vitro. Incubation of heart explant cultures with either alpha(2)antiplasmin (alpha(2)AP), a major physiological plasmin inhibitor, or anti-annexin II IgG, blocked EMT by approximately 80%, and 50%, respectively. Anti-annexin II IgG-mediated inhibition of EMT was overcome by the addition of recombinant TGF-beta3. Upon treatment with anti-annexin II IgG or alpha(2)AP, conditioned medium from heart explant cultures showed absence of the active fragment of TGF-beta3 by Western blot analysis and a approximately 50% decrease in TGF-beta specific bioactivity. Our results suggest that annexin II-mediated plasmin activity regulates the release of active TGF-beta during cardiac valve development in the avian heart

Recent preliminary data suggest that vaccination with Alzheimer A beta might reduce senile plaque load and stabilize cognitive decline in human Alzheimer disease. To examine the mechanisms and consequences of anti-A beta-antibody formation in a species more closely related to humans, rhesus monkeys (Macaca mulatta) were vaccinated with aggregated A beta 1-42. Immunized monkeys developed anti-A beta titers exceeding 1:1000, and their plasma A beta levels were 5- to 10-fold higher than the plasma A beta levels observed in monkeys vaccinated with aggregated amylin. These data support the use of nonhuman primates to model certain phenomena associated with vaccination of humans with aggregated Alzheimer A beta

We expressed and characterized two sHsps, StHsp19.7 and StHsp14.0, from a thermoacidophilic crenarchaeon, Sulfolobus tokodaii strain 7. StHsp19.7 forms a filamentous structure consisting of spherical particles and lacks molecular chaperone activity. Fractionation of Sulfolobus extracts by size exclusion chromatography with immunoblotting indicates that StHsp19.7 exists as a filamentous structure in vivo. On the other hand, StHsp14.0 exists as a spherical oligomer like other sHsps. It showed molecular chaperone activity to protect thermophilic 3-isopropylmalate dehydrogenase (IPMDH) from thermal aggregation at 87 degrees C. StHsp14.0 formed variable-sized complexes with denatured IPMDH at 90 degrees C. Using StHsp14.0 labeled with fluorescence or biotin probe and magnetic separation, subunit exchanges between complexes were demonstrated. This is the first report on the filament formation of sHsp and also the high molecular chaperone activity of thermophilic archaeal sHsps.