Biomedical subjects

S G Babb

Publications and source records attributed to S G Babb.

4 recordsLinked to original sources

PubMed2002

Up-regulation of cadherin-2 and cadherin-4 in regenerating visual structures of adult zebrafish.

Cadherins are homophilic cell adhesion molecules that control development of a variety of tissues and maintenance of adult structures. In this study, we examined expression of zebrafish cadherin-2 (Cdh2, N-cadherin) and cadherin-4 (Cdh4, R-cadherin) in the visual system of adult zebrafish after eye or optic nerve lesions using immunocytochemistry and immunoblotting. Both Cdh2 and Cdh4 immunoreactivities were specifically up-regulated in regenerating retina and/or the optic pathway. Furthermore, temporal expression patterns of these two cadherins were distinct during the regeneration of the injured tissues. Cadherins have been shown to regulate axonal outgrowth in the developing nervous system, but this is the first report, to our knowledge, of increased cadherin expression associated with axonal regeneration in the vertebrate central nervous system. Our results suggest that both Cdh2 and Cdh4 may be important for regeneration of injured retinal ganglion cell axons.

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PubMed2001

Zebrafish E-cadherin: expression during early embryogenesis and regulation during brain development.

Zebrafish E-cadherin (cdh1) cell adhesion molecule cDNAs were cloned. We investigated spatial and temporal expression of cdh1 during early embryogenesis. Expression was observed in blastomeres, the anterior mesoderm during gastrulation, and developing epithelial structures. In the developing nervous system, cdh1 was detected at the pharyngula stage (24 hpf) in the midbrain-hindbrain boundary (MHB). Developmental regulation of MHB formation involves wnt1 and pax2.1. wnt1 expression preceded cdh1 expression during MHB formation, and cdh1 expression in the MHB was dependent on normal development of this structure.

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PubMed1997

Fimbrin in podosomes of monocyte-derived osteoclasts.

Fimbrin, an actin-bundling protein, is a component of the osteoclast adhesion complexes called podosomes. In this study, we (1) determined the localization of fimbrin in the mature rabbit osteoclast as well as in differentiating osteoclasts using the avian monocyte-derived osteoclast differentiation model, (2) characterized the distribution and accumulation of three fimbrin isotypes (T, L, and I) in avian monocytes as they fused to form multinucleate osteoclast-like cells, and (3) report for the first time, a close spatial relationship between podosomes and microtubules using fimbrin as a marker of the podosome. Immunofluorescence using anti-T-fimbrin, anti-L-fimbrin, and pan-isotype-anti-fimbrin antibodies, showed that fimbrin is an integral component of the podosome core in the mature rabbit osteoclast and in the monocyte-derived osteoclast throughout differentiation. Anti-I-fimbrin, however, did not show immunoreactivity in these cultures. These studies also show that in the avian model of monocyte-derived osteoclast differentiation, day 2 cells (D2) are predominantly mononucleate and have few podosomes. By days 4 and 6 in culture (D4 and D6), many cells have fused and punctate rows of podosomes are commonly observed at cell margins. Analysis by Western blot of protein accumulation showed that after an initial small rise from D2 to D4, L-fimbrin levels remained relatively constant from D4 to D6. However, T-fimbrin protein levels increase steadily from D2 to D6, suggesting that it may be related to the increase in podosome formation as monocytes fuse to form osteoclasts. Finally, we examined the distribution of podosomes relative to other cytoskeletal elements such as microtubules and intermediate filaments. Double immunofluorescence labeling using anti-fimbrin and anti-tubulin showed podosomes lying adjacent to microtubules at cell margins. When osteoclasts were treated with nocodazole (1 X 10(-6) M) to disrupt microtubules, the distribution of podosomes became more random and was no longer confined to the cell periphery. These results suggest that microtubule-podosome interactions may play a role in osteoclast adhesion.

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PubMedDate not supplied

Differential expression of cadherin-2 and cadherin-4 in the developing and adult zebrafish visual system.

Cadherins are homophilic cell adhesion molecules that control development of a variety of tissues and maintenance of adult structures. Although cadherins have been implicated in the development of the brain, including the visual system, in several vertebrate species, little is known of their role in zebrafish. In this study, we examined distribution of cadherin-2 (Cdh2, N-cadherin) in the visual system of developing and adult zebrafish using both immunocytochemical and in situ hybridization methods, and we compared Cdh2 distribution to that of the previously reported and closely related cadherin-4 (Cdh4, R-cadherin). As in other vertebrates, in zebrafish embryos Cdh2 was widely expressed in the early nervous system, but its expression became more restricted as development proceeded. Cdh4 was not detectable until later in development, at about the time when the first ganglion cells are generated. Cdh2 and Cdh4 were expressed in distinct regions of developing visual structures, including the lens. We hypothesize that the differential expression of these two cadherins in developing zebrafish visual structures reflects functionally different roles in the development of the vertebrate visual system.

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