Expression and involvement of gicerin, a cell adhesion molecule, in the development of chick optic tectum

CD146, a therapeutic target involved in cell plasticity

Since its identification as a marker for advanced melanoma in the 1980s, CD146 has been found to have multiple functions in both physiological and pathological processes, including embryonic development, tissue repair and regeneration, tumor progression, fibrosis disease, and inflammations. Subsequent research has revealed that CD146 is involved in various signaling pathways as a receptor or co-receptor in these processes. This correlation between CD146 and multiple diseases has sparked interest in its potential applications in diagnosis, prognosis, and targeted therapy. To better comprehend the versatile roles of CD146, we have summarized its research history and synthesized findings from numerous reports, proposing that cell plasticity serves as the underlying mechanism through which CD146 contributes to development, regeneration, and various diseases. Targeting CD146 would consequently halt cell state shifting during the onset and progression of these related diseases. Therefore, the development of therapy targeting CD146 holds significant practical value.

Novel subdomains of the mouse olfactory bulb defined by molecular heterogeneity in the nascent external plexiform and glomerular layers

Background

In the mouse olfactory system, the role of the olfactory bulb in guiding olfactory sensory neuron (OSN) axons to their targets is poorly understood. What cell types within the bulb are necessary for targeting is unknown. What genes are important for this process is also unknown. Although projection neurons are not required, other cell-types within the external plexiform and glomerular layers also form synapses with OSNs. We hypothesized that these cells are important for targeting, and express spatially differentially expressed guidance cues that act to guide OSN axons within the bulb.

Results

We used laser microdissection and microarray analysis to find genes that are differentially expressed along the dorsal-ventral, medial-lateral, and anterior-posterior axes of the bulb. The expression patterns of these genes divide the bulb into previously unrecognized subdomains. Interestingly, some genes are expressed in both the medial and lateral bulb, showing for the first time the existence of symmetric expression along this axis. We use a regeneration paradigm to show that several of these genes are altered in expression in response to deafferentation, consistent with the interpretation that they are expressed in cells that interact with OSNs.

Conclusion

We demonstrate that the nascent external plexiform and glomerular layers of the bulb can be divided into multiple domains based on the expression of these genes, several of which are known to function in axon guidance, synaptogenesis, and angiogenesis. These genes represent candidate guidance cues that may act to guide OSN axons within the bulb during targeting.

Molecular cloning and analysis of the mouse gicerin gene

Gicerin is a cell adhesion molecule, which has five immunoglobulin-like loop structures in an extracellular domain followed by a single transmembrane domain and a short cytoplasmic tail. We have reported that gicerin participates in neurite extension and structural organization of the nervous system, and its expression in the nervous system is high during the development and dramatically decreased after birth. To elucidate the mechanism how the expression of gicerin is regulated, we performed a genomic cloning of a mouse gicerin. A fragment of 16 kbp genomic clone contained 8 kbp gicerin gene composed of 16 exons with 6 kbp upstream region. Genomic cloning revealed that two isoforms of gicerin were generated by an alternative splicing of exon 15 results in cytoplasmic domains composed of either 63 or 21 amino acids. As for an expressional regulation of gicerin, we found that the mRNA content of gicerin in PC12 cells was regulated by cAMP. Quantitative-PCR analysis revealed that forskolin induced four-fold increase of gicerin mRNA. To characterize the involvement of its promoter region, we examined the promoter activity in PC12 cells by a luciferase-reporter assay. We found that a CRE site located at 60 bp upstream of gicerin gene was responsible for the increase of its mRNA induced by forskolin.

Gicerin/CD146 is involved in neurite extension of NGF-treated PC12 cells

Gicerin/CD146 is a cell adhesion molecule, which belongs to the immunoglobulin (Ig) superfamily. We have reported that it has a homophilic binding activity, which participates in the neurite extension from embryonic neurons. To elucidate how gicerin is involved in the neurite extension mechanism, we employed PC12 cells, which expresses gicerin/CD146. PC12 cells extend longer neurites by nerve growth factor (NGF) on gicerin substrate than on without gicerin substrate, which indicates that gicerin participates in neurite extension by NGF. We also found that the expression of gicerin in PC12 cells is induced by NGF. Over-expression of gicerin also promotes neurite extension by gicerin-gicerin homophilic interaction. These findings suggested that increase of gicerin expression by NGF promotes the gicerin-gicerin homophilic interaction resulting in the neurite extension.