Cadherin-20 expression by motor neurons is regulated by Sonic hedgehog during spinal cord development

Magnetic mesoporous silica nanoparticles loaded with peptides for the targeted repair of cavernous nerve injury underlying erectile dysfunction

Erectile dysfunction (ED) is a common male sexual disorder characterized by repeated or persistent difficulty in achieving or maintaining an erection. It can arise from various factors, with cavernous nerve injury (CNI) from radical prostatectomy being a predominant cause of iatrogenic ED, posing significant clinical concerns. The complexity of cavernous tissue damage in CNI-induced ED (CNIED) often results in poor efficacy and resistance to conventional vascular ED treatments. To address CNI-induced ED, this study developed a system of magnetic mesoporous silica nanoparticles (MSNs) loaded with peptides for targeted treatment. Core-shell Fe3O4-coated MSNs were used as drug carriers and loaded with RADA16-I/RAD-RGI peptides (PD) to create a neurotrophic microenvironment to treat peripheral nerve defects. Furthermore, the neuro-targeting peptide HLNILSTLWKYR (PT) was grafted onto MSNs. The in vivo therapeutic effect was evaluated using a rat bilateral cavernous nerve injury (BCNI) model. The results showed that the neuro-targeted Fe3O4@SiO2-PT-PD nanoparticles significantly promoted regeneration of the cavernous nerve and restored erectile function. This promising strategy offers significant clinical potential for treating CNI-induced ED. Nanomedicine technology has the potential to not only improve treatment outcomes but also reduce side effects in healthy cells, paving the way for more accurate targeted repair of cavernous nerve damage.

Cadherin-7 enhances Sonic Hedgehog signalling by preventing Gli3 repressor formation during neural tube patterning

Sonic Hedgehog (Shh) is a ventrally enriched morphogen controlling dorsoventral patterning of the neural tube. In the dorsal spinal cord, Gli3 protein bound to suppressor-of-fused (Sufu) is converted into Gli3 repressor (Gli3R), which inhibits Shh-target genes. Activation of Shh signalling prevents Gli3R formation, promoting neural tube ventralization. We show that cadherin-7 (Cdh7) expression in the intermediate spinal cord region is required to delimit the boundary between the ventral and the dorsal spinal cord. We demonstrate that Cdh7 functions as a receptor for Shh and enhances Shh signalling. Binding of Shh to Cdh7 promotes its aggregation on the cell membrane and association of Cdh7 with Gli3 and Sufu. These interactions prevent Gli3R formation and cause Gli3 protein degradation. We propose that Shh can act through Cdh7 to limit intracellular movement of Gli3 protein and production of Gli3R, thus eliciting more efficient activation of Gli-dependent signalling.

Restricted expression of classic cadherins in the spinal cord of the chicken embryo

Classic cadherins belong to the family of cadherin genes and play important roles in neurogenesis, neuron migration, and axon growth. In the present study, we compared the expression patterns of 10 classic cadherins (Cdh2, Cdh4, Cdh6, Cdh7, Cdh8, Cdh9, Cdh11, Cdh12, Cdh18, and Cdh20) in the developing chicken spinal cord (SP) by in situ hybridization. Our results indicate that each of the investigated cadherins exhibits a spatially restricted and temporally regulated pattern of expression. At early developmental stages (E2.5–E3), Cdh2 is expressed throughout the neuroepithelial layer. Cdh6 is strongly positive in the roof plate and later also in the floor plate. Cdh7, Cdh11, Cdh12, and Cdh20 are expressed in restricted regions of the basal plate of the SP. At intermediate stages of development (E4–E10), specific expression profiles are observed for all investigated cadherins in the differentiating mantle layer along the dorsoventral, mediolateral, and rostrocaudal dimensions. Expression profiles are especially diverse for Cdh2, Cdh4, Cdh8, Cdh11, and Cdh20 in the dorsal horn, while different pools of motor neurons exhibit signal for Cdh6, Cdh7, Cdh8, Cdh9, Cdh12, and Cdh20 in the ventral horn. Interestingly, subpopulations of cells in the dorsal root ganglion express combinations of different cadherins. In the surrounding tissues, such as the boundary cap cells and the notochord, the cadherins are also expressed differentially. The highly regulated spatiotemporal expression patterns of the classic cadherins indicate that these genes potentially play multiple and diverse roles during the development of the SP and its surrounding tissues.

ADAM10 negatively regulates neuronal differentiation during spinal cord development

Members of the ADAM (a disintegrin and metalloprotease) family are involved in embryogenesis and tissue formation via their proteolytic function, cell-cell and cell-matrix interactions. ADAM10 is expressed temporally and spatially in the developing chicken spinal cord, but its function remains elusive. In the present study, we address this question by electroporating ADAM10 specific morpholino antisense oligonucleotides (ADAM10-mo) or dominant-negative ADAM10 (dn-ADAM10) plasmid into the developing chicken spinal cord as well as by in vitro cell culture investigation. Our results show that downregulation of ADAM10 drives precocious differentiation of neural progenitor cells and radial glial cells, resulting in an increase of neurons in the developing spinal cord, even in the prospective ventricular zone. Remarkably, overexpression of the dn-ADAM10 plasmid mutated in the metalloprotease domain (dn-ADAM10-me) mimics the phenotype as found by the ADAM10-mo transfection. Furthermore, in vitro experiments on cultured cells demonstrate that downregulation of ADAM10 decreases the amount of the cleaved intracellular part of Notch1 receptor and its target, and increases the number of βIII-tubulin-positive cells during neural progenitor cell differentiation. Taken together, our data suggest that ADAM10 negatively regulates neuronal differentiation, possibly via its proteolytic effect on the Notch signaling during development of the spinal cord.

Regulation of cadherin expression in nervous system development

This review addresses our current understanding of the regulatory mechanisms for classical cadherin expression during development of the vertebrate nervous system. The complexity of the spatial and temporal expression patterns is linked to morphogenic and functional roles in the developing nervous system. While the regulatory networks controlling cadherin expression are not well understood, it is likely that the multiple signaling pathways active in the development of particular domains also regulate the specific cadherins expressed at that time and location. With the growing understanding of the broader roles of cadherins in cell-cell adhesion and non-adhesion processes, it is important to understand both the upstream regulation of cadherin expression and the downstream effects of specific cadherins within their cellular context.

Expression of delta-protocadherins in the spinal cord of the chicken embryo

Protocadherins constitute the largest subfamily of cadherin genes and are widely expressed in the nervous system. In the present study, we cloned eight members of the delta-protocadherin subfamily of cadherins (Pcdh1, Pcdh7, Pcdh8, Pcdh9, Pcdh10, Pcdh17, Pcdh18, and Pcdh19) from the chicken, and investigated their expression in the developing chicken spinal cord by in situ hybridization. Our results showed that each of the investigated delta-protocadherins exhibits a spatially restricted and temporally regulated pattern of expression. Pcdh1, Pcdh8, Pcdh18, and Pcdh19 are expressed in restricted dorsoventral domains of the neuroepithelial layer at early developmental stages (E2.5–E4). In the differentiating mantle layer, specific expression profiles are observed for all eight delta-protocadherins along the dorsoventral, mediolateral, and rostrocaudal dimensions at intermediate stages of development (E6–E10). Expression profiles are especially diverse in the motor column, where different pools of motor neurons exhibit signal for subsets of delta-protocadherins. In the dorsal root ganglion, subpopulations of cells express combinations of Pcdh1, Pcdh7, Pcdh8, Pcdh9, Pcdh10, and Pcdh17. The ventral boundary cap cells are positive for Pcdh7, Pcdh9, and Pcdh10. Signals for Pcdh8, Pcdh18, and Pcdh19 are found in the meninges. Surrounding tissues, such as the notochord, dermomyotome, and sclerotome also exhibit differential expression patterns. The highly regulated spatiotemporal expression patterns of delta-protocadherins suggest that they have multiple and diverse functions during development of the spinal cord and its surrounding tissues.

Gene transfer into older chicken embryos by ex ovo electroporation

The chicken embryo provides an excellent model system for studying gene function and regulation during embryonic development. In ovo electroporation is a powerful method to over-express exogenous genes or down-regulate endogenous genes in vivo in chicken embryos(1). Different structures such as DNA plasmids encoding genes(2-4), small interfering RNA (siRNA) plasmids(5), small synthetic RNA oligos(6), and morpholino antisense oligonucleotides(7) can be easily transfected into chicken embryos by electroporation. However, the application of in ovo electroporation is limited to embryos at early incubation stages (younger than stage HH20--according to Hamburg and Hamilton)(8) and there are some disadvantages for its application in embryos at later stages (older than stage HH22--approximately 3.5 days of development). For example, the vitelline membrane at later stages is usually stuck to the shall membrane and opening a window in the shell causes rupture of the vessels, resulting in death of the embryos; older embryos are covered by vitelline and allantoic vessels, where it is difficult to access and manipulate the embryos; older embryos move vigorously and is difficult to control the orientation through a relatively small window in the shell. In this protocol we demonstrate an ex ovo electroporation method for gene transfer into chicken embryos at late stages (older than stage HH22). For ex ovo electroporation, embryos are cultured in Petri dishes(9) and the vitelline and allantoic vessels are widely spread. Under these conditions, the older chicken embryos are easily accessed and manipulated. Therefore, this method overcomes the disadvantages of in ovo electroporation applied to the older chicken embryos. Using this method, plasmids can be easily transfected into different parts of the older chicken embryos(10-12).

Cadherin-19 expression is restricted to myelin-forming cells in the chicken embryo

We cloned chicken cadherin-19 that demonstrates high similarity to human and rat cadherin-19. Chicken cadherin-19 is a type II classic cadherin that is located on the long arm of chicken chromosome 2 and is composed of 13 exons and 12 introns. The expression profile of cadherin-19 was analyzed by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization during chicken embryonic development. Its expression starts at E2.5, then gradually increases to reach a peak at E20. In contrast to previous results obtained in rat, chicken cadherin-19 is expressed both in Schwann cells and oligodendrocytes, also at late stages of development. We found no other cell type positive for cadherin-19 in the chicken embryo throughout development, suggesting that cadherin-19 is selectively expressed by myelin-forming cells and might play a role in myelin formation. The sequence of cadherin-19 shares high similarity with that of cadherin-7 and cadherin-20, and the three genes form a cluster on chromosome 2. Their expression patterns, however, are rather distinct although partial overlap is observed. For example, cadherin-19 and cadherin-7 are co-expressed by Schwann cells but not by oligodendrocytes. Moreover, a subset of interneurons express cadherin-7 but not cadherin-19 or cadherin-20. Despite their close genetic relation, the three cadherins have acquired functions in rather different cell types during nervous system development.