Temporal and spatial expression of CCN3 during retina development

The matricellular protein Drosophila Cellular Communication Network Factor is required for synaptic transmission and female fertility

Within the extracellular matrix, matricellular proteins are dynamically expressed nonstructural proteins that interact with cell surface receptors, growth factors, and proteases, as well as with structural matrix proteins. The cellular communication network factors family of matricellular proteins serve regulatory roles to regulate cell function and are defined by their conserved multimodular organization. Here, we characterize the expression and neuronal requirement for the Drosophila cellular communication network factor family member. Drosophila cellular communication network factor is expressed in the nervous system throughout development including in subsets of monoamine-expressing neurons. Drosophila cellular communication network factor-expressing abdominal ganglion neurons innervate the ovaries and uterus and the loss of Drosophila cellular communication network factor results in reduced female fertility. In addition, Drosophila cellular communication network factor accumulates at the synaptic cleft and is required for neurotransmission at the larval neuromuscular junction. Analyzing the function of the single Drosophila cellular communication network factor family member will enhance our potential to understand how the microenvironment impacts neurotransmitter release in distinct cellular contexts and in response to activity.

Regenerating CNS myelin: Emerging roles of regulatory T cells and CCN proteins

Efficient myelin regeneration in the central nervous system (CNS) requires the migration, proliferation and differentiation of oligodendrocyte progenitor cells (OPC) into myelinating oligodendrocytes. In demyelinating diseases such as multiple sclerosis (MS), this regenerative process can fail, and therapies targeting myelin repair are currently completely lacking in the clinic. The immune system is emerging as a key regenerative player in many tissues, such as muscle and heart. We recently reported that regulatory T cells (Treg) are required for efficient CNS remyelination. Furthermore, Treg secrete CCN3, a matricellular protein from the CCN family, implicated in regeneration of other tissues. Treg-derived CCN3 promoted oligodendrocyte differentiation and myelination. In contrast, previous studies showed that CCN2 inhibited myelination. These studies highlight the need for further scrutiny of the roles that CCN proteins play in myelin development and regeneration. Collectively, these findings open up exciting avenues of research to uncover the regenerative potential of the adaptive immune system.

CCN3 secreted by prostaglandin E2 inhibits intimal cushion formation in the rat ductus arteriosus

The ductus arteriosus (DA), an essential fetal shunt between the pulmonary trunk and the descending aorta, changes its structure during development. Our previous studies have demonstrated that prostaglandin E₂ (PGE₂)-EP4 signaling promotes intimal cushion formation (ICF) by activating the migration of DA smooth muscle cells via the secretion of hyaluronan. We hypothesized that, in addition to hyaluronan, PGE₂ may secrete other proteins that also regulate vascular remodeling in the DA. In order to detect PGE₂ stimulation-secreted proteins, we found that CCN3 protein was increased in the culture supernatant in the presence of PGE₂ in a dose-dependent manner by nano-flow liquid chromatography coupled with tandem mass spectrometry analysis and enzyme-linked immunosorbent assay. Quantitative RT-PCR analysis revealed that PGE₂ stimulation tended to increase the expression levels of CCN3 mRNA in DA smooth muscle cells. Immunohistochemical analysis revealed that CCN3 was highly localized in the entire smooth muscle layers and the endothelium of the DA. Furthermore, exogenous CCN3 inhibited PGE₂-induced ICF in the ex vivo DA tissues. These results suggest that CCN3 is a secreted protein of the DA smooth muscle cells induced by PGE₂ to suppress ICF of the DA. The present study indicates that CCN3 could be a novel negative regulator of ICF in the DA to fine-tune the PGE₂-mediated DA remodeling.

Matricellular proteins of the Cyr61/CTGF/NOV (CCN) family and the nervous system

Matricellular proteins are secreted proteins that exist at the border of cells and the extracellular matrix (ECM). However, instead of playing a role in structural integrity of the ECM, these proteins, that act as modulators of various surface receptors, have a regulatory function and instruct a multitude of cellular responses. Among matricellular proteins are members of the Cyr61/CTGF/NOV (CCN) protein family. These proteins exert their activity by binding directly to integrins and heparan sulfate proteoglycans and activating multiple intracellular signaling pathways. CCN proteins also influence the activity of growth factors and cytokines and integrate their activity with integrin signaling. At the cellular level, CCN proteins regulate gene expression and cell survival, proliferation, differentiation, senescence, adhesion, and migration. To date, CCN proteins have been extensively studied in the context of osteo- and chondrogenesis, angiogenesis, and carcinogenesis, but the expression of these proteins is also observed in a variety of tissues. The role of CCN proteins in the nervous system has not been systematically studied or described. Thus, the major aim of this review is to introduce the CCN protein family to the neuroscience community. We first discuss the structure, interactions, and cellular functions of CCN proteins and then provide a detailed review of the available data on the neuronal expression and contribution of CCN proteins to nervous system development, function, and pathology.

CCN3 overexpression inhibits growth of callosal projections via upregulation of RAB25

The cysteine-rich 61/connective tissue growth factor 3 (CCN3) is a member of the CCN family of secreted multifunctional proteins involved in a variety of cellular processes including migration, adhesion, and differentiation. Previous studies have shown that CCN3 is expressed in the developing rat central nervous system, and enhanced CCN3 expression is highly correlated with tumorigenesis. However, the expression pattern and influence of abnormal CCN3 expression during mouse cortical development remains to be elucidated. Here, we show that CCN3 expression in mice is first detectable at embryonic day 15 and increases until postnatal day 21. We overexpressed CCN3 in mouse cortical neurons using uni- and bilateral electroporation. Our in vivo overexpression experiments showed that elevated CCN3 expression inhibited the axonal outgrowth of callosal projection neurons. Moreover, we identified the small GTPase RAB25 as a downstream effector molecule of CCN3 using transcriptomic analysis with CCN3 overexpressed in cortical tissue. In vivo ectopic expression of RAB25 or the dominant-negative RAB25-T26N also revealed that the GTPase activity of RAB25 is involved in the CCN3-mediated regulation of neuronal outgrowth. Taken together, our results suggest that tight regulation of CCN3 expression is necessary for normal cortical neuronal connectivity during development, and RAB25 negatively regulates neuronal differentiation as a downstream effector of CCN3.