Cloning and expression of murine SC1, a gene product homologous to SPARC

Heart failure-related genes associated with oxidative stress and the immune landscape in lung cancer

Background

Lung cancer is a common comorbidity of heart failure (HF). The early identification of the risk factors for lung cancer in patients with HF is crucial to early diagnosis and prognosis. Furthermore, oxidative stress and immune responses are the two critical biological processes shared by HF and lung cancer. Therefore, our study aimed to select the core genes in HF and then investigate the potential mechanisms underlying HF and lung cancer, including oxidative stress and immune responses through the selected genes.

Methods

Differentially expressed genes (DEGs) were analyzed for HF using datasets extracted from the Gene Expression Omnibus database. Functional enrichment analysis was subsequently performed. Next, weighted gene co-expression network analysis was performed to select the core gene modules. Support vector machine models, the random forest method, and the least absolute shrinkage and selection operator (LASSO) algorithm were applied to construct a multigene signature. The diagnostic values of the signature genes were measured using receiver operating characteristic curves. Functional analysis of the signature genes and immune landscape was performed using single-sample gene set enrichment analysis. Finally, the oxidative stress-related genes in these signature genes were identified and validated in vitro in lung cancer cell lines.

Results

The DEGs in the GSE57338 dataset were screened, and this dataset was then clustered into six modules using weighted gene co-expression network analysis; MEblue was significantly associated with HF (cor = -0.72, p < 0.001). Signature genes including extracellular matrix protein 2 (ECM2), methyltransferase-like 7B (METTL7B), meiosis-specific nuclear structural 1 (MNS1), and secreted frizzled-related protein 4 (SFRP4) were selected using support vector machine models, the LASSO algorithm, and the random forest method. The respective areas under the curve of the receiver operating characteristic curves of ECM2, METTL7B, MNS1, and SFRP4 were 0.939, 0.854, 0.941, and 0.926, respectively. Single-sample gene set enrichment analysis revealed significant differences in the immune landscape of the patients with HF and healthy subjects. Functional analysis also suggested that these signature genes may be involved in oxidative stress. In particular, METTL7B was highly expressed in lung cancer cell lines. Meanwhile, the correlation between METTL7B and oxidative stress was further verified using flow cytometry.

Conclusion

We identified that ECM2, METTL7B, MNS1, and SFRP4 exhibit remarkable diagnostic performance in patients with HF. Of note, METTL7B may be involved in the co-occurrence of HF and lung cancer by affecting the oxidative stress immune responses.

The Matricellular Protein Hevin Is Involved in Alcohol Use Disorder

Astrocytic-secreted matricellular proteins have been shown to influence various aspects of synaptic function. More recently, they have been found altered in animal models of psychiatric disorders such as drug addiction. Hevin (also known as Sparc-like 1) is a matricellular protein highly expressed in the adult brain that has been implicated in resilience to stress, suggesting a role in motivated behaviors. To address the possible role of hevin in drug addiction, we quantified its expression in human postmortem brains and in animal models of alcohol abuse. Hevin mRNA and protein expression were analyzed in the postmortem human brain of subjects with an antemortem diagnosis of alcohol use disorder (AUD, n = 25) and controls (n = 25). All the studied brain regions (prefrontal cortex, hippocampus, caudate nucleus and cerebellum) in AUD subjects showed an increase in hevin levels either at mRNA or/and protein levels. To test if this alteration was the result of alcohol exposure or indicative of a susceptibility factor to alcohol consumption, mice were exposed to different regimens of intraperitoneal alcohol administration. Hevin protein expression was increased in the nucleus accumbens after withdrawal followed by a ethanol challenge. The role of hevin in AUD was determined using an RNA interference strategy to downregulate hevin expression in nucleus accumbens astrocytes, which led to increased ethanol consumption. Additionally, ethanol challenge after withdrawal increased hevin levels in blood plasma. Altogether, these results support a novel role for hevin in the neurobiology of AUD.

Parallel evolution of ameloblastic scpp genes in bony and cartilaginous vertebrates

In bony vertebrates, skeletal mineralization relies on the secretory calcium-binding phosphoproteins (Scpp) family whose members are acidic extracellular proteins posttranslationally regulated by the Fam20°C kinase. As scpp genes are absent from the elephant shark genome, they are currently thought to be specific to bony fishes (osteichthyans). Here, we report a scpp gene present in elasmobranchs (sharks and rays) that evolved from local tandem duplication of sparc-L 5′ exons and show that both genes experienced recent gene conversion in sharks. The elasmobranch scpp is remarkably similar to the osteichthyan scpp members as they share syntenic and gene structure features, code for a conserved signal peptide, tyrosine-rich and aspartate/glutamate-rich regions, and harbor putative Fam20°C phosphorylation sites. In addition, the catshark scpp is coexpressed with sparc-L and fam20°C in tooth and scale ameloblasts, similarly to some osteichthyan scpp genes. Despite these strong similarities, molecular clock and phylogenetic data demonstrate that the elasmobranch scpp gene originated independently from the osteichthyan scpp gene family. Our study reveals convergent events at the sparc-L locus in the two sister clades of jawed vertebrates, leading to parallel diversification of the skeletal biomineralization toolkit. The molecular evolution of sparc-L and its coexpression with fam20°C in catshark ameloblasts provides a unifying genetic basis that suggests that all convergent scpp duplicates inherited similar features from their sparc-L precursor. This conclusion supports a single origin for the hypermineralized outer odontode layer as produced by an ancestral developmental process performed by Sparc-L, implying the homology of the enamel and enameloid tissues in all vertebrates.

Characterization of Hevin (SPARCL1) Immunoreactivity in Postmortem Human Brain Homogenates

Hevin is a matricellular glycoprotein that plays important roles in neural developmental processes such as neuronal migration, synaptogenesis and synaptic plasticity. In contrast to other matricellular proteins whose expression decreases when development is complete, hevin remains highly expressed, suggesting its involvement in adult brain function. In vitro studies have shown that hevin can have different post-translational modifications. However, the glycosylation pattern of hevin in the human brain remains unknown, as well as its relative distribution and localization. The present study provides the first thorough characterization of hevin protein expression by Western blot in postmortem adult human brain. Our results demonstrated two major specific immunoreactive bands for hevin: an intense band migrating around 130 kDa, and a band migrating around 100 kDa. Biochemical assays revealed that both hevin bands have a different glycosylation pattern. Subcellular fractionation showed greater expression in membrane-enriched fraction than in cytosolic preparation, and a higher expression in prefrontal cortex (PFC) compared to hippocampus (HIP), caudate nucleus (CAU) and cerebellum (CB). We confirmed that a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) and matrixmetalloproteinase 3 (MMP-3) proteases digestion led to an intense double band with similar molecular weight to that described as SPARC-like fragment (SLF). Finally, hevin immunoreactivity was also detected in human astrocytoma, meningioma, cerebrospinal fluid and serum samples, but was absent from any blood cell type.

ECM2 and GLT8D2 in human pulmonary artery hypertension: fruits from weighted gene co-expression network analysis

Background

Pulmonary artery hypertension (PAH) is an incurable disease with a high mortality rate. Current medications ameliorate symptoms but cannot target adverse vascular remodeling. New therapeutic strategies for PAH need to be established.

Methods

Using the weighted gene coexpression network analysis (WGCNA) algorithm, we constructed a coexpression network of dataset GSE117261 from the Gene Expression Omnibus (GEO) database. Key modules were identified by the relationship between module eigengenes and clinical traits. Hub genes were screened out based on gene significance (GS), module membership (MM), and mean pulmonary artery pressure (mPAP). External validations were conducted in GSE48149 and GSE113439. Functional enrichment and immune cell infiltration were analyzed using Metascape and CIBERSORTx.

Results

The WGCNA analysis revealed 13 coexpression modules. The pink module had the highest correlation with PAH in terms of module eigengene (r=0.79; P=2e-18) and module significance (MS =0.43). Functional enrichment indicated genes in the pink module contributed to the immune system process and extracellular matrix (ECM). In the pink module, ECM2 (GS =0.65, MM =0.86, ρ=0.407, P=0.0019) and GLT8D2 (GS =0.63, MM =0.85, ρ=0.443, P=0.006) were identified as hub genes. For immune cells infiltration in PAH lung tissue, hub genes were positively correlated with M2 macrophages and resting mast cells, and were negatively correlated with monocytes, neutrophils, and CD4-naïve T cells.

Conclusions

Our research identified 2 hub genes ECM2 and GLT8D2 related to PAH. The functions of these hub genes were involved in the immune process and ECM, indicating that they might serve as candidate therapeutic targets for PAH.

PD-L1 expression with QR1 and E1L3N antibodies according to histological ovarian cancer subtype: A series of 232 cases

Therapeutic strategies for epithelial ovarian cancers are evolving with the advent of immunotherapy, such as PD-L1 inhibitors, with encouraging results. However, little data are available on PDL-1 expression in ovarian cancers. Thus, we set out to determine the PD-L1 expression according to histological subtype. We evaluated the expression of two PD-L1 clones – QR1 and E1L3N – with two scores, one based on the percentage of labeled tumor cells (tumor proportion score, TPS) and the other on labeled immune cells (combined proportion score, CPS) in a consecutive retrospective series of 232 ovarian cancers. PD-L1 expression was more frequent in high grade serous carcinoma (27.5% with E1L3N clone and 41.5% with QR1 clone), grade 3 endometrioid carcinoma (25% with E1L3N clone and 50% with QR1 clone), and clear-cell carcinomas (27.3% with E1L3N clone and 29.6% with QR1 clone) than other histological subtypes with CPS score. Using the CPS score, 17% of cases were labeled with E1L3N vs 28% with QR1. Using the TPS score, 14% of cases were positive to E1L3N vs 17% for QR1. For TPS and CPS, respectively, 77% and 78% of the QR1 cases were concordant with E1L3N for the thresholds of 1%. Overall and progression-free survival between PD-L1 positive and PD-L1 negative patients were not different across all histological types, and each subtype in particular for serous carcinomas expressing PD-L1. Expression of PD-L1 is relatively uncommon in epithelium ovarian tumors. When positive, usually <10% of tumor cells are labeled. QR1 clone and CPS appear the best tools to evaluate PD-L1 expression.

Species-, organ- and cell-type-dependent expression of SPARCL1 in human and mouse tissues

SPARCL1 is a matricellular protein with anti-adhesive, anti-proliferative and anti-tumorigenic functions and is frequently downregulated in tumors such as colorectal carcinoma or non-small cell lung cancer. Studies have identified SPARCL1 as an angiocrine tumor suppressor secreted by tumor vessel endothelial cells, thereby exerting inhibitory activity on angiogenesis and tumor growth, in colorectal carcinoma. It is unknown whether SPARCL1 may exert these homeostatic functions in all organs and in other species. Therefore, SPARCL1 expression was comparatively analysed between humans and mice in a systematic manner. Murine Sparcl1 (mSparcl1) is most strongly expressed in the lung; expressed at an intermediate level in most organs, including the large intestine; and absent in the liver. In human tissues, SPARCL1 (hSPARCL1) was detected in all organs, with the strongest expression in the stomach, large intestine and lung, mostly consistent with the murine expression pattern. A striking difference between human and murine tissues was the absence of mSparcl1 expression in murine livers, while human livers showed moderate expression. Furthermore, mSparcl1 was predominantly associated with mural cells, whereas hSPARCL1 was detected in both mural and endothelial cells. Human SPARCL1 expression was downregulated in different carcinomas, including lung and colon cancers. In conclusion, this study revealed species-, organ- and cell-type-dependent expression of SPARCL1, suggesting that its function may not be similar between humans and mice.

Astrocyte-microglial association and matrix composition are common events in the natural history of primary familial brain calcification

Primary familial brain calcification (PFBC) is an age-dependent and rare neurodegenerative disorder characterized by microvascular calcium phosphate deposits in the deep brain regions. Known genetic causes of PFBC include loss-of-function mutations in genes involved in either of three processes-platelet-derived growth factor (PDGF) signaling, phosphate homeostasis or protein glycosylation-with unclear molecular links. To provide insight into the pathogenesis of PFBC, we analyzed murine models of PFBC for the first two of these processes in Pdgfb^ret/ret and Slc20a2^-/- mice with regard to the structure, molecular composition, development and distribution of perivascular calcified nodules. Analyses by transmission electron microscopy and immunofluorescence revealed that calcified nodules in both of these models have a multilayered ultrastructure and occur in direct contact with reactive astrocytes and microglia. However, whereas nodules in Pdgfb^ret/ret mice were large, solitary and smooth surfaced, the nodules in Slc20a2^-/- mice were multi-lobulated and occurred in clusters. The regional distribution of nodules also differed between the two models. Proteomic analysis and immunofluorescence stainings revealed a common molecular composition of the nodules in the two models, involving proteins implicated in bone homeostasis, but also proteins not previously linked to tissue mineralization. While the brain vasculature of Pdgfb^ret/ret mice has been reported to display reduced pericyte coverage and abnormal permeability, we found that Slc20a2^-/- mice have a normal pericyte coverage and no overtly increased permeability. Thus, lack of pericytes and increase in permeability of the blood-brain barrier are likely not the causal triggers for PFBC pathogenesis. Instead, gene expression and spatial correlations suggest that astrocytes are intimately linked to the calcification process in PFBC.

Cartography of hevin-expressing cells in the adult brain reveals prominent expression in astrocytes and parvalbumin neurons

Hevin, also known as SPARC-like 1, is a member of the secreted protein acidic and rich in cysteine family of matricellular proteins, which has been implicated in neuronal migration and synaptogenesis during development. Unlike previously characterized matricellular proteins, hevin remains strongly expressed in the adult brain in both astrocytes and neurons, but its precise pattern of expression is unknown. The present study provides the first systematic description of hevin mRNA distribution in the adult mouse brain. Using isotopic in situ hybridization, we showed that hevin is strongly expressed in the cortex, hippocampus, basal ganglia complex, diverse thalamic nuclei and brainstem motor nuclei. To identify the cellular phenotype of hevin-expressing cells, we used double fluorescent in situ hybridization in mouse and human adult brains. In the mouse, hevin mRNA was found in the majority of astrocytes but also in specific neuronal populations. Hevin was expressed in almost all parvalbumin-positive projection neurons and local interneurons. In addition, hevin mRNA was found in: (1) subsets of other inhibitory GABAergic neuronal subtypes, including calbindin, cholecystokinin, neuropeptide Y, and somatostatin-positive neurons; (2) subsets of glutamatergic neurons, identified by the expression of the vesicular glutamate transporters VGLUT1 and VGLUT2; and (3) the majority of cholinergic neurons from motor nuclei. Hevin mRNA was absent from all monoaminergic neurons and cholinergic neurons of the ascending pathway. A similar cellular profile of expression was observed in human, with expression of hevin in parvalbumin interneurons and astrocytes in the cortex and caudate nucleus as well as in cortical glutamatergic neurons. Furthermore, hevin transcript was enriched in ribosomes of astrocytes and parvalbumin neurons providing a direct evidence of hevin mRNAs translation in these cell types. This study reveals the unique and complex expression profile of the matricellular protein hevin in the adult brain. This distribution is compatible with a role of hevin in astrocytic-mediated adult synaptic plasticity and in the regulation of network activity mediated by parvalbumin-expressing neurons.

Evolution of dental tissue mineralization: an analysis of the jawed vertebrate SPARC and SPARC-L families

BACKGROUND

The molecular bases explaining the diversity of dental tissue mineralization across gnathostomes are still poorly understood. Odontodes, such as teeth and body denticles, are serial structures that develop through deployment of a gene regulatory network shared between all gnathostomes. Dentin, the inner odontode mineralized tissue, is produced by odontoblasts and appears well-conserved through evolution. In contrast, the odontode hypermineralized external layer (enamel or enameloid) produced by ameloblasts of epithelial origin, shows extensive structural variations. As EMP (Enamel Matrix Protein) genes are as yet only found in osteichthyans where they play a major role in the mineralization of teeth and others skeletal organs, our understanding of the molecular mechanisms leading to the mineralized odontode matrices in chondrichthyans remains virtually unknown.

RESULTS

We undertook a phylogenetic analysis of the SPARC/SPARC-L gene family, from which the EMPs are supposed to have arisen, and examined the expression patterns of its members and of major fibrillar collagens in the spotted catshark Scyliorhinus canicula, the thornback ray Raja clavata, and the clawed frog Xenopus tropicalis. Our phylogenetic analyses reveal that the single chondrichthyan SPARC-L gene is co-orthologous to the osteichthyan SPARC-L1 and SPARC-L2 paralogues. In all three species, odontoblasts co-express SPARC and collagens. In contrast, ameloblasts do not strongly express collagen genes but exhibit strikingly similar SPARC-L and EMP expression patterns at their maturation stage, in the examined chondrichthyan and osteichthyan species, respectively.

CONCLUSIONS

A well-conserved odontoblastic collagen/SPARC module across gnathostomes further confirms dentin homology. Members of the SPARC-L clade evolved faster than their SPARC paralogues, both in terms of protein sequence and gene duplication. We uncover an osteichthyan-specific duplication that produced SPARC-L1 (subsequently lost in pipidae frogs) and SPARC-L2 (independently lost in teleosts and tetrapods).Our results suggest the ameloblastic expression of the single chondrichthyan SPARC-L gene at the maturation stage reflects the ancestral gnathostome situation, and provide new evidence in favor of the homology of enamel and enameloids in all gnathostomes.

Effect of ECM2 expression on bovine skeletal muscle-derived satellite cell differentiation

Extracellular matrix components have important regulatory functions during cell proliferation and differentiation. In recent study, extracellular matrix were shown to have a strong effect on skeletal muscle differentiation. Here, we aimed to elucidate the effects of extracellular matrix protein 2 (ECM2), an extracellular matrix component, on the differentiation of bovine skeletal muscle-derived satellite cells (MDSCs). Western blot and immunofluorescence analyses were used to elucidate the ECM2 expression pattern in bovine MDSCs during differentiation in vitro. CRISPR/Cas9 technology was used to activate or inhibit ECM2 expression to study its effects on the in vitro differentiation of bovine MDSCs. ECM2 expression was shown to increase gradually during bovine MDSC differentiation, and the levels of this protein were higher in more highly differentiated myotubes. ECM2 activation promoted MDSC differentiation, whereas its suppression inhibited the differentiation of these cells. Here, for the first time, we demonstrated the importance of ECM2 expression during bovine MDSC differentiation; these results could lead to treatments that help to increase beef cattle muscularity.

Functional Analysis of the Matricellular Protein SPARC with Novel Monoclonal Antibodies

SPARC (osteonectin, BM-40) is a matricellular glycoprotein that is expressed in many embryogenic and adult tissues undergoing remodeling or repair. SPARC modulates cellular interaction with the extracellular matrix (ECM), inhibits cell adhesion and proliferation, and regulates growth factor activity. To explore further the function and activity of this protein in tissue homeostasis, we have developed several monoclonal antibodies (MAbs) that recognize distinct epitopes on SPARC. The MAbs bind to SPARC with high affinity and identify SPARC by ELISA, Western blotting, immunoprecipitation, immunocytochemistry, and/or immunohistochemistry. The MAbs were also characterized in functional assays for potential alteration of SPARC activity. SPARC binds to collagen I and laminin-1 through an epitope defined by MAb 293; this epitope is not involved in the binding of SPARC to collagen III. The other MAbs did not interfere with the binding of SPARC to collagen I or III or laminin-1. Inhibition of the anti-adhesive effect of SPARC on endothelial cells by MAb 236 was also observed. Functional analysis of SPARC in the presence of these novel MAbs now confirms that the activities ascribed to this matricellular protein can be assigned to discrete subdomains.

Matricellular proteins in the trabecular meshwork: review and update

Abstract Primary open-angle glaucoma (POAG) is a leading cause of blindness worldwide, and intraocular pressure (IOP) is an important modifiable risk factor. IOP is a function of aqueous humor production and aqueous humor outflow, and it is thought that prolonged IOP elevation leads to optic nerve damage over time. Within the trabecular meshwork (TM), the eye's primary drainage system for aqueous humor, matricellular proteins generally allow cells to modulate their attachments with and alter the characteristics of their surrounding extracellular matrix (ECM). It is now well established that ECM turnover in the TM affects outflow facility, and matricellular proteins are emerging as significant players in IOP regulation. The formalized study of matricellular proteins in TM has gained increased attention. Secreted protein acidic and rich in cysteine (SPARC), myocilin, connective tissue growth factor (CTGF), and thrombospondin-1 and -2 (TSP-1 and -2) have been localized to the TM, and a growing body of evidence suggests that these matricellular proteins play an important role in IOP regulation and possibly the pathophysiology of POAG. As evidence continues to emerge, these proteins are now seen as potential therapeutic targets. Further study is warranted to assess their utility in treating glaucoma in humans.

Hevin plays a pivotal role in corneal wound healing

Background

Hevin is a matricellular protein involved in tissue repair and remodeling via interaction with the surrounding extracellular matrix (ECM) proteins. In this study, we examined the functional role of hevin using a corneal stromal wound healing model achieved by an excimer laser-induced irregular phototherapeutic keratectomy (IrrPTK) in hevin-null (hevin^-/-) mice. We also investigated the effects of exogenous supplementation of recombinant human hevin (rhHevin) to rescue the stromal cellular components damaged by the excimer laser.

Methodology/Principal Findings

Wild type (WT) and hevin^-/- mice were divided into three groups at 4 time points- 1, 2, 3 and 4 weeks. Group I served as naïve without any treatment. Group II received epithelial debridement and underwent IrrPTK using excimer laser. Group III received topical application of rhHevin after IrrPTK surgery for 3 days. Eyes were analyzed for corneal haze and matrix remodeling components using slit lamp biomicroscopy, in vivo confocal microscopy, light microscopy (LM), transmission electron microscopy (TEM), immunohistochemistry (IHC) and western blotting (WB). IHC showed upregulation of hevin in IrrPTK-injured WT mice. Hevin^-/- mice developed corneal haze as early as 1-2 weeks post IrrPTK-treatment compared to the WT group, which peaked at 3-4 weeks. They also exhibited accumulation of inflammatory cells, fibrotic components of ECM proteins and vascularized corneas as seen by IHC and WB. LM and TEM showed activated keratocytes (myofibroblasts), inflammatory debris and vascular tissues in the stroma. Exogenous application of rhHevin for 3 days reinstated inflammatory index of the corneal stroma similar to WT mice.

Conclusions/Significance

Hevin is transiently expressed in the IrrPTK-injured corneas and loss of hevin predisposes them to aberrant wound healing. Hevin^-/- mice develop early corneal haze characterized by severe chronic inflammation and stromal fibrosis that can be rescued with exogenous administration of rhHevin. Thus, hevin plays a pivotal role in the corneal wound healing.

A dynamic history of gene duplications and losses characterizes the evolution of the SPARC family in eumetazoans

The vertebrates share the ability to produce a skeleton made of mineralized extracellular matrix. However, our understanding of the molecular changes that accompanied their emergence remains scarce. Here, we describe the evolutionary history of the SPARC (secreted protein acidic and rich in cysteine) family, because its vertebrate orthologues are expressed in cartilage, bones and teeth where they have been proposed to bind calcium and act as extracellular collagen chaperones, and because further duplications of specific SPARC members produced the small calcium-binding phosphoproteins (SCPP) family that is crucial for skeletal mineralization to occur. Both phylogeny and synteny conservation analyses reveal that, in the eumetazoan ancestor, a unique ancestral gene duplicated to give rise to SPARC and SPARCB described here for the first time. Independent losses have eliminated one of the two paralogues in cnidarians, protostomes and tetrapods. Hence, only non-tetrapod deuterostomes have conserved both genes. Remarkably, SPARC and SPARCB paralogues are still linked in the amphioxus genome. To shed light on the evolution of the SPARC family members in chordates, we performed a comprehensive analysis of their embryonic expression patterns in amphioxus, tunicates, teleosts, amphibians and mammals. Our results show that in the chordate lineage SPARC and SPARCB family members were recurrently recruited in a variety of unrelated tissues expressing collagen genes. We propose that one of the earliest steps of skeletal evolution involved the co-expression of SPARC paralogues with collagenous proteins.

The molecular profiles of neural stem cell niche in the adult subventricular zone

Neural stem cells (NSCs) reside in a unique microenvironment called the neurogenic niche and generate functional new neurons. The neurogenic niche contains several distinct types of cells and interacts with the NSCs in the subventricular zone (SVZ) of the lateral ventricle. While several molecules produced by the niche cells have been identified to regulate adult neurogenesis, a systematic profiling of autocrine/paracrine signaling molecules in the neurogenic regions involved in maintenance, self-renewal, proliferation, and differentiation of NSCs has not been done. We took advantage of the genetic inducible fate mapping system (GIFM) and transgenic mice to isolate the SVZ niche cells including NSCs, transit-amplifying progenitors (TAPs), astrocytes, ependymal cells, and vascular endothelial cells. From the isolated cells and microdissected choroid plexus, we obtained the secretory molecule expression profiling (SMEP) of each cell type using the Signal Sequence Trap method. We identified a total of 151 genes encoding secretory or membrane proteins. In addition, we obtained the potential SMEP of NSCs using cDNA microarray technology. Through the combination of multiple screening approaches, we identified a number of candidate genes with a potential relevance for regulating the NSC behaviors, which provide new insight into the nature of neurogenic niche signals.

Secreted protein acidic and rich in cysteines-like 1 suppresses aggressiveness and predicts better survival in colorectal cancers

PURPOSE

Secreted protein acidic and rich in cysteines-like 1 (SPARCL1) is an extracellular matrix glycoprotein with malignancy-suppressing potential. The hypothesis that SPARCL1 reduces cancer invasiveness and predicts better survival in colorectal cancers (CRC) was investigated.

EXPERIMENTAL DESIGN

Stable SPARCL1 transfectants, RKO-SPARCL1, and corresponding vector control were constructed and implanted into nude mice to generate a mouse xenograft model of liver metastasis. Also, a retrospective outcome study was conducted on the COH set (222 CRCs) and ZJU set (412 CRCs). The protein expression level of SPARCL1 was determined by immunohistochemistry. The Kaplan-Meier and Cox analyses were used for survival analysis. The association of SPARCL1 with mesenchymal-epithelial transition (MET) was examined by reverse transcription PCR (RT-PCR) and Western blot analysis.

RESULTS

The ectopic expression of SPARCL1 significantly reduced the potential for anchorage-independent growth, migration, invasion and induced cell differentiation in RKO and SW620 cells. In mouse xenograft model, the expression of SPARCL1 significantly reduced the liver metastasis (P < 0.01). The patient-based studies revealed that the expression of SPARCL1 was related to better differentiation (P < 0.01), less lymph node involvement [OR, 0.67; 95% confidence interval (CI), 0.45-1.00], and less distant metastasis (OR, 0.38; 95% CI, 0.18-0.79). The Kaplan-Meier and Cox analysis showed that the expression of SPARCL1 was associated with better overall survival (log-rank: P < 0.01; HR, 0.57; 95% CI, 0.39-0.84). Transfection of SPARCL1 induced MET of colon cancer cells.

CONCLUSION

SPARCL1 functions as a tumor suppressor promoting differentiation possibly via MET, which inhibits the aggressiveness of CRCs.

Effect of hevin deletion in mice and characterization in trabecular meshwork

PURPOSE

Hevin is a matricellular protein and the result of a gene duplication of SPARC. SPARC-null mice have lower intraocular pressure (IOP). The function of hevin in trabecular meshwork (TM) is unknown. The authors hypothesized that hevin is expressed in TM and has a functional consequence on IOP.

METHODS

Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting were performed to identify transcription and protein expression in TM and cultured TM cells. Toluidine blue stain was performed to compare anterior segments in wild-type (WT) and hevin-null mice. Confocal microscopy localized the structural distribution of hevin in human TM and hevin/SPARC in mouse anterior segments. IOP was measured in WT (C57BL6 × 129SvJ) and hevin-null mice using both rebound tonometry and cannulation tonometry. Central corneal thickness (CCT) was measured by ocular coherence tomography. Cultured TM cells were treated with TGF-β2 because TGF-β2 is associated with primary open-angle glaucoma.

RESULTS

Hevin mRNA and protein were expressed in TM tissues but not in cultured TM cells. No structural differences were observed in anterior segments of WT and hevin-null mice. IOP between hevin-null (n = 46) and WT (n = 44) mice was equivalent (15.3 ± 1.92 mm Hg and 15.9 ± 2.01 mm Hg, respectively; P = 0.15). CCT was similar between hevin-null and WT mice (107.95 ± 5.06 μm and 106.76 ± 3.46 μm, respectively; P = 0.11). TGF-β2 did not induce hevin, whereas SPARC expression was induced in a dose-dependent manner in human TM cell cultures.

CONCLUSIONS

Hevin does not appear to be critical to regulating IOP. Hevin is expressed in TM but, in contrast to SPARC, does not appear to be regulated by TGF-β2.

Expression, functional, and structural analysis of proteins critical for otoconia development

Otoconia, developed during late gestation and perinatal stages, couple mechanic force to the sensory hair cells in the vestibule for motion detection and bodily balance. In the present work, we have investigated whether compensatory deposition of another protein(s) may have taken place to partially alleviate the detrimental effects of Oc90 deletion by analyzing a comprehensive list of plausible candidates, and have found a drastic increase in the deposition of Sparc-like 1 (aka Sc1 or hevin) in Oc90 null versus wt otoconia. We show that such up-regulation is specific to Sc1, and that stable transfection of Oc90 and Sc1 full-length expression constructs in NIH/3T3 cells indeed promotes matrix calcification. Analysis and modeling of Oc90 and Sc1 protein structures show common features that may be critical requirements for the otoconial matrix backbone protein. Such information will serve as the foundation for future regenerative purposes.

Two families of Xenopus tropicalis skeletal genes display well-conserved expression patterns with mammals in spite of their highly divergent regulatory regions

The origin of bone and cartilage, and their subsequent diversification in specific vertebrate lineages, is intimately linked to the precise transcriptional control of genes involved in matrix mineralization. It is not yet clear, however, to which extent the osteoblasts, osteocytes, and chondrocytes of each of the major vertebrate groups express similar sets of genes. In this study we have focused on the evolution of two independent families of genes that code for extracellular matrix components of the skeleton and that include secreted protein, acidic, cysteine-rich (SPARC), bone sialoprotein (BSP) and dentin matrix protein 1 (DMP1) paralogues, and the osteocalcin (OC) and matrix gla protein (MGP) paralogues. Analyzing developing Xenopus tropicalis skeletal elements, we show that the expression patterns of these genes are well conserved with mammals. The fact that only a few osteoblasts express DMP1, while only some osteocytes express SPARC and BSP, reveals a significant degree of molecular heterogeneity for these two populations of X. tropicalis cells, similarly to what has been described in mouse. Although the cis-regulatory modules (CRM) of the mammalian OC, DMP1, and BSP orthologs have been functionally characterized, we found no evidence of sequence similarity between these regions and the X. tropicalis genome. Furthermore, these regulatory elements evolve rapidly, as they are only poorly conserved between human and rodents. Therefore, the SPARC/DMP1/BSP and the OC/MGP families provide a good paradigm to study how transcriptional output can be maintained in skeletal cells despite extensive sequence divergence of CRM.

Processing of the matricellular protein hevin in mouse brain is dependent on ADAMTS4

The matricellular SPARC family member hevin (SPARC-like 1/SPARCL-1/SC1/Mast9) contributes to neural development and alters tumor progression in a range of mammalian models. The distribution of hevin in mouse tissues was reexamined with a novel monoclonal antibody that discriminates between hevin and its ortholog SPARC. We now report proteolysis of hevin in many tissues, with the most extensive processing in the brain. We demonstrate a cleavage site within the hevin sequence for the neural tissue proteinase ADAMTS4. Digestion of hevin by ADAMTS4 in vitro produced fragments similar to those present in brain lysates. Monoclonal antibodies revealed a SPARC-like fragment generated from hevin that was co-localized with ADAMTS4 in vivo. We show that proteolysis of hevin by ADAMTS4 in the mouse cerebellum is important for the normal development of this tissue. In conclusion, we have identified the fragmentation of hevin by ADAMTS4 in the mouse brain and propose that this specific proteolysis is integral to cell morphology and extracellular matrix deposition in the developing brain.

Absence of SPARC results in increased cardiac rupture and dysfunction after acute myocardial infarction

The matricellular protein SPARC (secreted protein, acidic and rich in cysteine, also known as osteonectin) mediates cell–matrix interactions during wound healing and regulates the production and/or assembly of the extracellular matrix (ECM). This study investigated whether SPARC functions in infarct healing and ECM maturation after myocardial infarction (MI). In comparison with wild-type (WT) mice, animals with a targeted inactivation of SPARC exhibited a fourfold increase in mortality that resulted from an increased incidence of cardiac rupture and failure after MI. SPARC-null infarcts had a disorganized granulation tissue and immature collagenous ECM. In contrast, adenoviral overexpression of SPARC in WT mice improved the collagen maturation and prevented cardiac dilatation and dysfunction after MI. In cardiac fibroblasts in vitro, reduction of SPARC by short hairpin RNA attenuated transforming growth factor β (TGF)–mediated increase of Smad2 phosphorylation, whereas addition of recombinant SPARC increased Smad2 phosphorylation concordant with increased Smad2 phosphorylation in SPARC-treated mice. Importantly, infusion of TGF-β rescued cardiac rupture in SPARC-null mice but did not significantly alter infarct healing in WT mice. These findings indicate that local production of SPARC is essential for maintenance of the integrity of cardiac ECM after MI. The protective effects of SPARC emphasize the potential therapeutic applications of this protein to prevent cardiac dilatation and dysfunction after MI.

Matricellular proteins in the trabecular meshwork

The trabecular meshwork is one of the primary tissues of interest in the normal regulation and dysregulation of intraocular pressure (IOP) that is a causative risk factor for primary open-angle glaucoma. Matricellular proteins generally function to allow cells to modulate their attachments with and alter the characteristics of their surrounding extracellular matrix (ECM). In non-ocular tissues, matricellular proteins generally increase fibrosis. Since ECM turnover is very important to the outflow facility, matricellular proteins may have a significant role in the regulation of IOP. The formalized study of matricellular proteins in trabecular meshwork is in its infancy. SPARC, thrombospondins-1 and -2, and tenascins-C and -X, and osteopontin have been localized to varying areas within the trabecular meshwork. Preliminary evidence indicates that SPARC and thrombospondin-1 play a role in the regulation of IOP and possibly the pathophysiology of glaucoma. These data show promise that matricellular proteins are involved in IOP dysregulation and are potential therapeutic targets. Further study is needed to clarify these roles.

Differential expression patterns of occ1-related genes in adult monkey visual cortex

We have previously revealed that occ1 is preferentially expressed in the primary visual area (V1) of the monkey neocortex. In our attempt to identify more area-selective genes in the macaque neocortex, we found that testican-1, an occ1-related gene, and its family members also exhibit characteristic expression patterns along the visual pathway. The expression levels of testican-1 and testican-2 mRNAs as well as that of occ1 mRNA start of high in V1, progressively decrease along the ventral visual pathway, and end of low in the temporal areas. Complementary to them, the neuronal expression of SPARC mRNA is abundant in the association areas and scarce in V1. Whereas occ1, testican-1, and testican-2 mRNAs are preferentially distributed in thalamorecipient layers including “blobs,” SPARC mRNA expression avoids these layers. Neither SC1 nor testican-3 mRNA expression is selective to particular areas, but SC1 mRNA is abundantly observed in blobs. The expressions of occ1, testican-1, testican-2, and SC1 mRNA were downregulated after monocular tetrodotoxin injection. These results resonate with previous works on chemical and functional gradients along the primate occipitotemporal visual pathway and raise the possibility that these gradients and functional architecture may be related to the visual activity–dependent expression of these extracellular matrix glycoproteins.

Evolutionary genetics of vertebrate tissue mineralization: the origin and evolution of the secretory calcium-binding phosphoprotein family

Three principal mineralized tissues are present in teeth; a highly mineralized surface layer (enamel or enameloid), body dentin, and basal bone. Similar tissues have been identified in the dermal skeleton of Paleozoic jawless vertebrates, suggesting their ancient origin. These dental tissues form on protein matrix and their mineralization is controlled by distinctive proteins. We have shown that many secretory calcium-binding phosphoproteins (SCPPs) are involved in tetrapod tissue mineralization. These SCPPs all originated from the common ancestral gene SPARCL1 (secreted protein, acidic, cysteine-rich like 1) that initially arose from SPARC. The SCPP family also includes a bird eggshell matrix protein, mammalian milk casein, and salivary proteins. The eggshell SCPP plays crucial roles in rigid eggshell production, milk SCPPs in efficient lactation and in the evolution of complex dentition, and salivary SCPPs in maintaining tooth integrity. A comparative analysis of the mammalian, avian, and amphibian genomes revealed a tandem duplication history of the SCPP genes in tetrapods. Although these tetrapod SCPP genes are fewer in teleost genomes, independent parallel duplication has created distinct SCPP genes in this lineage. These teleost SCPPs are also used for enameloid and dentin mineralization, implying essential roles of SCPPs for dental tissue mineralization in osteichthyans. However, the SCPPs used for tetrapod enamel and teleost enameloid, as well as tetrapod dentin and teleost dentin, are all different. Thus, the evolution of vertebrate mineralized tissues seems to be explained by phenogenetic drift: while mineralized tissues are retained during vertebrate evolution, the underlying genetic basis has extensively drifted.

SPARC and Hevin expression correlate with tumour angiogenesis in hepatocellular carcinoma

Both Secreted Protein Acidic and Rich in Cysteine (SPARC) and Hevin are multifunctional matricellular glycoproteins. Recent experimental studies suggested that Hevin and SPARC together diminish angiogenesis, but their significance in hepatocellular carcinoma (HCC) remains unclear. This study aimed to correlate SPARC and Hevin expression with angiogenesis and clinicopathological features in HCC. SPARC and Hevin protein and mRNA expression in HCC specimens were assessed by immunostaining, immunoblotting, and quantitative reverse transcriptase-polymerase chain reaction. Tumour microvessel density (MVD) was assessed by CD34 immunostaining. The role of SPARC and Hevin in HCC was further assessed in an in vivo nude mice xenograft model. Both SPARC and Hevin mRNA levels were significantly higher in tumours than in non-tumourous livers. A significant correlation between tumour SPARC and Hevin mRNA levels was found. Moreover, SPARC protein localized in the tumour sinusoidal area correlated significantly with Hevin protein localized in HCC cells. Truncated forms of SPARC and Hevin proteins were detected in clinical samples. Truncated SPARC protein localized in the tumour sinusoidal area correlated significantly with tumour MVD. On the other hand, overexpression of full-length SPARC in tumour xenografts in athymic nude mice significantly delayed tumour growth, and this delay was related to a decrease in tumour angiogenesis. Expression of Hevin protein within HCC cells was related to the presence of tumour encapsulation and the absence of hepatitis B surface antigen in clinical samples. Overexpression of Hevin in tumour xenografts also significantly delayed tumour growth. In conclusion, this study has shown that SPARC and Hevin are upregulated in HCC compared with non-tumourous liver, and that they are inter-related at both mRNA and protein levels. Moreover, both SPARC and Hevin were related to HCC angiogenesis and tumour progression.

SPARC-like 1 regulates the terminal phase of radial glia-guided migration in the cerebral cortex

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.

Matricellular homologs in the foreign body response: hevin suppresses inflammation, but hevin and SPARC together diminish angiogenesis

Implanted foreign materials, used to restore or assist tissue function, elicit an initial acute inflammatory response followed by chronic fibrosis that leads to the entrapment of the biomaterial in a thick, poorly vascularized collagenous capsule. Matricellular proteins, secreted macromolecules that interact with extracellular matrix proteins but do not in themselves serve structural roles, have been identified as important mediators of the foreign body response that includes inflammation, angiogenesis, and collagen synthesis and assembly. In this report we delineate functions of hevin and SPARC, two homologs of the SPARC family of matricellular proteins, in the foreign body response. Despite their sequence similarity, hevin and SPARC mediate different aspects of this fibrotic response. Using mice with targeted gene deletions, we show that hevin is central to the progression of biomaterial-induced inflammation whereas SPARC regulates the formation of the collagenous capsule. Although vascular density within the capsule is unaltered in the absence of either protein, SPARC-hevin double-null capsules show substantially increased numbers of vessels, indicating compensatory functions for these two proteins in the inhibition of angiogenesis. These results provide important information for further development of implant technology.

SPARC and tumor growth: where the seed meets the soil?

Matricellular proteins mediate interactions between cells and their extracellular environment. This functional protein family includes several structurally unrelated members, such as SPARC, thrombospondin 1, tenascin C, and osteopontin, as well as some homologs of these proteins, such as thrombospondin 2 and tensascin X. SPARC, a prototypic matricellular protein, and its homolog hevin, have deadhesive effects on cultured cells and have been characterized as antiproliferative factors in some cellular contexts. Both proteins are produced at high levels in many types of cancers, especially by cells associated with tumor stroma and vasculature. In this Prospect article we summarize evidence for SPARC and hevin in the regulation of tumor cell growth, differentiation, and metastasis, and we propose that matricellular proteins such as these perform critical functions in desmoplastic responses of tumors that culminate in their dissemination and eventual colonization of other sites.

Hevin/SC1, a matricellular glycoprotein and potential tumor-suppressor of the SPARC/BM-40/Osteonectin family

Hevin is an extracellular matrix-associated, secreted glycoprotein belonging to the secreted protein acidic and rich in cysteine (SPARC) family of matricellular proteins. It contains three conserved structural domains that are implicated in the regulation of cell adhesion, migration, and proliferation. Hevin is expressed during embryogenesis and tissue remodeling and is especially prominent in brain and vasculature. Its down-regulation in a number of cancers and the possibility of its functional compensation by SPARC has led to recent interest in hevin as a tumor suppressor and regulator of angiogenesis.

Genetic basis for the evolution of vertebrate mineralized tissue

Mineralized tissue is vital to many characteristic adaptive phenotypes in vertebrates. Three primary tissues, enamel (enameloid), dentin, and bone, are found in the body armor of ancient agnathans and mammalian teeth, suggesting that these two organs are homologous. Mammalian enamel forms on enamel-specific proteins such as amelogenin, whereas dentin and bone form on collagen and many acidic proteins, such as SPP1, coordinately regulate their mineralization. We previously reported that genes for three major enamel matrix proteins, five proteins necessary for dentin and bone formation, and milk caseins and salivary proteins arose from a single ancestor by tandem gene duplications and form the secretory calcium-binding phosphoprotein (SCPP) family. Gene structure and protein characteristics show that SCPP genes arose from the 5' region of ancestral sparcl1 (SPARC-like 1). Phylogenetic analysis on SPARC and SPARCL1 suggests that the SCPP genes arose after the divergence of cartilaginous fish and bony fish, implying that early vertebrate mineralization did not use SCPPs and that SPARC may be critical for initial mineralization. Consistent with this inference, we identified SPP1 in a teleost genome but failed to find any genes orthologous to mammalian enamel proteins. Based on these observations, we suggest a scenario for the evolution of vertebrate tissue mineralization, in which body armor initially formed on dermal collagen, which acted as a reinforcement of dermis. We also suggest that mammalian enamel is distinct from fish enameloid. Their similar nature as a hard structural overlay on exoskeleton and teeth is because of convergent evolution.

Expression and characterization of murine hevin (SC1), a member of the SPARC family of matricellular proteins

Hevin, also known as SC1, MAST 9, SPARC-like 1, RAGS1 and ECM2, is a member of the SPARC-related family of matricellular proteins. Mouse hevin is 53% identical to mouse SPARC, and both proteins share a follistatin-like module and an extracellular Ca(2+)-binding (E-C) domain. SPARC functions as a modulator of cell-matrix interactions, a regulator of growth factor activity, a de-adhesive protein, and a cell cycle inhibitor. Although the functions of mouse hevin are unknown, its human orthologue has been shown to be de-adhesive for endothelial cells. We now report the production of recombinant mouse hevin in insect cells through the use of a baculoviral expression system and its purification by anion-exchange, size-exclusion chromatography, and isoelectric focusing. Furthermore, we have produced rat anti-hevin monoclonal antibodies (MAbs) that have been characterized by indirect and capture ELISAs, immunoblotting, immunoprecipitation, and immunohistochemistry (IHC). Recombinant hevin, present as a soluble factor or bound to tissue-culture plastic, inhibited the spreading of bovine aortic endothelial cells in vitro. IHC analysis of hevin in normal human and mouse tissues revealed a limited expression pattern in many tissues, with particularly dominant staining in dermis, ducts, vasculature, muscle, and brain. In lung and pancreatic tumor xenografts, we found distinct reactivity with MAbs that were selective for stromal cells, tumor cells, and/or endothelial cells. Although similar to SPARC in its anti-adhesive activities, hevin nevertheless exhibits a distinctive histological distribution that, in certain invasive tumors, is associated with desmoplasia.

Expression of the matricellular protein SPARC in murine lens: SPARC is necessary for the structural integrity of the capsular basement membrane

SPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matricellular glycoprotein that modulates cell proliferation, adhesion, migration, and extracellular matrix (ECM) production. Although SPARC is generally abundant in embryonic tissues and is diminished in adults, we have found that the expression of SPARC in murine lens persists throughout embryogenesis and adulthood. Our previous studies showed that targeted ablation of the SPARC gene in mice results in cataract formation, a pathology attributed partially to an abnormal lens capsule. Here we provide evidence that SPARC is not a structural component of the lens capsule. In contrast, SPARC is abundant in lens epithelial cells, and newly differentiated fiber cells, with stable expression in wild-type mice up to 2 years of age. Pertubation of the lens capsule in animals lacking SPARC appears to be a consequence of the invasion of the lens cells situated beneath the capsule. Immunoreactivity for SPARC in the lens cells was uneven, with minimal reactivity in the epithelial cells immediately anterior to the equator. These epithelial cells appeared essentially noninvasive in SPARC-null mice, in comparison to the centrally located anterior epithelial cells, in which strong labeling by anti-SPARC IgG was observed. The posterior lens fibers exhibited cytoplasmic extensions into the posterior lens capsule, which was severely damaged in SPARC-null lenses. The expression of SPARC in wild-type lens cells, together with the abnormal lens capsule in SPARC-null mice, indicated that the structural integrity of the lens capsule is dependent on the matricellular protein SPARC. The effects of SPARC in the lens appear to involve regulation of lens epithelial and fiber cell morphology and functions rather than deposition as a structural component of the lens capsule.

Effect of hyperthermia on the transport of mRNA encoding the extracellular matrix glycoprotein SC1 into Bergmann glial cell processes

SC1 is an extracellular matrix glycoprotein that is related to the multifunctional protein SPARC. These matricellular members play regulatory roles in modulating cellular interactions. SC1 expression is enriched in the central nervous system during embryonic and postnatal development as well as in the adult brain. In the rat cerebellum, SC1 is expressed at high levels in Bergmann glial cells and their radial fibers which project into the synaptic-rich molecular layer. At specific stages of development and in the adult, SC1 mRNA is selectively transported into cellular processes of these cells. In the present study, we have examined the effect of whole-body hyperthermia on the transport of SC1 mRNA in Bergmann glial cells of the rat cerebellum. Our results show that SC1 mRNA transport is diminished at 10 and 15 h post-hyperthermia, but returns to control levels by 24 h after heat shock. One of the characteristics of a heat shock on cells grown in tissue culture is a collapse of the cytoskeletal network. Intact components of the cytoskeleton are necessary for the transport of mRNA into peripheral processes of cells. However, in vivo hyperthermia does not appear to affect the morphology of the intermediate filament proteins GFAP, vimentin, or the beta-tubulin component of microtubules in Bergmann glial cell processes. During the hyperthermic time course, levels of vimentin protein increase, which is reflected by immunoreactivity of activated astrocytes and microvasculature in cerebellar white matter.

Proliferative vitreoretinopathy: risk factors and pathobiology

Proliferative vitreoretinopathy (PVR) is still a major cause of failure of retinal detachment surgery. Despite a dramatic increase in our pathobiologic knowledge of PVR during the last 10 years, little of this information has been used to modify the surgical management of the disease, and, thus, the anatomic and functional results are still unsatisfactory. Collaborative research involving clinicians and basic researchers must be encouraged. PVR must be considered a multifactorial disease caused by interaction of several cells and intra- and extraocular factors. Therefore, therapeutic options based on the inhibition of one factor or phenomenon may be regarded with scepticism. To prevent PVR, it is necessary to determine the factors involved in its development, and because of its relatively small prevalence, large, prospective, multicenter studies seem necessary. In addition, clinical research must not be underestimated. PVR affects both sides of the retina and the retina itself, a point to which little attention has been paid and that is critical for surgical results. Therefore, a new classification that provides information about clinical relevance, such as the evolutionary stages of the disease (biologic activity) and the degree of surgical difficulty (location of the fibrotic process), seems necessary.

[Microinfusion experiment for mice and its application to pharmacological studies]

It is urgently necessary to clarify functions of uncharacterized proteins. To understand life processes, we must investigate the functions and networks of proteins expressed from genomic DNA. In the near future, microinfusion experiments will become a more important method for analyzing uncharacterized function of proteins in vivo. Here we provide a practical manual for performing microinfusion experiments in mice. We also describe our experiment in which we performed a single injection of morphine following Secreted Protein Acidic and Rich in Cysteine (SPARC) infusion into the basolateral amygdala of previously uninjected mice and found markedly enhanced locomotor activity. We discuss the utility of microinfusion experiments in mice.

Differential mRNA expression of the related extracellular matrix glycoproteins SC1 and SPARC in the rat embryonic nervous system and skeletal structure

SPARC is a multifunctional extracellular matrix glycoprotein that shares partial sequence homology with SC1. These extracellular matrix molecules are thought to play important roles in modulating cellular interactions. In vitro, SPARC has been shown to exhibit anti-adhesive activity. In the present investigation, in situ hybridization is used to compare the expression patterns of SC1 and SPARC mRNA in the rat embryo. Results show that SC1 and SPARC expression is spatially and temporally regulated. SC1 mRNA is strongly expressed in the embryonic brain and spinal cord, whereas SPARC mRNA is enriched in craniofacial cartilage and skeletal structures. This differential expression pattern in the rat embryo suggests that SC1 plays an important role in the developing nervous system, whereas SPARC participates primarily in events associated with skeletal development. However at embryonic day 17, SC1 and SPARC mRNA show parallel expression patterns in areas of the cerebellum undergoing cell migratory events.

SPARC, a matricellular protein: at the crossroads of cell-matrix communication

SPARC is a multifunctional glycoprotein that belongs to the matricellular group of proteins. It modulates cellular interaction with the extracellular matrix (ECM) by its binding to structural matrix proteins, such as collagen and vitronectin, and by its abrogation of focal adhesions, features contributing to a counteradhesive effect on cells. SPARC inhibits cellular proliferation by an arrest of cells in the G1 phase of the cell cycle. It also regulates the activity of growth factors, such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF)-2, and vascular endothelial growth factor (VEGF). The expression of SPARC in adult animals is limited largely to remodeling tissue, such as bone, gut mucosa, and healing wounds, and it is prominent in tumors and in disorders associated with fibrosis. The crystal structure of two of the three domains of the protein has revealed a novel follistatin-like module and an extracellular calcium-binding (EC) module containing two EF-hand motifs. The follistatin-like module and the EC module are shared by at least four other proteins that comprise a family of SPARC-related genes. Targeted disruption of the SPARC locus in mice has shown that SPARC is important for lens transparency, as SPARC-null mice develop cataracts shortly after birth. SPARC is a prototypical matricellular protein that functions to regulate cell-matrix interactions and thereby influences many important physiological and pathological processes.

SPARC, a matricellular protein: at the crossroads of cell-matrix

SPARC is a multifunctional glycoprotein that belongs to the matricellular group of proteins. It modulates cellular interaction with the extracellular matrix (ECM) by its binding to structural matrix proteins, such as collagen and vitronectin, and by its abrogation of focal adhesions, features contributing to a counteradhesive effect on cells. SPARC inhibits cellular proliferation by an arrest of cells in the G1 phase of the cell cycle. It also regulates the activity of growth factors, such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF)-2, and vascular endothelial growth factor (VEGF). The expression of SPARC in adult animals is limited largely to remodeling tissue, such as bone, gut mucosa, and healing wounds, and it is prominent in tumors and in disorders associated with fibrosis. The crystal structure of two of the three domains of the protein has revealed a novel follistatin-like module and an extracellular calcium-binding (EC) module containing two EF-hand motifs. The follistatin-like module and the EC module are shared by at least four other proteins that comprise a family of SPARC-related genes. Targeted disruption of the SPARC locus in mice has shown that SPARC is important for lens transparency, as SPARC-null mice develop cataracts shortly after birth. SPARC is a prototypical matricellular protein that functions to regulate cell-matrix interactions and thereby influences many important physiological and pathological processes.

Isolation of novel mouse genes differentially expressed in brain using cDNA microarray

The major issue in the post-genome sequencing era is determination of gene expression patterns in variety of biological systems. A microarray system is a powerful technology for analyzing the expression profile of thousands of genes at one experiment. In this study, we identified highly expressed genes in mouse brain using the cDNA microarray carrying 2304 cDNAs derived from oligo-capped mouse cDNA library. Nine genes were highly expressed in adult mouse brain compared to kidney, liver, and skeletal muscle. Tissue distribution analysis by reverse transcription-coupled polymerase chain reaction (RT-PCR) revealed that consistent with the microarray data, all of the selected 9 genes were predominantly expressed in the brain. A database search showed that 5 of the 9 genes, MBP, SC1, HiAT3, S100 protein-beta, and SNAP25, were previously known to be expressed at high level in the brain and in the nervous system. One gene was highly sequenced similar to rat S-Rex-s/human NSP-C, suggesting that the gene is a mouse homologue. The remaining three genes did not match to known genes in the GenBank/EMBL database, indicating that these are novel genes highly expressed in the brain. Taken together, our cDNA microarray system can be an excellent tool for identifying differentially expressed genes in mouse brain.

Increased sensitivity to the stimulant effects of morphine conferred by anti-adhesive glycoprotein SPARC in amygdala

Repeated administration of morphine substantially increases its locomotor-enhancing activity, a phenomenon termed locomotor sensitization. Here we show that secreted protein acidic and rich in cysteine (SPARC), an anti-adhesive glycoprotein present in the basolateral amygdala, contributes to the establishment of locomotor sensitization. The morphine-induced increase in SPARC levels in the basolateral amygdala persisted after morphine withdrawal and coincided with the duration of locomotor sensitization. Moreover, a single injection of morphine after SPARC infusion into the basolateral amygdala of previously uninjected mice substantially enhanced locomotor activity. Thus, SPARC may be an important element for establishing locomotor sensitization to morphine.

Osteopenia and decreased bone formation in osteonectin-deficient mice

Bone continuously remodels in response to mechanical and physiological stresses, allowing vertebrates to renew bone as adults. Bone remodeling consists of the cycled synthesis and resorption of collagenous and noncollagenous extracellular matrix proteins, and an imbalance in this process can lead to disease states such as osteoporosis, or more rarely, osteopetrosis. There is evidence that the extracellular matrix glycoprotein osteonectin or secreted protein acidic and rich in cysteine (BM-40) may be important in bone remodeling. Osteonectin is abundant in bone and is expressed in areas of active remodeling outside the skeleton. In vitro studies indicate that osteonectin can bind collagen and regulate angiogenesis, metalloproteinase expression, cell proliferation, and cell-matrix interactions. In some osteopenic states, such as osteogenesis imperfecta and selected animal models for bone fragility, osteonectin expression is decreased. To determine the function of osteonectin in bone, we used contact x-ray, histomorphometry, and Northern blot analysis to characterize the skeletal phenotype of osteonectin-null mice. We found that osteonectin-null mice have decreased bone formation and decreased osteoblast and osteoclast surface and number, leading to decreased bone remodeling with a negative bone balance and causing profound osteopenia. These data indicate that osteonectin supports bone remodeling and the maintenance of bone mass in vertebrates.

Extracellular matrix-associated protein Sc1 is not essential for mouse development

Sc1 is an extracellular matrix-associated protein whose function is unknown. During early embryonic development, Sc1 is widely expressed, and from embryonic day 12 (E12), Sc1 is expressed primarily in the developing nervous system. This switch in Sc1 expression at E12 suggests an importance for nervous-system development. To gain insight into Sc1 function, we used gene targeting to inactivate mouse Sc1. The Sc1-null mice showed no obvious deficits in any organs. These mice were born at the expected ratios, were fertile, and had no obvious histological abnormalities, and their long-term survival did not differ from littermate controls. Therefore, the function of Sc1 during development is not critical or, in its absence, is subserved by another protein.

SPARC, a matricellular glycoprotein with important biological functions

SPARC (secreted protein, acidic and rich in cysteine) is a unique matricellular glycoprotein that is expressed by many different types of cells and is associated with development, remodeling, cell turnover, and tissue repair. Its principal functions in vitro are counteradhesion and antiproliferation, which proceed via different signaling pathways. SPARC consists of three domains, each of which has independent activity and unique properties. The extracellular calcium binding module and the follistatin-like module have been recently crystallized. Specific interactions between SPARC and growth factors, extracellular matrix proteins, and cell surface proteins contribute to the diverse activities described for SPARC in vivo and in vitro. The location of SPARC in the nuclear matrix of certain proliferating cells, but only in the cytosol of postmitotic neurons, indicates potential functions of SPARC as a nuclear protein, which might be involved in the regulation of cell cycle progression and mitosis. High levels of SPARC have been found in adult eye, and SPARC-null mice exhibit cataracts at 1-2 months of age. This animal model provides an excellent opportunity to confirm and explore some of the properties of SPARC, to investigate cataractogenesis, and to study SPARC-related family proteins, e.g., SC1/hevin, a counteradhesive matricellular protein that might functionally compensate for SPARC in certain tissues.(J Histochem Cytochem 47:1495-1505, 1999)

Collagen accumulation is decreased in SPARC-null mice with bleomycin-induced pulmonary fibrosis

Secreted protein acidic and rich in cysteine (SPARC) has been shown to be coexpressed with type I collagen in tissues undergoing remodeling and wound repair. We speculated that SPARC is required for the accumulation of collagen in lung injury and that its absence would attenuate collagen accumulation. Accordingly, we have assessed levels of collagen in SPARC-null mice in an intratracheal bleomycin-injury model of pulmonary fibrosis. Eight- to ten-week-old SPARC-null and wild-type (WT) mice received bleomycin (0.0035 U/g) or saline intratracheally and were subsequently killed after 14 days. Relative levels of SPARC mRNA were increased 2.7-fold (P < 0.001) in bleomycin-treated WT lungs in comparison with saline-treated lungs. Protein from bleomycin-treated WT lung contained significantly more hydroxyproline (191.9 microg/lung) than protein from either bleomycin-treated SPARC-null lungs or saline-treated WT and SPARC-null lungs (147.4 microg/lung, 125.4 microg/lung, and 113. 0 microg/lung, respectively; P < 0.03). These results indicate that SPARC is increased in response to lung injury and that accumulation of collagen, as indicated by hydroxyproline content, is attenuated in the absence of SPARC. The properties of SPARC as a matricellular protein associated with cell proliferation and matrix turnover are consistent with its participation in the development of pulmonary fibrosis.

Matrix and the retinal pigment epithelium in proliferative retinal disease

In their normal state, RPE cell are strongly adherent to Bruch's membrane. Certain pathological conditions such as retinal detachment cause an injury-type response (probably augmented or induced by the local accumulation of a variety of substances which modulate cell behaviour) in which RPE begin to dissociate from the membrane. This RPE-Bruch's membrane separation may be mediated by proteins with counter-adhesive properties and proteolytic enzymes, partly derived from the RPE themselves. Concomitant with the RPE disassociation, the cells begin to lose tertiary differentiation characteristics and gain macrophage-like features. When the "free" RPE arrive at the surface of the neuroretina, they may attach to or create a provisional matrix. Some of the cells adopt a fibroblast-like phenotype. This phenotype is similar to that of the dermal fibroblast during cutaneous wound repair and the fibroblastic RPE synthesise the types of matrix components found in healing skin wounds. Many of these molecules in turn further modulate the activities of the cells via several families of cell surface receptors, while the RPE continue to remodel the new matrix with a range of proteolytic enzymes. The resulting tissue (or membrane) has many of the features of a contractile scar and is the hallmark of the condition known as proliferative vitreoretinopathy (PVR). Thus the development of PVR, and the resulting tractional distortion of the neuroretina, appears to be dependent on RPE-matrix interactions. The interactions present a number of potential therapeutic targets for the management of the disorder.

SPARC is expressed by ganglion cells and astrocytes in bovine retina

SPARC (secreted protein, acidic and rich in cysteine)/osteonectin is a matricellular, counteradhesive glycoprotein that disrupts cell-matrix interactions, interacts with growth factors and components of extracellular matrix, and modulates the cell cycle, but appears to subserve only minor structural roles. SPARC is expressed in a variety of tissues during embryogenesis and remodeling and is believed to regulate vascular morphogenesis and cellular differentiation. Although usually limited in normal adult tissues, SPARC is expressed at significant levels in the adult central nervous system. Using a monoclonal antibody against bovine bone osteonectin, we have determined the localization of SPARC in newborn (3-day-old) and adult (4-8-year-old) normal bovine retinas. SPARC was present in the soma of ganglion cells and strong reactivity was found in ganglion cell axons. Muller cells displayed no immunoreactivity, but SPARC was present in retinal astrocytes that were identified by the astrocyte marker glial fibrillary acidic protein (GFAP). Newborn calf retina showed a staining pattern similar to that of adult retina but exhibited significantly reduced levels of SPARC. Minimal levels of SPARC protein were also detected in some capillaries of the inner retina of both newborn and adult animals, whereas large vessels were negative. The presence of SPARC in the retina was confirmed by Western blotting of retinal extracts. These data indicate that SPARC originating from bot h neurons and glia of the inner retina may be an important modulator of retinal angiogenesis. The increased expression of SPARC in adult relative to newborn retinal tissue also indicates that SPARC has an ongoing role in the maintenance of retinal functions.