CD36 deficiency leads to choroidal involution via COX2 down-regulation in rodents.

BACKGROUND: In the Western world, a major cause of blindness is age-related macular degeneration (AMD). Recent research in angiogenesis has furthered the understanding of choroidal neovascularization, which occurs in the "wet" form of AMD. In contrast, very little is known about the mechanisms of the predominant, "dry" form of AMD, which is characterized by retinal atrophy and choroidal involution. The aim of this study is to elucidate the possible implication of the scavenger receptor CD36 in retinal degeneration and choroidal involution, the cardinal features of the dry form of AMD. METHODS AND FINDINGS: We here show that deficiency of CD36, which participates in outer segment (OS) phagocytosis by the retinal pigment epithelium (RPE) in vitro, leads to significant progressive age-related photoreceptor degeneration evaluated histologically at different ages in two rodent models of CD36 invalidation in vivo (Spontaneous hypertensive rats (SHR) and CD36-/- mice). Furthermore, these animals developed significant age related choroidal involution reflected in a 100%-300% increase in the avascular area of the choriocapillaries measured on vascular corrosion casts of aged animals. We also show that proangiogenic COX2 expression in RPE is stimulated by CD36 activating antibody and that CD36-deficient RPE cells from SHR rats fail to induce COX2 and subsequent vascular endothelial growth factor (VEGF) expression upon OS or antibody stimulation in vitro. CD36-/- mice express reduced levels of COX2 and VEGF in vivo, and COX2-/- mice develop progressive choroidal degeneration similar to what is seen in CD36 deficiency. CONCLUSIONS: CD36 deficiency leads to choroidal involution via COX2 down-regulation in the RPE. These results show a novel molecular mechanism of choroidal degeneration, a key feature of dry AMD. These findings unveil a pathogenic process, to our knowledge previously undescribed, with important implications for the development of new therapies.

A new factor stimulating peptidoglycan hydrolysis to separate daughter cells in Caulobacter crescentus.

Cell division in Gram-negative bacteria involves the co-ordinated invagination of the three cell envelope layers to form two new daughter cell poles. This complex process starts with the polymerization of the tubulin-like protein FtsZ into a Z-ring at mid-cell, which drives cytokinesis and recruits numerous other proteins to the division site. These proteins are involved in Z-ring constriction, inner- and outer-membrane invagination, peptidoglycan remodelling and daughter cell separation. Three papers in this issue of Molecular Microbiology, from the teams of Lucy Shapiro, Martin Thanbichler and Christine Jacobs-Wagner, describe a novel protein, called DipM for Division Involved Protein with LysM domains, that is required for cell division in Caulobacter crescentus. DipM localizes to the mid-cell during cell division, where it is necessary for the hydrolysis of the septal peptidoglycan to remodel the cell wall. Loss of DipM results in severe defects in cell envelope constriction, which is deleterious under fast-growth conditions. State-of-the-art microscopy experiments reveal that the peptidoglycan is thicker and that the cell wall is incorrectly organized in DipM-depleted cells compared with wild-type cells, demonstrating that DipM is essential for reorganizing the cell wall at the division site, for envelope invagination and cell separation in Caulobacter.

Developmental effects of basic fibroblast growth factor and platelet-derived growth factor on glial cells in a three-dimensional cell culture system.

In order to study peptide growth factor action in a three-dimensional cellular environment, aggregating cell cultures prepared from 15-day fetal rat telencephalon were grown in a chemically defined medium and treated during an early developmental stage with either bovine fibroblast growth factor (bFGF) or platelet-derived growth factor (PDGF homodimers AA and BB). A single dose (5-50 ng/ml) of either growth factor given to the cultures on day 3 greatly enhanced the developmental increase of the two glia-specific enzyme activities, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and glutamine synthetase (GS), whereas it had relatively little effect on total protein and DNA content. Distinct patterns of dose-dependency were found for CNP and GS stimulation. At low concentrations of bFGF (0.5-5 ng/ml) and at all PDGF concentrations applied, the oligodendroglial marker enzyme CNP was the most affected. A relatively small but significant mitogenic effect was observed after treatment with PDGF, particularly at higher concentrations or after repetitive stimulation. The two PDGF homodimers AA and BB were similar in their biological effects and potency. The present results show that under histotypic conditions both growth factors, bFGF and PDGF, promote the maturation rather than the proliferation of immature oligodendrocytes and astrocytes.

Controlled contrast transcranial Doppler and arterial blood gas analysis to quantify shunt through patent foramen ovale.

BACKGROUND AND PURPOSE: A right-to-left shunt can be identified by contrast transcranial Doppler ultrasonography (c-TCD) at rest and/or after a Valsalva maneuver (VM) or by arterial blood gas (ABG) measurement. We assessed the influence of controlled strain pressures and durations during VM on the right-to-left passage of microbubbles, on which depends the shunt classification by c-TCD, and correlated it with the right-to-left shunt evaluation by ABG measurements in stroke patients with patent foramen ovale (PFO). METHODS: We evaluated 40 stroke patients with transesophageal echocardiography-documented PFO. The microbubbles were recorded with TCD at rest and after 4 different VM conditions with controlled duration and target strain pressures (duration in seconds and pressure in cm H2O, respectively): V5-20, V10-20, V5-40, and V10-40. The ABG analysis was performed after pure oxygen breathing in 34 patients, and the shunt was calculated as percentage of cardiac output. RESULTS: Among all VM conditions, V5-40 and V10-40 yielded the greatest median number of microbubbles (84 and 95, respectively; P<0.01). A significantly larger number of microbubbles were detected in V5-40 than in V5-20 (P<0.001) and in V10-40 than in V10-20 (P<0.01). ABG was not sensitive enough to detect a shunt in 31 patients. CONCLUSIONS: The increase of VM expiratory pressure magnifies the number of microbubbles irrespective of the strain duration. Because the right-to-left shunt classification in PFO is based on the number of microbubbles, a controlled VM pressure is advised for a reproducible shunt assessment. The ABG measurement is not sensitive enough for shunt assessment in stroke patients with PFO.

Coactivated platelet-derived growth factor receptor {alpha} and epidermal growth factor receptor are potential therapeutic targets in intimal sarcoma.

Intimal sarcoma (IS) is a rare, malignant, and aggressive tumor that shows a relentless course with a concomitant low survival rate and for which no effective treatment is available. In this study, 21 cases of large arterial blood vessel IS were analyzed by immunohistochemistry and fluorescence in situ hybridization and selectively by karyotyping, array comparative genomic hybridization, sequencing, phospho-kinase antibody arrays, and Western immunoblotting in search for novel diagnostic markers and potential molecular therapeutic targets. Ex vivo immunoassays were applied to test the sensitivity of IS primary tumor cells to the receptor tyrosine kinase (RTK) inhibitors imatinib and dasatinib. We showed that amplification of platelet-derived growth factor receptor α (PDGFRA) is a common finding in IS, which should be considered as a molecular hallmark of this entity. This amplification is consistently associated with PDGFRA activation. Furthermore, the tumors reveal persistent activation of the epidermal growth factor receptor (EGFR), concurrent to PDGFRA activation. Activated PDGFRA and EGFR frequently coexist with amplification and overexpression of the MDM2 oncogene. Ex vivo immunoassays on primary IS cells from one case showed the potency of dasatinib to inhibit PDGFRA and downstream signaling pathways. Our findings provide a rationale for investigating therapies that target PDGFRA, EGFR, or MDM2 in IS. Given the clonal heterogeneity of this tumor type and the potential cross-talk between the PDGFRA and EGFR signaling pathways, targeting multiple RTKs and aberrant downstream effectors might be required to improve the therapeutic outcome for patients with this disease.

A positive FGFR3/FOXN1 feedback loop underlies benign skin keratosis versus squamous cell carcinoma formation in humans.

Seborrheic keratoses (SKs) are common, benign epithelial tumors of the skin that do not, or very rarely, progress into malignancy, for reasons that are not understood. We investigated this by gene expression profiling of human SKs and cutaneous squamous cell carcinomas (SCCs) and found that several genes previously connected with keratinocyte tumor development were similarly modulated in SKs and SCCs, whereas the expression of others differed by only a few fold. In contrast, the tyrosine kinase receptor FGF receptor-3 (FGFR3) and the transcription factor forkhead box N1 (FOXN1) were highly expressed in SKs, and close to undetectable in SCCs. We also showed that increased FGFR3 activity was sufficient to induce FOXN1 expression, counteract the inhibitory effect of EGFR signaling on FOXN1 expression and differentiation, and induce differentiation in a FOXN1-dependent manner. Knockdown of FOXN1 expression in primary human keratinocytes cooperated with oncogenic RAS in the induction of SCC-like tumors, whereas increased FOXN1 expression triggered the SCC cells to shift to a benign SK-like tumor phenotype, which included increased FGFR3 expression. Thus,we have uncovered a positive regulatory loop between FGFR3 and FOXN1 that underlies a benign versus malignant skin tumor phenotype.

Domains of p85cdc10 required for function of the fission yeast DSC-1 factor.

p85cdc10 is a component of the S.pombe DSC-1 complex, which is thought to mediate periodic transcription of genes in late G1. In order to understand the role of p85cdc10 in the function of this complex, we have analysed which domains of p85cdc10 are required for biological activity and the formation of a stable DSC-1 complex in vitro, both in cdc10 temperature sensitive and null backgrounds. No DSC-1 activity is found in the absence of p85cdc10 and the activity of the complex is reduced or absent in all cdc10ts mutants tested. Full biological activity and rescue of a cdc10::ura4+ null allele requires the N-terminal domain, the cdc10/SWI6 repeats and the helical C-terminal region. In the absence of p85cdc10, both the C-terminal and cdc10/SWI6 repeat domains are required for DSC-1 activity in vitro. In a cdc10ts background, rescue of DSC-1 activity and complementation of mutants, requires only expression of the C-terminal domain, though the presence of the cdc10/SWI6 motifs enhances its activity. The N-terminal domain, alone, or in combination with the cdc10/SWI6 motifs, does not have biological activity, and does not restore DSC-1 activity. We conclude that both the C-terminal domain of p85cdc10 is critical for formation of the DSC-1 complex and that the cdc10/SWI6 motifs also play a role, perhaps by stabilizing the complex. Our data also suggest that the S.pombe DSC-1 complex contains more than one molecule of p85cdc10.