No abstract

Ether lipids (ELs), particularly plasmalogens, are essential constituents of the mammalian central nervous system. The physiological role of ELs, in vivo, however is still enigmatic. In the present study, we characterized a mouse model carrying a targeted deletion of the peroxisomal dihydroxyacetonephosphate acyltransferase gene that results in the complete lack of ELs. Investigating the cerebellum of these mice, we observed: (i) defects in foliation patterning and delay in precursor granule cell migration, (ii) defects in myelination and concomitant reduction in the level of myelin basic protein, (iii) disturbances in paranode organization by extending the Caspr distribution and disrupting axo-glial septate-like junctions, (iv) impaired innervation of Purkinje cells by both parallel fibers and climbing fibers and (v) formation of axon swellings by the accumulation of inositol-tris-phosphate receptor 1 containing smooth ER-like tubuli. Functionally, conduction velocity of myelinated axons in the corpus callosum was significantly reduced. Most of these phenotypes were already apparent at P20 but still persisted in 1-year-old animals. In summary, these data show that EL deficiency results in severe developmental and lasting structural alterations at the cellular and network level of the cerebellum, and reveal an important role of ELs for proper brain function. Common molecular mechanisms that may underlie these phenotypes are discussed.

Hydrocephalus is a common congenital anomaly. LCAM1 and MPDZ (MUPP1) are the only known human gene loci associated with non‐syndromic hydrocephalus. To investigate functions of the tight junction‐associated protein Mpdz, we generated mouse models. Global Mpdz gene deletion or conditional inactivation in Nestin‐positive cells led to formation of supratentorial hydrocephalus in the early postnatal period. Blood vessels, epithelial cells of the choroid plexus, and cilia on ependymal cells, which line the ventricular system, remained morphologically intact in Mpdz‐deficient brains. However, flow of cerebrospinal fluid through the cerebral aqueduct was blocked from postnatal day 3 onward. Silencing of Mpdz expression in cultured epithelial cells impaired barrier integrity, and loss of Mpdz in astrocytes increased RhoA activity. In Mpdz‐deficient mice, ependymal cells had morphologically normal tight junctions, but expression of the interacting planar cell polarity protein Pals1 was diminished and barrier integrity got progressively lost. Ependymal denudation was accompanied by reactive astrogliosis leading to aqueductal stenosis. This work provides a relevant hydrocephalus mouse model and demonstrates that Mpdz is essential to maintain integrity of the ependyma.

The aim of this study was to investigate the effect of inhibiting a v b 3 /a v b 5 integrins by cilengitide in experimentally induced breast cancer bone metastases using noninvasive imaging techniques. For this purpose, nude rats bearing established breast cancer bone metastases were treated with cilengitide, a small molecule inhibitor of a v b 3 and a v b 5 integrins (75 mg/kg, five days per week; n 5 12 rats) and compared to vehicle-treated control rats (n 5 12). In a longitudinal study, conventional magnetic resonance imaging (MRI) and flat panel volumetric computed tomography were used to assess the volume of the soft tissue tumor and osteolysis, respectively, and dynamic contrast-enhanced (DCE-) MRI was performed to determine functional parameters of the tumor vasculature reflecting blood volume and blood vessel permeability. In rats treated with cilengitide, VCT and MRI showed that osteolytic lesions and the respective bone metastatic soft tissue tumors progressed more slowly than in vehicle-treated controls. DCE-MRI indicated a decrease in blood volume and an increase in vessel permeability and immunohistology revealed increased numbers of immature vessels in cilengitide-treated rats compared to vehicle controls. In conclusion, treatment of experimental breast cancer bone metastases with cilengitide resulted in pronounced antiresorptive and antitumor effects, suggesting that a v b 3 /a v b 5 inhibition may be a promising therapeutic approach for bone metastases.Bone metastases occur frequently in many human malignancies including breast, prostate and lung carcinoma. The stimulation of osteoclasts by tumor cells proliferating within the bone marrow is a feature of the pathogenesis of bone metastases, and both the tumor and the bone microenvironment must be considered when strategies for therapy of bone metastases are developed.1 Bisphosphonates are potent inhibitors of osteoclast function that have been used over the last decades to treat patients with bone metastases. However, they do not induce regression of bone metastases. This, together with the adverse effects associated with bisphosphonate therapy such as osteonecrosis of the jaw and renal toxicity, emphasize the urgent need for the development of novel therapies that can be applied alternatively and as combination partners to target bone metastases more effectively.Integrins are a family of 24 transmembrane proteins that integrate extracellular and intracellular activities. Besides their role in promoting physical adhesion, integrin signaling can induce cell spreading, migration, survival, proliferation and differentiation.2 The a v b 3 integrin interacts with several extracellular matrix (ECM) proteins including vitronectin, fibronectin, osteopontin, bone sialoprotein (BSP) and fibrinogen. 3,4 It is strongly expressed on activated tumor endothelial cells, whereas on resting endothelial cells in nondiseased tissues, its expression is generally low. [5][6][7] In the pathogenesis of bone metastases, osteoclasts too express a v b 3 integrin, and selec...