Loss of ATF2 function leads to cranial motoneuron degeneration during embryonic mouse development.

The AP-1 family transcription factor ATF2 is essential for development and tissue maintenance in mammals. In particular, ATF2 is highly expressed and activated in the brain and previous studies using mouse knockouts have confirmed its requirement in the cerebellum as well as in vestibular sense organs. Here we present the analysis of the requirement for ATF2 in CNS development in mouse embryos, specifically in the brainstem. We discovered that neuron-specific inactivation of ATF2 leads to significant loss of motoneurons of the hypoglossal, abducens and facial nuclei. While the generation of ATF2 mutant motoneurons appears normal during early development, they undergo caspase-dependent and independent cell death during later embryonic and foetal stages. The loss of these motoneurons correlates with increased levels of stress activated MAP kinases, JNK and p38, as well as aberrant accumulation of phosphorylated neurofilament proteins, NF-H and NF-M, known substrates for these kinases. This, together with other neuropathological phenotypes, including aberrant vacuolisation and lipid accumulation, indicates that deficiency in ATF2 leads to neurodegeneration of subsets of somatic and visceral motoneurons of the brainstem. It also confirms that ATF2 has a critical role in limiting the activities of stress kinases JNK and p38 which are potent inducers of cell death in the CNS.

Feedback regulation of p38 activity via ATF2 is essential for survival of embryonic liver cells.

The ATF2 transcription factor is phosphorylated by the stress-activated mitogen-activated protein kinases (MAPKs) JNK and p38. We show that this phosphorylation is essential for ATF2 function in vivo, since a mouse carrying mutations in the critical phosphorylation sites has a strong phenotype identical to that seen upon deletion of the DNA-binding domain. In addition, combining this mutant with a knockout of the ATF2 homolog, ATF7, results in embryonic lethality with severe abnormalities in the developing liver and heart. The mutant fetal liver is characterized by high levels of apoptosis in developing hepatocytes and haematopoietic cells. Furthermore, we observe a significant increase in active p38 due to loss of a negative feedback loop involving the ATF2-dependent transcriptional activation of MAPK phosphatases. In embryonic liver cells, this increase drives apoptosis, since it can be suppressed by chemical inhibition of p38. Our findings demonstrate the importance of finely regulating the activities of MAPKs during development.

Clinical and radiographic analysis of accurate restoration of the joint line in revision total knee arthroplasty.

A clinical and radiographic analysis was performed on 89 consecutive revision total knee arthroplasties. The postoperative joint line position was evaluated and correlated with the clinical outcome. The joint line position was evaluated radiographically. Average follow-up was 8.2 years (24-197 months). Clinical outcome values were correlated to joint line position. More improvement was seen with recreation of the normal joint line to within +/-4 mm of the normal unaffected knee for Knee Society Score, average total arc of motion, flexion, and extension. There was a significant difference found for all 4 variables when combined outliers were compared with goal range (-4 to 4 mm). In this study, clinical outcome was improved if the joint line was accurately reproduced.

Imaging apoptosis in vivo using 124I-annexin V and PET.

Abnormal regulation of apoptosis is an important pathogenic mechanism in many diseases including cancer. Techniques to assess apoptosis in living organisms are limited and, in the case of solid organs, restricted to histological examination of biopsy samples. We investigated the use of (124)I-annexin V, which binds to phosphatidylserine (PS) on the surface of apoptotic cells, as a potential positron emission tomography (PET) radioligand for the noninvasive measurement of apoptosis in vivo. Annexin V and a similar-sized protein, ovalbumin, were directly labelled with (124)I. We report the validation of (124)I-annexin V in vitro and in an animal model of liver apoptosis that has not previously been used to test iodinated annexin V. Also, for the first time, we report metabolite analysis of (124)I-annexin V and the correlation of (124)I-annexin V uptake with apoptotic density (AD). Sixfold more (124)I-annexin V was associated with Jurkat cells after apoptosis induction, indicating that PS binding by annexin V was preserved after iodination. (124)I-ovalbumin did not demonstrate increased uptake in apoptotic cells. In normal BDF-1 mice, the radioligand was rapidly cleared, but some in vivo dehalogenation resulted in the accumulation of activity in the thyroid and stomach content. PET images demonstrated uptake of (124)I-annexin V but not (124)I-ovalbumin in apoptotic liver lesions. In vivo (124)I-annexin V uptake, derived from PET images, correlated with histologically derived AD (r=.86, P<.01). These results demonstrate that (124)I-annexin V is localised to anti-Fas-induced apoptosis, in contrast to (124)I-ovalbumin, which did not show preferential uptake in the apoptotic liver.

High level expression and purification of the Epstein-Barr virus encoded cytokine viral interleukin 10: efficient removal of endotoxin.

To characterize the structural and functional properties of viral interleukin 10 (vIL-10), its cDNA was cloned into the bacterial expression vector pMAL-c2, which directs the synthesis of the inserted gene as a fusion protein with maltose binding protein (MBP). The MBP-vIL-10 fusion protein was expressed in Escherichia coli and purified from cell lysates using amylose resin chromatography. Viral interleukin 10 (IL-10) was released from the fusion protein by cleavage with the proteolytic enzyme factor Xa. We show that vIL-10 will bind to heparin and use this property to purify vIL-10 from factor Xa cleaved products and trace contaminants using heparin agarose chromatography. A simple one-step procedure is described for the removal of endotoxins from heavily contaminated vIL-10 preparations. The protocol exploits the high binding affinity of MBP for amylose resin or vIL-10 for heparin and the ability of Triton-X114 to dissociate endotoxins from proteins. The biological activity of purified vIL-10 was demonstrated through its ability to inhibit interferon gamma (IFN-gamma) production by mitogen activated peripheral blood mononuclear cells and to down-regulate HLA-class II expression on activated monocytes/macrophages. The availability of an efficient expression and purification strategy for vIL-10 together with appropriate assays will contribute to a greater understanding of how vIL-10 has evolved to retain and modify those activities of cellular IL-10 best suited for Epstein-Barr virus (EBV)'s specialized niche within the host.

5T4 interacts with TIP-2/GIPC, a PDZ protein, with implications for metastasis.

Overexpression of the 5T4 transmembrane glycoprotein can have marked effects on both the actin cytoskeleton and cell migration. Using a yeast two-hybrid approach, we describe a novel interaction between 5T4 and TIP-2/GIPC, a cytoplasmic interacting protein containing a PDZ domain. The cytoplasmic tail of 5T4 contains a class I PDZ-binding motif (Ser-Asp-Val) and we demonstrate that this region, in particular the terminal valine, is required for 5T4 interaction with TIP-2/GIPC. HeLa cells expressing hemagglutinin-tagged TIP-2/GIPC (HA-TIP-2/GIPC) have an altered distribution of endogenous 5T4, which colocalizes with HA-TIP-2/GIPC, thus supporting an interaction. Furthermore, TIP-2/GIPC can be coimmunoprecipitated with 5T4 from HeLa cell lysates. Identification of the 5T4 and TIP-2/GIPC interaction provides the first link between 5T4 and the actin cytoskeleton. Since other proteins, like 5T4, associate with TIP-2/GIPC and are linked with cancer, we explore the possibility that TIP-2/GIPC may be a common factor involved in the cancer process.