SynCAM1: another polysialylated protein beside NCAM in the postnatal mouse brain

Sialinsäuren lassen sich als posttranslationale Modifikationen in fast allen Glyko-konjugaten von Vertebraten in Form von Monosialinsäuren nachweisen. Im Gegensatz hierzu wurde Polysialinsäure (PolySia), ein lineares Homopolymer aus alpha2,8-verknüpften N-Acetylneuraminsäureresten, an lediglich vier Glykoproteinen beob-achtet, wobei das neuronale Zelladhäsionsmolekül (NCAM) das Bedeutendste ist. Die Polysialylierung von NCAM beeinflusst essentielle Funktionen, beispielsweise die Synaptogenese, das neurale pathfinding und die synaptische Plastizität. Folglich lassen sich die höchsten PolySia-Level während der Gehirnentwicklung und -reifung nachweisen. Des Weiteren spielt PolySia-NCAM eine Rolle in pathologischen Pro-zessen wie der Tumorgenese (Glioblastom, multiples Myelom), der Schizophrenie und neuronalen Reparaturprozessen. Die Tatsache, dass ein vollständiges Fehlen bei Knock-out-Mäusen zu einem frühen Tod führt, unterstreicht die Bedeutsamkeit von PolySia in Vertebraten. Mit dieser Arbeit konnte gezeigt werden, dass neben NCAM auch das synaptische Zelladhäsionsmolekül SynCAM1 im perinatalen Mäusegehirn polysialyliert wird. Bei SynCAM1 handelt es sich ebenfalls um ein Adhäsionsprotein, welches die Gehirn-reifung und insbesondere die Synaptogenese beeinflusst. SynCAM1 ist auch in weiteren Organen, bzw. Geweben (Hoden, Lunge und Leber) beschrieben und an wichtigen physiologischen Regulationsmechanismen, u.a. in der Tumorgenese des Mammakarzinoms, des Hepatozellulären Karzinoms sowie des kleinzelligen Bronchialkarzinoms beteiligt. Für die Identifikation des potentiellen polysialylierten Proteins wurden Gehirnlysate von postnatalen NCAM-Knock-out-Mäusen verwendet. Das durch Immunpräzipitation isolierte Protein konnte mittels Massenspektrometrie als SynCAM1 identifiziert werden. Die Ergebnisse zeigen, dass SynCAM1 sowohl in Abwesenheit, als auch physiologisch in der Gegenwart von NCAM in vivo polysialyliert wird und somit davon ausgegangen werden kann, dass es an der Gehirnentwicklung beteiligt ist. Weiterführende Versuche zeigten, dass die PolySia bei SynCAM1 an N-Glykanen der ersten IG-Domäne gebunden ist und sich aus mehr als 40 Sialinsäuren zusammensetzen kann. Dies ist die erste Arbeit, welche polysialyliertes SynCAM1 als einen weiteren Träger von PolySia während der neuronalen Entwicklung nachweisen konnte. Weitere Forschungsarbeiten sind aber nötig, um die genaue funktionelle Rolle von polysialyliertem SynCAM1 innerhalb und vielleicht auch außerhalb des neuronalen Systems zu charakterisieren.Sialic acids are found as post-translational modifications in nearly all glycoconjugates of vertebrates and mostly occur as monosialyl units. In contrast, polysialic acid (polySia), a linear homopolymer of alpha2,8-linked N-acetylneuraminic acid, was only detected in four glycoproteins and the neural cell adhesion molecule (NCAM) represents its main carrier. The polysialylation of NCAM affects essential functions such as synaptogenesis, neural pathfinding and synaptic plasticity. Consequently, the highest levels of polySia can be detected during brain development and maturation. Furthermore, polysialylated NCAM plays a role in pathological processes like tumorgenesis (glioblastoma, multiple myeloma), schizophrenia and neuronal repair processes. The fact that a complete absence in knockout-mice leads to an early death highlights the importance of polySia in vertebrates. The present thesis showed that the synaptic cell adhesion molecule SynCAM1 is polysialylated besides NCAM in the perinatal mouse brain. SynCAM1 is an adhesion protein, which affects the brain maturation and particularly the synaptogenesis. SynCAM1 is also described in other organs (testes, lung and liver) and is involved in physiological key mechanisms including the tumorgenesis of breast cancer, the hepatocellular carcinoma and small cell lung cancer. For the identification of further potential polysialylated proteins brain lysates of postnatal NCAM-knockout-mice were used. The polySia carrier was isolated by immune-precipitation and generated tryptic peptide mass fingerprint led to the identification of SynCAM1. The results showed that SynCAM1 is polysialated both in the absence and in the presence of NCAM in vivo. Thus, the polysialylated form of SynCAM1 may influence the brain development. Further experiments showed that polySia was linked to N-glycans of the first IG-domain and consisted of more than 40 sialic acid residues. This is the first study, which described polysialylated SynCAM1 as a further target of polysialylation during the neural development. However additional studies are needed to characterize the precise function of polySia-SynCAM1 in the neural system and other physiological processes

Low-dose CT pulmonary angiography on a 15-year-old CT scanner: a feasibility study

Background Computed tomography (CT) low-dose (LD) imaging is used to lower radiation exposure, especially in vascular imaging; in current literature, this is mostly on latest generation high-end CT systems. Purpose To evaluate the effects of reduced tube current on objective and subjective image quality of a 15-year-old 16-slice CT system for pulmonary angiography (CTPA). Material and Methods CTPA scans from 60 prospectively randomized patients (28 men, 32 women) were examined in this study on a 15-year-old 16-slice CT scanner system. Standard CT (SD) settings were 100 kV and 150 mAs, LD settings were 100 kV and 50 mAs. Attenuation of the pulmonary trunk, various anatomic landmarks, and image noise were quantitatively measured; contrast-to-noise ratios (CNR) and signal-to-noise ratios (SNR) were calculated. Three independent blinded radiologists subjectively rated each image series using a 5-point grading scale. Results CT dose index (CTDI) in the LD series was 66.46% lower compared to the SD settings (2.49 ± 0.55 mGy versus 7.42 ± 1.17 mGy). Attenuation of the pulmonary trunk showed similar results for both series (SD 409.55 ± 91.04 HU; LD 380.43 HU ± 93.11 HU; P = 0.768). Subjective image analysis showed no significant differences between SD and LD settings regarding the suitability for detection of central and peripheral PE (central SD/LD, 4.88; intra-class correlation coefficients [ICC], 0.894/4.83; ICC, 0.745; peripheral SD/LD, 4.70; ICC, 0.943/4.57; ICC, 0.919; all P > 0.4). Conclusion The LD protocol, on a 15-year-old CT scanner system without current high-end hardware or post-processing tools, led to a dose reduction of approximately 67% with similar subjective image quality and delineation of central and peripheral pulmonary arteries

Single-source chest-abdomen-pelvis cancer staging on a third generation dual-source CT system: comparison of automated tube potential selection to second generation dual-source CT

BACKGROUND: Evaluation of latest generation automated attenuation-based tube potential selection (ATPS) impact on image quality and radiation dose in contrast-enhanced chest-abdomen-pelvis computed tomography examinations for gynaecologic cancer staging. METHODS: This IRB approved single-centre, observer-blinded retrospective study with a waiver for informed consent included a total of 100 patients with contrast-enhanced chest-abdomen-pelvis CT for gynaecologic cancer staging. All patients were examined with activated ATPS for adaption of tube voltage to body habitus. 50 patients were scanned on a third-generation dual-source CT (DSCT), and another 50 patients on a second-generation DSCT. Predefined image quality setting remained stable between both groups at 120 kV and a current of 210 Reference mAs. Subjective image quality assessment was performed by two blinded readers independently. Attenuation and image noise were measured in several anatomic structures. Signal-to-noise ratio (SNR) was calculated. For the evaluation of radiation exposure, CT dose index (CTDIvol) values were compared. RESULTS: Diagnostic image quality was obtained in all patients. The median CTDIvol (6.1 mGy, range 3.9-22 mGy) was 40 % lower when using the algorithm compared with the previous ATCM protocol (median 10.2 mGy · cm, range 5.8-22.8 mGy). A reduction in potential to 90 kV occurred in 19 cases, a reduction to 100 kV in 23 patients and a reduction to 110 kV in 3 patients of our experimental cohort. These patients received significantly lower radiation exposure compared to the former used protocol. CONCLUSION: Latest generation automated ATPS on third-generation DSCT provides good diagnostic image quality in chest-abdomen-pelvis CT while average radiation dose is reduced by 40 % compared to former ATPS protocol on second-generation DSCT