Cep192, a Novel Missing Link between the Centrosomal Core and Corona in Dictyostelium Amoebae.

The Dictyostelium centrosome is a nucleus-associated body with a diameter of approx. 500 nm. It contains no centrioles but consists of a cylindrical layered core structure surrounded by a microtubule-nucleating corona. At the onset of mitosis, the corona disassembles and the core structure duplicates through growth, splitting, and reorganization of the outer core layers. During the last decades our research group has characterized the majority of the 42 known centrosomal proteins. In this work we focus on the conserved, previously uncharacterized Cep192 protein. We use superresolution expansion microscopy (ExM) to show that Cep192 is a component of the outer core layers. Furthermore, ExM with centrosomal marker proteins nicely mirrored all ultrastructurally known centrosomal substructures. Furthermore, we improved the proximity-dependent biotin identification assay (BioID) by adapting the biotinylase BioID2 for expression in Dictyostelium and applying a knock-in strategy for the expression of BioID2-tagged centrosomal fusion proteins. Thus, we were able to identify various centrosomal Cep192 interaction partners, including CDK5RAP2, which was previously allocated to the inner corona structure, and several core components. Studies employing overexpression of GFP-Cep192 as well as depletion of endogenous Cep192 revealed that Cep192 is a key protein for the recruitment of corona components during centrosome biogenesis and is required to maintain a stable corona structure.

Pre-orchiectomy tumor marker levels should not be used for International Germ Cell Consensus Classification (IGCCCG) risk group assignment.

PURPOSE: To investigate whether the use of pre-orchiectomy instead of pre-chemotherapy tumor marker (TM) levels has an impact on the International Germ Cell Consensus Classification (IGCCCG) risk group assignment in patients with metastatic germ cell tumors (GCT). METHODS: Demographic and clinical information of all patients treated for primary metastatic testicular non-seminomatous GCT in our tertiary care academic center were extracted from medical charts. IGCCCG risk group assignment was correctly performed with pre-chemotherapy marker levels and additionally with pre-orchiectomy marker levels. Agreement between pre-chemotherapy and pre-orchiectomy risk group assignments was assessed using Cohen's kappa. RESULTS: Our cohort consisted of 83 patients. The use of pre-orchiectomy TMs resulted in an IGCCCG risk group upstaging in 12 patients (16%, 8 patients from good to intermediate risk and 4 patients from intermediate to poor risk) and a downstaging in 1 patient (1.2%, from intermediate- to good-risk). The agreement between pre-orchiectomy and pre-chemotherapy IGCCCG risk groups resulted in a Cohen's kappa of 0.888 (p < 0.001). CONCLUSIONS: Using pre-orchiectomy TMs can result in incorrect IGCCCG risk group assignment, which in turn can impact on the clinical management and follow-up of patients with metastatic GCT. Thus, adherence to the IGCCCG standard using pre-chemotherapy TMs levels is recommended.

Systemic inflammatory markers have independent prognostic value in patients with metastatic testicular germ cell tumours undergoing first-line chemotherapy.

BACKGROUND: The prognostic utility of systemic inflammatory markers has so far not been investigated in patients with metastatic testicular germ cell tumours (GCTs). METHODS: International Germ Cell Cancer Cooperative Group (IGCCCG) risk groups and blood-based systemic inflammatory markers (haemoglobin, leukocytes, platelets (P), neutrophils (N), lymphocytes (L), C-reactive protein (CRP) and albumin) of 146 patients undergoing first-line chemotherapy for GCT were retrieved. In addition, N to L ratio (NLR), P to L ratio and the systemic immune-inflammation index (SII=N × P/L) were calculated. The prognostic ability of these markers for overall survival (OS) were assessed using regression analyses and Kaplan-Meier curves with log-rank tests. RESULTS: In univariate Cox regression, low haemoglobin and albumin as well as high leukocytes, N, NLR, SII and CRP were associated with a shorter OS. In multivariable Cox regression analyses, high leukocyte (hazard ratio (HR) 1.274 (95% confidence interval (CI) 1.057-1.535); P=0.011) and N count (1.470 (1.092-1.980); P=0.011), higher NLR (84.5 (2.2-3193.4); P=0.017) and SII (12.15 (1.17-126.26); P=0.037) remained independent prognostic predictors for OS besides the IGCCCG risk groups. CONCLUSIONS: Systemic inflammatory markers might have prognostic utility for patients with metastatic GCT. The planned IGCCCG update could be an opportunity to test these markers in a larger data set.

Neurofibromin controls macropinocytosis and phagocytosis in Dictyostelium.

Cells use phagocytosis and macropinocytosis to internalise bulk material, which in phagotrophic organisms supplies the nutrients necessary for growth. Wildtype Dictyostelium amoebae feed on bacteria, but for decades laboratory work has relied on axenic mutants that can also grow on liquid media. We used forward genetics to identify the causative gene underlying this phenotype. This gene encodes the RasGAP Neurofibromin (NF1). Loss of NF1 enables axenic growth by increasing fluid uptake. Mutants form outsized macropinosomes which are promoted by greater Ras and PI3K activity at sites of endocytosis. Relatedly, NF1 mutants can ingest larger-than-normal particles using phagocytosis. An NF1 reporter is recruited to nascent macropinosomes, suggesting that NF1 limits their size by locally inhibiting Ras signalling. Our results link NF1 with macropinocytosis and phagocytosis for the first time, and we propose that NF1 evolved in early phagotrophs to spatially modulate Ras activity, thereby constraining and shaping their feeding structures.