Avian influenza virus hemagglutinins H2, H4, H8, and H14 support a highly pathogenic phenotype

High-pathogenic avian influenza viruses (HPAIVs) evolve from low-pathogenic precursors specifying the HA serotypes H5 or H7 by acquisition of a polybasic HA cleavage site. As the reason for this serotype restriction has remained unclear, we aimed to distinguish between compatibility of a polybasic cleavage site with H5/H7 HA only and unique predisposition of these two serotypes for insertion mutations. To this end, we introduced a polybasic cleavage site into the HA of several low-pathogenic avian strains with serotypes H1, H2, H3, H4, H6, H8, H10, H11, H14, or H15, and rescued HA reassortants after cotransfection with the genes from either a low-pathogenic H9N2 or high-pathogenic H5N1 strain. Oculonasal inoculation with those reassortants resulted in varying pathogenicity in chicken. Recombinants containing the engineered H2, H4, H8, or H14 in the HPAIV background were lethal and exhibited i.v. pathogenicity indices of 2.79, 2.37, 2.85, and 2.61, respectively, equivalent to naturally occurring H5 or H7 HPAIV. Moreover, the H2, H4, and H8 reassortants were transmitted to some contact chickens. The H2 reassortant gained two mutations in the M2 proton channel gate region, which is affected in some HPAIVs of various origins. Taken together, in the presence of a polybasic HA cleavage site, non-H5/H7 HA can support a highly pathogenic phenotype in the appropriate viral background, indicating requirement for further adaptation. Therefore, the restriction of natural HPAIV to serotypes H5 and H7 is likely a result of their unique predisposition for acquisition of a polybasic HA cleavage site.     

Structural evolution of the membrane-coating module of the nuclear pore complex

The coatomer module of the nuclear pore complex borders the cylinder-like nuclear pore-membrane domain of the nuclear envelope. In evolution, a single coatomer module increases in size from hetero-heptamer (Saccharomyces cerevisiae) to hetero-octamer (Schizosaccharomyces pombe) to hetero-nonamer (Metazoa). Notably, the heptamer–octamer transition proceeds through the acquisition of the nucleoporin Nup37. How Nup37 contacts the heptamer remained unknown. Using recombinant nucleoporins, we show that Sp-Nup37 specifically binds the Sp-Nup120 member of the hetero-heptamer but does not bind an Sc-Nup120 homolog. To elucidate the Nup37–Nup120 interaction at the atomic level, we carried out crystallographic analyses of Sp-Nup37 alone and in a complex with an N-terminal, ∼110-kDa fragment of Sp-Nup120 comprising residues 1–950. Corroborating structural predictions, we determined that Nup37 folds into a seven-bladed β-propeller. Several disordered surface regions of the Nup37 β-propeller assume structure when bound to Sp-Nup120. The N-terminal domain of Sp-Nup120^1–950 also folds into a seven-bladed propeller with a markedly protruding 6D–7A insert and is followed by a contorted helical domain. Conspicuously, this 6D–7A insert contains an extension of 50 residues which also is highly conserved in Metazoa but is absent in Sc-Nup120. Strikingly, numerous contacts with the Nup37 β-propeller are located on this extension of the 6D–7A insert. Another contact region is situated toward the end of the helical region of Sp-Nup120^1–950. Our findings provide information about the evolution and the assembly of the coatomer module of the nuclear pore complex.     

Cholelithiasis and markers of nonalcoholic fatty liver disease in patients with metabolic risk factors

Cholelithiasis and nonalcoholic fatty liver disease (NAFLD) share the same risk factors. The aim of our study was to explore the relationship between these two conditions and to identify independent predictors of both diseases in a cohort of patients with metabolic risk factors. Consecutive patients with metabolic risk factors referred to the outpatient clinic during a one-year period were included. Cholelithiasis was defined by the presence of gallstones on abdominal ultrasound examination at inclusion or previously performed cholecystectomy. NAFLD was defined by the presence of at least one surrogate marker such as elevated alanine aminotransferase and/or gamma-glutamyl transpeptidase and/or ultrasound signs of fatty liver. Other common liver diseases were thoroughly excluded. The prevalence of cholelithiasis among patients with and without NAFLD was determined and clinical and laboratory parameters were identified as predictors of NAFLD by multivariate logistic regression. In total, 482 consecutive patients were included: mean age 61 years; 61% were women; 52% of patients had more than 2 metabolic risk factors (obesity, type 2 diabetes, hypertension, hypertriglyceridemia, or low HDL cholesterol). NAFLD and cholelithiasis were present in 41% and 34% of all patients, respectively. Significantly higher prevalence of cholelithiasis was found among patients with NAFLD compared with patients without NAFLD (47% vs. 26%, respectively; p < 0.0001). In multivariate logistic regression model, type 2 diabetes (odds ratio (OR) = 1.99), BMI above 25 kg/m(2) (OR = 1.78), and cholelithiasis (OR = 1.77) were identified as independent predictors of NAFLD. Fifty six percent of patients with cholelithiasis had NAFLD compared with 33% of patients without cholelithiasis (p < 0.0001). Multivariate logistic regression identified age above 50 years (OR = 3.46), NAFLD (OR = 1.92), triglycerides above 1.7 mmol/l (OR = 1.91), BMI above 25 kg/m(2) (OR = 1.84), and total cholesterol concentration (OR = 0.711) as independent predictors of cholelithiasis. In conclusion, patients with metabolic risk factors and cholelithiasis suffer significantly more often from NAFLD compared with the reference group. Cholelithiasis represents an independent risk factor of NAFLD in addition to metabolic risk factors and could be regarded as an additional risk factor of liver damage in patients with NAFLD. Furthermore, NAFLD is an independent risk factor for cholelithiasis and might represent a pathogenetic link between the metabolic syndrome and cholelithiasis.     

The phenotype of human STK4 deficiency

We describe a novel clinical phenotype associating T- and B-cell lymphopenia, intermittent neutropenia, and atrial septal defects in 3 members of a consanguineous kindred. Their clinical histories included recurrent bacterial infections, viral infections, mucocutaneous candidiasis, cutaneous warts, and skin abscesses. Homozygosity mapping and candidate gene sequencing revealed a homozygous premature termination mutation in the gene STK4 (serine threonine kinase 4, formerly having the symbol MST1). STK4 is the human ortholog of Drosophila Hippo, the central constituent of a highly conserved pathway controlling cell growth and apoptosis. STK4-deficient lymphocytes and neutrophils exhibit enhanced loss of mitochondrial membrane potential and increased susceptibility to apoptosis. STK4 deficiency is a novel human primary immunodeficiency syndrome.     

Left ventricular mass and function with reduced-fat or reduced-carbohydrate hypocaloric diets in overweight and obese subjects

In animals, carbohydrate and fat composition during dietary interventions influenced cardiac metabolism, structure, and function. Because reduced-carbohydrate and reduced-fat hypocaloric diets are commonly used in the treatment of obesity, we investigated whether these interventions differentially affect left ventricular mass, cardiac function, and blood pressure. We randomized 170 overweight and obese subjects (body mass index, 32.9±4.4; range, 26.5-45.4 kg/m(2)) to 6-month hypocaloric diets with either reduced carbohydrate intake or reduced fat intake. We obtained cardiac MRI and ambulatory blood pressure recordings over 24 hours before and after 6 months. Ninety subjects completing the intervention period had a full cardiac MRI data set. Subjects lost 7.3±4.0 kg (7.9±3.8%) with reduced-carbohydrate diet and 6.2±4.2 kg (6.7±4.4%) with reduced-fat diet (P<0.001 within each group; P=not significant between interventions). Caloric restriction led to similar significant decreases in left ventricular mass with low-carbohydrate diets (5.4±5.4 g) or low-fat diets (5.2±4.8 g; P<0.001 within each group; P=not significant between interventions). Systolic and diastolic left ventricular function did not change with either diet. The 24-hour systolic blood pressure decreased similarly with both interventions. Body weight change (β=0.33; P=0.02) and percentage of ingested n-3 polyunsaturated fatty acids (β=-0.27; P=0.03) predicted changes in left ventricular mass. In conclusion, weight loss induced by reduced-fat diets or reduced-carbohydrate diets similarly improved left ventricular mass in overweight and obese subjects over a 6-month period. However, n-3 polyunsaturated fatty acid ingestion may have an independent beneficial effect on left ventricular mass.     

Disorders of Balance and Gait in Essential Tremor Are Associated with Midline Tremor and Age

Disorders of balance and gait have been observed in patients with essential tremor (ET), but their association with tremor severity remains unclear. This study aimed to evaluate postural instability and gait changes in ET patients and to investigate their relationship to tremor characteristics with regard to cerebellar dysfunction as a possible common pathogenetic mechanism in ET. Thirty ET patients (8F, mean (SD) age 55.8 (17.8), range 19–81 years) and 25 normal controls (7F, 53.0 (17.7), 19–81) were tested with the scales of Activities-specific Balance Confidence (ABC), Fullerton Advanced Balance (FAB), and International Cooperative Ataxia Rating Scale (ICARS). Posturography and gait were assessed using a Footscan® system. Tremor was evaluated by the Fahn–Tolosa–Marin Tremor Rating Scale (TRS) and accelerometry in five upper limb positions. A mean (SD) TRS sum score of 27.0 (13.2) corresponded to mild to moderate tremor severity in most patients. In comparison with controls, ET subjects exhibited lower tandem gait velocity (0.21 vs. 0.26 m/s, P?=?0.028), more missteps (0.57 vs. 0.12, P?=?0.039), and increased postural sway in tandem stance (sway area 301.1 vs. 202.9 mm², P?=?0.045). In normal gait, step width increased with the midline tremor subscore of TRS (Pearson r?=?0.60, P?=?0.046). Moreover, significant correlations were found between age and quantitative measures of normal and tandem gait in ET patients but not in controls. ABC, FAB, and ICARS scores did not significantly differ between patients and controls. In conclusion, gait and balance alterations in ET patients occur even without subjective complaints. Their relationship with midline tremor and dependence on age suggest a connection with cerebellar dysfunction.