Characterization of the pathway for transport of the cytoadherence-mediating protein, PfEMP1, to the host cell surface in malaria parasite-infected erythrocytes.

The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family of antigenically diverse proteins is expressed on the surface of human erythrocytes infected with the malaria parasite P. falciparum, and mediates cytoadherence to the host vascular endothelium. In this report, we show that export of PfEMP1 is slow and inefficient as it takes several hours to traffic newly synthesized proteins to the erythrocyte membrane. Upon removal by trypsin treatment, the surface-exposed population of PfEMP1 is not replenished during subsequent culture indicating that there is no cycling of PfEMP1 between the erythrocyte surface and an intracellular compartment. The role of Maurer's clefts as an intermediate sorting compartment in trafficking of PfEMP1 was investigated using immunoelectron microscopy and proteolytic digestion of streptolysin O-permeabilized parasitized erythrocytes. We show that PfEMP1 is inserted into the Maurer's cleft membrane with the C-terminal domain exposed to the erythrocyte cytoplasm, whereas the N-terminal domain is buried inside the cleft. Transfer of PfEMP1 to the erythrocyte surface appears to involve electron-lucent extensions of the Maurer's clefts. Thus, we have delineated some important aspects of the unusual trafficking mechanism for delivery of this critical parasite virulence factor to the erythrocyte surface

AO-classification of thoracic and lumbar fractures—reproducibility utilizing radiographs and clinical information

This study was designed to assess the inter-observer reliability and intra-observer reproducibility of standard radiographic evaluation of 150 thoraco-lumbar fractures using the AO-classification. The influence of clinical information on agreement levels was also evaluated. Six observers (two junior and four senior residents) evaluated the radiographic images. The injuries were classified by each observer as either type A, B or C according to the AO-classification system and the levels of agreement were documented. After 3 months the injuries were again classified with the addition of the clinical findings of each patient and the level of agreement evaluated. The level of agreement was measured using Cohen’s κ-test. The overall inter-observer agreement was rated as fair (0.291) in the first session and moderate (0.403) in the second. Intra-observer values ranged from slight (0.181) to moderate (0.488). The increased level of agreement in the second session was attributed to the value of additional clinical information, the learning curve of the junior residents and the simplicity of the classification

Dysmorphic features, simplified gyral pattern and 7q11.23 duplication reciprocal to the Williams-Beuren deletion.

We report a patient with mild pachygyria, ascertained during a screening of subjects with abnormal neuronal migration and/or epilepsy, having a 7q11.23 duplication reciprocal to the Williams-Beuren critical region (WBCR) deletion. He exhibited speech delay and mental retardation together to type II trigonocephaly and other abnormalities. The proband's mother carried the same imbalance, though her phenotype was milder and no abnormal conformation of the cranium was reported. She had suffered a few seizures in infancy, as already described in other duplicated subjects. This genomic imbalance, now described in 17 subjects, including one parent for each of the four probands, is associated with a variable phenotype. Speech impairment is present in most cases; no distinctive facial gestalt is recognizable; seizures have been reported in four subjects and brain magnetic resonance, performed in eight cases, resulted abnormal in six, while detected abnormal neuronal migration in two. Although the clinical description of additional cases is needed to delineate a definite phenotypic core for WBCR duplications, trigonocephaly, also reported in another dup(7)(q11.23) patient, is possibly a trait that, together with speech impairment, may call for clinically oriented specific screening. Abnormal development of the cerebral cortex, reported also in the Williams-Beuren deletion, suggests that at least one gene is present in the critical region whose deletion/duplication impairs neuronal migration

Loss-of-function mutations in IGSF1 cause an X-linked syndrome of central hypothyroidism and testicular enlargement

Item does not contain fulltextCongenital central hypothyroidism occurs either in isolation or in conjunction with other pituitary hormone deficits. Using exome and candidate gene sequencing, we identified 8 distinct mutations and 2 deletions in IGSF1 in males from 11 unrelated families with central hypothyroidism, testicular enlargement and variably low prolactin concentrations. IGSF1 is a membrane glycoprotein that is highly expressed in the anterior pituitary gland, and the identified mutations impair its trafficking to the cell surface in heterologous cells. Igsf1-deficient male mice show diminished pituitary and serum thyroid-stimulating hormone (TSH) concentrations, reduced pituitary thyrotropin-releasing hormone (TRH) receptor expression, decreased triiodothyronine concentrations and increased body mass. Collectively, our observations delineate a new X-linked disorder in which loss-of-function mutations in IGSF1 cause central hypothyroidism, likely secondary to an associated impairment in pituitary TRH signaling