No abstract

The kidney filter represents a unique assembly of podocyte epithelial cells that tightly enwrap the glomerular capillaries with their foot processes and the interposed slit diaphragm. So far, very little is known about the guidance cues and polarity signals required to regulate proper development and maintenance of the glomerular filtration barrier. We now identify Par3, Par6, and atypical protein kinase C (aPKC) polarity proteins as novel Neph1-Nephrin-associated proteins. The interaction was mediated through the PDZ domain of Par3 and conserved carboxyl terminal residues in Neph1 and Nephrin. Par3, Par6, and aPKC localized to the slit diaphragm as shown in immunofluorescence and immunoelectron microscopy. Consistent with a critical role for aPKC activity in podocytes, inhibition of glomerular aPKC activity with a pseudosubstrate inhibitor resulted in a loss of regular podocyte foot process architecture. These data provide an important link between cell recognition mediated through the Neph1-Nephrin complex and Par-dependent polarity signaling and suggest that this molecular interaction is essential for establishing the three-dimensional architecture of podocytes at the kidney filtration barrier.

Multiple endocrine neoplasia type 2 is characterized by germline mutations in RET. For exon 10, comprehensive molecular and corresponding phenotypic data are scarce. The International RET Exon 10 Consortium, comprising 27 centers from 15 countries, analyzed patients with RET exon 10 mutations for clinical-risk profiles. Presentation, age-dependent penetrance, and stage at presentation of medullary thyroid carcinoma (MTC), pheochromocytoma, and hyperparathyroidism were studied. A total of 340 subjects from 103 families, age 4-86, were registered. There were 21 distinct single nucleotide germline mutations located in codons 609 (45 subjects), 611 (50), 618 (94), and 620 (151). MTC was present in 263 registrants, pheochromocytoma in 54, and hyperparathyroidism in 8 subjects. Of the patients with MTC, 53% were detected when asymptomatic, and among those with pheochromocytoma, 54%. Penetrance for MTC was 4% by age 10, 25% by 25, and 80% by 50. Codon-associated penetrance by age 50 ranged from 60% (codon 611) to 86% (620). More advanced stage and increasing risk of metastases correlated with mutation in codon position (609→620) near the juxtamembrane domain. Our data provide rigorous bases for timing of premorbid diagnosis and personalized treatment/prophylactic procedure decisions depending on specific RET exon 10 codons affected.

Neph proteins are evolutionarily conserved members of the immunoglobulin superfamily of adhesion proteins and regulate morphogenesis and patterning of different tissues. They share a common protein structure consisting of extracellular immunoglobulin-like domains, a transmembrane region, and a carboxyl terminal cytoplasmic tail required for signaling. Neph orthologs have been widely characterized in invertebrates where they mediate such diverse processes as neural development, synaptogenesis, or myoblast fusion. Vertebrate Neph proteins have been described first at the glomerular filtration barrier of the kidney. Recently, there has been accumulating evidence suggesting a function of Neph proteins also outside the kidney. Here we demonstrate that Neph1, Neph2, and Neph3 are expressed differentially in various tissues during ontogenesis in mouse and chicken. Neph1 and Neph2 were found to be amply expressed in the central nervous system while Neph3 expression remained localized to the cerebellum anlage and the spinal cord. Outside the nervous system, Neph mRNAs were also differentially expressed in branchial arches, somites, heart, lung bud, and apical ectodermal ridge. Our findings support the concept that vertebrate Neph proteins, similarly to their Drosophila and C. elegans orthologs, provide guidance cues for cell recognition and tissue patterning in various organs which may open interesting perspectives for future research on Neph1-3 controlled morphogenesis.

Limb buds develop from lateral plate-derived stationary mesenchyme and are invaded by cells from extrinsic regions. The largest populations of these cells are myogenic precursor cells that originate from the lateral dermomyotomes. After detachment under the influence of SF/HGF, myogenic precursor cells migrate in a proximo-distal direction and populate a dorsal and ventral zone. The patterning mechanism leading to the segregation of dorsal and ventral myogenic cells is at present not understood. Lmx1b, a LIM homeodomain transcription factor expressed in the dorsal mesenchyme of the developing limb bud, forms a sharp dorso-ventral boundary of expression within the limb. We have investigated the mechanisms of dorso-ventral patterning of muscle precursor cells in the limb buds with respect to Lmx1b expression using quail-chick chimeras and transgenic mice. Although cells appeared to be capable of migrating either ventrally or dorsally, their migration was restricted to the position they had attained during normal development or in the experimental situation. They were never found to cross the dorso-ventral boundary. Immunohistochemistry and histological analysis of mice carrying a LacZ reporter gene under the control of the endogenous Lmx1b locus confirmed that myogenic precursors in the limb bud were devoid of Lmx1b expression. In addition, it was shown that Lmx1b is not only expressed at early stages of limb development but maintains its pattern, at least until after birth. The present study provides new insights into migratory pathways of myogenic precursor cells and reveals details of Lmx1b expression on a cellular basis within the limb.

Adhesion molecules of the immunoglobulin superfamily (IgSF) are essential for neuronal synapse development across evolution and control various aspects of synapse formation and maturation. Neph2, also known as Kirrel3, is an IgSF adhesion molecule implicated in synapse formation, synaptic transmission and ultrastructure. In humans, defects in the NEPH2 gene have been associated with neurodevelopmental disorders such as Jacobsen syndrome, intellectual disability, and autism-spectrum disorders. However, the precise role in development and function of the nervous system is still unclear. Here, we present the histomorphological and phenotypical analysis of a constitutive Neph2-knockout mouse line. Knockout mice display defects in auditory sensory processing, motor skills, and hyperactivity in the home-cage analysis. Olfactory, memory and metabolic testing did not differ from controls. Despite the wide-spread expression of Neph2 in various brain areas, no gross anatomic defects could be observed. Neph2 protein could be located at the cerebellar pinceaux. It interacted with the pinceau core component neurofascin and other synaptic proteins thus suggesting a possible role in cerebellar synapse formation and circuit assembly. Our results suggest that Neph2/Kirrel3 acts on the synaptic ultrastructural level and neuronal wiring rather than on ontogenetic events affecting macroscopic structure. Neph2-knockout mice may provide a valuable rodent model for research on autism spectrum diseases and neurodevelopmental disorders.

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A 79-year-old Caucasian male had traveled for 3 months in the Ukraine and Kazakhstan, where he was hospitalized for 3 weeks because of decompensated chronic heart failure, New York Heart Association (NYHA) classification 3. Acute myocardial infarction was ruled out. No further diagnostic workup was done for the swollen right leg. Two weeks later, an inflammation on the right knee (several centimeters in diameter) with a central necrosis appeared and within a few days developed into a cutaneous pyogenic abscess. During the 4 days following, further deep skin abscesses developed distally on the same leg. During the whole hospitalization, the patient was afebrile. Oral antibiotic therapy (regimen unknown) was given and the patient discharged. He continued his travel in the Ukraine for another 3 weeks.Directly after his return, the patient was hospitalized for deep vein thrombosis with consecutive central pulmonary embolism. Within the previous 2 months, he had lost 10 kg of weight. On admission, his white blood cell count was 15.6 ϫ 10 9 cells/liter with 78% neutrophils. His C-reactive protein level was moderately elevated (77 mg/liter), and his alanine aminotransferase (ALT) level was thrice the normal value. A chest computed tomography (CT) scan showed, besides the pulmonary embolism, pneumonia of the right upper lobe and two small nodules without surrounding infiltration in both upper