Mutations in HPCA Cause Autosomal-Recessive Primary Isolated Dystonia

Reports of primary isolated dystonia inherited in an autosomal-recessive (AR) manner, often lumped together as “DYT2 dystonia,” have appeared in the scientific literature for several decades, but no genetic cause has been identified to date. Using a combination of homozygosity mapping and whole-exome sequencing in a consanguineous kindred affected by AR isolated dystonia, we identified homozygous mutations in HPCA, a gene encoding a neuronal calcium sensor protein found almost exclusively in the brain and at particularly high levels in the striatum, as the cause of disease in this family. Subsequently, compound-heterozygous mutations in HPCA were also identified in a second independent kindred affected by AR isolated dystonia. Functional studies suggest that hippocalcin might play a role in regulating voltage-dependent calcium channels. The identification of mutations in HPCA as a cause of AR primary isolated dystonia paves the way for further studies to assess whether “DYT2 dystonia” is a genetically homogeneous condition or not.     

Rheb1 is required for mTORC1 and myelination in postnatal brain development

mTor kinase is involved in cell growth, proliferation, and differentiation. The roles of mTor activators, Rheb1 and Rheb2, have not been established in?vivo. Here, we report that Rheb1, but not Rheb2, is critical for embryonic survival and mTORC1 signaling. Embryonic deletion of Rheb1 in neural progenitor cells?abolishes mTORC1 signaling in developing brain and increases mTORC2 signaling. Remarkably, embryonic and early postnatal brain development appears grossly normal in these Rheb1f/f,Nes-cre mice with the notable exception of deficits of myelination. Conditional expression of Rheb1 transgene in neural progenitors increases mTORC1 activity and promotes myelination in the brain. In addition the Rheb1 transgene rescues mTORC1 signaling and hypomyelination in the Rheb1f/f,Nes-cre mice. Our study demonstrates that Rheb1 is essential for mTORC1 signaling and myelination in the brain, and suggests that mTORC1 signaling plays a role in selective cellular adaptations, rather than general cellular viability.     

The stability and complexity of antibody responses to the major surface antigen of Plasmodium falciparum are associated with age in a malaria endemic area

Individuals that are exposed to malaria eventually develop immunity to the disease with one possible mechanism being the gradual acquisition of antibodies to the range of parasite variant surface antigens in their local area. Major antibody targets include the large and highly polymorphic Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) family of proteins. Here, we use a protein microarray containing 123 recombinant PfEMP1-DBLα domains (VAR) from Papua New Guinea to seroprofile 38 nonimmune children (<4 years) and 29 hyperimmune adults (≥15 years) from the same local area. The overall magnitude, prevalence and breadth of antibody response to VAR was limited at <2 years and 2-2.9 years, peaked at 3-4 years and decreased for adults compared with the oldest children. An increasing proportion of individuals recognized large numbers of VAR proteins (>20) with age, consistent with the breadth of response stabilizing with age. In addition, the antibody response was limited in uninfected children compared with infected children but was similar in adults irrespective of infection status. Analysis of the variant-specific response confirmed that the antibody signature expands with age and infection. This also revealed that the antibody signatures of the youngest children overlapped substantially, suggesting that they are exposed to the same subset of PfEMP1 variants. VAR proteins were either seroprevalent from early in life, (<3 years), from later in childhood (≥3 years) or rarely recognized. Group 2 VAR proteins (Cys2/MFK-REY+) were serodominant in infants (<1-year-old) and all other sequence subgroups became more seroprevalent with age. The results confirm that the anti-PfEMP1-DBLα antibody responses increase in magnitude and prevalence with age and further demonstrate that they increase in stability and complexity. The protein microarray approach provides a unique platform to rapidly profile variant-specific antibodies to malaria and suggests novel insights into the acquisition of immunity to malaria.     

Lessons and revelations from biomimetic syntheses

Biomimetic synthesis describes the field of organic chemistry that aims to emulate the natural, biosynthetic processes toward natural products. As well as providing insight into how molecules are formed in nature, the benefits of this approach to total synthesis are numerous and extend beyond the gains typical of traditional synthesis. For example, using biosynthetic proposals to design a synthetic route can highlight alternative methods to the desired target. The pursuit of biomimetic syntheses also promotes the development of new reactions to prove or disprove a biosynthetic proposal or to unravel mechanistic implications of a proposed biosynthesis and can lead to the identification of new natural products. Here we look at some recent compelling examples and examine how biomimetic synthesis has led to the discovery of new procedures and principles that would not have been found by other approaches.     

Taxonomy of Eurotium species isolated from meju

Eurotium strains were isolated from 77 loaves of meju (dried fermented soybeans), in various regions of Korea from 2008 to 2010. Morphological characteristics and DNA sequences of β-tubulin were examined. They were identified as Eurotium amstelodami, E. chevalieri, E. herbariorum, E. repens, E. rubrum, and E. tonophilum. Of these species, E. chevalieri and E. tonophilum had not been previously reported in association with meju. E. chevalieri and E. repens were the species isolated most frequently. This paper summarizes the morphological characteristics of six Eurotium species and provides key to identify the species from meju.     

Hydrophobic-domain-dependent protein-protein interactions mediate the localization of GPAT enzymes to ER subdomains

The endoplasmic reticulum (ER) is a dynamic organelle that consists of numerous regions or 'subdomains' that have discrete morphological features and functional properties. Although it is generally accepted that these subdomains differ in their protein and perhaps lipid compositions, a clear understanding of how they are assembled and maintained has not been well established. We previously demonstrated that two diacylglycerol acyltransferase enzymes (DGAT1 and DGAT2) from tung tree (Vernicia fordii) were located in different subdomains of ER, but the mechanisms responsible for protein targeting to these subdomains were not elucidated. Here we extend these studies by describing two glycerol-3-phosphate acyltransferase-like (GPAT) enzymes from tung tree, GPAT8 and GPAT9, that both colocalize with DGAT2 in the same ER subdomains. Measurement of protein-protein interactions using the split-ubiquitin assay revealed that GPAT8 interacts with itself, GPAT9 and DGAT2, but not with DGAT1. Furthermore, mutational analysis of GPAT8 revealed that the protein's first predicted hydrophobic region, which contains an amphipathic helix-like motif, is required for interaction with DGAT2 and for DGAT2-dependent colocalization in ER subdomains. Taken together, these results suggest that the regulation and organization of ER subdomains is mediated at least in part by higher-ordered, hydrophobic-domain-dependent homo- and hetero-oligomeric protein-protein interactions.     

P38 mitogen-activated protein kinase inhibitor, FR167653, inhibits parathyroid hormone related protein-induced osteoclastogenesis and bone resorption

p38 mitogen-activated protein kinase (MAPK) acts downstream in the signaling pathway that includes receptor activator of NF-κB (RANK), a powerful inducer of osteoclast formation and activation. We investigated the role of p38 MAPK in parathyroid hormone related protein (PTHrP)-induced osteoclastogenesis in vitro and PTHrP-induced bone resorption in vivo. The ability of FR167653 to inhibit osteoclast formation was evaluated by counting the number of tartrate-resistant acid phosphatase positive multinucleated cells (TRAP-positive MNCs) in in vitro osteoclastgenesis assays. Its mechanisms were evaluated by detecting the expression level of c-Fos and nuclear factor of activated T cells c1 (NFATc1) in bone marrow macrophages (BMMs) stimulated with sRANKL and M-CSF, and by detecting the expression level of osteoprotegerin (OPG) and RANKL in bone marrow stromal cells stimulated with PTHrP in the presence of FR167653. The function of FR167653 on bone resorption was assessed by measuring the bone resorption area radiographically and by counting osteoclast number per unit bone tissue area in calvaria in a mouse model of bone resorption by injecting PTHrP subcutaneously onto calvaria. Whole blood ionized calcium levels were also recorded. FR167653 inhibited PTHrP-induced osteoclast formation and PTHrP-induced c-Fos and NFATc1 expression in bone marrow macrophages, but not the expression levels of RANKL and OPG in primary bone marrow stromal cells treated by PTHrP. Furthermore, bone resorption area and osteoclast number in vivo were significantly decreased by the treatment of FR167653. Systemic hypercalcemia was also partially inhibited. Inhibition of p38 MAPK by FR167653 blocks PTHrP-induced osteoclastogenesis in vitro and PTHrP-induced bone resorption in vivo, suggesting that the p38 MAPK signaling pathway plays a fundamental role in PTHrP-induced osteoclastic bone resorption.     

Protective effect of prenatal water restriction on offspring cardiovascular homeostasis in response to hemorrhage

We determined the cardiovascular and AVP responses of prenatally dehydrated (PreDehy) neonates to intravascular hemorrhage. Ewes with singleton fetuses were subjected to water restriction from 110 days of gestation to full term to achieve hypernatremia of 8-10 meq/l. Water and food were provided ad libitum to control ewes. After delivery, water and food were provided ad libitum to ewes from both groups, and newborns were allowed to nurse ad libitum. At 15 +/- 2 days of age, PreDehy and control lambs were prepared with bladder and femoral catheters and studied at 25 +/- 2 days of age. After a 2-h basal period, lambs were hemorrhaged to 30% of blood volume over 1 h (0.5% of blood volume/min) and monitored 1 h after hemorrhage. Neonatal arterial blood pressure was measured, and blood samples were collected. Basal plasma sodium levels, plasma osmolality, hematocrit, and mean arterial pressure were increased in PreDehy lambs compared with controls. Both groups had similar basal AVP levels and heart rate. In response to hemorrhage, all parameters remained significantly elevated in PreDehy lambs. Blood pressure decreased less in PreDehy lambs than in controls. The hemorrhage-AVP threshold (percent blood volume withdrawal at which plasma AVP values significantly increased) was markedly elevated (20 vs. 15%) and peak hemorrhage-induced AVP plasma levels were lower (5.6 +/- 1.5 vs. 10.1 +/- 1.5 pg/ml, P < 0.01) in PreDehy lambs than in controls. Thus offspring of dehydrated ewes demonstrate enhanced AVP secretory responses to hypotension. Despite potential long-term adverse effects of systemic hypertension, these results suggest a protective effect of prenatal water restriction on offspring cardiovascular homeostasis during blood volume reduction.