Mutation in the Gene Encoding Ubiquitin Ligase LRSAM1 in Patients with Charcot-Marie-Tooth Disease

Charcot-Marie-Tooth disease (CMT) represents a family of related sensorimotor neuropathies. We studied a large family from a rural eastern Canadian community, with multiple individuals suffering from a condition clinically most similar to autosomal recessive axonal CMT, or AR-CMT2. Homozygosity mapping with high-density SNP genotyping of six affected individuals from the family excluded 23 known genes for various subtypes of CMT and instead identified a single homozygous region on chromosome 9, at 122,423,730–129,841,977 Mbp, shared identical by state in all six affected individuals. A homozygous pathogenic variant was identified in the gene encoding leucine rich repeat and sterile alpha motif 1 (LRSAM1) by direct DNA sequencing of genes within the region in affected DNA samples. The single nucleotide change mutates an intronic consensus acceptor splicing site from AG to AA. Direct analysis of RNA from patient blood demonstrated aberrant splicing of the affected exon, causing an obligatory frameshift and premature truncation of the protein. Western blotting of immortalized cells from a homozygous patient showed complete absence of detectable protein, consistent with the splice site defect. LRSAM1 plays a role in membrane vesicle fusion during viral maturation and for proper adhesion of neuronal cells in culture. Other ubiquitin ligases play documented roles in neurodegenerative diseases. LRSAM1 is a strong candidate for the causal gene for the genetic disorder in our kindred.     

Comparative 3D quantitative analyses of trapeziometacarpal joint surface curvatures among living catarrhines and fossil hominins

Comparisons of joint surface curvature at the base of the thumb have long been made to discern differences among living and fossil primates in functional capabilities of the hand. However, the complex shape of this joint makes it difficult to quantify differences among taxa. The purpose of this study is to determine whether significant differences in curvature exist among selected catarrhine genera and to compare these genera with hominin¹ fossils in trapeziometacarpal curvature. Two 3D approaches are used to quantify curvatures of the trapezial and metacarpal joint surfaces: (1) stereophotogrammetry with nonuniform rational B‐spline (NURBS) calculation of joint curvature to compare modern humans with captive chimpanzees and (2) laser scanning with a quadric‐based calculation of curvature to compare modern humans and wild‐caught Pan, Gorilla, Pongo, and Papio. Both approaches show that Homo has significantly lower curvature of the joint surfaces than does Pan. The second approach shows that Gorilla has significantly more curvature than modern humans, while Pongo overlaps with humans and African apes. The surfaces in Papio are more cylindrical and flatter than in Homo. Australopithecus afarensis resembles African apes more than modern humans in curvatures, whereas the Homo habilis trapezial metacarpal surface is flatter than in all genera except Papio. Neandertals fall at one end of the modern human range of variation, with smaller dorsovolar curvature. Modern human topography appears to be derived relative to great apes and Australopithecus and contributes to the distinctive human morphology that facilitates forceful precision and power gripping, fundamental to human manipulative activities. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc. ¹ The term “hominin” refers to members of the tribe Hominini, which includes modern humans and fossil species that are related more closely to modern humans than to extant species of chimpanzees, Wood and Lonergan (2008). Hominins are in the family Hominidae with great apes.     

Hsp70/Hsc70 regulates the effect phosphorylation has on stabilizing ataxin-1

Spinocerebellar ataxia type 1 (SCA1) is an inherited neurodegenerative disorder. The mutation causing SCA1 is an expansion in the polyglutamine tract of the ATXN1 protein. Previous work demonstrated that phosphorylation of mutant ATXN1 at serine 776 (S776), a putative Akt phosphorylation site, is critical for pathogenesis. To examine this pathway further, we utilized a cell-transfection system that allowed the targeting of Akt to either the cytoplasm or the nucleus. In contrast to HeLa cells, we found that Akt targeted to the cytoplasm increased the degradation of ATXN1 in Chinese hamster ovary cells. However, Akt targeted to the cytoplasm failed to destabilize ATXN1 if Hsp70/Hsc70 was present. Thus, Hsp70/Hsc70 can regulate ATXN1 levels in concert with phosphorylation of ATXN1 at S776.     

Severe acute respiratory syndrome coronavirus evades antiviral signaling: role of nsp1 and rational design of an attenuated strain

The severe acute respiratory syndrome (SARS) epidemic was caused by the spread of a previously unrecognized infectious agent, the SARS-associated coronavirus (SARS-CoV). Here we show that SARS-CoV could inhibit both virus- and interferon (IFN)-dependent signaling, two key steps of the antiviral response. We mapped a strong inhibitory activity to SARS-CoV nonstructural protein 1 (nsp1) and show that expression of nsp1 significantly inhibited the activation of all three virus-dependent signaling pathways. We show that expression of nsp1 significantly inhibited IFN-dependent signaling by decreasing the phosphorylation levels of STAT1 while having little effect on those of STAT2, JAK1, and TYK2. We engineered an attenuated mutant of nsp1 in SARS-CoV through reverse genetics, and the resulting mutant virus was viable and replicated as efficiently as wild-type virus in cells with a defective IFN response. However, mutant virus replication was strongly attenuated in cells with an intact IFN response. Thus, nsp1 is likely a virulence factor that contributes to pathogenicity by favoring SARS-CoV replication.     

Histone acetylation and chromatin pattern in cancer. A review

Chromatin phenotype is known to be significantly disrupted in cancer. This has been demonstrated in many morphologic studies on cancer and in recent years by the application of digital texture analysis for quantitative evaluation of chromatin phenotype in neoplasia. Studies have consistently demonstrated the role of chromatin phenotype as a biomarker of diagnosis and prognosis. The underlying molecular mechanisms for chromatin reorganization and its role as a biomarker are largely unknown, but epigenetic processes are likely to be a main factor that not only modify chromatin arrangement but in doing so alter gene expression profiles in a reversible fashion. Of the range of epigenetic modifications that might control chromatin phenotype, histone acetylation is a strong candidate because of its role in the direct modification of chromatin, both through local relaxation of nucleosomal structure and recruitment of chromatin remodeling complexes. The reversible nature of histone acetylation is therapeutically attractive for treatment of aberrant histone acetylation; however, it still remains to be seen whether histone deacetylase inhibitors are clinically applicable or for use primarily as valuable research tools. This review explores the role of histone acetylation in cancer development, as a potential therapeutic candidate and a potential biomarker in tissue pathology.     

Improved phylogenetic resolution of toxic and non-toxic Alexandrium strains using a concatenated rDNA approach

Dinoflagellates of the genus Alexandrium are known producers of paralytic shellfish toxins. Species within the genus have similar phenotypes making morphological identification problematical. The use of Alexandrium rDNA sequence data is therefore increasing, resulting in the improved resolution of evolutionary relationships by phylogenetic inferences. However, the true branching pattern within Alexandrium remains unresolved, with minimal support shown for the main phylogentic branch. The aim of this study is to improve phylogenetic resolution via a concatenated rDNA approach with a broad sample of taxa, allowing inference of the evolutionary pattern between species and toxins. 27 Alexandrium strains from 10 species were tested with HPLC for PSP toxin presence and additionally sequenced for 18S, ITS1, 5.8S, ITS2 and 28S rDNA before being phylogenetically inferred together with all available orthologous sequences from NCBI. The resulting alignment is the largest to date for the genus, in terms of both inferred characters and taxa, thus allowing for the improved phylogenetic resolution of evolutionary patterns there in. No phylogenetic pattern between PSP producing and non-producing strains could be established, however the terminal tamarense complex was shown to produce more PSP analogues than basal clades. Additionally, we distinguish a high number of polymorphic regions between the two copies of A. fundyense rDNA, thus allowing us to demonstrate the presence of chimeric sequences within GenBank, as well as a possible over estimation of diversification within the tamarense complex.