A Biallelic Variant of the RNA Exosome Gene, EXOSC4, Associated With Neurodevelopmental Defects Impairs RNA Exosome Function and Translation

The RNA exosome is an evolutionarily conserved complex required for both precise RNA processing and decay. Pathogenic variants in EXOSC genes, which encode structural subunits of this complex, are linked to several autosomal recessive disorders. Here, we describe a missense allele of the EXOSC4 gene that causes a collection of clinical features in two affected siblings. This missense variant (NM_019037.3: exon3:c.560T\u3eC) changes a leucine residue within a conserved region of EXOSC4 to proline (p.Leu187Pro). The two affected individuals show prenatal growth restriction, failure to thrive, global developmental delay, intracerebral and basal ganglia calcifications, and kidney failure. Homozygosity for the damaging variant was identified by exome sequencing with Sanger sequencing to confirm segregation. To explore the functional consequences of this amino acid change, we modeled EXOSC4-L187P in the corresponding budding yeast protein, Rrp41 (Rrp41-L187P). Cells that express Rrp41-L187P as the sole copy of the essential Rrp41 protein show growth defects. Steady-state levels of both Rrp41-L187P and EXOSC4-L187P are decreased compared to controls, and EXOSC4-L187P shows decreased copurification with other RNA exosome subunits. RNA exosome target transcripts accumulate in rrp41-L187P cells, including the 7S precursor of 5.8S rRNA. Polysome profiles show a decrease in actively translating ribosomes in rrp41-L187P cells as compared to control cells with the incorporation of 7S pre-rRNA into polysomes. This work adds EXOSC4 to the structural subunits of the RNA exosome that have been linked to human disease and defines foundational molecular defects that could contribute to the adverse phenotypes caused by EXOSC pathogenic variants

From Architectured Materials to Large-Scale Additive Manufacturing

The classical material-by-design approach has been extensively perfected by materials scientists, while engineers have been optimising structures geometrically for centuries. The purpose of architectured materials is to build bridges across themicroscale ofmaterials and themacroscale of engineering structures, to put some geometry in the microstructure. This is a paradigm shift. Materials cannot be considered monolithic anymore. Any set of materials functions, even antagonistic ones, can be envisaged in the future. In this paper, we intend to demonstrate the pertinence of computation for developing architectured materials, and the not-so-incidental outcome which led us to developing large-scale additive manufacturing for architectural applications

A Comparative Investigation of Sintering Methods for Polymer 3D Printing Using Selective Separation Shaping (SSS)

Selective Separating Shaping (SSS) is a novel additive manufacturing process which is capable of processing polymeric, metallic, ceramic and cementitious materials. In earlier experiments, the capabilities of SSS in fabrication of metallic, ceramic, cement-based and polymeric parts have been demonstrated. The focus of this research has been on exploration of sintering methods in SSS for successful fabrication of polymeric parts. The SSS machine has been used to build specimens made of polyamide (PA6) material. Bonds between layers under two different thermal sintering methods are investigated to achieve better control over shrinkage and maintain effective binding between layers. ImageJ platform and binary surface plots have been used for image processing and evaluating final porosity under each heating mechanism. Further investigations are carried out on properties of the base materials and the choice of sintering mechanism to further improve resolution of final parts.Mechanical Engineerin

Translation Initiation Factors eIF3 and HCR1 Control Translation Termination and Stop Codon Read-Through in Yeast Cells

Translation is divided into initiation, elongation, termination and ribosome recycling. Earlier work implicated several eukaryotic initiation factors (eIFs) in ribosomal recycling in vitro. Here, we uncover roles for HCR1 and eIF3 in translation termination in vivo. A substantial proportion of eIF3, HCR1 and eukaryotic release factor 3 (eRF3) but not eIF5 (a well-defined “initiation-specific” binding partner of eIF3) specifically co-sediments with 80S couples isolated from RNase-treated heavy polysomes in an eRF1-dependent manner, indicating the presence of eIF3 and HCR1 on terminating ribosomes. eIF3 and HCR1 also occur in ribosome- and RNA-free complexes with both eRFs and the recycling factor ABCE1/RLI1. Several eIF3 mutations reduce rates of stop codon read-through and genetically interact with mutant eRFs. In contrast, a slow growing deletion of hcr1 increases read-through and accumulates eRF3 in heavy polysomes in a manner suppressible by overexpressed ABCE1/RLI1. Based on these and other findings we propose that upon stop codon recognition, HCR1 promotes eRF3·GDP ejection from the post-termination complexes to allow binding of its interacting partner ABCE1/RLI1. Furthermore, the fact that high dosage of ABCE1/RLI1 fully suppresses the slow growth phenotype of hcr1? as well as its termination but not initiation defects implies that the termination function of HCR1 is more critical for optimal proliferation than its function in translation initiation. Based on these and other observations we suggest that the assignment of HCR1 as a bona fide eIF3 subunit should be reconsidered. Together our work characterizes novel roles of eIF3 and HCR1 in stop codon recognition, defining a communication bridge between the initiation and termination/recycling phases of translation

Selective Separation Shaping of Polymeric Parts

Additive manufacturing (AM), or 3D printing has enjoyed a recent surge of attention over the past decade. AM is a process in which digital 3D design data is used as input to build physical objects by combining sequence layers of material. By increasing demand in use of additive manufacturing for fabrication of end-user parts, there is considerable interest in developing new techniques which can offer high quality customized parts at low cost. Selective Separation Shaping (SSS) is a new AM technology developed with the goal of fabricating low cost, high resolution 3D parts. The main advantage of SSS is that this process enables building fully functional pieces without the need of any intermediate binder or high cost laser operation. This process has been primarily applied to metallic, and ceramic materials and test cases were successfully built. There has been no study on fabrication of parts using polymeric material and the goal of this research is to examine successful fabrication of polymer parts. Nylon 6,6 has been used as starting base material and several test cases were fabricated to identify key factors in success of this process. Different classes of nylon are studied to achieve better understanding of material properties on success of fabrication and achieve an effective binding between layers. Finally, 3D printed parts built by SSS are presented.Mechanical Engineerin