Single-Electron Charging Effects in Hybrid Organic/Inorganic Nanomembrane-Based Junctions

The controllable transfer of a single electron in devices (SEDs) is one of the viable trends for a new generation of technology. However, novel applications demand innovative strategies to fabricate and evaluate SEDs. Here, we report a hybrid organic/inorganic SED that combines an ensemble of physisorbed, semiconducting molecular layers (SMLs) and Au nanoclusters embedded in the transport channel by in situ, field-induced metal migration. The SED is fabricated using an integrative platform based on rolled-up nanomembranes (rNMs) to connect ultrathin SMLs from the top, forming large-area tunnel junctions. The combination of high electric fields (1–4 MV/cm), electrode point contacts, low temperatures (10 K), and ultrathin molecular layers (<10 nm) lead to field-induced migration of Au electrode nanoparticles inward the SML of the junction channel. This phenomenon can be either observed in the as-prepared rNM junctions or intentionally induced by the application of high electric fields (>1 MV/cm). The propelled electrode particles become trapped in the soft molecular material, acting as Coulomb islands positioned in between a double-barrier tunnel junction. As a result, the hybrid organic/inorganic rNM junctions present single-charge effects, namely Coulomb blockade and Coulomb staircase. Such an in situ, field-induced metal migration process opens possibilities to create novel and complex SEDs by using different molecular materials. From another perspective, the reported metal diffusion in such nanoscale junctions deserves attention as it can occasionally mask molecule-dependent responses

Altered mRNA Splicing, Chondrocyte Gene Expression and Abnormal Skeletal Development due to <i>SF3B4</i> Mutations in Rodriguez Acrofacial Dysostosis

<div><p>The acrofacial dysostoses (AFD) are a genetically heterogeneous group of inherited disorders with craniofacial and limb abnormalities. Rodriguez syndrome is a severe, usually perinatal lethal AFD, characterized by severe retrognathia, oligodactyly and lower limb abnormalities. Rodriguez syndrome has been proposed to be a severe form of Nager syndrome, a non-lethal AFD that results from mutations in <i>SF3B4</i>, a component of the U2 small nuclear ribonucleoprotein particle (U2 snRNP). Furthermore, a case with a phenotype intermediate between Rodriguez and Nager syndromes has been shown to have an <i>SF3B4</i> mutation. We identified heterozygosity for <i>SF3B4</i> mutations in Rodriguez syndrome, confirming that the phenotype is a dominant disorder that is allelic with Nager syndrome. The mutations led to reduced SF3B4 synthesis and defects in mRNA splicing, primarily exon skipping. The mutations also led to reduced expression in growth plate chondrocytes of target genes, including the <i>DLX5</i>, <i>DLX6</i>, <i>SOX9</i>, and <i>SOX6</i> transcription factor genes, which are known to be important for skeletal development. These data provide mechanistic insight toward understanding how <i>SF3B4</i> mutations lead to the skeletal abnormalities observed in the acrofacial dysostoses.</p></div

SF3B4 and DLX5 are co-expressed in the human growth plate.

<p>Immunohistochemical staining of the distal femur growth plate from a control fetus with (A) anti-SF3B4 and (B) anti-DLX5 antibodies. The hypertrophic zone is marked with double arrows. The periosteum is identified by white arrows. Images were obtained at 20X (SF3B4) and 10X (DLX5) magnification. Scale bars are 100 μM.</p

Mutations in <i>SF3B4</i>.

<p>(A,B) Electropherogram representation of genomic DNA fragments from controls (top), (A) case R14-123A (bottom), (B) case R08-269B (bottom). (C) The insertion in the <i>SF3B4</i> cDNA of R14-123A (bottom) as compared with control (top). The positions of the insertion mutations are indicated by arrows. (D) Schematic diagram of predicted protein alterations caused by <i>SF3B4</i> frameshift mutations. The blue bars correspond to the reference amino acid sequence and the red bars indicate altered amino acid sequences that begin at the mutation site. RNA recognition motifs (RRM) are shown as purple ovals.</p

Summary of the ultrasound, clinical and radiographic findings.

<p>Summary of the ultrasound, clinical and radiographic findings.</p

Pronounced disorganization of hypertrophic chondrocytes caused by <i>SF3B4</i> mutations.

<p>Toluidine blue staining of the distal femur growth plate from (A) a control fetus, (B) R14-123A, (C) R08-269A and (D) R08-269B. The hypertrophic zone is marked with double arrows. Images were obtained at 20X magnification. Scale bars are 100 μM.</p

SF3B4 mutation leads to altered splicing.

<p>(A) Bar graph representation of altered splicing events in case R08-269A. The number of events in each category is indicated, with exon exclusion to the left (blue bars) and exon inclusion to the right (red bars). (B) GO enrichment analysis of alternative splicing events. The number of genes in each GO term is shown. SE, skipped exon; MXE, mutually exclusive exon; A5SS, alternative 5’ splice site; A3SS, alternative 3’ splice site; RI, retained intron.</p

SF3B4 mutation leads to altered gene expression.

<p>(A) GO analysis of down-regulated genes in growth plate chondrocytes from case R08-269A. The number of genes in each GO term is indicated. (B-E) Expression changes of (B) <i>DLX5</i>, (C) <i>SOX6</i>, (D) <i>SOX9</i> and (E) <i>SF3B4</i>. The gene expression is represented as FPKM values. (F) Real-time quantitative RT-PCR validation of the RNA-seq data. mRNA expression was normalized to <i>GAPDH</i>. **p<0.01. (G) From top to bottom, enriched <i>DLX5</i>, <i>DLX6</i>, <i>SOX5</i> and <i>SOX9</i> binding motifs among the promoter regions of the down-regulated genes. The p values for motif enrichment are shown in parentheses below each motif.</p

Skeletal developmental genes with reduced expression in R08-269A.

<p>Skeletal developmental genes with reduced expression in R08-269A.</p

Radiographic phenotypes of cases R14-123A and R08-269A & B.

<p>(A) A/P radiograph of the chest of R14-123^a showing small scapulae, 11 ribs, and abnormally formed hypoplastic humeri with radioulnar synostosis. (B) Hand radiograph showing oligodactyly, hypoplastic carpal bones and preaxial polydactyly. (C) Bilateral lower extremities showing hypoplastic or absent fibulae with small stippled calcanei. (D) A/P radiograph of R08-269A showing hypoplastic radii, oligodactyly, absent thumbs, thin fibulae, and club foot. (E) A/P radiograph of R08-269B showing 11 ribs, absent radii and ulnae.</p