👤 Dana A Osborne

Glaucoma is a progressive neurodegenerative disease that affects retinal ganglion cells (RGCs), ultimately leading to vision loss. In this study, we investigated gene therapy-mediated transduction of RGCs and examined axonal transport changes in the optic nerve using a viral vector designed to upregulate tropomyosin receptor kinase B (TrkB) expression. TrkB expression was evaluated in retinae and optic nerves of rats following genetic intravitreal delivery of AAV2-TrkB. Axonal transport and preliminary mitochondrial changes were assessed in optic nerves by immunohistochemical staining for kinesin and voltage-dependent anion channel (VDAC), a mitochondrial component. The results revealed an approximately 30% increase in TrkB expression in the retina, which was confirmed to be vector-driven by a P2A tag attached to the TrkB protein. This increased protein expression could be seen independent of injury and in eyes with elevated intraocular pressure. Observations along the optic nerve of rats treated with AAV2-TrkB revealed elevated transport of TrkB along axons (50% in TrkB, 120% in P2A tag) and significant increases in kinesin (12%) and VDAC (16%) immunoreactivity. This study provides early indications that improving TrkB expression in the eye may increase anterograde transport of motor proteins, which in turn could improve mitochondrial transport within the optic nerve. Show less

Base editors can correct disease-causing genetic variants. After a neonate had received a diagnosis of severe carbamoyl-phosphate synthetase 1 deficiency, a disease with an estimated 50% mortality in early infancy, we immediately began to develop a customized lipid nanoparticle-delivered base-editing therapy. After regulatory approval had been obtained for the therapy, the patient received two infusions at approximately 7 and 8 months of age. In the 7 weeks after the initial infusion, the patient was able to receive an increased amount of dietary protein and a reduced dose of a nitrogen-scavenger medication to half the starting dose, without unacceptable adverse events and despite viral illnesses. No serious adverse events occurred. Longer follow-up is warranted to assess safety and efficacy. (Funded by the National Institutes of Health and others.). Show less

G-quadruplexes (G4s) are secondary DNA and RNA structures stabilized by positive cations in a central channel formed by stacked tetrads of Hoogsteen base-paired guanines. G4s form from G-rich sequences across the genome, whose biased distribution in regulatory regions points towards a gene-regulatory role. G4s can themselves be regulated by helicases, such as DHX36 (aliases: G4R1 and RHAU), which possess the necessary activity to resolve these stable structures. G4s have been shown to both positively and negatively regulate gene expression when stabilized by ligands, or through the loss of helicase activity. Using Show less

Williams syndrome (WS) is a relatively rare microdeletion disorder that occurs in as many as 1:7,500 individuals. WS arises due to the mispairing of low-copy DNA repetitive elements at meiosis. The deletion size is similar across most individuals with WS and leads to the loss of one copy of 25-27 genes on chromosome 7q11.23. The resulting unique disorder affects multiple systems, with cardinal features including but not limited to cardiovascular disease (characteristically stenosis of the great arteries and most notably supravalvar aortic stenosis), a distinctive craniofacial appearance, and a specific cognitive and behavioural profile that includes intellectual disability and hypersociability. Genotype-phenotype evidence is strongest for ELN, the gene encoding elastin, which is responsible for the vascular and connective tissue features of WS, and for the transcription factor genes GTF2I and GTF2IRD1, which are known to affect intellectual ability, social functioning and anxiety. Mounting evidence also ascribes phenotypic consequences to the deletion of BAZ1B, LIMK1, STX1A and MLXIPL, but more work is needed to understand the mechanism by which these deletions contribute to clinical outcomes. The age of diagnosis has fallen in regions of the world where technological advances, such as chromosomal microarray, enable clinicians to make the diagnosis of WS without formally suspecting it, allowing earlier intervention by medical and developmental specialists. Phenotypic variability is considerable for all cardinal features of WS but the specific sources of this variability remain unknown. Further investigation to identify the factors responsible for these differences may lead to mechanism-based rather than symptom-based therapies and should therefore be a high research priority. Show less

The carbohydrate response element binding protein (ChREBP), a basic helix-loop-helix/leucine zipper transcription factor, plays a critical role in the control of lipogenesis in the liver. To identify the direct targets of ChREBP on a genome-wide scale and provide more insight into the mechanism by which ChREBP regulates glucose-responsive gene expression, we performed chromatin immunoprecipitation-sequencing and gene expression analysis. We identified 1153 ChREBP binding sites and 783 target genes using the chromatin from HepG2, a human hepatocellular carcinoma cell line. A motif search revealed a refined consensus sequence (CABGTG-nnCnG-nGnSTG) to better represent critical elements of a functional ChREBP binding sequence. Gene ontology analysis shows that ChREBP target genes are particularly associated with lipid, fatty acid and steroid metabolism. In addition, other functional gene clusters related to transport, development and cell motility are significantly enriched. Gene set enrichment analysis reveals that ChREBP target genes are highly correlated with genes regulated by high glucose, providing a functional relevance to the genome-wide binding study. Furthermore, we have demonstrated that ChREBP may function as a transcriptional repressor as well as an activator. Show less

Nearly 10% of all pancreatic cancer (PCA) results from genetic predisposition. Although abnormalities in sporadic PCA have been described, little is known about the genetics of heritable PCA. The purpose of this study was to identify novel genes expressed in patients with a presumed genetic predisposition or "familial" PCA. We defined "familial" PCA as patients having one or more first-degree relatives with biopsy-proven adenocarcinoma of the pancreas. Using a PCR-based subtractive and enrichment procedure, representational difference analysis (RDA), pancreatic tumor cDNA was reverse-transcribed from pooled poly(A)+ mRNA from six such patients (tester) and compared to pooled cDNA from five normal pancreata (driver). Tumor-specific gene fragments were identified and confirmed to be overexpressed in familial PCA by comparative RT-PCR. Six PCA cell lines, 11 sporadic tumors, 5 neuroendocrine tumors, and 3 chronic pancreatitis tissues were screened to determine the specificity of these genes. Sequence analysis revealed several sequences of unknown significance and six genes previously described in neoplasia/carcinogenesis: Apolipoprotein A4, CEA, Keratin 19, Stratifin (14-3-3 sigma), Trefoil Factor, and Calcium Binding Protein S100 A6. Screening of cell lines and pancreatic tissue types showed varying degrees of specificity for familial and sporadic PCA. The APO-A4 gene was up-regulated in familial PCA. The pattern of frequency in all screened tissue suggests that these genes are associated with conditions that produce significant desmoplastic responses and are difficult to differentiate from chronic inflammatory processes. Apolipoprotein A4 is preferentially expressed in familial patients, suggesting that the importance of fatty acid synthesis in carcinogenesis be investigated further. Show less