Longitudinal imaging highlights preferential basal ganglia circuit atrophy in Huntington's disease

Huntington's disease is caused by a CAG repeat expansion in the Huntingtin gene (HTT), coding for polyglutamine in the Huntingtin protein, with longer CAG repeats causing earlier age of onset. The variable 'Age' × ('CAG'-L), where 'Age' is the current age of the individual, 'CAG' is the repeat length and L is a constant (reflecting an approximation of the threshold), termed the 'CAG Age Product' (CAP) enables the consideration of many individuals with different CAG repeat expansions at the same time for analysis of any variable and graphing using the CAG Age Product score as the X axis. Structural MRI studies have showed that progressive striatal atrophy begins many years prior to the onset of diagnosable motor Huntington's disease, confirmed by longitudinal multicentre studies on three continents, including PREDICT-HD, TRACK-HD and IMAGE-HD. However, previous studies have not clarified the relationship between striatal atrophy, atrophy of other basal ganglia structures, and atrophy of other brain regions. The present study has analysed all three longitudinal datasets together using a single image segmentation algorithm and combining data from a large number of subjects across a range of CAG Age Product score. In addition, we have used a strategy of normalizing regional atrophy to atrophy of the whole brain, in order to determine which regions may undergo preferential degeneration. This made possible the detailed characterization of regional brain atrophy in relation to CAG Age Product score. There is dramatic selective atrophy of regions involved in the basal ganglia circuit-caudate, putamen, nucleus accumbens, globus pallidus and substantia nigra. Most other regions of the brain appear to have slower but steady degeneration. These results support (but certainly do not prove) the hypothesis of circuit-based spread of pathology in Huntington's disease, possibly due to spread of mutant Htt protein, though other connection-based mechanisms are possible. Therapeutic targets related to prion-like spread of pathology or other mechanisms may be suggested. In addition, they have implications for current neurosurgical therapeutic approaches, since delivery of therapeutic agents solely to the caudate and putamen may miss other structures affected early, such as nucleus accumbens and output nuclei of the striatum, the substantia nigra and the globus pallidus

Single-cell RNA sequencing reveals cancer stem-like cells and dynamics in tumor microenvironment during cholangiocarcinoma progression

Cholangiocarcinoma is a malignancy of the bile ducts that is driven by activities of cancer stem-like cells and characterized by a heterogeneous tumor microenvironment. To better understand the transcriptional profiles of cancer stem-like cells and dynamics in the tumor microenvironment during the progression of cholangiocarcinoma, we performed single-cell RNA analysis on cells collected from three different timepoints of tumorigenesis in a YAP/AKT mouse model. Bulk RNA sequencing data from TCGA (The Cancer Genome Atlas program) and ICGC cohorts were used to verify and support the finding. In vitro and in vivo experiments were performed to assess the stemness of cancer stem-like cells. We identified Tm4sf1high malignant cells as cancer stem-like cells. Across timepoints of cholangiocarcinoma formation in YAP/AKT mice, we found dynamic change in cancer stem-like cell/stromal/immune cell composition. Nevertheless, the dynamic interaction among cancer stem-like cells, immune cells, and stromal cells at different timepoints was elaborated. Collectively, these data serve as a useful resource for better understanding cancer stem-like cell and malignant cell heterogeneity, stromal cell remodeling, and immune cell reprogramming. It also sheds new light on transcriptomic dynamics during cholangiocarcinoma progression at single-cell resolution

Genetic Discovery and Risk Characterization in Type 2 Diabetes across Diverse Populations

Genomic discovery and characterization of risk loci for type 2 diabetes (T2D) have been conducted primarily in individuals of European ancestry. We conducted a multiethnic genome-wide association study of T2D among 53,102 cases and 193,679 control subjects from African, Hispanic, Asian, Native Hawaiian, and European population groups in the Population Architecture Genomics and Epidemiology (PAGE) and Diabetes Genetics Replication and Meta-analysis (DIAGRAM) Consortia. In individuals of African ancestry, we discovered a risk variant in th

Multi-ancestry genome-wide association meta-analysis of Parkinson?s disease

Although over 90 independent risk variants have been identified for Parkinson’s disease using genome-wide association studies, most studies have been performed in just one population at a time. Here we performed a large-scale multi-ancestry meta-analysis of Parkinson’s disease with 49,049 cases, 18,785 proxy cases and 2,458,063 controls including individuals of European, East Asian, Latin American and African ancestry. In a meta-analysis, we identified 78 independent genome-wide significant loci, including 12 potentially novel loci (MTF2, PIK3CA, ADD1, SYBU, IRS2, USP8, PIGL, FASN, MYLK2, USP25, EP300 and PPP6R2) and fine-mapped 6 putative causal variants at 6 known PD loci. By combining our results with publicly available eQTL data, we identified 25 putative risk genes in these novel loci whose expression is associated with PD risk. This work lays the groundwork for future efforts aimed at identifying PD loci in non-European populations

Biological and biophysical properties of T cell antigen receptor (TCR) transmembrane peptides in cell membranes

The T cell antigen receptor (TCR) is a complex cell surface receptor comprising at least seven transmembrane—spanning proteins. The complete assembly of these subunits is a requirement for cell surface receptor expression and function. A nine amino acid sequence in the TCR 0t chain transmembrane domain is critical for the correct assembly and function of the TCR. Our laboratory has synthesised a peptide corresponding to this sequence (core peptide; CP: GLBILLLKV) and shown that it is capable of suppressing the immune response in a number of animal models of inflammation including the well characterised adjuvant induced arthritis model in rats. To further investigate the hypothesis that the mechanism of CP action is to disrupt TCR complex in the plasma membrane, this thesis examined the biological and biophysical properties of TCR sequence derived peptides and their relationship to the TCR in cell membranes. The thesis is divided into three sections. The first defines that the site of CP action is in cell membrane; the second, the localization and relationship between CP and the TCR in cell membranes and; the third, the interaction of CP with T cell plasma membrane lipid components using whole cell nuclear magnetic resonance (IH-NMR) spectroscopy

Fibroblast activation protein in cell biology and liver fibrosis

Fibroblast activation protein (FAP) is a type 11 cell surface protein of the dipeptidyl peptidase IV (DPIV) gene family. FAP has two peptidase activities, DP activity and a recently reported narrow prolyl endopeptidase activity, which is restricted to Gly-Pro derived substrates. The only known natural substrate of FAP is a collagen type I (CN-I) specific gelatinase activity. In contrast, as the closest relative of PAP, DPIV has only DP activity. Nine chemokines, including CXCL12, are DPIV substrates and DPIV binds to fibronectin (FN). The natural ligands of FAP are unknown. FAP is not detectable in most normal adult tissue whereas DPIV expression is ubiquitous. In chronic liver injury, FAP is selectively expressed by activated hepatic stellate cells (HSC) and myofibroblasts, the major cell types that contribute to fibrosis, while DPIV is mainly expressed by hepatocytes and also by T cells, endothelium, and bile duct cells. To investigate the relationship of F AP with fibrillar extracellular matrix (ECM) in cirrhotic liver, frozen sections of human cirrhotic livers were examined using twocolour immunofluorescence and the novel technique of second harmonic generation (SHG) microscopy, which specifically detects fibrous collagen. Collagen fibrils were visualised at high resolution by SHG and were thereby seen to lie alongside FAP positive HSC. All FAP-positive HSC were also strongly immunopositive for CN—I and FN. Cell adhesion and migration are essential in pathologic processes that involve wound healing, such as chronic liver disease. To examine the effects of FAP on in vitro cell adhesion, wound healing, transwell cell invasion, proliferation and apoptosis, green fluorescent protein (GFP) fusion proteins of FAP and DPIV were expressed in a human epithelial cell line 293T. The FAP fusion protein was also expressed in the human activated HSC cell line LX-2. In epithelial cells, cells overexpressing FAP showed reduced adhesion to plates coated with CN-I, FN or Matrigel (P<0.05). In contrast, DPIV overexpression increased cell adhesion to FN (P<0.01) but had no effect on adhesion to CN-I or Matrigel. In a cell monolayer wound healing assay, cells overexpressing either FAP or DPIV exhibited less migration into the wound on plastic coated with CN-I, FN or Matrigel (P<0.05). Concordantly, cells overexpressing FAP or DPIV exhibited reduced migration towards CN-I, FN or Matrigel in the absence or presence of TGF-B] in transwells. Cells overexpressing either protein enhanced staurosporine streptomyces (STS)-stimulated apoptosis. DPIV and FAP overexpression increased cell proliferation. Ablating the enzyme activity of FAP by point mutations at Ser624 or Glu203/Glu204 did not influence any of the results. Neither DPIV nor FAP co-localized with the actin cytoskeleton, or altered cytoskeletal morphology. Overexpressing DPIV or F AP increased expression levels of tissue inhibitor of matrix metalloproteinase (TIMP) 1 and CD44 and depressed B—catenin and discoidin domain receptor (DDR) 1 expression. In stellate cells, cells overexpressing FAP showed enhanced adhesion to plates coated with CN-I, FN or Matrigel (P<0.05) and exhibited more migration into the wound (P<0.05) on plastic coated with CN-I, FN or Matrigel in a wound healing assay, and enhanced migration towards CN—I or FN in the absence or presence of TGF-Bl in transwells. Overexpression of FAP did not trigger apoptosis, but did enhance STS-stimulated apoptosis. FAP overexpression increased LX-2 cell proliferation. Removal of the enzyme activities of FAP by point mutation did not influence the results