Biology subjects

Faheem, M.

Publications and source records attributed to Faheem, M..

4 recordsLinked to original sources

bioRxiv2022

Complex multiple introductions drive fall armyworm invasions into Asia and Australia

The fall armyworm (FAW) Spodoptera frugiperda is thought to have undergone a rapid west-to-east spread since 2016 when it was first identified in western Africa. Between 2018 and 2020, it was also recorded from South Asia (SA), Southeast Asia (SEA), East Asia (EA), and Pacific/Australia (PA). Population genomic analyses enabled the understanding of pathways, population sources, and gene flow in this notorious agricultural pest species. Using neutral single nucleotide polymorphic (SNP) DNA markers, we detected genome introgression that suggested most populations were overwhelmingly C- and R-strain hybrids. SNP and mitochondrial DNA markers identified multiple introductions that were most parsimoniously explained by anthropogenic-assisted spread, i.e., associated with international trade of live/fresh plants and plant products, and involved bridgehead populations in countries to enable successful pest establishment in neighbouring countries. Distinct population genomic signatures between Myanmar and China do not support the African origin spread nor the Myanmar source population to China hypotheses. Significant genetic differentiation between populations from different Australian states supported multiple pathways involving distinct SEA populations. Our study identified Asia as a biosecurity hotspot and a FAW genetic melting pot, and demonstrated the use of genome analysis to disentangle preventable human-assisted pest introductions from unpreventable natural pest spread.

evolutionary biology↗

bioRxiv2018

CNTN5-/+ or EHMT2-/+ iPSC-Derived Neurons from Individuals with Autism Develop Hyperactive Neuronal Networks

Induced pluripotent stem cell (iPSC)-derived cortical neurons are increasingly used as a model to study developmental aspects of Autism Spectrum Disorder (ASD), which is clinically and genetically heterogeneous. To study the complex relationship of rare (penetrant) variant(s) and common (weaker) polygenic risk variant(s) to ASD, \"isogenic\" iPSC-derived neurons from probands and family-based controls, for modeling, is critical. We developed a standardized set of procedures, designed to control for heterogeneity in reprogramming and differentiation, and generated 53 different iPSC-derived glutamatergic neuronal lines from 25 participants from 12 unrelated families with ASD (14 ASD-affected individuals, 3 unaffected siblings, 8 unaffected parents). Heterozygous de novo (7 families; 16p11.2, NRXN1, DLGAP2, CAPRIN1, VIP, ANOS1, THRA) and rare-inherited (2 families; CNTN5, AGBL4) presumed-damaging variants were characterized in ASD risk genes/loci. In three additional families, functional candidates for ASD (SET), and combinations of putative etiologic variants (GLI3/KIF21A and EHMT2/UBE2I combinations in separate families), were modeled. We used a large-scale multi-electrode array (MEA) as our primary high-throughput phenotyping assay, followed by patch clamp recordings. Our most compelling new results revealed a consistent spontaneous network hyperactivity in neurons deficient for CNTN5 or EHMT2. Our biobank of iPSC-derived neurons and accompanying genomic data are available to accelerate ASD research.

neuroscience↗

bioRxiv2018

Complete Disruption of Autism-Susceptibility Genes by Gene-Editing Predominantly Reduces Functional Connectivity of Isogenic Human Neurons

Autism Spectrum Disorder is phenotypically and genetically heterogeneous, but genomic analyses have identified candidate susceptibility genes. We present a CRISPR gene editing strategy to insert a protein tag and premature termination sites creating an induced pluripotent stem cell (iPSC) knockout resource for functional studies of 10 ASD-relevant genes (AFF2/FMR2, ANOS1, ASTN2, ATRX, CACNA1C, CHD8, DLGAP2, KCNQ2, SCN2A, TENM1). Neurogenin 2 (NEUROG2)-directed differentiation of iPSCs allowed production of cortical excitatory neurons, and mutant proteins were not detectable. RNAseq revealed convergence of several neuronal networks. Using both patch-clamp and multi-electrode array approaches, the electrophysiological deficits measured were distinct for different mutations. However, they culminated in a consistent reduction in synaptic activity, including reduced spontaneous excitatory post-synaptic current frequencies in AFF2/FMR2-, ASTN2-, ATRX-, KCNQ2- and SCN2A-null neurons. Despite ASD susceptibility genes belonging to different gene ontologies, isogenic stem cell resources can reveal common functional phenotypes, such as reduced functional connectivity.

neuroscience↗

bioRxiv2018

The molecular structure of Schistosoma mansoni PNP isoform 2 provides insights into the nucleotide selectivity of PNPs

Purine nucleoside phosphorylases (PNPs) play an important role in the blood fluke parasite Schistosoma mansoni as a key enzyme of the purine salvage pathway. Here we present the structural and kinetic characterization of a new PNP isoform from S. mansoni, named as SmPNP2. Screening of different ligands using a thermofluorescence approach indicated cytidine and cytosine as potential ligands. The binding of cytosine was confirmed by isothermal titration calorimetry, with a KD of 27 M, and kinetic parameters for cytidine catalysis were obtained by ITC resulting in a KM of 76.3 M. SmPNP2 also displays catalytic activity against inosine and adenosine, making it the first described PNP with robust catalytic activity towards both pyrimidines and purines. Crystallographic structures of SmPNP2 with different ligands were obtained and comparison of these structures with the previously described S. mansoni PNP (SmPNP1) provided clues for the unique capability of SmPNP2 to bind pyrimidines. When compared with the structure of SmPNP1, substitutions in the vicinity of SmPNP2 active site alter the architecture of the nucleoside base binding site allowing an alternative binding mode for nucleosides, with a 180{degrees} rotation from the canonical binding mode. The remarkable plasticity of this binding site deepens the understanding of the correlation between structure and nucleotide selectivity, offering new ways to analyses PNP activity.\n\nAuthor SummarySchistosoma mansoni is a human parasite dependent on purine salvage for purine bases supply. Purine nucleoside phosphorylase (PNP) is a key enzyme in this pathway. It carries two PNP isoforms, one previously characterized (SmPNP1) and one unknown (SmPNP2). Here we present the crystallographic structure of SmPNP2 and its complex with cytosine, cytidine, ribose-l-phosphate, adenine, hypoxanthine, and tubercidin. Cytidine and cytosine were identified as ligands of SmPNP2 using a thermofluorescence approach. Binding of cytosine was proven by Isothermal Titration Calorimetry (ITC) and cytidine, inosine, and adenosine kinetic parameters were also obtained. Purine bases showed different binding in the active site, rotated 180{degrees} from the canonical binding mode. Its the first report showing a Low Molecular Mass PNP capable of catalyzing both types of nucleotide bases. The SmPNP2 odd behavior sheds a new light on the Schistosoma mansonis life cycle metabolic adaptation.

biochemistry↗