Biology subjects

Sanders, M. J.

Publications and source records attributed to Sanders, M. J..

5 recordsLinked to original sources

bioRxiv2021

Compound- and fiber type-selective requirement of AMPKγ3 for insulin-independent glucose uptake in skeletal muscle

Objective: The metabolic master-switch AMP-activated protein kinase (AMPK) mediates insulin-independent glucose uptake in muscle and regulates the metabolic activity of brown and beige adipose tissue (BAT). The regulatory AMPK{gamma}3 isoform is uniquely expressed in skeletal muscle and also potentially in BAT. Here, we investigated the role that AMPK{gamma}3 plays in mediating skeletal muscle glucose uptake and whole-body glucose clearance in response to small-molecule activators that act on AMPK via distinct mechanisms. We also assessed if {gamma}3 plays a role in adipose thermogenesis and browning. Methods: Global AMPK{gamma}3 knockout (KO) mice were generated. A systematic whole-body, tissue and molecular phenotyping linked to glucose homeostasis was performed in {gamma}3 KO and wild type (WT) mice. Glucose uptake in glycolytic and oxidative skeletal muscle ex vivo, as well as blood glucose clearance in response to small molecule AMPK activators that target nucleotide-binding domain of {gamma} subunit (AICAR) and allosteric drug and metabolite (ADaM) site located at the interface of the and {beta} subunit (991, MK-8722) were assessed. Oxygen consumption, thermography, and molecular phenotyping with a {beta}3-adrenergic receptor agonist (CL-316,243) treatment were performed to assess BAT thermogenesis, characteristics and function. Results: Genetic ablation of {gamma}3 did not affect body weight, body composition, physical activity, and parameters associated with glucose homeostasis under chow or high fat diet. {gamma}3 deficiency had no effect on fiber-type composition, mitochondrial content and components, or insulin-stimulated glucose uptake in skeletal muscle. Glycolytic muscles in {gamma}3 KO mice showed a partial loss of AMPK2 activity, which was associated with reduced levels of AMPK2 and {beta}2 subunit isoforms. Notably, {gamma}3 deficiency resulted in a selective loss of AICAR-, but not MK-8722-induced blood glucose-lowering in vivo and glucose uptake specifically in glycolytic muscle ex vivo. We detected {gamma}3 in BAT and found that it preferentially interacts with 2 and {beta}2. We observed no differences in oxygen consumption, thermogenesis, morphology of BAT and inguinal white adipose tissue (iWAT), or markers of BAT activity between WT and {gamma}3 KO mice. Conclusions: These results demonstrate that {gamma}3 plays a key role in mediating AICAR- but not ADaM site binding drug-stimulated blood glucose clearance and glucose uptake specifically in glycolytic skeletal muscle. We also showed that {gamma}3 is dispensable for thermogenesis and browning of iWAT.

physiology↗

bioRxiv2021

Long-read assembly and comparative evidence-based reanalysis of Cryptosporidium genome sequences reveal new biological insights

Cryptosporidiosis is a leading cause of waterborne diarrheal disease globally and an important contributor to mortality in infants and the immunosuppressed. Despite its importance, the Cryptosporidium community still relies on a fragmented reference genome sequence from 2004. Incomplete reference sequences hamper experimental design and interpretation. We have generated a new C. parvum IOWA genome assembly supported by PacBio and Oxford Nanopore long-read technologies and a new comparative and consistent genome annotation for three closely related species C. parvum, C. hominis and C. tyzzeri. The new C. parvum IOWA reference genome assembly is larger, gap free and lacks ambiguous bases. This chromosomal assembly recovers 13 of 16 possible telomeres and raises a new hypothesis for the remaining telomeres and associated subtelomeric regions. Comparative annotation revealed that most "missing" orthologs are found suggesting that species differences result primarily from structural rearrangements, gene copy number variation and SNVs in C. parvum, C. hominis and C. tyzzeri. We made >1,500 C. parvum annotation updates based on experimental evidence. They included new transporters, ncRNAs, introns and altered gene structures. The new assembly and annotation revealed a complete DNA methylase Dnmt2 ortholog. 190 genes under positive selection including many new candidates were identified using the new assembly and annotation as reference. Finally, possible subtelomeric amplification and variation events in C. parvum are detected that reveal a new level of genome plasticity that will both inform and impact future research.

genomics↗

bioRxiv2019

Global genome diversity of the Leishmania donovani complex

Protozoan parasites of the Leishmania donovani complex - L. donovani and L. infantum - cause the fatal disease visceral leishmaniasis. We present the first comprehensive genome-wide global study, with 151 cultured field isolates representing most of the geographical distribution. L. donovani isolates separated into five groups that largely coincide with geographical origin but vary greatly in diversity. In contrast, the majority of L. infantum samples fell into one globally-distributed group with little diversity. This picture is complicated by several hybrid lineages. Identified genetic groups vary in heterozygosity and levels of linkage, suggesting different recombination histories. We characterise chromosome-specific patterns of aneuploidy and identified extensive structural variation, including known and suspected drug resistance loci. This study reveals greater genetic diversity than suggested by geographically-focused studies, provides a resource of genomic variation for future work and sets the scene for a new understanding of the evolution and genetics of the Leishmania donovani complex.

genomics↗

bioRxiv2019

Transcriptional and genomic parallels between the monoxenous parasite Herpetomonas muscarum and Leishmania

Trypanosomatid parasites are causative agents of important human and animal diseases such as sleeping sickness and leishmaniasis. Most trypanosomatids are transmitted to their mammalian hosts by insects, often belonging to Diptera (or true flies). These are called dixenous trypanosomatids since they infect two different hosts, in contrast to those that infect just insects (monoxenous). However, it is still unclear whether dixenous and monoxenous trypanosomatids interact similarly with their insect host, as fly-monoxenous trypanosomatid interaction systems are rarely reported and under-studied - despite being common in nature. Here we present the genome of monoxenous trypanosomatid Herpetomonas muscarum and discuss its transcriptome during in vitro culture and during infection of its natural insect host Drosophila melanogaster. The H. muscarum genome is broadly syntenic with that of human parasite Leishmania major. We also found strong similarities between the H. muscarum transcriptome during fruit fly infection, and those of Leishmania during sand fly infections. Overall this suggests Drosophila-Herpetomonas is a suitable model for less accessible insect-trypanosomatid host-parasite systems such as sand fly-Leishmania.\n\nAuthor SummaryTrypanosomes and Leishmania are parasites that cause serious Neglected Tropical Diseases (NTDs) in the worlds poorest people. Both of these are dixenous trypanosomatids, transmitted to humans and other mammals by biting flies. They are called dixenous as they can establish infections in two different types of hosts - insect vectors and mammals. In contrast, monoxenous trypanosomatids usually only infect insects. Despite establishment in the insects midgut being key to transmission of NTDs, events during early establishment inside the insect are still unclear in both dixenous and monoxenous parasites. Here, we study the interaction between a model insect - the fruit fly Drosophila melanogaster - and its natural monoxenous trypanosomatid parasite Herpetomonas muscarum. We show that both the genome of this parasite, and gene regulation at early stages of infection have strong parallels with Leishmania. This work has begun to identify evolutionarily conserved aspects of the process by which trypanosomatids establish in insects, thus potentially highlighting key checkpoints necessary for transmission of dixenous parasites. In turn, this might inform new strategies to control trypanosomatid NTDs.

microbiology↗

bioRxiv2017

Single-cell transcriptomics of malaria parasites

Single-cell RNA-sequencing is revolutionising our understanding of seemingly homogeneous cell populations, but has not yet been applied to single cell organisms. Here, we established a method to successfully investigate transcriptional variation across individual malaria parasites. We discover an unexpected, discontinuous program of transcription during asexual growth previously masked by bulk analyses, and uncover novel variation among sexual stage parasites in their expression of gene families important in host-parasite interactions.

genomics↗