Biology subjects

Butt, A. M.

Publications and source records attributed to Butt, A. M..

5 recordsLinked to original sources

bioRxiv2022

Subthreshold serotonin signals combined by the G proteins Gαq and Gαs activate the C. elegans egg-laying muscles

Individual neuron or muscle cells express many G protein coupled receptors (GPCRs) for neurotransmitters and neuropeptides. It remains unclear how these cells integrate multiple GPCR signals that all must act through the same few G proteins. We investigated how two serotonin GPCRs, Gq-coupled SER-1 and Gs-coupled SER-7, function together on the C. elegans egg-laying muscles to promote contraction and thus cause eggs to be laid. Using receptor null mutations and cell-specific knockdowns, we found that serotonin signaling through either SER-1/Gq or SER-7/Gs alone does not induce egg laying, but these subthreshold signals can combine to promote egg laying. However, using designer receptors or optogenetics to artificially induce high levels of either Gq signaling or Gs signaling in the muscles was sufficient to induce egg laying. Conversely, knocking down both Gq and Gs in the egg-laying muscle cells induced egg-laying defects stronger than those of a ser-7 ser-1 double knockout. These results suggest that, in the egg-laying muscles, multiple GPCRs for serotonin and other signals each produce weak effects that individually do not result in strong behavioral outcomes. However, they can combine to produce sufficient levels of Gq and Gs signaling to promote muscle activity and egg laying.

neuroscience↗

bioRxiv2020

Functional genomic analyses highlights a shift in Gpr17-regulated cellular processes in oligodendrocyte progenitor cells (OPC) and underlying myelin dysregulation in the aged forebrain

Brain aging is characterised by a decline in neuronal function and associated cognitive deficits. There is increasing evidence that myelin disruption is an important factor that contributes to the age-related loss of brain plasticity and repair responses. In the brain, myelin is produced by oligodendrocytes, which are generated throughout life by oligodendrocyte progenitor cells (OPCs). Currently, a leading hypothesis points to aging as a major reason for the ultimate breakdown of remyelination in Multiple Sclerosis (MS). However, an incomplete understanding of the cellular and molecular processes underlying brain aging hinders the development of regenerative strategies. Here, our combined systems biology and neurobiological approach demonstrates that oligodendroglial and myelin genes are amongst the most altered in the aging mouse cortex. This was underscored by the identification of causal links between signaling pathways and their downstream transcriptional networks that define oligodendroglial disruption in aging. The results highlighted that the G-protein coupled receptor GPR17 is central to the disruption of OPC in aging and this was confirmed by genetic fate mapping and cellular analyses. Finally, we used systems biology strategies to identify therapeutic agents that rejuvenate OPC and restore myelination in age-related neuropathological contexts.

neuroscience↗

bioRxiv2020

Accelerated dystrophy and decay of oligodendrocyte precursor cells in the APP/PS1 model of Alzheimer's-like pathology

Myelin disruption is a feature of natural aging and of Alzheimers disease (AD). In the CNS, myelin is produced by oligodendrocytes, which are generated throughout life by oligodendrocyte progenitor cells (OPCs). Here, we examined age-related changes in OPCs in APP/PS1 mice, a model for AD-like pathology, compared with non-transgenic (Tg) age-matched controls. Analysis was performed in the CA1 area of the hippocampus following immunolabelling for NG2 with the nuclear dye Hoescht, to identify OPC and OPC sister cells, a measure of OPC replication, together with Gpr17 and Olig2 for oligodendrocytes and myelin basic protein (MBP) immunostaining as a measure of myelination. The results indicate a decrease in the number of OPCs between 9 and 14 months in natural ageing and this occurred earlier at 9 months in APP/PS1 mice, without further decline at 14 months. The number of OPC sister cells was unaltered in natural aging, but declined significantly at 14-months in APP/PS1 mice. The number of GPR17+ and Olig2+ oligodendrocytes was not altered in APP/PS1, whereas MBP immunostaining increased between 9 and 14 months in natural ageing, but not in APP/PS1 mice. Notably, OPCs displayed marked morphological changes at 14 months in APP/PS1 mice, characterized by an overall shrinkage of OPC process domains and increased process branching, characteristic of reactive pathological changes. The results indicate that OPC and myelin disruption are pathological signs in the APP/PS1 mouse model of AD.

neuroscience↗

bioRxiv2020

Synaptic silencing affects the density and complexity of oligodendrocyte precursor cells in the adult mouse hippocampus

Oligodendrocyte progenitor cells (OPCs) are responsible for generating oligodendrocytes, the myelinating cells of the CNS. Life-long myelination is promoted by neuronal activity and is essential for neural network plasticity and learning. OPCs are known to contact synapses and it is proposed that neuronal synaptic activity in turn regulates OPC proliferation and differentiation. To examine this in the adult, we performed unilateral injection of the synaptic blocker botulinum neurotoxin A (BoNT/A) into the hippocampus of adult mice. We confirm BoNT/A cleaves SNAP-25 in the CA1 are of the hippocampus, which has been proven to block neurotransmission. Notably, synaptic silencing by BoNT/A significantly decreased OPC density and caused their shrinkage, as determined by immunolabelling for the OPC marker NG2. Inhibition of synaptic activity resulted in an overall decrease in the number of OPC processes, as well as a decrease in their lengths and branching frequency. These data indicate that synaptic activity is important for maintaining adult OPC numbers and cellular integrity, which is relevant to pathological scenarios characterized by decreased synaptic activity.

neuroscience↗

bioRxiv2019

Myosin XI Interacting with a RabE GTPase Is Required for Polarized Growth

The fundamental eukaryotic process of intracellular trafficking requires the interconnected activity of molecular motors trafficking vesicular cargo within a dynamic cytoskeletal network. However, in plants, few mechanistic details are known about how molecular motors associate with their secretory cargo to support the ubiquitous processes of polarized growth and cell division. A yeast two-hybrid screen of a Physcomitrella patens library identified a RabE GTPase as an interactor of myosin XI and subsequently demonstrated all five RabE members interact with myosin XI. Consistent with a role in polarized transport, we observed RabE at the growing cell apex and at the expanding cell plate during cell division. An in vivo cross-correlation analysis of fluorescently tagged RabE and myosin XI revealed that both species are spatiotemporally coupled, demonstrating their simultaneous involvement in polarized growth. To determine if myosin XI and RabE are directly coupled, we first computationally predicted myosin XI:RabE interface through a homology modeling-directed approach. We identified a structurally conserved residue on myosin XI, V1422, that when mutated abolished RabE binding in the yeast two-hybrid system and resulted in unpolarized plants instead of the characteristic network of filamentous cells when regenerated from single cells. Together, this work demonstrates the requirement of a direct myosin XI:RabE interaction for polarized growth in plants.

cell biology↗