Biology subjects

Scott, S. J.

Publications and source records attributed to Scott, S. J..

4 recordsLinked to original sources

bioRxiv2020

Evidence that polyploidy in esophageal adenocarcinoma originates from mitotic slippage caused by defective chromosome attachments

Polyploidy is present in many cancer types and is increasingly recognized as an important factor in promoting chromosomal instability, genome evolution, and heterogeneity in cancer cells. However, the mechanisms that trigger polyploidy in cancer cells are largely unknown. In this study, we investigated the origin of polyploidy in esophageal adenocarcinoma (EAC), a highly heterogenous cancer, using a combination of genomics and cell biology approaches in EAC cell lines, organoids, and tumors. We found the EAC cells and organoids present specific mitotic defects consistent with problems in the attachment of chromosomes to the microtubules of the mitotic spindle. Time-lapse analyses confirmed that EAC cells have problems in congressing and aligning their chromosomes, which can ultimately culminate in mitotic slippage and polyploidy. Furthermore, whole-genome sequencing, RNA-seq, and quantitative immunofluorescence analyses revealed alterations in the copy number, expression, and cellular distribution of several proteins known to be involved in the mechanics and regulation of chromosome dynamics during mitosis. Together, these results provide evidence that an imbalance in the amount of proteins implicated in the attachment of chromosomes to spindle microtubules is the molecular mechanism underlying mitotic slippage in EAC. Our findings that the likely origin of polyploidy in EAC is mitotic failure caused by problems in chromosomal attachments not only improves our understanding of cancer evolution and diversification, but may also aid in the classification and treatment of EAC and possibly other highly heterogeneous cancers.

cancer biology↗

bioRxiv2020

Synchronization of human retinal pigment ephitilial-1 (RPE-1) cells in mitosis

Human retinal pigment ephitilial-1 (RPE-1) cells are increasingly being used as a model to study mitosis because they represent a non-transformed alternative to cancer cell lines, such as HeLa cervical adenocarcinoma cells. However, the lack of an efficient method to synchronize RPE-1 cells in mitosis precludes their application for large-scale biochemical and proteomics assays. Here we report a protocol to synchronize RPE-1 cells based on sequential treatments with the Cdk4/6 inhibitor PD 0332991 (palbociclib) and the microtubule depolymerizing drug nocodazole. With this method, the vast majority (80-90%) of RPE-1 cells arrested at prometaphase and exited mitosis synchronously after release from nocodazole. Furthermore, we show that this protocol could be successfully employed for the characterization of the protein-protein interaction network of the kinetochore protein Ndc80 by immunoprecipitation coupled with mass spectrometry. This synchronization method significantly expands the versatility and applicability of RPE-1 cells to the study of cell division and might be applied to other cell lines that do not respond to treatments with DNA synthesis inhibitors.

cell biology↗

bioRxiv2018

Cerebral amyloid angiopathy and comparative analysis of amyloid-β protein in birds

Senile plaques and cerebral amyloid angiopathy (CAA) are well-documented in various mammals, and several species even exhibit neurofibrillary tangle (NFT). However, we know far less about whether such symptoms are present in birds. Therefore, here we clarified the occurrence and pathogenesis of avian a{beta}-related lesions, analyzing the a{beta} amino-acid sequence across 28 birds at multiple life stages, representing 15 species, 14 genera, and 9 nine families. We also determined the expected a{beta} amino-acid sequence after comparing data from the brains of nine birds (seven species) with publicly available NCBI data. We observed CAA and senile plaque-like deposition only in a female Amazon parrot, estimated to be around 30-40 years old. We identified two A{beta} depositions (40 and 42) in the same location that correspond to A{beta} 6-42. Additionally, we observed severe A{beta} deposition, accompanied by severe hemorrhaging, in blood vessels of the superficial and deep portions of the brain. These lesions were directly related to the cause of death. Of 40 bird species, 36 exhibited type 1 A{beta} amino-acid sequences, similar to humans. Given that all of these birds were old, our results suggest that A{beta} is deposited primarily as CAA as the animals age. This report is the first clinically based description of CAA in birds. Interspecific variation likely exists because we identified species that did not exhibit A{beta} deposition even when the birds are old enough. However, even birds of the same taxonomic status differed in whether they possessed or lacked A{beta} deposition. Thus, other factors besides A{beta} amino-acid sequence could influence this symptom.

pathology↗

bioRxiv2018

Interaction of taste and place coding in the hippocampus

An animals survival depends on finding food, and the memory of food and contexts are often linked. Given that the hippocampus is required for spatial and contextual memory, it is reasonable to expect related coding of space and food stimuli in hippocampal neurons. However, relatively little is known about how the hippocampus responds to tastes, the most central sensory property of food. In this study, we examined the taste-evoked responses and spatial firing properties of single units in the dorsal CA1 hippocampal region as male rats received a battery of taste stimuli differing in both chemical composition and palatability within a specific spatial context. We identified a subset of hippocampal neurons that responded to tastes, some of which were place cells. These taste and place responses had a distinct interaction: taste-responsive cells tended to have less spatially specific firing fields, and place cells only responded to tastes delivered inside their place field. Like neurons in the amygdala and lateral hypothalamus, hippocampal neurons discriminated between tastes predominantly on the basis of palatability, with taste-selectivity emerging concurrently with palatability-relatedness; these responses did not reflect movement or arousal. However, hippocampal taste responses emerged several hundred msec later than responses in other parts of the taste system, suggesting that the hippocampus does not influence real-time taste decisions, instead associating the hedonic value of tastes with a particular context. This incorporation of taste responses into existing hippocampal maps could be one way that animals use past experience to locate food sources.\n\nSignificance statementFinding food is essential for animals survival, and taste and context memory are often linked. While hippocampal responses to space and contexts have been well characterized, little is known about how the hippocampus responds to tastes. Here, we identified a subset of hippocampal neurons that discriminated between tastes based on palatability. Cells with stronger taste responses typically had weaker spatial responses, and taste responses were confined to place cells firing fields. Hippocampal taste responses emerged later than in other parts of the taste system, suggesting that the hippocampus does not influence taste decisions, but rather, associates the hedonic value of tastes consumed within a particular context. This could be one way that animals use past experience to locate food sources.

neuroscience↗