Biology subjects

Massey, D.

Publications and source records attributed to Massey, D..

3 recordsLinked to original sources

bioRxiv2023

Incomplete Reprogramming of DNA Replication Timing in Induced Pluripotent Stem Cells

Induced pluripotent stem cells (iPSC) are a widely used cell system and a foundation for cell therapy. Differences in gene expression, DNA methylation, and chromatin conformation, which have the potential to affect differentiation capacity, have been identified between iPSCs and embryonic stem cells (ESCs). Less is known about whether DNA replication timing - a process linked to both genome regulation and genome stability - is efficiently reprogrammed to the embryonic state. To answer this, we profiled and compared genome-wide replication timing between ESCs, iPSCs, and cells reprogrammed by somatic cell nuclear transfer (NT-ESCs). While NT-ESCs replicated their DNA in a manner indistinguishable from ESCs, a subset of iPSCs exhibit delayed replication at heterochromatic regions containing genes downregulated in iPSC with incompletely reprogrammed DNA methylation. DNA replication delays were not the result of gene expression and DNA methylation aberrations and persisted after differentiating cells to neuronal precursors. Thus, DNA replication timing can be resistant to reprogramming and lead to undesirable phenotypes in iPSCs, establishing it as an important genomic feature to consider when evaluating iPSC lines.

genetics↗

bioRxiv2021

Sequencing Micronuclei Reveals the Landscape of Chromosomal Instability

Genome instability (GIN) is a main contributing factor to congenital and somatic diseases, but its sporadic occurrence in individual cell cycles makes it difficult to study mechanistically. One profound manifestation of GIN is the formation of micronuclei (MN), the engulfment of chromosomes or chromosome fragments in their own nuclear structures separate from the main nucleus. Here, we developed MN-seq, an approach for sequencing the DNA contained within micronuclei. We applied MN-seq to mice with mutations in Mcm4 and Rad9a, which disrupt DNA replication, repair, and damage responses. Data analysis and simulations show that centromere presence, fragment length, and a heterogenous landscape of chromosomal fragility all contribute to the patterns of DNA present within MN. In particular, we show that long genes, but also gene-poor regions, are associated with chromosome breaks that lead to the enrichment of particular genomic sequences in MN, in a genetic background-specific manner. Finally, we introduce single-cell micronucleus sequencing (scMN-seq), an approach to sequence the DNA present in MN of individual cells. Together, sequencing micronuclei provides a systematic approach for studying GIN and reveals novel molecular associations with chromosome breakage and segregation.

genomics↗

bioRxiv2020

Risk factors associated with canine overweightness and obesity in an owner-reported survey

BackgroundOverweightness and obesity in dogs are associated with negative health outcomes. A better understanding of risk factors associated with canine weight is fundamental to identifying preventative interventions and treatments. In this cross-sectional study, we used a direct to consumer approach to collect body condition scores (BCS), as well as demographic, diet, and lifestyle data on 4,446 dogs. BCS was assessed by owners using a 9-point system and categorized as ideal (BCS 4-5), overweight (BCS 6), and obese (BCS 7+). Following univariate analyses, a stepwise procedure was used to select variables which were included in multivariate logistic regression models. One model was created to compare ideal to all overweight and obese dogs, and another was created to compare ideal to obese dogs only. We then used Elastic Net selection and XGBoost variable importance measures to validate these results. ResultsOverall, 1,480 (33%) of dogs were reported to be overweight or obese, of which 356 (8% total) of dogs were reported to be obese. Seven factors were significantly associated with both overweightness/obesity and obesity alone in all three analyses (stepwise, Elastic Net, and XGBoost): diet composition, probiotic supplementation, treat quantity, exercise, age, food motivation level, and pet appetite. Neutering was also associated with overweightness/obesity in all analyses. ConclusionsThis study recapitulated established risk factors associated with BCS (age, exercise, neutering). Moreover, we elucidated associations between previously examined risk factors and BCS (diet composition, treat consumption, and temperament) and identified a novel factor (probiotic supplementation). Specifically, relative to dogs on fresh food diets, BCS was higher in dogs eating dry food both alone and in combination with other foods. Furthermore, dogs receiving probiotics, but not other forms of supplementation, were more likely to have an ideal BCS. Future studies should corroborate these findings with experimental manipulations.

bioinformatics↗