RESUMEN
BACKGROUND: Exposure to intrauterine obesity can disrupt clock gene rhythmicity in animal models. The aim of this pilot study was to determine if maternal obesity alters rhythmic expression of core clock in mesenchymal stem cells (MSCs) from umbilical cords of human infants born to mothers with obesity (Ob-MSC) vs. normal weight (NW-MSC). METHODS: We compared in vitro rhythmic expression patterns of core clock (BMAL1, CLOCK, PER2) and clock-output (NR1D1), components in undifferentiated Ob-MSCs (n = 3) vs. NW-MSCs (n = 3). MSCs were harvested every 2 h, following a dexamethasone shock, for 30 h. Adipogenesis or myogenesis was induced in vitro and markers of adipogenesis and fat storage were assessed, respectively. RESULTS: We detected significant rhythmicity in expression patterns of BMAL1, PER2, and NR1D1 at the group level in Ob- and NW-MSCs (p < 0.05). PER2 oscillatory amplitude was 3-fold higher in Ob-MSCs vs. NW-MSCs (p < 0.006). During adipogenesis, Ob-MSCs had higher PPARγ protein content (p = 0.04) vs. NW-MSC. During myogenesis, Ob-MSCs had higher saturated triacylglycerols (p = 0.04) vs. NW-MSC. CONCLUSION: Rhythmic expressions of BMAL1, PER2, and NR1D1 are detectable in undifferentiated MSCs. Higher PER2 oscillatory amplitude was paralleled by higher markers of fat storage during differentiation in Ob-MSCs vs. NW-MSCs, and supports that the core clock and cellular metabolism may be linked in infant MSCs.
Asunto(s)
Relojes Circadianos , Células Madre Mesenquimatosas , Embarazo , Animales , Lactante , Humanos , Femenino , Proyectos Piloto , Factores de Transcripción ARNTL/genética , Relojes Circadianos/genética , Obesidad , Expresión GénicaRESUMEN
Understanding the conditions that allow speciation to occur is difficult because most research has focused on either long-lived organisms or asexual microorganisms. We propagated bacteriophage λ, a virus with rapid generations and frequent recombination, on two Escherichia coli host genotypes that expressed either the LamB or OmpF receptor. When supplied with either single host (allopatry), phage λ improved its binding to the available receptor while losing its ability to use the alternative. When evolving on both hosts together (sympatry), the viruses split into two lineages with divergent receptor preferences. Although the level of divergence varied among replicates, some lineages evolved reproductive isolation via genetic incompatibilities. This outcome indicates that, under suitable conditions, allopatric and sympatric speciation can occur with similar ease.
Asunto(s)
Adaptación Biológica/genética , Bacteriófago lambda/genética , Especiación Genética , Simpatría , Proteínas de la Membrana Bacteriana Externa/metabolismo , Escherichia coli/metabolismo , Escherichia coli/virología , Porinas/metabolismo , Receptores Virales/metabolismo , Aislamiento Reproductivo , Cultivo de VirusRESUMEN
The processes responsible for the evolution of key innovations, whereby lineages acquire qualitatively new functions that expand their ecological opportunities, remain poorly understood. We examined how a virus, bacteriophage λ, evolved to infect its host, Escherichia coli, through a novel pathway. Natural selection promoted the fixation of mutations in the virus's host-recognition protein, J, that improved fitness on the original receptor, LamB, and set the stage for other mutations that allowed infection through a new receptor, OmpF. These viral mutations arose after the host evolved reduced expression of LamB, whereas certain other host mutations prevented the phage from evolving the new function. This study shows the complex interplay between genomic processes and ecological conditions that favor the emergence of evolutionary innovations.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa/metabolismo , Bacteriófago lambda/genética , Escherichia coli/virología , Evolución Molecular , Mutación , Porinas/metabolismo , Receptores Virales/metabolismo , Proteínas de la Cola de los Virus/genética , Alelos , Proteínas de la Membrana Bacteriana Externa/genética , Bacteriófago lambda/fisiología , Escherichia coli/genética , Escherichia coli/metabolismo , Genoma Bacteriano , Genoma Viral , Polimorfismo de Nucleótido Simple , Porinas/genética , Receptores Virales/genética , Selección Genética , Proteínas de la Cola de los Virus/química , Proteínas de la Cola de los Virus/metabolismoRESUMEN
The dynamics of host susceptibility to parasites are often influenced by trade-offs between the costs and benefits of resistance. We assayed changes in the resistance to three viruses in six lines of Escherichia coli that had been evolving for almost 45,000 generations in their absence. The common ancestor of these lines was completely resistant to T6, partially resistant to T6* (a mutant of T6 with altered host range), and sensitive to λ. None of the populations changed with respect to resistance to T6, whereas all six evolved increased susceptibility to T6*, probably ameliorating a cost of resistance. More surprisingly, however, the majority of lines evolved complete resistance to λ, despite not encountering that virus during this period. By coupling our results with previous work, we infer that resistance to λ evolved as a pleiotropic effect of a beneficial mutation that downregulated an unused metabolic pathway. The strong parallelism between the lines implies that selection had almost deterministic effects on the evolution of these patterns of host resistance. The opposite outcomes for resistance to T6* and λ demonstrate that the evolution of host resistance under relaxed selection cannot be fully predicted by simple trade-off models.