Biology subjects

Molteni, C.

Publications and source records attributed to Molteni, C..

3 recordsLinked to original sources

bioRxiv2022

Variola virus is as old as the earliest historical lines of evidence suggest

Archaeovirology efforts provided a rich portrait of the evolutionary history of variola virus (VARV), the causative agent of smallpox. These studies revealed frequent viral lineage extinction and a relatively recent origin of VARV as a human pathogen ([~] 1,700 years ago, ya). This contrasts with historical records suggesting the presence of smallpox as early as 3,500 ya. By performing an analysis of ancestry components in modern, historic, and ancient VARV genomes, we unveil the progressive drifting of VARV lineages from a common ancestral population and we show that a small proportion of Viking-Age ancestry persisted until the 18th century. After the split of the P-I and P-II lineages, which occurred before the onset of smallpox vaccination, the former (but not the latter) experienced a severe bottleneck. We suggest this was due to the distinct epidemiology of the two lineages, which display remarkably different disease severity. As for the emergence of VARV, we corrected time estimates by accounting for the time-dependent rate phenomenon. Using this approach, we estimate that VARV emerged earlier than 3,800 ya, thus supporting its presence in ancient societies, including Egypt, as pockmarked mummies suggest. ImportanceNow eradicated, smallpox was one of the most devastating human diseases, causing the death of at least 300 million people in the 20th century. Humans were the only known host of variola virus, but the time-frame of its emergence in our species has been a matter of debate. Specifically, molecular dating suggested a relatively recent origin, whereas historical sources indicated the presence of VARV in ancient societies. By applying population genetic methods, we analyzed the ancestry components in modern and historic VARV genomes, and we found a progressive drifting of VARV lineages from a common ancestral population. By accounting for the common observation that rates of viral evolution scale negatively with the time-frame of measurement, we estimated that VARV emerged earlier than 3800 years ago. Thus, out data settle a controversy and provide novel insight into the origin and evolution of one of the most historically relevant human pathogens.

evolutionary biology↗

bioRxiv2021

Combined free energy calculation and machine learning methods for understanding ligand unbinding kinetics

The determination of drug residence times, which define the time an inhibitor is in complex with its target, is a fundamental part of the drug discovery process. Synthesis and experimental measurements of kinetic rate constants are, however, expensive, and time-consuming. In this work, we aimed to obtain drug residence times computationally. Furthermore, we propose a novel algorithm to identify molecular design objectives based on ligand unbinding kinetics. We designed an enhanced sampling technique to accurately predict the free energy profiles of the ligand unbinding process, focusing on the free energy barrier for unbinding. Our method first identifies unbinding paths determining a corresponding set of internal coordinates (IC) that form contacts between the protein and the ligand, it then iteratively updates these interactions during a series of biased molecular-dynamics (MD) simulations to reveal the ICs that are important for the whole of the unbinding process. Subsequently, we performed finite temperature string simulations to obtain the free energy barrier for unbinding using the set of ICs as a complex reaction coordinate. Importantly, we also aimed to enable further design of drugs focusing on improved residence times. To this end, we developed a supervised machine learning (ML) approach with inputs from unbiased "downhill" trajectories initiated near the transition state (TS) ensemble of the string unbinding path. We demonstrate that our ML method can identify key ligand-protein interactions driving the system through the TS. Some of the most important drugs for cancer treatment are kinase inhibitors. One of these kinase targets is Cyclin Dependent Kinase 2 (CDK2), an appealing target for anticancer drug development. Here, we tested our method using two different CDK2 inhibitors for potential further development of these compounds. We compared the free energy barriers obtained from our calculations with those observed in available experimental data. We highlighted important interactions at the distal ends of the ligands that can be targeted for improved residence times. Our method provides a new tool to determine unbinding rates, and to identify key structural features of the inhibitors that can be used as starting points for novel design strategies in drug discovery.

biophysics↗

bioRxiv2021

Extraction and high-throughput sequencing of oak heartwood DNA: assessing the feasibility of genome-wide DNA methylation profiling

Tree ring features are affected by environmental factors and therefore are the basis for dendrochronological studies to reconstruct past environmental conditions. Oak wood often provides the data for these studies because of the durability of oak heartwood and hence the availability of samples spanning long time periods of the distant past. Wood formation is regulated in part by epigenetic mechanisms such as DNA methylation. Studies of the methylation state of DNA preserved in oak heartwood thus could identify epigenetic tree ring features informing on past environmental conditions. In this study, we aimed to establish protocols for the extraction of DNA, the high-throughput sequencing of whole-genome DNA libraries (WGS) and the profiling of DNA methylation by whole-genome bisulfite sequencing (WGBS) for oak (Quercus spp.) heartwood drill cores taken from the trunks of living standing trees spanning the AD 1776-2014 time period. Heartwood contains little DNA, and large amounts of phenolic compounds known to hinder the preparation of high-throughput sequencing libraries. Whole-genome and DNA methylome library preparation and sequencing consistently failed for oak heartwood samples more than 100 and 50 years of age, respectively. DNA fragmentation increased with sample age and was exacerbated by the additional bisulfite treatment step during methylome library preparation. Relative coverage of the non-repetitive portion of the oak genome was sparse. These results suggest that quantitative methylome studies of oak hardwood will likely be limited to relatively recent samples and will require a high sequencing depth to achieve sufficient genome coverage.

plant biology↗