Biology subjects

Hartman, D.

Publications and source records attributed to Hartman, D..

3 recordsLinked to original sources

bioRxiv2026

The Effects of Mean Temperature and Diurnal Temperature Range on West Nile Virus Transmission

Temperature is a major driver of arbovirus transmission, and a changing climate is expected to affect this process significantly. Most experimental studies rely on constant temperatures and overlook realistic daily temperature fluctuations that impact vector-pathogen interactions. The nonlinear relationship between temperature and vector traits responsible for pathogen transmission suggests that daily fluctuating temperatures produce phenotypes important for transmission distinct from those at constant temperatures. Here, we tested whether realistic variations in mean temperature and diurnal temperature range (DTR) influence West Nile virus (WNV) transmission. We experimentally infected colonized Culex tarsalis with WNV-infectious blood meals and maintained them under constant and fluctuating temperature regimes. We quantified how temperature, DTR, and incubation time shaped several outcomes (infection, dissemination, infectiousness, WNV loads in mosquito saliva and mosquito survival). We also integrated survival and infectiousness probabilities to infer implications for transmission. We observed strong effects of temperature on the WNV infection dynamics, viral loads and mosquito survival. Although the probability of initial infection was similar among all temperature regimes, dissemination and infectiousness were constrained by temperature. Dissemination and infectiousness were highest at 26{degrees}C and reduced at cooler (22{degrees}C) and warmer (30{degrees}C) temperatures. Fluctuating temperatures significantly decreased infection and dissemination probabilities, while the probability of becoming infectious was driven primarily by mean temperature rather than DTR. Mosquito survival probability was temperature dependent, and fluctuating regimes increased mortality risk by 1.95-fold. Integrating mosquito survival and infectiousness dynamics demonstrated that, although at higher temperatures the extrinsic incubation period is shorter, reduced mosquito lifespan can limit viral transmission. Together, these results indicate that overall WNV transmission is affected by temperature-dependent viral dynamics and host physiological constraints. Fluctuating temperature regimes significantly delay viral dissemination within the host, especially at the optimal temperature (26{degrees}C). Measurement of infection outcomes under constant temperatures treatments may lead to over/under estimation of transmission parameters in epidemiological models, therefore integrating fluctuating temperature treatments into mechanistic models of transmission can improve estimates of when and where WNV transmission is most likely to occur.

ecology↗

bioRxiv2022

On the origin and evolution of the mosquito male-determining factor Nix

The mosquito family Culicidae is divided into two subfamilies named the Culicinae and Anophelinae. Nix, the dominant male-determining factor, has only been found in the culicines Aedes aegypti and Ae. albopictus, two important arboviral vectors that belong to the subgenus Stegomyia. Here we performed sex-specific whole-genome sequencing and RNAseq of divergent mosquito species and explored additional male-inclusive datasets to investigate the distribution of Nix. Except for the Culex genus, Nix homologs were found in all species surveyed from the Culicinae subfamily, including 12 additional species from three highly divergent tribes comprising 4 genera, suggesting Nix originated at least 133-165 MYA. Heterologous expression of one of three divergent Nix ORFs in Ae. aegypti resulted in partial masculinization of genetic females as evidenced by morphology and doublesex splicing. It is not clear whether insufficient transgene expression or sequence divergence or both are responsible for the lack of phenotype for the other two. Phylogenetic analysis suggests Nix is related to femaleless (fle), a recently described intermediate sex-determining factor found exclusively in anopheline mosquitoes. Nix from all species has a conserved structure, including three RNA-recognition motifs (RRMs), as does fle. However, Nix has evolved at a much faster rate than fle. The RRM3 of both Nix and fle are related to the single RRM of a widely distributed and conserved splicing factor transformer-2 (tra2). RRM3-based phylogenetic analysis suggests this domain in Nix and fle may have evolved from tra2 in a common ancestor of mosquitoes. Our results provide insights into the evolution of sex-determination and homomorphic sex chromosomes in mosquitoes, and will inform broad applications of mosquito-control strategies based on manipulating sex ratios towards the non-biting males.

evolutionary biology↗

bioRxiv2019

Super-resolution imaging reveals the evolution of higher-order chromatin folding in early carcinogenesis

Aberrant chromatin structure is a hallmark in cancer cells and has long been used for clinical diagnosis of cancer. However, underlying higher-order chromatin folding during malignant transformation remains elusive, due to the lack of molecular scale resolution. Using optimized stochastic optical reconstruction microscopy (STORM) for pathological tissue (PathSTORM), we uncovered a gradual decompaction and fragmented higher-order chromatin folding throughout all stages of carcinogenesis in multiple tumor types, even prior to the tumor formation. Our integrated imaging, genomic, and transcriptomic analyses reveal the functional consequences in enhanced formation of transcription factories, spatial juxtaposition with relaxed nanosized chromatin domains and impaired genomic stability. We also demonstrate the potential of imaging higher-order chromatin decompaction to detect high-risk precursors that cannot be distinguished by conventional pathology. Taken together, our findings reveal the gradual decompaction and fragmentation of higher-order chromatin structure as an enabling characteristic in early carcinogenesis to facilitate malignant transformation, which may improve cancer diagnosis, risk stratification, and prevention.\n\nSIGNIFICANCEGenomic DNA is folded into a higher-order structure that regulates transcription and maintains genomic stability. Although much progress has been made on understanding biochemical characteristics of epigenetic modifications in cancer, the higher-order folding of chromatin structure remains largely unknown. Using optimized super-resolution microscopy, we uncover de-compacted and fragmented chromatin folding in tumor initiation and stepwise progression in multiple tumor types, even prior to the presence of tumor cells. This study underlines the significance of unfolding higher-order chromatin structure as an enabling characteristic to promote tumorigenesis, which may facilitate the development and evaluation of new preventive strategies. The potential of imaging higher-order chromatin folding to improve cancer detection and risk stratification is demonstrated by detecting high-risk precursors that cannot be distinguished by conventional pathology.

cancer biology↗