Biology subjects

Hoffman, J. R.

Publications and source records attributed to Hoffman, J. R..

3 recordsLinked to original sources

bioRxiv2025

Helitrons are enriched in lichenized fungi with long generation lengths and small distribution sizes

Mobile genetic elements (MGEs) have the potential to drive genome evolution by introducing mutations and causing structural instability and chromosomal rearrangements, particularly under conditions like environmental or genetic stress. In this study, we generated 18 new long-read based reference genomes for lichenized fungi, which form obligate mutualistic symbioses with algae or cyanobacteria. We used the new genomes and 10 publically available genomes to investigate the relationships between species traits (i.e., dominant reproductive mode, distribution size, and generation length) and the abundance and spatial distribution of MGEs using a phylogenetic comparative framework. We found that species with smaller distribution sizes and longer generation lengths had a higher genomic DNA transposon load. Specifically, their genomes were enriched with Rolling Circle transposons, which contradicts previous research that has identified high proportions of retrotransposons in rare species. Disproportionate distributions of MGEs in rare and range-restricted species may disrupt genomic stability, decrease fitness, and be reflective of species experiencing a greater degree of stress. Conversely, greater MGE activity may be an important source of novel genetic diversity in isolated populations with limited gene flow. Further research is needed to understand the potential mechanisms driving MGE proliferation in rare species genomes, and if MGE content is predictive of increased extinction risk.

genomics↗

bioRxiv2021

Sex-specific topology of the nociceptive circuit shapes dimorphic behavior in C. elegans

How sexually dimorphic behavior is encoded in the nervous system is poorly understood. Here, we characterize the dimorphic nociceptive behavior in C. elegans and study the underlying circuits, which are composed of the same neurons but are wired differently. We show that while sensory transduction is similar in the two sexes, the downstream network topology markedly shapes behavior. We fit a network model that replicates the observed dimorphic behavior in response to external stimuli, and use it to predict simple network rewirings that would switch the behavior between the sexes. We then show experimentally that these subtle synaptic rewirings indeed flip behavior. Strikingly, when presented with aversive cues, rewired males were compromised in finding mating partners, suggesting that network topologies that enable efficient avoidance of noxious cues have a reproductive "cost". Our results present a deconstruction of the design of a neural circuit that controls sexual behavior, and how to reprogram it.

neuroscience↗

bioRxiv2018

RESISTANCE TRAINING DOES NOT INDUCE UNIFORM ADAPTATIONS TO QUADRICEPS MUSCLES

Resistance training may differentially affect morphological adaptations along the length of uni-articular and bi-articular muscles. The purpose of this study was to compare changes in muscle morphology along the length of the rectus femoris (RF) and vastus lateralis (VL) in response to resistance training. Following a 2-wk preparatory phase, 15 resistance-trained men (24.0 {+/-} 3.0 y, 90.0 {+/-} 13.8 kg, 174.9 {+/-} 20.7 cm) completed pre-training (PRE) assessments of muscle thickness (MT), pennation angle (PA), cross-sectional area (CSA), and echo-intensity in the RF and VL at 30, 50, and 70% of each muscles length; fascicle length (FL) was estimated from respective measurements of MT and PA within each muscle and region. Participants then began a high intensity, low volume (4 x 3 - 5 repetitions, 3min rest) lower-body resistance training program, and repeated all PRE-assessments after 8 weeks (2 d {middle dot} wk-1) of training (POST). Although three-way (muscle [RF, VL] x region [30, 50, 70%] x time [PRE, POST]) repeated measures analysis of variance did not reveal significant interactions for any assessment of morphology, significant simple (muscle x time) effects were observed for CSA (p = 0.002) and FL (p = 0.016). Specifically, average CSA changes favored the VL (2.96 {+/-} 0.69 cm2, pp < 0.001) over the RF (0.59 {+/-} 0.20 cm2, p = 0.011), while significant decreases in average FL were noted for the RF (-1.03 {+/-} 0.30 cm, p = 0.004) but not the VL (-0.05 {+/-} 0.36 cm, p = 0.901). No other significant differences were observed. The findings of this study demonstrate the occurrence of non-homogenous adaptations in RF and VL muscle size and architecture following 8 weeks of high-intensity resistance training in resistance-trained men. However, training does not appear to influence region-specific adaptations in either muscle.

physiology↗