Biology subjects

Preston, K.

Publications and source records attributed to Preston, K..

3 recordsLinked to original sources

bioRxiv2024

Maf-family bZIP transcription factor NRL interacts with RNA-binding proteins and R-loops in retinal photoreceptors

RNA-binding proteins (RBPs) perform diverse functions including the regulation of chromatin dynamics and the coupling of transcription with RNA processing. However, our understanding of their actions in mammalian neurons remains limited. Using affinity purification, yeast-two-hybrid and proximity ligation assays, we identified interactions of multiple RBPs with NRL, a Maf-family bZIP transcription factor critical for retinal rod photoreceptor development and function. In addition to splicing, many NRL-interacting RBPs are associated with R-loops, which form during transcription and increase during photoreceptor maturation. Focusing on DHX9 RNA helicase, we demonstrate that its expression is modulated by NRL and that the NRL-DHX9 interaction is positively influenced by R-loops. ssDRIP-Seq analysis reveals both stranded and unstranded R-loops at distinct genomic elements, characterized by active and inactive epigenetic signatures and enriched at neuronal genes. NRL binds to both types of R-loops, suggesting an epigenetically independent function. Our findings suggest additional functions of NRL during transcription and highlight complex interactions among transcription factors, RBPs, and R-loops in regulating photoreceptor gene expression in the mammalian retina.

molecular biology↗

bioRxiv2023

Evaluating the neural underpinnings of motivation for walking exercise

BackgroundMotivation is critically important for rehabilitation, exercise, and motor performance, but its neural basis is poorly understood. Recent correlational research suggests that superior frontal gyrus medial area 9 (SFG9m) may be involved in motivation for walking activity. This study experimentally evaluated brain activity changes in periods of additional motivation during walking exercise, and tested how these brain activity changes relate to self-reported exercise motivation and walking speed. MethodsNon-disabled adults (N=26; 65% female; 25 {+/-} 5 years old) performed a vigorous exercise experiment involving 20 trials of maximal speed overground walking. Half of the trials were randomized to include extra motivation stimuli (lap timer, tracked best lap time and verbal encouragement). Wearable nearinfrared spectroscopy measured oxygenated hemoglobin responses ({Delta}HbO2) from frontal lobe regions, including the SFG9m, primary motor, dorsolateral prefrontal, anterior prefrontal, supplementary motor and dorsal premotor cortices. ResultsCompared with standard trials, participants walked faster during extra-motivation trials (2.67 vs. 2.43 m/s; p<0.0001) and had higher {Delta}HbO2 in all tested brain regions. This extra motivation effect on {Delta}HbO2 was greatest for SFG9m (+703 {micro}M) compared with other regions (+45 to +354 {micro}M; p[≤]0.04). Greater SFG9m activity was correlated with more self-determined motivation for exercise and faster walking speed. ConclusionsSimple motivational stimuli during walking exercise seem to upregulate widespread brain regions, especially SFG9m. This could help explain the positive effects of motivational feedback on gait outcomes observed in prior rehabilitation research. Thus, these findings provide a potential biologic basis for the benefits of motivational stimuli, elicited with clinically-feasible methods during walking exercise. Future clinical studies could build on this information to develop prognostic biomarkers and test novel brain stimulation targets for enhancing exercise motivation (e.g. SFG9m).

neuroscience↗

bioRxiv2019

Spontaneous polyploids and antimutators compete during the evolution of mutator cells

Heterozygous mutations affecting DNA polymerase (Pol) exonuclease domains and homozygous inactivation of mismatch repair (MMR) each generate "mutator" phenotypes capable of driving tumorigenesis. Cancers with both defects exhibit an explosive increase in mutation burden that appears to reach a threshold, consistent with selection acting against further mutation accumulation. In haploid yeast, simultaneous defects in polymerase proofreading and MMR select for "antimutator" mutants that suppress the mutator phenotype. We report here that spontaneous polyploids also escape this "error-induced extinction" and routinely out-compete antimutators in evolved haploid cultures. We performed similar experiments to explore how diploid yeast adapt to the mutator phenotype. We first evolved cells with homozygous mutations affecting proofreading and MMR, which we anticipated would favor tetraploid emergence. While tetraploids arose with a low frequency, in most cultures, a single antimutator clone rose to prominence carrying biallelic mutations affecting the polymerase mutator alleles. Variation in mutation rate between subclones from the same culture suggests there exists continued selection pressure for additional antimutator alleles. We then evolved diploid yeast modeling MMR-deficient cancers with the most common heterozygous exonuclease domain mutation (POLE-P286R). Although these cells grew robustly, within 120 generations, all subclones carried truncating or nonsynonymous mutations in the POLE-P286R homologous allele (pol2-P301R) that suppressed the mutator phenotype as much as 100-fold. Independent adaptive events in the same culture were common. Our findings suggest that analogous tumor cell populations may adapt to the threat of extinction by polyclonal mutations that neutralize the POLE mutator allele and preserve intra-tumoral genetic diversity for future adaptation.

cancer biology↗