Biology subjects

Aldrich, J. C.

Publications and source records attributed to Aldrich, J. C..

3 recordsLinked to original sources

bioRxiv2025

DLK inhibition has sex-specific effects on neuroprotection and locomotor recovery after spinal cord injury

Spinal cord injury (SCI) causes devastating functional deficits, in part due to neuroinflammation, oxidative stress, and excitotoxicity that drive death of lesion-adjacent viable neurons. Dual leucine zipper kinase (DLK) is a neuron-enriched kinase that responds to cellular stress by activating the c-Jun N-terminal kinase (JNK) pathway, driving both stress-responsive gene expression and neuronal apoptosis. We hypothesized that SCI would robustly activate DLK signaling and that acute pharmacological inhibition of DLK would suppress JNK pathway activation, thereby enhancing neuroprotection and locomotor recovery in our mouse model of moderate contusion SCI. Using western blotting, we observed that SCI induced strong and sustained activation of the JNK pathway in the injured spinal cord starting at 4 hours post-injury through 7 days. Complementary analysis of single-nucleus RNA-seq revealed that DLK expression is highly enriched in neurons across all injury phases. Following SCI, neurons exhibited robust, time-dependent upregulation of multiple DLK-responsive transcripts, consistent with sustained pathway activation during the acute and subacute periods. Systemic treatment with the selective DLK inhibitor IACS-52825 effectively suppressed intraspinal JUN activation in a dose-dependent manner. However, unexpectedly, treatment delayed functional recovery and expanded lesion volume by 71% in male mice with no significant effect in females. These findings highlight the complex roles of DLK signaling after SCI, revealing a need to understand the sex-specific molecular mechanisms that modulate injury outcomes. Future studies should further optimize timing, location, and cellular targeting of DLK therapeutic strategies to improve neuroprotection and neurologic recovery after SCI.

neuroscience↗

bioRxiv2024

Genome-Wide Association Study and transcriptome analysis reveals a complex gene network that regulates opsin gene expression and cell fate determination in Drosophila R7 photoreceptor cells.

BackgroundAn animals ability to discriminate between differing wavelengths of light (i.e., color vision) is mediated, in part, by a subset of photoreceptor cells that express opsins with distinct absorption spectra. In Drosophila R7 photoreceptors, expression of the rhodopsin molecules, Rh3 or Rh4, is determined by a stochastic process mediated by the transcription factor spineless. The goal of this study was to identify additional factors that regulate R7 cell fate and opsin choice using a Genome Wide Association Study (GWAS) paired with transcriptome analysis via RNA-Seq. ResultsWe examined Rh3 and Rh4 expression in a subset of fully-sequenced inbred strains from the Drosophila Genetic Reference Panel and performed a GWAS to identify 42 naturally-occurring polymorphisms--in proximity to 28 candidate genes--that significantly influence R7 opsin expression. Network analysis revealed multiple potential interactions between the associated candidate genes, spineless and its partners. GWAS candidates were further validated in a secondary RNAi screen which identified 12 lines that significantly reduce the proportion of Rh3 expressing R7 photoreceptors. Finally, using RNA-Seq, we demonstrated that all but four of the GWAS candidates are expressed in the pupal retina at a critical developmental time point and that five are among the 917 differentially expressed genes in sevenless mutants, which lack R7 cells. ConclusionsCollectively, these results suggest that the relatively simple, binary cell fate decision underlying R7 opsin expression is modulated by a larger, more complex network of regulatory factors. Of particular interest are a subset of candidate genes with previously characterized neuronal functions including neurogenesis, neurodegeneration, photoreceptor development, axon growth and guidance, synaptogenesis, and synaptic function.

genomics↗

bioRxiv2023

Effects of circadian disruption via dim light at night in C57BL6/J mice on recoveryafter spinal cord injury

Spinal cord injury (SCI) can cause long-lasting locomotor deficits, pain, and mood disorders. Anatomical and functional outcomes are exacerbated by inflammation after SCI, which causes secondary damage. One promising target after SCI is manipulating the circadian system, which optimizes biology and behavior for time of day - including neuroimmune responses and mood- related behaviors. Circadian disruption after SCI is likely worsened by a disruptive hospital environment, which typically includes dim light-at-night (dLAN). Here, we hypothesized that mice subjected to SCI, then placed in dLAN, would exhibit worsened locomotor deficits, pain- like behavior, and anxiety-depressive-like symptoms compared to mice maintained in light days with dark nights (LD). C57BL/6J mice received sham surgery or moderate T9 contusion SCI, then were placed permanently in LD or dLAN. dLAN after SCI did not worsen locomotor deficits; rather, SCI-dLAN mice showed slight improvement in open-field locomotion at the final timepoint. Although dLAN did not alter SCI-induced heat hyperalgesia, SCI-dLAN mice exhibited an increase in mechanical allodynia at 13 days post-SCI compared to SCI-LD mice. SCI-LD and SCI-dLAN mice had similar outcomes using sucrose preference (depressive-like) and open-field (anxiety-like) tests. At 21 dpo, SCI-dLAN mice had reduced preference for a novel juvenile compared to SCI-LD, implying that dLAN combined with SCI may worsen this mood-related behavior. Finally, lesion size was similar between SCI-LD and SCI-dLAN mice. Therefore, newly placing C57BL/6J mice in dLAN after SCI had modest effects on locomotor, pain-like, and mood-related behaviors. Future studies should consider whether clinically-relevant circadian disruptors, alone or in combination, could be ameliorated to enhance outcomes after SCI.

neuroscience↗