This study investigates the neural mechanisms underlying chronotype variation across Drosophilid species, with a focus on the differences between species with morning activity preference (AMP flies) and species with evening activity preference (PMP flies). While small ventral lateral neurons (s-LNvs) are classically understood as central circadian pacemakers in D. melanogaster, comparative analysis across multiple species reveals a striking deviation from this model. Using Drosophila Activity Monitor (DAM) assays and immunocytochemistry targeting pigment dispersing factor (PDF), we show that PMP species consistently lack PDF+ s-LNvs yet retain robust circadian rhythmicity and the ability to entrain to both phase delay and phase advance conditions. Despite this absence, PMP flies maintain dorsal PDF projections, suggesting compensatory circuit rewiring, potentially through large ventral lateral neurons (l-LNvs) or novel PDF+ neurons observed in certain species. In contrast, AMP species retain s-LNvs, and variation in their number correlates with differences in entrainment speed, supporting a modulatory rather than essential role for these neurons. Together, these findings challenge the traditional view of s-LNvs as the sole circadian pacemakers and instead suggest that they primarily influence temporal activity bias. This study is highly relevant in exploring the evolving field of study in chronotypes and circadian behavior and sets up the foundation of future studies into chronotypic behavior in humans.

The gene cyp19a1b encodes brain aromatase, an enzyme that converts androgens into estrogens in teleost fish. In the highly social cichlid Astatotilapia burtoni, we recently reported unpublished findings showing that cyp19a1b is not required for aggression in males, but cyp19a1b-knockout (KO) females exhibited high levels of male-typical aggression toward males. As part of this ongoing work, this project examines whether sex-typical behavior toward females is disrupted in cyp19a1b-KO male and female A. burtoni. I assessed mating behavior in 9 KO and 7 wild-type (WT) male focal cichlids. Each male was paired with a WT female in dyad mating assays. All interactions were recorded and scored using BORIS (Behavioral Observation Research Interactive Software). Each male was dissected immediately after assaying, and brains were fixed with PFA and embedded for future histological analysis. I am currently applying these protocols to study KO and WT females interacting with WT stimulus females. Results show that KO males exhibited fewer lead swims, a courtship behavior, and increased latency to court compared to WT males. These results suggest that brain aromatase could play a role in the development of typical mating behaviors in male cichlids. We suspect that brain aromatase will also be essential in regulating female mating behavior. This project offers a novel view into how brain aromatase dictates feminization, masculinization, and overall reproductive ability in cichlids.

Depression affects millions worldwide, yet the circuit-level mechanisms underlying transcranial magnetic stimulation (TMS) therapies remain poorly understood. Accelerated intermittent theta-burst stimulation (aiTBS) targeting the prefrontal cortex (PFC) is an FDA-approved TMS protocol for depression. This study investigates whether aiTBS-induced activation of somatostatin-expressing (SST) interneurons in the PFC persists seven days post-stimulation in a chronic stress mouse model. Using a novel focal, high-intensity rodent TMS coil that mimics clinical aiTBS, 12 chronically stressed mice were assigned to treatment groups (n=6 stimulated, n=6 sham control). Brains were harvested seven days post-treatment and cryosectioned into 60μm sections. Three PFC sections per brain were immunohistochemically stained for SST neurons, Fos (neuronal activity marker), and neuronal nuclei. Stained sections were imaged via apotome microscopy with z-stacks, and Fos-positive SST neuron ratios were quantified using ImageJ. While no significant difference in SST interneuron activity was found between groups, overall neuronal activity was significantly lower in the stimulated group - suggesting aiTBS may instead persistently modulate parvalbumin (PV) interneurons, a major inhibitory cell class in the PFC. We will continue this study by employing dual SST/PV staining to further characterize these effects. This study will advance our understanding of TMS circuit mechanisms and potentially guide improvements in depression treatment protocol.

Axon degeneration and subsequent demyelination, and chronic inflammation are characteristic of white matter injury in conditions such as traumatic spinal cord injury and multiple sclerosis, where efficient myelin debris clearance is critical for recovery. During demyelination, astrocytes modulate microglial function, shaping debris clearance and the lipid-rich environment that influences inflammation and repair. Preliminary data indicate that astrocyte-derived CCN1 regulates microglial phagocytic capacity, but whether this pathway is conserved across demyelinating contexts and relevant to human disease remains unknown. Mechanistically, CCN1 astrocytes seem to regulate lipid buffering after myelin damage. In wild-type conditions, they balance cholesterol efflux and storage following microglial phagocytosis of myelin debris. In CCN1 knockout (KO), this balance is disrupted, leading to cholesterol dysregulation and increased neuroinflammation. This project tests the hypothesis that astrocytic CCN1 orchestrates a conserved microglial injury response that supports lipid handling and debris clearance. We will assess whether CCN1-mediated astrocyte–microglia signaling is conserved in toxin-mediated demyelination using the cuprizone model. Using wild-type and CCN1 cKO mice, we will perform phenotypic and transcriptomic analyses across key stages of demyelination and remyelination.

Spinocerebellar ataxia type 4 (SCA4) is a dominant ataxia caused by exonic GGC repeat expansion in the ZFHX3 gene reported in families of Swedish descent. Recently, our group performed large scale screening of ~700 undiagnosed ataxia patients, identifying SCA4 expansions in 3 unrelated families of self-identified European ancestry. To assess whether these expansions arose from the Swedish founder mutation or an alternative ancestry, we performed comparative haplotype analysis of a collection of 14 previously identified single nucleotide polymorphisms (SNPs) associated with expansion in various Swedish patients. One family only had 6 of the 14 SNPs but these were contiguous and closest to the expansion. The other 2 families were found to be distantly related and carried all 14 SNPs, suggesting this may be an ancestral haplotype. To assess for specificity of this haplotype, we examined 423 undiagnosed ataxia subjects using exome sequencing data to examine either the 6 coding SNPs nearest ZFHX3 or a minimal subset of 4 SNPs located within the expansion itself. No subjects were found with a complete haplotype for either set of SNPs but we observed 226 individuals with 1-4 of the 6 SNPs and a single patient with 3 of the 4 minimal SNP subset but no subjects had an expanded ZFHX3 allele, showing specificity of this haplotype. These results clarify the genetic architecture of the ZFHX3 expansion and suggest an ancestral signature that further supports a common Swedish founder with recombination-driven variation among descendants.