The inner ear is crucial for both hearing and balance and undergoes rapid changes during embryonic, fetal, and postnatal stages. Its complex structure poses challenges in studying auditory systems, especially the organ of Corti responsible for sound perception. Hair cells (HC’s) within the cochlea are essential for hearing, and their loss in mammals results in permanent deafness due to their inability to regenerate. We recently established Early B cell factor 1 (Ebf1) as an important factor for the development of the cochlea. Our lab’s work with conditional knockout (cKO) mouse models revealed that Ebf1 restricts sensory development within the cochlear duct. The Slc26a9-Cre Ebf1cKO model deletes on embryonic day (E) 9.5. We have seen over 2-fold increases in HC’s and their associated support cells (SCs). We have developed a tamoxifen-inducible Sox2Cre recombinase mice model for precise timing of genetic manipulation within the cochlea. Specific temporal activation of tamoxifen-inducible Sox2Cre recombinase in the cochlea will uncover critical regulatory time periods for the establishment of the sensory domain. Activation of tamoxifen-inducible Sox2Cre at embryonic day 11/12 only shows an increase in inner hair cells. These findings lead us to ask, what’s the critical window for Ebf1’s regulatory role in cochlear development? To determine the optimal window for Ebf1's regulatory role, I will activate the Cre expressed in Sox2 Ebf1-cKO mice with tamoxifen at different embryonic days (9-14) via oral gavage. Immunostaining experiments utilizing HC markers (Myo7a), inner HC markers (Vglut3), and SC markers (Sox2) will be conducted. I will quantify HC densities and cochlear length of Sox2 Ebf1-cKO and littermate control mice. Due to tamoxifen toxicity, samples will consist of embryonic day E18 specimens. Anticipated results include varying HC numbers, innervation and the presence of ectopic sensory patches. This study will offer valuable insight into the temporal dynamics of Ebf1's regulatory role.

Atherosclerosis is characterized by the accumulation of lipids, inflammatory cells, and fibrous tissue in arterial walls, forming plaques. Plaque accumulation can lead to stenosis and potentially severe outcomes such as myocardial infarction or stroke. The gut microbiome, including Collinsella aerofaciens, is believed to play a role in the prevention or development of atherosclerosis. Gut bacteria can directly influence systemic inflammation, a factor correlated with the pathogenesis of atherosclerosis, and produce metabolites that alter the disease course. This study explores the potential link between C. aerofaciens and atherosclerosis by investigating the abundance of C. aerofaciens in the gut microbiome of individuals with and without atherosclerosis. We collected 179 stool samples from participants at the Kisumu District Hospital HIV Clinic in Kenya and conducted a comprehensive analysis of their gut microbiomes. 100 participants had carotid ultrasonography, categorized as showing atherosclerosis with visible plaque or intima medial thickness ≥ 0.7 mm. We employed bacterial 16S ribosomal RNA gene sequencing to characterize the stool microbial composition and noted that the relative abundance of C. aerofaciens was 2.6-fold less in participants with atherosclerosis (p=0.006). To validate these findings, I employed a Quantitative Polymerase Chain Reaction with a cloned plasmid control for targeted quantification of C. aerofaciens. We found 6.9-fold more C. aerofaciens copies per total 16S in Kenyan adults without atherosclerosis versus with (p=0.020). This suggests a potential protective or mitigating role for this bacterium in cardiovascular health. Future work could include assessing changes in C. aerofaciens abundance over time and its association with cardiovascular disease progression. Additionally, in vitro or preclinical studies could reveal the specific mechanisms by which C. aerofaciens influences atherosclerosis development and progression. This research contributes to our understanding of the intricate interplay between the gut microbiome and atherosclerosis, offering insights that may inform future therapeutic strategies and personalized interventions for cardiovascular diseases.

Perinatal asphyxia or hypoxia, where the infant brain does not receive enough oxygen or blood flow, commonly occurs in premature newborns and is one of the leading causes of neonatal mortality worldwide. Survivors often have altered white matter with cognitive impairments, motor deficits, and increased rates of cerebral palsy. There is currently no standard treatment for preterm brain injury, so there is a critical need to research neuroprotective strategies as well as ways to assess their impact. The ferret is a promising model species for studying preterm brain injury due to its gyrified brain and white-to-gray matter ratio, which are similar to that of the human brain. The gyrification index (GI) can be used to assess cortical development and is calculated using magnetic resonance imaging (MRI) images. These are analyzed using ImageJ software to perform hemispheric tracing by dividing an internal trace, including the gyri and sulci, by an external trace that excludes them. A higher GI is indicative of a larger cortical surface area. This project seeks to evaluate the effects of postnatal (P) age on post-hypoxic-ischemic (HI) gyrification in two ferret models. In both models, HI ferrets underwent bilateral carotid artery ligation and exposure to hypoxia, differing by date of surgery, with randomly assigned control animals not undergoing surgery. Model One ferrets underwent surgery at P10 (extremely preterm equivalent) and tissue collection at P70, and Model Two ferrets underwent surgery at P17 (late preterm equivalent) and tissue collection at P42. I hypothesize that GI will be affected by HI injury, with both age of injury and age of assessment altering GI relative to control animals. Contextualizing age differences in GI could help inform future therapy regimens to treat infants with premature brain injury.

Traumatic brain injury (TBI) is caused by an external force to the head, resulting in brain injury and is a major cause of death, particularly in adults 75 years and older who are at increased risk of falls which can lead to disability. Humans have a natural response to impact and strain called the Valsalva maneuver, which leads to an increased pressure in the chest and abdomen, which can result in a neuroprotective increase in intracranial pressure (ICP). However, most people are unable to anticipate TBIs and cannot perform their own Valsalva maneuver. Using a ferret model of TBI, the neuroprotective effects of externally-stimulated Valsalva-like response will be assessed. Ferrets are used to model human TBIs because the cortical thickness and layer distribution of their brains are more akin to humans in the ferret compared to rodents. The ferrets will be randomized to one of the three groups: control, TBI+sham valsalva, and TBI+valsalva. To show that the intracranial pressure of ferrets can be transiently increased, an inflatable cuff will be utilized to exert pressure on the abdomen, resulting in a partial Valsalva maneuver. TBI will be induced in the ferrets using a closed-head impact, and the neuroprotective effects of increased ICP from the inflatable abdominal cuff will be assessed using a battery of motor and cognitive tests before and after the TBI event, additionally, brain injury and neuroprotection will be evaluated using histopathology. I hypothesize that the Valsalva maneuver induced by the inflatable abdominal cuff will reduce behavioral deficits resulting from impact. If the behavioral deficits are reduced, this study can work to inform future interventions for TBI, such as environment-sensing wearable devices for high risk populations.

Mobile genes are commonly found in bacteria, and they are capable of being transferred between unrelated bacterial cells via a process termed horizontal gene transfer (HGT). Mobile genes that undergo HGT can evolve in various “host” bacteria and thereby evolve in several different genomic backgrounds. In a recent publication, my lab constructed a mathematical model to assess the effects of HGT (i.e “host-switching”) on mobile gene evolution. I have built upon this work by probing additional factors that may influence mobile gene evolution. In phase one of my project, I compared the original evolutionary model used in the publication to a newly expanded, more ecologically realistic model in which growth rates of the bacteria depend on resource availability. To compare the models, I ran simulations with both models on a set of bacterial-host pairs and compared the resulting evolutionary outcomes from both models. I found that the categorical effect of HGT occurring (i.e. HGT confers a higher, lower, or neutral change in host fitness) was the same across both models, indicating that ecological factors are less predictive of mobile gene evolutionary outcomes. For the second phase of my experiment, I assessed the effect of variable HGT rate on mobile gene evolutionary outcomes. I ran simulations using a set of bacterial host-pairs while varying the HGT rate along a biologically relevant range, and found a positive correlation between HGT rate and the magnitude of positive fitness effects conferred by a mobile gene that has undergone HGT. This indicates that HGT rates play an important role in governing the evolutionary outcomes of mobile genes. Using evolutionary simulations has allowed us to gain insight into the predictive factors governing mobile gene evolution and thereby mobile gene-containing bacterial evolution. This is especially important, as many genes conferring antibiotic resistance are mobile.