Myotonic dystrophy type 1 (DM1) is a genetic disease that causes many serious health conditions in a variety of tissues including skeletal muscle stiffening and cardiac conduction disorders. This disease affects 1 in 2,300 people worldwide and is the most common form of muscular dystrophy. DM1 is caused by a CTG repeat expansion, which in lay terms means that in a gene, there's a sequence of 10 CTG DNA bases. However, in a specific part of the gene responsible for making messenger RNA (mRNA), the number of CTG repeats increases significantly. This unusual mRNA sequence is linked to the development of the disease. This mutated mRNA (messenger RNA) disables the splicing regulator muscle-blind-like 1 (MBNL1) gene and ultimately causes disease. It does this by sequestering and limiting the MBNL1s critical role in splicing mRNA (figure 1). In my proposed research project, I am focusing on cardiac function when testing adeno-associated viral vector (AAV)-mediated systemic delivery of the MBNL1 gene to increase MBNL1 protein expression in muscle. The lab found that body-wide delivery of AAV vectors with CK8-intron-MBNL1, which expressed MBNL1 only in striated muscle, was toxic in the hearts of mice and caused death (figure 2). Over the last few months, my mentor Matt Karolak and I have learned together methods such as echocardiography and tissue histological techniques to determine whether it is possible to prevent MBNL1 protein production and its damaging effects in the heart while still expressing MBNL1 protein in skeletal muscle for therapeutic disease benefits.

Traumatic brain injury (TBI) is recognized as a risk factor for neurodegenerative diseases, but the underlying mechanisms remain unclear. This study aimed to investigate how localized brain injury alters pathologic protein aggregation associated with neurodegenerative disease, focusing on hyperphosphorylated tau (p-tau) and beta-amyloid deposition in brain parenchyma adjacent to chronic contusion. Using brain donors from the University of Washington Brain Repository, cases with a diagnosis of chronic contusion were identified. Beta-amyloid and p-tau deposition were assessed in sections adjacent to the contusion and in contralateral sections without contusion (internal control). Manual counting and HALO imaging software were utilized to quantify the highest density of neuritic plaques/neurofibrillary tangles and overall deposition of abnormal protein in grey matter, respectively. Statistical analyses were performed to compare deposition in contusion versus control sections. Preliminary data was collected in 9 cases, predominantly male with a median age of 79 years. Neurofibrillary tangles were significantly higher in sections with contusion compared to internal controls (p=0.0188), with a similar trend observed for neuritic plaques (p=0.0723). HALO software analysis confirmed increased deposition of both proteins in the contusion compared to control sections (p=0.0391 for both p-tau and beta-amyloid). These findings support that TBI may modulate neurodegeneration by increasing p-tau and beta-amyloid deposition and underscores the importance of further research into the relationship between TBI and neurodegenerative diseases. Next, I will expand our cohort with more cases from the last few years and plan to compare brain contusion in mid-life to contusion occurring after the age of 65. In addition to assessing abnormal protein deposition, I will also examine the neuroinflammatory response. I expect to find greater levels of neuroinflammation as well as increased tau and beta-amyloid aggregation in the older age group as the neuroinflammatory response becomes prolonged during aging.

Traumatic brain injury (TBI) is one of the most prominent environmental risk factors for neurodegenerative disease, including Alzheimer’s disease (AD) and chronic traumatic encephalopathy (CTE). Both AD and CTE are characterized by the accumulation of abnormal phosphorylated tau (p-tau) protein in neurons in the brain in addition to other pathologies. In CTE in particular, the p-tau deposition occurs around the vasculature at the sulcal depths of the brain. Inhibitory neurons are the brakes of neuronal circuits in the brain and many previous studies using animal models have revealed a deficit or loss of inhibitory neurons after TBI. Some inhibitory neurons even have a special role in monitoring the vasculature of the brain, where the p-tau accumulates in CTE. However, no one has evaluated whether these inhibitory neurons are affected by p-tau pathology after human TBI. Here, I evaluate whether p-tau pathology accumulates in inhibitory neurons in ten cases of CTE and ten cases of brain contusion that have associated p-tau pathology compared to a positive control group (ten cases of AD without any history of head injury). Double-staining immunohistochemistry labeled with different colored chromagens is performed using three different inhibitory neuron markers (parvalbumin (PV), somatostatin (SOM) and TAC1R) combined with an antibody for the abnormal phosphorylated tau protein. Using the Halo image analysis system, the colocalization module is used to determine if p-tau accumulates in inhibitory neuron subtypes. These results will be confirmed with immunofluorescence and 3D confocal microscopy. I anticipate that inhibitory neurons, especially ones associated with vasculature (TAC1R+) will be affected by p-tau pathology in contusion and CTE cases, but not in positive controls. This project will give further insight into possible mechanisms of circuit and neuronal dysfunction that may occur after head injury and have therapeutic implications.