Amelia Dayton Meiotic recombination is regulated by dosage of synaptonemal complex proteins
Meiosis is a specialized cell division that produces haploid gametes, such as sperm and eggs. To ensure each parental genome is inherited properly, cells must pair homologous chromosomes, induce DNA double-strand breaks, repair these breaks as crossovers, and segregate the chromosomes. The synaptonemal complex (SC), a large protein structure, assembles between homologs and facilitates crossing over, which ensures accurate chromosome segregation. Using Caenorhabditis elegans, previous work in the Libuda lab showed that two SC proteins, SYP-2 and SYP-3, have dosage-dependent functions in regulating crossing over. SYP-2 dosage is critical for regulating early crossover steps, while SYP-3 dosage influences the timing of crossover establishment. Crossovers are nonrandomly positioned on chromosomes, and whether SYP dosage influences crossover position remains unclear. To this end, I am using single nucleotide polymorphisms to characterize the positions and rates of crossovers in cells with altered SYP-2 and SYP-3 dosages. Preliminary data on Chromosome X shows that SYP-dosage is crucial for proper crossover positioning. Since the sex chromosomes often behave differently from autosomes, I am also determining the effect of SYP-dosage on crossovers across Chromosome II to establish whether autosomes show similar changes in crossover positioning. Overall, these experiments will define the dosage-dependent manner that SYP-2 and SYP-3 regulate recombination to promote fertility.
Karly Fear Design and Characterization of BMP-2 Protein Binders to Augment Non-Union Fracture Healing
Each year, over 630,000 people in the US suffer from non-union bone fractures, or fractures that do not heal completely without further medical intervention. To improve bone healing in non-union fractures, researchers have shown that bone morphogenetic protein 2 (BMP-2) improves bone regeneration. However, it is critical to fine tune the physiological dose and spatiotemporal control of BMP-2 release from a delivery biomaterial to avoid adverse side effects such as abnormal bone growth. I leverage the structural and biophysical insight of molecular modeling and design to generate protein binders predicted to control the release of BMP-2 into a fracture site via affinity interactions. I characterize subsequent protein binder designs using yeast surface display and flow cytometry. Over 1,000 designs are tested using this high-throughput computational and experimental pipeline and I will further characterize the toxicity, stability, and structure of a subset of these designs for practical application.
Kevin Mueller Lrig3 is Required for Colonic Regeneration Following Acute Inflammatory Injury
The mouse colon is a tightly regulated organ responsible for secreting mucus and absorbing water, which is carried out by colonic crypts; small U-shaped invaginations in the colon’s epithelial tissue. The excision of the protein Lrig3 has been characterized in homeostasis and is defined by more nuclei per crypt, increased mucosal area, and an expanded stem cell compartment consisting of more Lrig1+ cells per crypt. While we now understand that Lrig3 plays an important role in homeostasis, it is currently unknown what role Lrig3 might play in colon-based diseases. The disease we chose to test first was the mouse model of ulcerative colitis. Our lab treated two cohorts of mice, one Wild Type (WT) and one Lrig3-/-, with a 3% Dextran Sodium Sulfate (DSS) solution over 6 days to induce inflammation. Both cohorts were allowed to recover for 24 hours before analysis. We found Lrig3-/- mice are more susceptible to DSS treatment and lack the colonic regenerative capability seen in WT mice. We then performed immunohistochemistry, dye, and enzymatic-based analyses to examine the expression profiles of proteins associated with regeneration of the colonic epithelium. We observed a decrease in cells expressing the stem and progenitor marker Lrig1 in Lrig3-/- mice compared to WT (p<0.01) and a decrease in the total cell number per crypt (p<0.001), however there was no change in proliferation. These data suggest Lrig3 is required for epithelial regeneration in DSS-modeled ulcerative colitis.
Tyler Ramos A Homeodomain Protein Generates Neuronal Diversity and Connectivity in the Drosophila Lamina
How we perceive and integrate our experiences is the result of an intricate network of diverse neuron types, each with specific connectivity. To generate different neurons, signals in precursors give each neuron its unique neuronal fate. Subsequently, a combination of proteins called homeodomain transcription factors (TFs) grant neurons proper synaptic connectivity. The processes of fate selection and synapse assembly are sequential actions that have been characterized separately but are deeply connected. It is unknown if a common regulator exists between these two developmental steps. Our purpose is to test if a homeodomain TF can function as a regulator of both neuronal fate and synaptic connectivity. To pursue this, we use the lamina neurons (L1-L5) of the fruit fly, Drosophila melanogaster. We show that homeodomain TF Brain-specific homeobox (Bsh) is expressed in lamina precursor cells, which suggests it may play a role in establishing lamina neuron fate. Using cell-specific knockdown and tracing methods, we found removing Bsh generates L1 and L3 neurons at the expense of L5 and L4 neurons, respectively. In L4 neurons, Bsh activates another protein, Apterous (Ap). Knockdown of Bsh and Ap in L4 neurons resulted in the loss of a synapse recognition molecule and altered synaptic connectivity. We propose that the homeodomain TF Bsh functions as a regulator of both neuronal fate and synaptic connectivity, which may be a conserved developmental mechanism across organisms.
