Faculty Bibliography

Precise control of neurite guidance during development is essential to ensure proper formation of neuronal networks and correct function of the central nervous system (CNS). How neuronal projections find their targets to generate appropriate synapses is not entirely understood. Although transcription factors are key molecules during neurogenesis, we do not know their entire function during the formation of networks in the CNS. Here, we used the Drosophila melanogaster optic lobe as a model for understanding neurite guidance during development. We assessed the function of Sox102F/SoxD, the unique Drosophila orthologue of the vertebrate SoxD family of transcription factors. SoxD is expressed in immature and mature neurons in the larval and adult lobula plate ganglia (one of the optic lobe neuropils), but is absent from glial cells, neural stem cells and progenitors of the lobula plate. SoxD RNAi knockdown in all neurons results in a reduction of the lobula plate neuropil, without affecting neuronal fate. This morphological defect is associated with an impaired optomotor response of adult flies. Moreover, knocking down SoxD only in T4/T5 neuronal types, which control motion vision, affects proper neurite guidance into the medulla and lobula. Our findings suggest that SoxD regulates neurite guidance, without affecting neuronal fate.

Staphylococcus aureus is an opportunistic pathogen that causes a range of serious infections associated with significant morbidity, by strains increasingly resistant to antibiotics. However, to date all candidate vaccines have failed to induce protective immune responses in humans. We need a more comprehensive understanding of the antigenic targets important in the context of human infection. To investigate infection-associated immune responses, patients were sampled at initial presentation and during convalescence from three types of clinical infection; skin and soft tissue infection (SSTI), prosthetic joint infection (PJI) and pediatric hematogenous osteomyelitis (PHO). Reactivity of serum IgG was tested with an array of recombinant proteins, representing over 2,652 in-vitro-translated open reading frames (ORFs) from a community-acquired methicillin-resistant S. aureus USA300 strain. High-level reactivity was demonstrated for 104 proteins with serum IgG in all patient samples. Overall, high-level IgG-reactivity was most commonly directed against a subset of secreted proteins. Although based on limited surveys, we found subsets of S. aureus proteins with differential reactivity with serum samples from patients with different clinical syndromes. Together, our studies have revealed a hierarchy within the diverse proteins of the S. aureus "immunome", which will help to advance efforts to develop protective immunotherapeutic agents.

Inherited or acquired alterations in the structure and function of connexin proteins have long been associated with disease. In the present work, we review current knowledge on the role of connexins in diseases associated with the heart, nervous system, cochlea, and skin, as well as cancer and pleiotropic syndromes such as oculodentodigital dysplasia (ODDD). Although incomplete by virtue of space and the extent of the topic, this review emphasizes the fact that connexin function is not only associated with gap junction channel formation. As such, both canonical and noncanonical functions of connexins are fundamental components in the pathophysiology of multiple connexin related disorders, many of them highly debilitating and life threatening. Improved understanding of connexin biology has the potential to advance our understanding of mechanisms, diagnosis, and treatment of disease.

Adipocytes undergo pronounced changes in size and behavior to support diverse tissue functions, but the mechanisms that control these changes are not well understood. Mammary gland-associated white adipose tissue (mgWAT) regresses in support of milk fat production during lactation and expands during the subsequent involution of milk-producing epithelial cells, providing one of the most marked physiological examples of adipose growth. We examined cellular mechanisms and functional implications of adipocyte and lipid dynamics in the mouse mammary gland (MG). Using in vivo analysis of adipocyte precursors and genetic tracing of mature adipocytes, we find mature adipocyte hypertrophy to be a primary mechanism of mgWAT expansion during involution. Lipid tracking and lipidomics demonstrate that adipocytes fill with epithelial-derived milk lipid. Furthermore, ablation of mgWAT during involution reveals an essential role for adipocytes in milk trafficking from, and proper restructuring of, the mammary epithelium. This work advances our understanding of MG remodeling and tissue-specific roles for adipocytes.

IQGAP1 is a scaffold protein involved in the assembly of adherens junctions. Our work has recently revealed a novel role for IQGAP1 in the regulation of tight junctions (TJ) through differential recruitment of claudins to the nascent TJ. Here, we discuss the potential mechanisms of this regulation, including IQGAP1 effects on CDC42, and IQGAP1 interactions with sorting/trafficking molecules (e.g. Exo70). Given the many roles of IQGAP1 and the large number of interacting partners, we focus our discussion of these functions in the context of junction formation, trafficking, growth factor signaling and cancer. We also propose a potential role for IQGAP1 in regulating epithelial integrity and compartmentalized signaling in epithelia.

Introduction: We will discuss recent progress in developing a single molecule nanotechnology to detect and characterize genomic translocations of diagnostic and prognostic significance in hematologic malignancies. In the clinical lab, fluorescent in situ hybridization (FISH) and PCR remain the mainstays; unfortunately, they fail in a meaningful fraction of cases, due either to insufficient resolution (FISH) or the fact that the vast majority of structural variant breakpoints are scattered widely and thus cannot be localized a priori for amplification by PCR. While microarrays can improve the detection of copy number variations, they are not a replacement for FISH, for example, because they cannot detect un-localized balanced translocations. Methods: In our approach, structural variations (indels and translocations) are identified by 'molecular barcoding', using targeted CRISPR-Cas9 DNA binding proteins as 'nanoparticles', identifiable with high-speed Atomic Force Microscopy (HSAFM). The resulting pattern and spacing of the markers allows precise identification of the genomic loci involved. Results: Using this novel technique, we mapped a known BCL2-IGH translocation present in the follicular lymphoma cell line DOHH-2, obtained commercially, and detected similar translocations in lymph node tissue samples from follicular lymphoma patients. We also present preliminary results showing detection and quantitation of a variety diagnostic targets including IGH-MYC translocations, and FLT3-ITD length polymorphisms. Conclusions: This approach has the potential to resolve diagnostic uncertainty in cases where fluorescent in situ hybridization (FISH) and PCR prove insufficient

Chronic diabetic ulcers are a common complication in patients with diabetes, often leading to lower limb amputations and even mortality. Stem cells have shown promise in promoting cutaneous wound healing by modulating inflammation, angiogenesis, and re-epithelialization. However, more effective delivery and engraftment strategies are needed to prolong transplanted stem cell lifespan and their pro-healing functions in a chronic wound environment to improve skin regeneration. In this study, an injectable poly(ethylene glycol) (PEG)-gelatin-based hydrogel system is examined to create a functional stem cell niche for the delivery of adipose-derived stem cells (ASCs) into diabetic wounds. Human ASCs are encapsulated into the in situ crosslinked hydrogels and cultured in a 3D topography. The encapsulated cells are well attached and spread inside the hydrogels, retaining viability, proliferation, and metabolic activity up to three weeks in vitro. Allogeneic ASCs are delivered to diabetic wounds by this hydrogel vehicle. It is found that stem cell retention is significantly improved in vivo with vehicle-mediated delivery. The ASC-hydrogel-based treatment decreases inflammatory cell infiltration, enhances neovascularization, and remarkably accelerates wound closure in diabetic mice. Together, these findings suggest this conveniently-applicable ASC-hydrogel-based skin substitute provides a promising potential for the treatment of chronic diabetic wounds.