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SummaryEphrins and Eph receptor tyrosine kinases are cell surface molecules that serve a multitude of functions in cell-cell communication in development, physiology and disease. EphA4 is a promiscuous member of the EphA subclass of Eph receptors and can bind to both EphrinAs and EphrinBs. In addition to its well-established roles in guiding the development of neuronal connectivity, EphA4 has been implicated for a role in synaptic plasticity, vascular formation, axon regeneration and central nervous system (CNS) repair following injury. However, the study of its role in the adult stage has been hampered by confounding developmental defects in EphA4 germline mutants. Here, we report the generation and molecular characterization of an EphA4 conditional allele along with a novel null allele with a knockin fluorescent reporter gene (mCFP). The conditional allele will be useful in ascertaining post-developmental and/or cell type-specific function of EphA4 in physiology, injury and disease. KeywordsEphA4; conditional allele; neural development; neural plasticity; cell-cell signaling Ephrins and their Eph receptors are best characterized for their roles in developmental axon guidance (Pasquale, 2008). Both the Ephrin ligands and the Eph receptors are divided into the A and B subclasses. In mammals, there are nine subclass A Eph (EphA) receptors that bind to five subclass A Ephrin (EphrinA) ligands, and five EphB receptors that bind to three EphrinB ligands. Crosstalk among ligands and receptors within a subclass is common, but a certain level of crosstalk also exists between subclasses. During neural development, Ephs and Ephrins are often expressed in a gradient fashion in neurons and/or their target tissues to guide the formation of topographic maps, which ensures the maintenance of the spatial order of neural information (Flanagan, 2006). In addition to their roles in axon guidance, Ephrins and Ephs have been implicated in variety of other biological processes both inside and outside of the nervous system, including dendritic spine morphology and synapse formation, synaptic function and plasticity, responses to a CNS injury, angiogenesis, immune function, tissue homeostasis and cancer (Goldshmit et al., 2006a;Goldshmit et al., 2006b;Klein, 2009;Kuijper et al., 2007;Lai and Ip, 2009;Murai et al., 2003;Pasquale, 2008 EphA4 is a member of the EphA subclass and can bind to both EphrinAs and EphrinBs. The promiscuous nature of its interaction with Ephrins makes EphA4 available to participate in a variety of cell-cell signaling events. EphA4 is expressed by multiple cell types during development, after injury, and in disease (Goldshmit et al., 2006a;Goldshmit et al., 2004;Oki et al., 2008;Pasquale, 2008;Ting et al., 2009). In addition to its roles in developmental axon guidance, it has been implicated for a role in synaptic plasticity, vascular formation, axon regeneration and CNS repair after injury (Goldshmit et al., 2006a;Goldshmit et al., 2004;Grunwald et al., 2004;Murai et al., 2003). Because of the complexities in E...

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Background. Indocyanine green fluorescent angiography (IcGA) has been used with success in guiding intraoperative management to prevent colorectal anastomotic complications. Prior studies in open and laparoscopic colorectal surgery, such as PILLAR II, have demonstrated a low anastomotic leak rate (1.4%). As the minimally invasive approach progresses from laparoscopic to robotic approach, the effect and safety of IcGA in assessing anastomotic perfusion in the latter deserve further investigation. Methods. The objective of the study was to determine the safety of IcGA in guiding intraoperative management of robotic assisted colorectal resection via perfusion assessment. The design was single-surgeon, retrospective case-control study. 74 patients underwent left-sided robotic assisted colorectal resection and anastomosis with IcGA guidance. 30 historical controls underwent left-sided robotic assisted colorectal resection and anastomosis without IcGA. Clinical, demographic, operative, and outcome variables were tabulated. Results. In the control group, 1 patient suffered a postoperative anastomotic stricture requiring no surgery, and 1 patient suffered an anastomotic dehiscence requiring return to the operating room. There were no anastomotic complications in the IcGA group, including 4 patients who underwent a change in the chosen level of anastomosis based on intraoperative IcGA. Conclusion. IcGA is safe to use as demonstrated by the very low rate of complications in this case series. It is also safe to rely on to guide re-resection and recreation of an anastomosis intraoperatively by demonstration of blood flow. This may help offset the loss of tactile feedback and assessment of tension in the robotic platform.

A 50-year-old African American male with Discoid Lupus Erythematosus (DLE) presented to the dermatology clinic for a rapidly enlarging left cheek mass. The mass failed to resolve with conservative measures. A biopsy revealed poorly differentiated Squamous Cell Carcinoma (SCC). He was referred to Head and Neck Surgery and successfully underwent a resection with free flap reconstruction. Postoperatively he did well. Squamous cell skin carcinomas arising from lesions of Discoid Lupus are rare and aggressive tumors with greater likelihood of metastases. Cases have been reported among patients with different clinical characteristics; we present a rare case arising in an African American male on the face and involving the ear.