Malignant Cerebral Ischemia in A COVID-19 Infected Patient: Case Review and Histopathological Findings.

Severe acute respiratory syndrome coronavirus (SARS-CoV-2) is responsible for an unprecedented worldwide pandemic that has severely impacted the United States. As the pandemic continues, a growing body of evidence suggests that infected patients may develop significant coagulopathy with resultant thromboembolic complications including deep vein thrombosis, pulmonary embolism, myocardial infarction, and ischemic stroke. However, this data is limited and comes from recent small case series and observational studies on stroke types, mechanisms, and outcomes.1-14 Furthermore, evidence on the role of therapeutic anticoagulation in SARS-CoV-2 infected patients with elevated inflammatory markers, such as D-dimer, is also limited. We report the case of a middle-aged patient who presented with a large vessel ischemic stroke likely resulting from an underlying inflammatory response in the setting of known novel coronavirus infection (COVID-19). Histopathologic analysis of the patient's ischemic brain tissue revealed hypoxic neurons, significant edema from the underlying ischemic insult, fibrin thrombi in small vessels, and fibroid necrosis of the vascular wall without any signs of vasculature inflammation. Brain biopsy was negative for the presence of SARS-CoV-2 RNA (RT-PCR assay). Along with a growing body of literature, our case suggests that cerebrovascular thromboembolic events in COVID-19 infection may be related to acquired hypercoagulability and coagulation cascade activation due to the release of inflammatory markers and cytokines, rather than virus-induced vasculitis. Further studies to investigate the mechanism of cerebrovascular thromboembolic events and their prevention is warranted.

Transcriptional repression of peri-implantation EMX2 expression in mammalian reproduction by HOXA10.

HOXA10 is necessary for mammalian reproduction; however, its transcriptional targets are not completely defined. EMX2, a divergent homeobox gene, is necessary for urogenital tract development. In these studies we identify and characterize the regulation of EMX2 by HOXA10. By using Northern analysis and in situ hybridization, we found that EMX2 is expressed in the adult urogenital tract in an inverse temporal pattern from HOXA10, suggestive of a negative regulatory relationship. Constitutive expression of HOXA10 diminished EMX2 mRNA, whereas blocking HOXA10 through the use of antisense resulted in high EMX2 mRNA expression. Deletional analysis of the EMX2 5' regulatory region revealed that a 150-bp element mediated transcriptional repression when cotransfected with pcDNA3.1/HOXA10 in transient-transfection assays. Binding of HOXA10 protein to this element was demonstrated by electrophoretic mobility shift assay and further localized to a consensus HOXA10 binding site within this element by DNase I footprinting. Site-directed mutagenesis abolished binding, as well as the negative transcriptional regulation. Transcriptional activation of empty spiracles, the Drosophila ortholog of EMX2, by Abdominal-B (HOXA10 ortholog) has been previously demonstrated. These findings demonstrate conservation of the transcription factor-target gene relationship, although the direction of regulation is reversed with possible evolutionary implications.

Direct regulation of beta3-integrin subunit gene expression by HOXA10 in endometrial cells.

Estrogen and progesterone regulate HOXA10 expression in the endometrium, where HOXA10 is necessary for implantation. The integrins are also involved in early embryo-endometrial interactions. Here we show that HOXA10 directly regulates beta3-integrin subunit expression in the endometrium, likely mediating the effect of sex steroids on beta3-integrin expression. beta3-Integrin expression was decreased in endometrium shown to have low HOXA10 expression. beta3-Integrin mRNA levels were increased in endometrial adenocarcinoma cells (Ishikawa) transfected with pcDNA3.1/HOXA10, and decreased in cells treated with HOXA10 antisense. Seven consensus HOXA10 binding sites were identified 5' of the beta3-integrin gene. Direct binding of HOXA10 protein to four sites was demonstrated by EMSA. Reporter gene expression increased in BT-20 cells cotransfected with pcDNA3.1/ HOXA10 and pGL3-promoter vector containing region F (encompassing all seven HOXA10 consensus sites). A 41-bp segment (Region A) showed highest affinity binding to HOXA10 protein. Increased reporter expression, equal in magnitude to that obtained with Region F, was obtained with Region A. HOXA10 protein binding within Region A was localized by deoxyribonuclease I footprinting. beta3-Integrin expression was directly up-regulated by HOXA10 through a 41-bp 5'-regulatory element. Sex steroids regulate the expression of endometrial beta3-integrin through a pathway involving HOXA10.