Patricia A. Kirby

Nedd4 controls animal growth by regulating IGF-1 signaling.

Nedd4 acts through Grb10 to enhance insulin-like growth factor signaling and control animal growth. A Growth-Promoting Ubiquitin Ligase Genetic knockout of the ubiquitin ligase Nedd4 decreases insulin-like growth factor 1 (IGF-1) and insulin signaling and causes delayed embryonic development, reduced growth and body weight, and neonatal lethality. Elevated Grb10 in the Nedd4-deficient cells appears to cause mislocalization of the IGF-1 receptor and prevent receptor signaling at the plasma membrane. Thus, by regulating the abundance of Grb10, a negative regulator of IGF-1 and insulin signaling, Nedd4 positively influences growth. The ubiquitin ligase Nedd4 has been proposed to regulate a number of signaling pathways, but its physiological role in mammals has not been characterized. Here we present an analysis of Nedd4-null mice to show that loss of Nedd4 results in reduced insulin-like growth factor 1 (IGF-1) and insulin signaling, delayed embryonic development, reduced growth and body weight, and neonatal lethality. In mouse embryonic fibroblasts, mitogenic activity was reduced, the abundance of the adaptor protein Grb10 was increased, and the IGF-1 receptor, which is normally present on the plasma membrane, was mislocalized. However, surface expression of IGF-1 receptor was restored in homozygous mutant mouse embryonic fibroblasts after knockdown of Grb10, and Nedd4−/− lethality was rescued by maternal inheritance of a disrupted Grb10 allele. Thus, in vivo, Nedd4 appears to positively control IGF-1 and insulin signaling partly through the regulation of Grb10 function.

Fatal Abusive Head Trauma Cases: Consequence of Medical Staff Missing Milder Forms of Physical Abuse

Objectives: Missed diagnosis of child abuse may lead to chronic abuse with potential for death. This paper reports 3 such cases. Methods: This is a retrospective chart review of 38 cases diagnosed as abusive head trauma between January 1, 2004 and December 31, 2006 at a university hospital. We sought to identify fatal cases with a past medical history of physical abuse that was missed by the medical staff. Results: Three cases (7.9%) had a past medical history of physical abuse that was missed by the medical staff. Infants were 2 males and 1 female. Their ages were 2.5, 3.5, and 6 months, respectively. Missed abuse episodes involved rib fractures, a metaphyseal tibial fracture, and a shaking episode, respectively. The intervals that had elapsed between the missed and the fatal abuse episodes were 24 hours, 12 days, and 6 weeks, respectively. Perpetrators of fatal head trauma were all biological fathers. One pled guilty, and 2 were convicted of involuntary manslaughter. The infants were in the care of the perpetrators of the fatal abuse episodes at the time the missed abuse episodes occurred. Conclusions: Physicians assessing children, especially infants, should be alert to indicators of abusive trauma to recognize abuse early on. Including abusive trauma in the differential diagnostic list and taking appropriate steps to rule out or confirm the diagnosis are of paramount importance in establishing child protective services and preventing further abuse and neglect that may at times be fatal.

Older donor livers show early severe histological activity, fibrosis, and graft failure after liver transplantation for hepatitis C.

Background. In hepatitis C virus (HCV)-positive liver transplant recipients, infection of the allograft and recurrent liver disease are important problems. Increased donor age has emerged as an important variable affecting patient and graft survival; however, specific age cutoffs and risk ratios for poor histologic outcomes and graft survival are not clear. Methods. A longitudinal database of all HCV-positive patients transplanted at our center during an 11-year period was used to identify 111 patients who received 124 liver transplants. Graft survival and histological endpoints (severe activity and fibrosis) of HCV infection in the allografts were compared as a function of donor age at transplantation. Results. By Kaplan-Meier analyses, older allografts showed earlier failure and decreased time to severe histological activity and fibrosis as compared with allografts from younger donors. By Cox proportional hazards analysis, older allografts were at greater risk for all severe histologic features and decreased graft survival as compared with younger allografts (P≤0.02 for all outcomes). Analysis of donor age as a dichotomous variable showed that donors greater than 60 yr were at high risk for deleterious histologic outcomes and graft failure. An age cutoff of 60 yr showed a sensitivity of 94% and specificity of 67% for worse graft survival by receiver operating characteristics curve. Conclusions. Advanced donor age is associated with more aggressive recurrent HCV and early allograft failure in HCV-positive liver transplant recipients. Consideration of donor age is important for decisions regarding patient selection, antiviral therapy, and organ allocation.

Lethal Infection of K18-hACE2 Mice Infected with Severe Acute Respiratory Syndrome Coronavirus

ABSTRACT The severe acute respiratory syndrome (SARS), caused by a novel coronavirus (SARS-CoV), resulted in substantial morbidity, mortality, and economic losses during the 2003 epidemic. While SARS-CoV infection has not recurred to a significant extent since 2003, it still remains a potential threat. Understanding of SARS and development of therapeutic approaches have been hampered by the absence of an animal model that mimics the human disease and is reproducible. Here we show that transgenic mice that express the SARS-CoV receptor (human angiotensin-converting enzyme 2 [hACE2]) in airway and other epithelia develop a rapidly lethal infection after intranasal inoculation with a human strain of the virus. Infection begins in airway epithelia, with subsequent alveolar involvement and extrapulmonary virus spread to the brain. Infection results in macrophage and lymphocyte infiltration in the lungs and upregulation of proinflammatory cytokines and chemokines in both the lung and the brain. This model of lethal infection with SARS-CoV should be useful for studies of pathogenesis and for the development of antiviral therapies.

Severe Feto-Placental Abnormalities Precede the Onset of Hypertension and Proteinuria in a Mouse Model of Preeclampsia

Abstract Preeclampsia is a prevalent and potentially devastating disorder of pregnancy. Characterized by a sudden spike in blood pressure and urinary protein levels, it is associated with significant obstetric complications. BPH/5 is an inbred mouse model of preeclampsia with borderline hypertension before pregnancy. BPH/5 mice develop hypertension, proteinuria, and endothelial dysfunction during late gestation (after E14.5). We hypothesized that BPH/5 mice might exhibit early feto-placental abnormalities before the onset of maternal disease. All placental cell lineages were present in BPH/5 mice. However, the fetal and placental weights were reduced, with abnormalities in all the placental zones observed starting early in gestation (E9.5-E12.5). The fractional area occupied by the junctional zone was significantly reduced at all gestational timepoints. Markedly fewer CDKN1C-stained trophoblasts were seen invading the proximal decidual zone, and this was accompanied by reductions in Cdkn1c gene expression. Trophoblast giant cell morphology and cytokeratin staining were not altered, although the mRNA levels of several giant cell-specific markers were significantly downregulated. The labyrinth layer displayed decreased branching morphogenesis of endothelial cells, with electron microscopy evidence of attenuated trophoblast layers. The maternal decidual arteries showed increased wall-to-lumen ratios with persistence of actin-positive smooth muscle cells. These changes translated into dramatically increased vascular resistance in the uterine arteries, as measured by pulse-wave Doppler. Collectively, these results support the hypothesis that defects at the maternal-fetal interface are primary causal events in preeclampsia, and further suggest the BPH/5 model is important for investigations of the underlying pathogenic mechanisms in preeclampsia.

Mice defective in Trpm6 show embryonic mortality and neural tube defects

The syndrome of hypomagnesemia with secondary hypocalcemia is caused by defective TRPM6. This protein is an ion channel that also contains a kinase in its C-terminus. It is usually diagnosed in childhood and, without treatment with supplemental Mg, affected children suffer from mental retardation, seizures and retarded development. We developed a mouse lacking Trpm6 in order to understand in greater detail the function of this protein. In contrast to our expectations, Trpm6(-/-) mice almost never survived to weaning. Many mice died by embryonic day 12.5. Most that survived to term had neural tube defects consisting of both exencephaly and spina bifida occulta, an unusual combination. Feeding dams a high Mg diet marginally improved offspring survival to weaning. The few Trpm6(-/-) mice that survived were fertile but matings between Trpm6(-/-) mice produced no viable pregnancies. Trpm6(+/-) mice had normal electrolytes except for modestly low plasma [Mg]. In addition, some Trpm6(+/-) mice died prematurely. Absence of Trpm6 produces an apparently different phenotype in mice than in humans. The presence of neural tube defects identifies a previously unsuspected role of Trpm6 in effecting neural tube closure. This genetic defect produces one of very few mouse models of spina bifida occulta. These results point to a critical role of Trpm6 in development and suggest an important role in neural tube closure.

Autograft-derived spinal cord mass following olfactory mucosal cell transplantation in a spinal cord injury patient

Over the last decade, human cell transplantation and neural stem cell trials have examined the feasibility and safety of these potential therapies for treatment of a variety of neurological disorders. However, significant safety concerns have surrounded these trials due to the possibility of ectopic, uncontrolled cellular growth and tumor formation. The authors present the case of an 18-year-old woman who sustained a complete spinal cord injury at T10-11. Three years after injury, she remained paraplegic and underwent olfactory mucosal cell implantation at the site of injury. She developed back pain 8 years later, and imaging revealed an intramedullary spinal cord mass at the site of cell implantation, which required resection. Intraoperative findings revealed an expanded spinal cord with a multicystic mass containing large amounts of thick mucus-like material. Histological examination and immunohistochemical staining revealed that the mass was composed mostly of cysts lined by respiratory epithelium, submucosal glands with goblet cells, and intervening nerve twigs. This is the first report of a human spinal cord mass complicating spinal cord cell transplantation and neural stem cell therapy. Given the prolonged time to presentation, safety monitoring of all patients with cell transplantation and neural stem cell implantation should be maintained for many years.

Toward an Understanding of Dural Ectasia: A Light Microscopy Study in a Murine Model of Marfan Syndrome

Study Design. Light microscopy study of the lumbar spinal meninges of a murine model of Marfan syndrome. Objective. Characterize the pathology of the lumbosacral meninges in Marfan syndrome, seeking clues to the pathophysiology behind dural ectasia. Summary of Background Data. Dural ectasia is common in Marfan syndrome. The etiology of dural ectasia is unknown, but is conjectured to be related to constitutionally weak spinal dura. The morphology of the lumbar dura in Marfan syndrome has not been described, as it has in other tissues affected by Marfan syndrome. Methods. The lumbosacral dura were removed from three 4-month-old mice, 1 homozygote (mgR/mgR) expressing the murine Marfan phenotype, 1 heterozygote expressing wild-type phenotype, and 1 homozygote wildtype. Hematoxylin and eosin, elastochrome, and immunohistochemical stains against activated transforming growth factor β, gelatinase A (matrix metalloproteinase-2), and gelatinase-B (matrix metalloproteinase-9) were used for light microscopic evaluation. Results. No difference was noted between the heterozygous and wild-type mice in dural connective tissue morphology. The homozygote (mgR/mgR) had a marked attenuation of the dura overall, in addition to elastic fiber disorganization. The homozygote dura also stained for increased presence of activated transforming growth factor β and matrix metalloproteinase-2, but not matrix metalloproteinase-9. Conclusions. These morphologic findings in the Marfan phenotype mouse mimic the findings of disordered elastic-fibers in other Marfan tissues and demonstrate gross attenuation of the tissue architecture, corroborating the theory that dural ectasia in Marfan syndrome results from hydrostatic pressure on weakened dura. These changes may be due in part to transforming growth factor β overactivation and gelatinase-A–mediated elastolysis and collagen breakdown.

Homozygous variegate porphyria: an evolving clinical syndrome.

Variegate porphyria is one of the most frequently encountered genetic conditions in South Africa. It is inherited as an autosomal dominant disease and in excess of 300 heterozygous cases have been studied by the Cape Town unit. Despite this, the homozygous condition has not previously been encountered in South Africa. We report two cases of homozygous variegate porphyria, one of whom represents the first South African case. We delineate a syndrome principally characterized by growth retardation, developmental delay, epileptic seizures, photosensitivity and an abnormal porphyrin excretion pattern. In addition we describe, in one case, two features not previously reported: skin disease in areas unexposed to light and a severe sensory neuropathy which may account at least in part for the hand deformities of this disorder.

FSH Receptor (FSHR) Expression in Human Extragonadal Reproductive Tissues and the Developing Placenta, and the Impact of Its Deletion on Pregnancy in Mice

ABSTRACT Expression and function of the follicle-stimulating hormone receptor (FSHR) in females were long thought to be limited to the ovary. Here, however, we identify extragonadal FSHR in both the human female reproductive tract and the placenta, and test its physiological relevance in mice. We show that in nonpregnant women FSHR is present on: endothelial cells of blood vessels in the endometrium, myometrium, and cervix; endometrial glands of the proliferative and secretory endometrium; cervical glands and the cervical stroma; and (at low levels) stromal cells and muscle fibers of the myometrium. In pregnant women, placental FSHR was detected as early as 8–10 wk of gestation and continued through term. It was expressed on: endothelial cells in fetal portions of the placenta and the umbilical cord; epithelial cells of the amnion; decidualized cells surrounding the maternal arteries in the maternal decidua; and the stromal cells and muscle fibers of the myometrium, with particularly strong expression at term. These findings suggest that FSHR expression is upregulated during decidualization and upregulated in myometrium as a function of pregnancy. The presence of FSHR in the placental vasculature suggests a role in placental angiogenesis. Analysis of genetically modified mice in which Fshr is lacking in fetal portions of the placenta revealed adverse effects on fetoplacental development. Our data further demonstrate FSHB and CGA mRNAs in placenta and uterus, consistent with potential local sources of FSH. Collectively, our data suggest heretofore unappreciated roles of extragonadal FSHR in female reproductive physiology.