Embryonic expression of the tumor-associated PAX3-FKHR fusion protein interferes with the developmental functions of Pax3

A unique chromosomal translocation involving the genes PAX3 and FKHR is characteristic of most human alveolar rhabdomyosarcomas. The resultant chimeric protein fuses the PAX3 DNA-binding domains to the transactivation domain of FKHR, suggesting that PAX3-FKHR exerts its role in alveolar rhabdomyosarcomas through dysregulation of PAX3-specific target genes. Here, we have produced transgenic mice in which PAX3-FKHR expression was driven by mouse Pax3 promoter/enhancer sequences. Five independent lines expressed PAX3-FKHR in the dorsal neural tube and lateral dermomyotome. Each line exhibited phenotypes that correlated with PAX3-FKHR expression levels and predominantly involved pigmentary disturbances of the abdomen, hindpaws, and tail, with additional neurological related alterations. Phenotypic severity could be increased by reducing Pax3 levels through matings with Pax3-defective Splotch mice, and interference between PAX3 and PAX3-FKHR was apparent in transcription reporter assays. These data suggest that the tumor-associated PAX3-FKHR fusion protein interferes with normal Pax3 developmental functions as a prelude to transformation.

The nuclear receptor PXR is a lithocholic acid sensor that protects against liver toxicity

The pregnane X receptor (PXR) is the molecular target for catatoxic steroids such as pregnenolone 16α-carbonitrile (PCN), which induce cytochrome P450 3A (CYP3A) expression and protect the body from harmful chemicals. In this study, we demonstrate that PXR is activated by the toxic bile acid lithocholic acid (LCA) and its 3-keto metabolite. Furthermore, we show that PXR regulates the expression of genes involved in the biosynthesis, transport, and metabolism of bile acids including cholesterol 7α-hydroxylase (Cyp7a1) and the Na+-independent organic anion transporter 2 (Oatp2). Finally, we demonstrate that activation of PXR protects against severe liver damage induced by LCA. Based on these data, we propose that PXR serves as a physiological sensor of LCA, and coordinately regulates gene expression to reduce the concentrations of this toxic bile acid. These findings suggest that PXR agonists may prove useful in the treatment of human cholestatic liver disease.

Neural fate of seen and unseen faces in visuospatial neglect: A combined event-related functional MRI and event-related potential study

To compare neural activity produced by visual events that escape or reach conscious awareness, we used event-related MRI and evoked potentials in a patient who had neglect and extinction after focal right parietal damage, but intact visual fields. This neurological disorder entails a loss of awareness for stimuli in the field contralateral to a brain lesion when stimuli are simultaneously presented on the ipsilateral side, even though early visual areas may be intact, and single contralateral stimuli may still be perceived. Functional MRI and event-related potential study were performed during a task where faces or shapes appeared in the right, left, or both fields. Unilateral stimuli produced normal responses in V1 and extrastriate areas. In bilateral events, left faces that were not perceived still activated right V1 and inferior temporal cortex and evoked nonsignificantly reduced N1 potentials, with preserved face-specific negative potentials at 170 ms. When left faces were perceived, the same stimuli produced greater activity in a distributed network of areas including right V1 and cuneus, bilateral fusiform gyri, and left parietal cortex. Also, effective connectivity between visual, parietal, and frontal areas increased during perception of faces. These results suggest that activity can occur in V1 and ventral temporal cortex without awareness, whereas coupling with dorsal parietal and frontal areas may be critical for such activity to afford conscious perception.

Speciation through homoploid hybridization between allotetraploids in peonies (Paeonia)

Phylogenies of Adh1 and Adh2 genes suggest that a widespread Mediterranean peony, Paeonia officinalis, is a homoploid hybrid species between two allotetraploid species, Paeonia peregrina and a member of the Paeonia arietina species group. Three phylogenetically distinct types of Adh sequences have been identified from both accessions of P. officinalis, of which two types are most closely related to the two homoeologous Adh loci of the P. arietina group and the remaining type came from one of the two Adh homoeologs of P. peregrina. The other Adh homoeolog of P. peregrina was apparently lost from the hybrid genome, possibly through backcrossing with the P. arietina group. This is a documentation of homoploid hybrid speciation between allotetraploid species in nature. This study suggests that hybrid speciation between allotetraploids can occur without an intermediate stage of genome diploidization or a further doubling of genome size.

Alterations in the regulation of androgen-sensitive Cyp 4a monooxygenases cause hypertension

Hypertension is a leading cause of cardiovascular, cerebral, and renal disease morbidity and mortality. Here we show that disruption of the Cyp 4a14 gene causes hypertension, which is, like most human hypertension, more severe in males. Male Cyp 4a14 (−/−) mice show increases in plasma androgens, kidney Cyp 4a12 expression, and the formation of prohypertensive 20-hydroxyarachidonate. Castration normalizes the blood pressure of Cyp 4a14 (−/−) mice and minimizes Cyp 4a12 expression and arachidonate ω-hydroxylation. Androgen replacement restores hypertensive phenotype, Cyp 4a12 expression, and 20-hydroxy-arachidonate formation. We conclude that the androgen-mediated regulation of Cyp 4a arachidonate monooxygenases is an important component of the renal mechanisms that control systemic blood pressures. These results provide direct evidence for a role of Cyp 4a isoforms in cardiovascular physiology, establish Cyp 4a14 (−/−) mice as a monogenic model for the study of cause/effect relationships between blood pressure, sex hormones, and P450 ω-hydroxylases, and suggest the human CYP 4A homologues as candidate genes for the analysis of the genetic and molecular basis of human hypertension.

An Arabidopsis VPS45p Homolog Implicated in Protein Transport to the Vacuole1

The Sec1p family of proteins is required for vesicle-mediated protein trafficking between various organelles of the endomembrane system. This family includes Vps45p, which is required for transport to the vacuole in yeast (Saccharomyces cerevisiae). We have isolated a cDNA encoding a VPS45 homolog from Arabidopsis thaliana (AtVPS45). The cDNA is able to complement both the temperature-sensitive growth defect and the vacuolar-targeting defect of a yeast vps45 mutant, indicating that the two proteins are functionally related. AtVPS45p is a peripheral membrane protein that associates with microsomal membranes. Sucrose-density gradient fractionation demonstrated that AtVPS45p co-fractionates with AtELP, a potential vacuolar protein sorting receptor, implying that they may reside on the same membrane populations. These results indicate that AtVPS45p is likely to function in the transport of proteins to the vacuole in plants.

Nutrient Load Reduction: Challenges facing the Chesapeake 2000 Agreement

The Chesapeake Bay is the largest estuary in the United States supporting a complex ecosystem that sustains many habitats and the organisms that depend on them. The bay also supports economic, recreational, and cultural activities to over 16 million people residing in the watershed. Changes within the watershed have caused excessive levels of nutrients, mainly nitrogen and phosphorous, to pollute the bay. The Chesapeake Bay Program, guided by a complex agreement, was created to address these and other issues and oversee the restoration of the bay. The most recent version of this agreement, the Chesapeake 2000, declares its continued commitment to restore the bay with over 100 goals to be met by the year 2010. Reports show that although intensive efforts have been made to promote nutrient reduction, very little reduction has actually resulted. This project described these efforts. The final results reveal obstacles affecting progress, shortcomings to current approaches and possible solutions for future implementation.