The Prosensory Function of Sox2 in the Chicken Inner Ear Relies on the Direct Regulation of Atoh1

The proneural gene Atoh1 is crucial for the development of inner ear hair cells and it requires the function of the transcription factor Sox2 through yet unknown mechanisms. In the present work, we used the chicken embryo and HEK293T cells to explore the regulation of Atoh1 by Sox2. The results show that hair cells derive from Sox2-positive otic progenitors and that Sox2 directly activates Atoh1 through a transcriptional activator function that requires the integrity of Sox2 DNA binding domain. Atoh1 activation depends on Sox transcription factor binding sites (SoxTFBS) present in the Atoh1 3′ enhancer where Sox2 directly binds, as shown by site directed mutagenesis and chromatin immunoprecipitation (ChIP). In the inner ear, Atoh1 enhancer activity is detected in the neurosensory domain and it depends on Sox2. Dominant negative competition (Sox2HMG-Engrailed) and mutation of the SoxTFBS abolish the reporter activity in vivo. Moreover, ChIP assay in isolated otic vesicles shows that Sox2 is bound to the Atoh1 enhancer in vivo. However, besides activating Atoh1, Sox2 also promotes the expression of Atoh1 negative regulators and the temporal profile of Atoh1 activation by Sox2 is transient suggesting that Sox2 triggers an incoherent feed-forward loop. These results provide a mechanism for the prosensory function of Sox2 in the inner ear. We suggest that sensory competence is established early in otic development through the activation of Atoh1 by Sox2, however, hair cell differentiation is prevented until later stages by the parallel activation of negative regulators of Atoh1 function

Uruguayan experience with cryopreserved arterial homografts

INTRODUCTION: We analyzed the Uruguayan experience with cryopreserved arterial homografts. We studied 55 medical records in the period from June 9, 2000 to April 7, 2007, including 41 from males and 14 from females, ranging from 36-78 years of age. The clinical indications were as follows: Group 1, revascularization of infrainguinal atherosclerotic occlusive disease by bypass due to the lack of availability of a suitable vein (n = 35); Group 2, substitution of an infected prosthetic grafts (n = 15); and Group 3, arteriovenous fistula (AVF) after failure of previous prosthetic loops by repeated thrombosis and/or infection in the absence of a vein (n = 5). RESULTS: Among Group 1, primary and secondary patency rates were 61% and 71%, respectively at 1 year with 15 complications, 3 infections, 8 thromboses, 2 aneurysms, 1 homograft degradation, and 1 death related to surgery. Among Group 2, the primary and secondary patency rates were 71% and 79%, respectively, at 1 year with 6 patients experiencing complications. Group 3 did not have complications with a primary patency rate of 67% at 1 year. CONCLUSIONS: The use of cryopreserved arterial homografts is a valid, accessible, and safe alternative in complicated vascular situations. In our country, it is a technology to consider for patients with critical limb ischemia, when the risk of a major amputation is high and it is not possible to have a suitable vein or prosthetic bypass. It can be an excellent alternative for the substitution of infected synthetic bypasses, especially to substitute in situ for an infected aortic graf

S-nitrosothiol depletion in amyotrophic lateral sclerosis

Recent data suggest that either excessive or deficient levels of protein S-nitrosylation may contribute to disease. Disruption of S-nitrosothiol (SNO) homeostasis may result not only from altered nitric oxide (NO) synthase activity but also from alterations in the activity of denitrosylases that remove NO groups. A subset of patients with familial amyotrophic lateral sclerosis (ALS) have mutations in superoxide dismutase 1 (SOD1) that increase the denitrosylase activity of SOD1. Here, we show that the increased denitrosylase activity of SOD1 mutants leads to an aberrant decrease in intracellular protein and peptide S-nitrosylation in cell and animal models of ALS. Deficient S-nitrosylation is particularly prominent in the mitochondria of cells expressing SOD1 mutants. Our results suggest that SNO depletion disrupts the function and/or subcellular localization of proteins that are regulated by S-nitrosylation such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and thereby contributes to ALS pathogenesis. Repletion of intracellular SNO levels with SNO donor compounds rescues cells from mutant SOD1-induced death. These results suggest that aberrant depletion of intracellular SNOs contributes to motor neuron death in ALS, and raises the possibility that deficient S-nitrosylation is a general mechanism of disease pathogenesis. SNO donor compounds may provide new therapeutic options for diseases such as ALS that are associated with deficient S-nitrosylation