MGRN1 depletion promotes intercellular adhesion in melanoma by upregulation of E-cadherin and inhibition of CDC42

Mahogunin Ring Finger 1 is an E3-ubiquitin ligase encoded by the color gene MGRN1. Our previous in vitro and in vivo studies demonstrated that Mgrn1 deletion in mouse melanoma cells induced cell differentiation and adhesion, and decreased cell motility and invasion on collagen I, and lung colonization in an in vivo model. Here, we investigated the role of MGRN1 on human melanoma cell morphology, adhesion and expression of genes/proteins involved in an EMT-like transition. We demonstrated that wild-type BRAF human melanoma cells adopted a clustering-like morphology on collagen I, with permanent MGRN1 abrogation resulting in bigger cell clusters. Enhanced intercellular adhesion was mostly mediated by induction of E-cadherin and higher co-localization with β-catenin. Transcriptional upregulation of E-cadherin likely occurred through downregulation of the ZEB1 repressor. Finally, pulldown assays showed reduced activation of CDC42 in the absence of MGRN1, which was reverted after E-cadherin silencing. Overall, these findings highlight a new MGRN1-dependent pathway regulating melanoma cell shape, motility, and invasion potential.

Donor characteristics that are associated with survival in liver transplant recipients older than 70 years with grafts

INTRODUCTION

The use of grafts from donors older than 70 years of age is increasing due to the decrease in the number of donors and the increase in waiting list patients.

MATERIAL AND METHODS

We undertook a univariate and multivariate analysis of 980 adult recipients of whole liver grafts, 129 of them from donors aged 70 years or older.

RESULTS

No differences were found in patient survival compared with recipients of younger grafts. There were no higher rates of rejection, vascular or biliary complications, postoperative bleeding, or infections, but older grafts were associated with graft dysfunction (P = .01) and a higher frequency of postoperative refractory ascites (P = .007), but without a greater need for retransplantation. As graft-associated factors, the joint presence in the donor of diabetes (P = .00; confidence interval [CI] = 0.04-0.117), hypertension (P = .00; CI = 0.22-0.39), and weight of more than 90 kg (P = .031; CI = 0.05-0.104) were suggestive of poor prognostic factors in recipient survival. Survival in hepatitis C virus (HCV) recipients or recipients aged older than 60 years was worse with donors aged older than 70 years, although not significantly so. With grafts from donors aged older than 80 years (n = 15), although patient survival rate was good (70% at 10 years), there was a higher rate of retransplantation (20%) and the early mortality rate was 13.3%.

CONCLUSIONS

Use of grafts from donors aged older than 70 years is safe, with similar survival to patients with younger grafts. The appearance of initial dysfunction with prolonged ascites may be due to a delay in reaching a correct functionality, but was not associated with increased mortality, complications, or need for retransplantation. It should also be avoided in recipients older than 60 years or with HCV. Grafts older than 80 years were associated with a good long-term patient survival but at the expense of a higher rate of retransplantation. However, it helps to reduce the time on the waiting list and, thus, mortality. We noted decreased survival associated with donor hypertension, diabetes, and obesity, so these donors should be selected more rigorously.

The 5,6-dihydroxyindole-2-carboxylic acid (DHICA) oxidase activity of human tyrosinase

Melanin synthesis in mammals is catalysed by at least three enzymic proteins, tyrosinase (monophenol dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) and tyrosinase-related proteins (tyrps) 1 and 2, whose genes map to the albino, brown and slaty loci in mice, respectively. Tyrosinase catalyses the rate-limiting generation of L-dopaquinone from L-tyrosine and is also able to oxidize L-dopa to L-dopaquinone. Conversely, mouse tyrp1, but not tyrosinase, catalyses the oxidation of the indolic intermediate 5,6-dihydroxyindole-2-carboxylic acid (DHICA) into the corresponding 5,6-indolequinone-2-carboxylic acid, thus promoting the incorporation of DHICA units into eumelanin. The catalytic activities of the human melanogenic enzymes are still debated. TYRP1 has been reported to lack DHICA oxidase activity, whereas tyrosinase appears to accelerate DHICA consumption, thus raising the question of DHICA metabolism in human melanocytes. Here we have used two different approaches, comparison of the catalytic activities of human melanocytic cell lines expressing the full set of melanogenic enzymes or deficient in TYRP1, and transient expression of TYR and tyr genes in COS7 cells, to demonstrate that human tyrosinase actually functions as a DHICA oxidase, as opposed to the mouse enzyme. Therefore, human tyrosinase displays a broader substrate specificity than its mouse counterpart, and might be at least partially responsible for the incorporation of DHICA units into human eumelanins.

[Benign esophageal strictures in toddlers and pre-school children. Results of endoscopic dilation]

BACKGROUND

The most frequent causes of dysphagia in children are benign strictures and therefore require special consideration.

OBJECTIVE

To evaluate safety and efficacy of endoscopic dilation in children with benign esophageal strictures. MATERIAL-METHODS-RESULTS: Twenty four consecutive children of 1.5 to 5.5 years (mean 3.5), with benign esophageal strictures were evaluated in a prospective manner over a 3-year period. The most frequent causes of esophageal stricture were caustic ingestion (Group A) and in Group B were included other benign strictures. Dilation was done on a weekly base using Savary-Gilliard bougies and was considered adequate, if the esophageal lumen could be dilated to 11 mm with complete relief of dysphagia. Of the 24 patients, 16 had corrosive strictures, 6 complications of gastroesophageal reflux and 2 post surgical strictures. Group A required a significantly higher number of session (14.3 +/- 10.84 vs 7.0 +/- 2.94 p: > 0.05), less free-time dysphagia (1.1 +/- 0.39 vs 2.6 +/- 0.95 months p: < 0.01) and a higher number of recurrences (3.12 +/- 1.12 vs 1.25 +/- 0.95 p: < 0.01). Two esophageal perforations occurred during a total of 292 dilation sessions (0.68%). There was one fatality.

CONCLUSIONS

Benign esophageal strictures in children can be treated effectively and with acceptable safety by means of endoscopic dilation.

Squamous cell carcinoma, malignant melanoma and malignant fibrous histiocytoma arising in burn scars

The most common cancer arising from an old burn scar is squamous cell carcinoma, while malignant melanoma is rare. There are only four reports in the literature on the combination of the more common tumour with a malignant melanoma and only two cases of malignant fibrous histiocytoma alone. This paper reports the first occurrence of the combination of all three types of cancer in burn scars of the same patient. The factors that promote malignant transformation, such as immunological factors and karyotype, are discussed. We also performed an immunohistochemical study using anti-p53 antibodies.

Reconstruction of the tragus after tumour excision

Reconstruction of the tragus is very difficult to perform and most techniques are described for the treatment of microtia where remnants of ear are used. The goal always consists in achieving a prominence that covers the canal. We present a novel and safe method, based on the vascularity of the lobule, that also provides a good appearance.

Coexistence of two chromatin structures in sperm nuclei of the bivalve mollusc Protothaca thaca

The chromatin of the spermatozoa from the bivalve mollusc Protothaca thaca, has a peculiar composition in which coexist core histones with sperm-specific proteins H1 and Pt1, the latter being a protein exhibiting features intermediate between histones and protamines. In this paper, we report an analysis of chromatin organization using micrococcal nuclease digestion, salt fractionation of soluble chromatin derived from nuclease digestion and crosslinking experiments. The results obtained indicate that it is possible to obtain two types of chromatin, one which is soluble, more accessible to micrococcal nuclease action and which does not contain Pt1, and another insoluble type, more resistant to micrococcal nuclease and enriched in protein Pt1. The crosslinking experiments show that the protein Pt1 interacts with itself and with core histones but not with sperm-specific H1. These results have led us to propose a special structural arrangement for this chromatin. Based in the data reported here we propose the coexistence in the genome of P. thaca of two interspersed chromatin domains, one nucleosomal and the other nonnucleosomal containing protein Pt1.

Nucleosomal organization of chromatin in sperm nuclei of the bivalve mollusc Aulacomya ater

The sperm nuclei of Aulacomya ater, family Mitylidae, contain three proteins (X, Aa5 and Aa6) which are specific to this cell type coexisting with a set of five somatic-type histones. Information about the chromatin structure resulting from this kind of association is scarce. Therefore, we have probed the structure of this sperm chromatin through digestion with micrococcal nuclease in combination with salt fractionation. The data obtained have allowed us to propose a nucleosomal arrangement for this chromatin. However, two types of nucleosomes would be present in agreement with their protein components.

[Alteration of the erythrocyte membrane skeleton by oxidative damage]

In order to assess the alterations mediated by oxidative agents in physiological and pathological conditions, polyacrylamide gel electrophoresis was performed with dodecyl sodium sulphate of red cell membranes previously subjected to oxidative stress with malonyl dialdehyde generation. The alterations of the normal proteic profile observed were related to the concentration and time of exposure to hydrogen peroxide. The red cell membranes were also treated with the following: (1) increasing doses of hydrogen peroxide with and without peroxidase, and (2) supernatant of neutrophils stimulated with digitonin or activated zymosan. No alterations of the membrane skeleton were appreciated under H2O2 treatment; on the contrary, severe alterations appeared after incubation with H2O2 + peroxidase, giving rise to several peptides with different molecular weight. Striking derangement of the proteic structure was induced by activated neutrophils, which was ascribed to release of proteolytic enzymes and activated oxygen compounds.

The interaction of the histone H1-related protein phi 0 with chromatin

Protein phi 0 is a unique protein which is present in the sperm of the sea cucumber, Holothuria tubulosa. It associates with histones, but its physiological role is unknown. From its amino acid composition and sequence, protein phi 0 can be considered as an H1-related protein. In this paper, we have studied its interaction with chicken erythrocyte chromatin particles of different complexity, from core particles to polynucleosomes. Addition of protein phi 0 results in marked chromatin insolubilization. The higher the molecular weight of the chromatin fragment, the lower is the phi 0/nucleosome molar ratio at which precipitation occurs, so that complete insolubilization of polynucleosomes is achieved at a phi 0/nucleosome molar ratio which is identical to that found in mature H. tubulosa spermatozoa. We have also found that the interaction of protein phi 0 with chromatin is cooperative. These findings contribute to clarification of the peculiar physico-chemical properties shown by H. tubulosa sperm chromatin and the role played by the phi 0 protein.

Heterogeneity of the histone-containing chromatin in sea cucumber spermatozoa. Distribution of the basic protein phi 0 and absence of non-histone proteins

Nuclei of spermatozoa of the sea cucumber Holothuria tubulosa contain the five somatic-type histones plus a sperm-specific histone H1 and a unique basic protein phi 0, which is related to H1 in amino acid composition. No proteins of the High Mobility Group (HMG) type have been detected. The structure of this chromatin has been probed nuclease digestion. Its behaviour is anomalous, since two distinct fractions of chromatin are recovered from these spermatozoa, which differ either in the presence or absence of the sperm-specific proteins H1 and phi 0. This heterogeneous distribution is not found in conventional materials, such as calf thymus or chicken erythrocytes. Proteins H1 and phi 0 are not uniformly distributed and may be localized in special regions of chromatin. Fragments containing long stretches of nucleosomes lacking both proteins can be recovered. At the same time, the chromatin fractions which contain these two proteins are shown to be less soluble. When an extensive digestion of chromatin is carried out yielding only nucleosomes and small oligomers, the H1 and phi 0 proteins redistribute themselves on chromatin, the two proteins acting in a cooperative fashion in this process. Cross-linking experiments carried out in whole cells indicate a proximity of phi 0 and H1, whereas no crosslinks have been detected between phi 0 and any of the four nucleosomal histones. The phi 0 protein may thus play a role similar to histone H1 and be only loosely associated with nucleosomal histones, but contribute to the structuration of chromatin during spermiogenesis.