Novel Deleterious Mutation in Steroid-5α-Reductase-2 in 46, XY Disorders of Sex Development: Case Report Study.

Background: Steroid-5α-reductase-2 (SRD5A2) and 17ß-hydroxysteroid dehydrogenase type 3 (17ß-HSD3) enzyme deficiencies are frequent causes of 46, XY disorder of sex development (46, XY DSD), where an infant with 46, XY has a female phenotype. We assessed the hydroxy-steroid-17ß-dehydrogenase-3 (HSD17B3)and SRD5A2 genes in twenty Iranian phenotypic females with 46,XY DSD. Materials and methods: All exons in HSD17B3 and SRD5A2 genes were subjected to PCR amplification followed by sequencing. Results: Of 20 identified 46, XY DSD patients, one had a homozygous missense 17ß-HSD3 mutation Ser65Leu (c.194C > T). We found 1 SRD5A2 novel homozygous missense mutation of Tyr242Asp (c.891T > G) in exon 5, which in-silico analyses revealed that this mutation may have deleterious impact on ligand binding site of SRD5A2 protein. Three other individuals harbored 17ß-HSD3 deficiencies without identified mutations. Conclusions: SRD5A2 and 17ß-HSD3 mutations are found in 10% of 46, XY DSD Iranian patients.

The role of BRAF V600E mutation as a potential marker for prognostic stratification of papillary thyroid carcinoma: a long-term follow-up study.

Abstract Papillary carcinoma is the most prevalent malignancy of thyroid gland, and its incidence has been recently increased. The BRAF(V600E) mutation is the most frequent genetic alteration in papillary thyroid carcinoma (PTC). The role of BRAF(V600E) mutation as a potential prognostic factor has been controversially reported in different studies, with short-term follow-up. In this study, we evaluated the role of BRAF(V600E) mutation as a potential marker for prognostic stratification of patients with PTC in long-term follow-up. We studied 69 PTC patients with a mean follow-up period of 63.9 months (median: 60 m). The BRAF(V600E) mutation was analyzed by PCR-single-strand conformational polymorphism and sequencing. The correlation between the presence or absence of the BRAF(V600E) mutation, clinicopathological features and prognosis of PTC patients were studied. The BRAF(V600E) mutation was found in 28 of 69 (40.6%) PTC patients, and it was significantly more frequent in older patients (p < 0.001), in advanced tumor stages (p = 0.006) and in patients with history of radiation exposure (p = 0.037). Incomplete response to treatment in PTC patients was significantly correlated with certain clinicopathological characteristics (follow-up time, distant metastases, advanced stage, first thyroglobulin (fTg) level, history of reoperation and external radiotherapy and delay in iodine therapy) but it was not related to the presence of BRAF(V600E) mutation. Prevalence of BRAF(V600E) mutation was 40.6% in patients with papillary thyroid cancer in northeast of Iran. The BRAF(V600E) mutation was associated with older age and advanced tumor stage but was not correlated with incomplete response during follow-up.

Proteomic screen reveals Fbw7 as a modulator of the NF-κB pathway.

Fbw7 is a ubiquitin-ligase that targets several oncoproteins for proteolysis, but the full range of Fbw7 substrates is not known. Here we show that by performing quantitative proteomics combined with degron motif searches, we effectively screened for a more complete set of Fbw7 targets. We identify 89 putative Fbw7 substrates, including several disease-associated proteins. The transcription factor NF-κB2 (p100/p52) is one of the candidate Fbw7 substrates. We show that Fbw7 interacts with p100 via a conserved degron and that it promotes degradation of p100 in a GSK3ß phosphorylation-dependent manner. Fbw7 inactivation increases p100 levels, which in the presence of NF-κB pathway stimuli, leads to increased p52 levels and activity. Accordingly, the apoptotic threshold can be increased by loss of Fbw7 in a p100-dependent manner. In conclusion, Fbw7-mediated destruction of p100 is a regulatory component restricting the response to NF-κB2 pathway stimulation.

Mutational analysis of uroporphyrinogen III cosynthase gene in Iranian families with congenital erythropoietic porphyria.

Porphyrias are rare metabolic hereditary diseases originating from defects in specific enzymes involved in the heme biosynthesis pathway. Congenital erythropoietic porphyria (CEP) is the rarest autosomal recessive porphyria resulting from a deficiency of uroporphyrinogen III cosynthase (UROS), the fourth enzyme in heme biosynthesis. CEP leads to an excessive production and accumulation of type Ι porphyrins in bone marrow, skin and several other tissues. Clinical manifestations are presented in childhood with severe cutaneous photosensitivity, blistering, scarring and deformation of the hands and the loss of eyebrows and eyelashes. Less than 200 cases of CEP have been reported to date. Four CEP patients and their family members were studied for the first time in Iran. A missense mutation in the UROS gene was identified in this family. A, T to C change at nucleotide 34313, leading to a substitution of Leucine by Proline at codon 237, was observed in the homozygous state in these 4 patients and heterozygous state in their parents. Our data from the Iranian population emphasizes the importance of codon 237 alone, given the rarity of this disease. This fact can be taken into consideration in the mutational analysis of UROS. This work emphasizes the advantages of molecular genetic techniques as diagnostic tools for the detection of clinically asymptomatic heterozygous mutation carriers as well as CEP within families.

Nucleolar organization, growth control and cancer.

The nucleolus is a dynamic region of the nucleus that is disassembled and reformed each cell cycle and whose size is correlated with cell growth rate. Nucleolar size is a prognostic measure of cancer disease severity and increasing evidence suggests a causative role of nucleolar lesions in many cancers. In recent work (Shiue et al. Oncogene 28, 1833-42, 2009) we showed that the c-Myc oncoprotein induces changes in the higher order structure of rDNA chromatin in the nucleolus of growth stimulated quiescent rat cells. Here we show that c-Myc induces similar changes in human cells, that c-Myc plays a role in the overall structural integrity of the nucleolus and that c-Myc and its antagonistic partner Mad1 interact to program the epigenetic status of rDNA chromatin. These changes are discussed in relation to current knowledge about nucleolar structure as well as the organization of chromosomes and transcription factories in nuclear regions outside the nucleolus.

Clinicopathological significance of E-cadherin, ß-catenin and p53 expression in gastric adenocarinoma.

BACKGROUND: E-cadherin/catenin complexes exert a role in cell adhesion. ß-catenin is a key player in Wnt signaling pathway in gastric cancer. P53 is a tumor suppressor gene which also regulates apoptosis. We assessed the expression of E-cadherin, ß-catenin and p53 in gastric adenocarcinoma, and their correlations with clinicopathological features. METHODS: Fifty six formalin-fixed, paraffin-embedded archival specimens of gastric adenocarcinoma were randomly included as cases. Adjacent tumor-free gastric mucosa of different premalignant stages was obtained from the cases. Immunohistochemical staining was performed to assess E-cadherin, ß-catenin and p53 expression. RESULTS: All chronic atrophic gastritis and intestinal metaplasia revealed normal membranous staining. Only one patient with dysplasia had abnormal expression of E-cadherin and ß-Catenin. Abnormal E-cadherin, ß-catenin and p53 expression was found in 50%, 48.2% and 76.8% of cancer specimens respectively. Abnormal expression of E-cadherin was significantly correlated with aberrant ß-catenin expression. Abnormal E-cadherin and ß-catenin expression were significantly correlated with depth of tumor invasion and advanced gastric cancer (p < 0.05), lower degree of differentiation and diffused tumor type (p < 0.001). Node metastasis was not influenced by abnormal expression of E-cadherin and ß-catenin. P53 was not associated with clinicopathological variables. CONCLUSIONS: Abnormal expression of the E-cadherin and ß-catenin were associated with each other and influenced by histogenesis of gastric cancer and malignant behavior of tumor but not significant in premalignant lesions. They are more frequent in diffuse type and associated with advanced gastric cancer. P53 alterations are more frequent in the Iranian population compared with others.

c-Myc associates with ribosomal DNA and activates RNA polymerase I transcription.

The c-Myc oncoprotein regulates transcription of genes that are associated with cell growth, proliferation and apoptosis. c-Myc levels are modulated by ubiquitin/proteasome-mediated degradation. Proteasome inhibition leads to c-Myc accumulation within nucleoli, indicating that c-Myc might have a nucleolar function. Here we show that the proteins c-Myc and Max interact in nucleoli and are associated with ribosomal DNA. This association is increased upon activation of quiescent cells and is followed by recruitment of the Myc cofactor TRRAP, enhanced histone acetylation, recruitment of RNA polymerase I (Pol I), and activation of rDNA transcription. Using small interfering RNAs (siRNAs) against c-Myc and an inhibitor of Myc-Max interactions, we demonstrate that c-Myc is required for activating rDNA transcription in response to mitogenic signals. Furthermore, using the ligand-activated MycER (ER, oestrogen receptor) system, we show that c-Myc can activate Pol I transcription in the absence of Pol II transcription. These results suggest that c-Myc coordinates the activity of all three nuclear RNA polymerases, and thereby plays a key role in regulating ribosome biogenesis and cell growth.

Accumulation of c-Myc and proteasomes at the nucleoli of cells containing elevated c-Myc protein levels.

c-Myc is a predominantly nuclear transcription factor that is a substrate for rapid turnover by the proteasome system. Cancer-related mutations in c-Myc lead to defects in its degradation and thereby contribute to the increase in its cellular level that is associated with the disease. Little is known about the mechanisms that target c-Myc to the proteasomes. By using a GFP fusion protein and live analysis we show that c-Myc shuttles between the nucleus and cytoplasm and thus it could be degraded in either compartment. Strikingly, at elevated levels of expression c-Myc accumulates at nucleoli in some cells, consistent with saturation of a nucleolus-associated degradation system in these cells. This idea is further supported by the observation that proteasome inhibitor treatment causes accumulation of c-Myc at the nucleoli of essentially all cells. Under these conditions c-Myc is relatively stably associated with the nucleolus, as would be expected if the nucleolus functions as a sequestration/degradation site for excess c-Myc. Furthermore, during elevated c-Myc expression or proteasome inhibition, nucleoli that are associated with c-Myc also accumulate proteasomes. c-Myc and proteasomes co-localise in intranucleolar regions distinct from the dense fibrillar component of the nucleolus. Based on these results we propose a model for c-Myc downregulation where c-Myc is sequestered at the nucleoli. Sequestration of c-Myc is accompanied by recruitment of proteasomes and may lead to subsequent degradation.