Familial breast/ovarian cancer and BRCA1/2 genetic screening: the role of immunohistochemistry as an additional method in the selection of patients.

Only 20-25% of families screened for BRCA1/2 mutations are found positive. Because only a positive result is informative, we studied the role of BRCA1/2 immunohistochemistry as an additional method for patient selection. From 53 high-risk-affected probands, 18 (34%) had available paraffin blocks of their tumors and were selected for this study. Mutation screening was done by conformation-sensitive gel electrophoresis and multiplex ligation-dependent probe amplification. For immunohistochemistry, 21 neoplastic specimens (15 breast carcinomas, 5 ovary neoplasms, and 1 rectal adenocarcinoma) were analyzed with BRCA1 (monoclonal antibody, Ab-1, oncogene) and BRCA2 (polyclonal antibody, Ab-2, oncogene) antibodies. Absence of the BRCA1 protein was confirmed in negative tumors by Western blotting. Seven patients were positive for BRCA1/2 mutations: 5 for BRCA1 and 2 for BRCA2. Four out of five positive patients had tumors negative for BRCA1 immunostaining, and the remaining 13 BRCA1-negative patients had positive BRCA1 immunostaining in all tumor samples. Sensitivity to predict for BRCA1 mutation carriers was 80%, and specificity was 100%, with a positive predictive value of 100% and a negative predictive value of 93%. This correlation was statistically significant (p=0.001). No correlation was observed for BRCA2. If larger studies confirm these results, high-risk patients with BRCA1-negative tumors should be screened first for this gene.     

Monstrous Tetrahymena with Intraclonal Variation in Structure Produced by Hereditary Modification of Normal Cells

SYNOPSIS Monstrous Tetrahymena pyriformis strain GL may be isolated after exposure of normal cells to numerous heat shocks, to flattening on agar or gelatin plates, or to viscous solutions of methyl cellulose. It is shown that in some cases the abnormalities are inherited and that this results in clones where the cells are different from each other and have various abnormalities with respect to cortical pattern, swimming and feeding behavior, and generation time. Furthermore, it is shown that these cells are produced rather than selected by the experimental treatments. Evidence is presented that growth without division is important for production of the abnormal organisms. The basis of the inheritance of the abnormalities is discussed.     

Genetic and evolutionary consequences of symbiosis

Permanent stable symbioses, primarily microbial, are analyzed as parasexual phenomena from the evolutionary point of view. Such associations bring together in single individuals heritable traits of high selective advantage in certain environments. By convergent evolution several types of associations have repeatedly arisen: motile photosynthetic forms, nitrogen fixing and wood digesting complexes, and so forth. Many examples are discussed from the point of view of the number of originally independent genomes that comprise the recognizable individuals.The level of partner integration in many associations is analyzed. Examples of many levels: genic, gene product, metabolite, behavioral, and the methods by which they can be distinguished are discussed.The literature concerning a large number of associations is reviewed: Methanobacillus; predatory and consortia bacteria; blue green algal sheath dwelling bacteria; anaerobic worm-bacterial; algal, and foreign chloroplast retention by heterotrophic eukaryotes (ciliates, coelenterates, mollusks); the double nucleated photosynthetic dinoflagellate (Peridinium balticum); hindgut microbes in termites and woodroaches (Pyrsonympha, Barbulanympha and their associated spirochetes and other bacteria); sand dwelling and other ciliates and their associated bacteria; and so forth. The status of observations and artificial systems claiming evidence for transfer of genes between very distantly related organisms is critically discussed.A continuum from nearly completely autonomous partners (e.g., zoochlorellae in invertebrate animals) to nearly unrecognizable merged components (e.g., gamma particles in Blastocladiella) is found to exist among examples of extant organisms. The diversity and prevalence of such associations support the concept that there are many precedents for the steps hypothesized in the serial endosymbiotic theory of the origin of eukaryotic cells.     

Microbial Metabolite Signaling Is Required for Systemic Iron Homeostasis

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The synergy of germline C634Y and V292M RET mutations in a northern Chinese family with multiple endocrine neoplasia type 2A

Genetic analysis for germline mutations of RET proto‐oncogene has provided a basis for individual management of medullary thyroid carcinoma (MTC) and pheochromocytoma. Most of compound mutations have more aggressive phenotypes than single point mutations, but the compound C634Y/V292M variant in MTC has never been reported. Thus, we retrospectively investigated synergistic effect of C634Y and V292M RET germline mutations in family members with multiple endocrine neoplasia type 2A. Nine of 14 family members in a northern Chinese family underwent RET mutation screening using next‐generation sequencing and PCR followed by direct bidirectional DNA sequencing. Clinical features of nine individuals were retrospectively carefully reviewed. In vitro, the scratch‐wound assay was used to investigate the difference between the cells carrying different mutations. We find no patients died of MTC. All 3 carriers of the V292M variant were asymptomatic and did not have biochemical or structural evidence of disease (age: 82, 62 and 58). Among 4 C634Y mutation carriers, 2 patients had elevated calcitonin with the highest (156 pg/mL) in an 87‐year‐old male. Two carriers of compound C634Y/V292M trans variant had bilateral MTC with pheochromocytoma or lymph node metastasis (age: 54 and 41 years, respectively). Further, the compound C634Y/V292M variant had a faster migration rate than either single point mutation in vitro (P < .05). In conclusion, the V292M RET variant could be classified as ‘likely benign’ according to ACMG (2015). The compound variant V292M/C634Y was associated with both more aggressive clinical phenotype and faster cell growth in vitro than was either single mutation.     

Transferrin-Directed Internalization and Cycling of Transferrin Receptor 2

Transferrin receptor 2 (TfR2) is a homologue of transferrin receptor 1 (TfR1) but has distinct functions from TfR1 in iron homeostasis. In keeping with its proposed role in iron sensing, previous studies showed that TfR2 has a short half-life and that holo-Tf stabilizes TfR2 by redirecting it from a degradative pathway to a recycling pathway. In this study, we characterized how the endocytosis, recycling and degradation of TfR2 relates to its function and differs from TfR1. TfR2 endocytosis was adaptor protein-2 (AP-2) dependent. Flow cytometry analysis showed that TfR1 and TfR2 utilized the same endocytic pathway only in the presence of holo-Tf, indicating that holo-Tf alters the interaction of TfR2 with the endocytic machinery. Unlike TfR1, phosphofurin acidic cluster sorting protein 1 (PACS-1) binds to the cytoplasmic domain of TfR2 and data suggest that PACS-1 is involved in the TfR2 recycling. Depletion of TSG101 by siRNA or expression of a dominant negative Vps4 inhibited TfR2 degradation, indicating that TfR2 degradation occurs through a multivesicular body (MVB) pathway. TfR2 degradation is not mediated through ubiquitination on the single lysine (K31) in the cytoplasmic domain or on the amino terminal residue. No ubiquitination of TfR2 by HA-ubiquitin was detected, indicating a lack of direct TfR2 ubiquitination involvement in its degradation.     

Novel A14841G mutation is associated with high penetrance of LHON/C4171A family

We report the clinical and genetic characterization of a Chinese LHON family carrying an ND1/C4171A mutation. This family has high penetrance of visual impairment and extremely low frequency of vision recovery, which is in marked contrast to previously reported results for Korean LHON families with the same mutation. Sequence analysis of the complete mtDNA in the partially defined East Asian haplogroup N9a1 revealed the presence of 29 other variants. A novel heteroplasmic A14841G mutation, one of the variants with a serine substituted for a highly conserved asparagine at amino acid 32 of Cytochrome b (Cytb), may play a synergistic role with the C4171A mutation, leading to significantly different clinical manifestations of LHON among these families. The study further confirmed that C4171A was a rare primary LHON mutation, and the mtDNA background could also contribute to the clinical manifestation of the LHON/C4171A mutation.     

DNA repair mechanisms in dividing and non-dividing cells

DNA damage created by endogenous or exogenous genotoxic agents can exist in multiple forms, and if allowed to persist, can promote genome instability and directly lead to various human diseases, particularly cancer, neurological abnormalities, immunodeficiency and premature aging. To avoid such deleterious outcomes, cells have evolved an array of DNA repair pathways, which carry out what is typically a multiple-step process to resolve specific DNA lesions and maintain genome integrity. To fully appreciate the biological contributions of the different DNA repair systems, one must keep in mind the cellular context within which they operate. For example, the human body is composed of non-dividing and dividing cell types, including, in the brain, neurons and glial cells. We describe herein the molecular mechanisms of the different DNA repair pathways, and review their roles in non-dividing and dividing cells, with an eye toward how these pathways may regulate the development of neurological disease.