Agenesis of the Corpus Callosum Due to Defective Glial Wedge Formation in Lhx2 Mutant Mice.

Establishment of the corpus callosum involves coordination between callosal projection neurons and multiple midline structures, including the glial wedge (GW) rostrally and hippocampal commissure caudally. GW defects have been associated with agenesis of the corpus callosum (ACC). Here we show that conditional Lhx2 inactivation in cortical radial glia using Emx1-Cre or Nestin-Cre drivers results in ACC. The ACC phenotype was characterized by aberrant ventrally projecting callosal axons rather than Probst bundles, and was 100% penetrant on 2 different mouse strain backgrounds. Lhx2 inactivation in postmitotic cortical neurons using Nex-Cre mice did not result in ACC, suggesting that the mutant phenotype was not autonomous to the callosal projection neurons. Instead, ACC was associated with an absent hippocampal commissure and a markedly reduced to absent GW. Expression studies demonstrated strong Lhx2 expression in the normal GW and in its radial glial progenitors, with absence of Lhx2 resulting in normal Emx1 and Sox2 expression, but premature exit from the cell cycle based on EdU-Ki67 double labeling. These studies define essential roles for Lhx2 in GW, hippocampal commissure, and corpus callosum formation, and suggest that defects in radial GW progenitors can give rise to ACC.

A 7-Year-Old Boy with Fever and Dark Urine.

A 7-Year-Old Boy with Fever and Dark UrineA 7-year-old boy with surgically repaired tetralogy of Fallot presented for evaluation of fever and dark urine. How do you approach the evaluation, and what is the diagnosis?

A system for addressing incidental findings in neuroimaging research.

When healthy subjects undergo brain imaging, incidental findings are not rare. The optimal response to such findings has been the focus of considerable discussion. The current report describes the operations and results of a system that provides a review of incidental findings by an appropriate medical professional. A web-based system was created whereby investigators performing brain MRI scans on healthy subjects could refer images with suspected concerns to a board certified radiologist who had a Certificate of Added Qualification in Neuroradiology. The specific details of this system are described. Among 27 scans suspected by an investigator of having a significant finding, all but one were referred by a researcher with a PhD. The most common concerns described by these investigators were for the possible presence of a cyst or of enlarged ventricles. The most common findings reported by the radiologist were Virchow-Robin spaces and cysts. Findings were generally of low clinical significance, with 1 major exception. Identifying the optimal response to incidental findings in neuroimaging research remains a challenge. The current report describes a system for providing expert assistance and so addresses these issues in the setting of suspected incidental findings. To our knowledge the current system is the first to provide a specific means for evaluation of incidental findings in neuroimaging research.

Methylation of the DFNA5 increases risk of lymph node metastasis in human breast cancer.

The pathogenesis of breast cancer involves multiple genetic and epigenetic events. In this study, we report an epigenetic alteration of DFNA5 in human breast cancer. DFNA5 gene was silenced in breast cancer cell lines that were methylated in the DFNA5 promoter, and restored by treatment with the demethylating agent, 5-aza-dC, and gene knock-down of DFNA5 increased cellular invasiveness in vitro. The mRNA expression of DFNA5 in breast cancer tissues was down-regulated as compared to normal tissues. Moreover, the DFNA5 promoter was found to be methylated in primary tumor tissues with high frequency (53%, 18/34). Quantitative methylation-specific PCR of DFNA5 clearly discriminated primary breast cancer tissues from normal breast tissues (15.3%, 2/13). Moreover, methylation status of DFNA5 was correlated with lymph node metastasis in breast cancer patients. Our data implicate DFNA5 promoter methylation as a novel molecular biomarker in human breast cancer.

The three-dimensional organization of telomeres in the nucleus of mammalian cells.

BACKGROUND: The observation of multiple genetic markers in situ by optical microscopy and their relevance to the study of three-dimensional (3D) chromosomal organization in the nucleus have been greatly developed in the last decade. These methods are important in cancer research because cancer is characterized by multiple alterations that affect the modulation of gene expression and the stability of the genome. It is, therefore, essential to analyze the 3D genome organization of the interphase nucleus in both normal and cancer cells. RESULTS: We describe a novel approach to study the distribution of all telomeres inside the nucleus of mammalian cells throughout the cell cycle. It is based on 3D telomere fluorescence in situ hybridization followed by quantitative analysis that determines the telomeres' distribution in the nucleus throughout the cell cycle. This method enables us to determine, for the first time, that telomere organization is cell-cycle dependent, with assembly of telomeres into a telomeric disk in the G2 phase. In tumor cells, the 3D telomere organization is distorted and aggregates are formed. CONCLUSIONS: The results emphasize a non-random and dynamic 3D nuclear telomeric organization and its importance to genomic stability. Based on our findings, it appears possible to examine telomeric aggregates suggestive of genomic instability in individual interphase nuclei and tissues without the need to examine metaphases. Such new avenues of monitoring genomic instability could potentially impact on cancer biology, genetics, diagnostic innovations and surveillance of treatment response in medicine.

Molecular markers in cutaneous squamous cell carcinoma.

Nonmelanoma skin carcinoma (NMSC) is the most frequent cancer in the USA with over 1.3 million new diagnoses a year; however due to an underappreciation of its associated mortality and growing incidence and its ability to be highly aggressive, the molecular mechanism is not well delineated. Whereas the molecular profiles of melanoma have been well characterized, those for cutaneous squamous cell carcinoma (cSCC) have trailed behind. This importance of the new staging paradigm is linked to the ability currently to better clinically cluster similar biologic behavior in order to risk-stratify lesions and patients. In this paper we discuss the trends in NMSC and the etiologies for the subset of NMSC with the most mortality, cutaneous SCC, as well as where the field stands in the discovery of a molecular profile. The molecular markers are highlighted to demonstrate the recent advances in cSCC.

Detectable BRAF mutation in serum DNA samples from patients with papillary thyroid carcinomas.

BACKGROUND.: An activating point mutation of the BRAF oncogene results in a V600E amino acid missense mutation found in a majority of papillary thyroid carcinomas (PTC). METHODS.: In this study, 28 matched tumor and serum samples obtained from patients with both benign and malignant thyroid disorders were analyzed for BRAF mutation using a gap-ligase chain reaction technique. RESULTS.: The BRAF mutation was absent in tumor DNA samples obtained from patients with benign adenomas, follicular neoplasms or carcinoma, and thyroid lymphoma. In contrast, 5 of 14 PTC tumors were positive for the BRAF mutation. Moreover, 3 of 14 patients with PTC were positive for BRAF mutation in serum and tumor. Of these 3 patients, 2 had lymph node metastasis and 2 had PTC in background of the Hashimoto's thyroiditis. CONCLUSIONS.: The detection of free circulating mutant BRAF in patients with PTC is possible and future studies are warranted to determine its clinical significance.

Presence of HPV DNA in convalescent salivary rinses is an adverse prognostic marker in head and neck squamous cell carcinoma.

Human papillomavirus (HPV) 16 is present in up to 60% of patients with head and neck squamous cell carcinoma (HNSCC) and confers a favorable prognosis in terms of recurrence and mortality. Previous reports demonstrated that HPV-16 DNA can be detected in the initial salivary rinses from these patients. In this study, we assessed the feasibility of post-treatment HPV DNA shed from the oral mucosa as a prognostic marker for persistent/recurrent head and neck cancer. Fresh tumor samples and pre- and post-treatment salivary rinses were collected from 59 patients with HNSCC. HPV-16 E6 and E7 DNA copy number in these samples were quantified by real time PCR. Twenty of 59 patients (33.9%) were HPV-16 positive in their tumors before treatment. Four of 20 HPV tumor positive patients ultimately developed recurrence, and two of these four patients were HPV-16 positive in surveillance salivary rinses (sensitivity=50%). Of the 39 (66.1%) HPV-16 negative patients on initial clinical presentation and the 16 HPV-16 positive patients who did not recur, none were HPV-16 positive in salivary rinses after treatment (specificity=100%). HPV-16 presence in follow-up salivary rinses preceded clinical detection of disease recurrence by an average of 3.5 months. Patients with presence of HPV-16 DNA in surveillance salivary rinses are at significant risk for recurrence. Quantitative measurement of salivary HPV-16 DNA has promise for surveillance and early detection of recurrence.

c-Myc induces chromosomal rearrangements through telomere and chromosome remodeling in the interphase nucleus.

In previous work, we showed that telomeres of normal cells are organized within the 3D space of the interphase nucleus in a nonoverlapping and cell cycle-dependent manner. This order is distorted in tumor cell nuclei where telomeres are found in close association forming aggregates of various numbers and sizes. Here we show that c-Myc overexpression induces telomeric aggregations in the interphase nucleus. Directly proportional to the duration of c-Myc deregulation, we observe three or five cycles of telomeric aggregate formation in interphase nuclei. These cycles reflect the onset and propagation of breakage-bridge-fusion cycles that are initiated by end-to-end telomeric fusions of chromosomes. Subsequent to initial chromosomal breakages, new fusions follow and the breakage-bridge-fusion cycles continue. During this time, nonreciprocal translocations are generated. c-Myc-dependent remodeling of the organization of telomeres thus precedes the onset of genomic instability and subsequently leads to chromosomal rearrangements. Our findings reveal that c-Myc possesses the ability to structurally modify chromosomes through telomeric fusions, thereby reorganizing the genetic information.