A role for cohesin in T-cell-receptor rearrangement and thymocyte differentiation.

Cohesin enables post-replicative DNA repair and chromosome segregation by holding sister chromatids together from the time of DNA replication in S phase until mitosis. There is growing evidence that cohesin also forms long-range chromosomal cis-interactions and may regulate gene expression in association with CTCF, mediator or tissue-specific transcription factors. Human cohesinopathies such as Cornelia de Lange syndrome are thought to result from impaired non-canonical cohesin functions, but a clear distinction between the cell-division-related and cell-division-independent functions of cohesion--as exemplified in Drosophila--has not been demonstrated in vertebrate systems. To address this, here we deleted the cohesin locus Rad21 in mouse thymocytes at a time in development when these cells stop cycling and rearrange their T-cell receptor (TCR) α locus (Tcra). Rad21-deficient thymocytes had a normal lifespan and retained the ability to differentiate, albeit with reduced efficiency. Loss of Rad21 led to defective chromatin architecture at the Tcra locus, where cohesion-binding sites flank the TEA promoter and the Eα enhancer, and demarcate Tcra from interspersed Tcrd elements and neighbouring housekeeping genes. Cohesin was required for long-range promoter-enhancer interactions, Tcra transcription, H3K4me3 histone modifications that recruit the recombination machinery and Tcra rearrangement. Provision of pre-rearranged TCR transgenes largely rescued thymocyte differentiation, demonstrating that among thousands of potential target genes across the genome, defective Tcra rearrangement was limiting for the differentiation of cohesin-deficient thymocytes. These findings firmly establish a cell-division-independent role for cohesin in Tcra locus rearrangement and provide a comprehensive account of the mechanisms by which cohesin enables cellular differentiation in a well-characterized mammalian system.

Increased Risk of Cerebrovascular Disease Among Patients With Neurofibromatosis Type 1: Population-Based Approach.

BACKGROUND AND PURPOSE: Although neurofibromatosis type 1 (NF1) may be associated with an incompletely understood vasculopathy, relative odds of stroke in this population is not known. METHODS: Using the 1998 to 2009 US Nationwide Inpatient Sample, we performed a case-control study matching cases of NF1 to controls without such a diagnosis. We then compared the odds of stroke between the 2 groups. We used multivariable logistic regression to adjust for known or suspected confounders. RESULTS: NF1 was associated with younger mean age at the time of stroke (41 versus 48) and a lower prevalence of stroke risk factors among adult patients. Pediatric patients with NF1, however, were more likely to have hypertension. Patients with NF1 were significantly more likely to be diagnosed with any stroke (odds ratio, 1.2; P<0.0001) than the general population. The odds of intracerebral hemorrhage were greatest among hemorrhagic stroke types analyzed (odds ratio, 1.9; P<0.0001). In the pediatric NF1 population, the odds of intracerebral hemorrhage were more dramatically elevated (odds ratio, 8.1; P<0.0001). The odds of ischemic stroke were also increased with NF1 in the pediatric (odds ratio, 3.4; P<0.0001) but not in the adult population. CONCLUSIONS: When compared with the general population, the odds of any type of stroke are significantly increased for patients with NF1, both adult and pediatric. This risk is most notable for hemorrhagic strokes although it is also increased for ischemic strokes in children. Physicians should be aware of the increased risk of stroke in this population, and consider stroke as a potential cause of new neurological symptoms.

Genome-wide identification of Ikaros targets elucidates its contribution to mouse B-cell lineage specification and pre-B-cell differentiation.

Ikaros family DNA-binding proteins are critical regulators of B-cell development. Because the current knowledge of Ikaros targets in B-cell progenitors is limited, we have identified genes that are bound and regulated by Ikaros in pre-B cells. To elucidate the role of Ikaros in B-cell lineage specification and differentiation, we analyzed the differential expression of Ikaros targets during the progression of multipotent to lymphoid-restricted progenitors, B- and T-cell lineage specification, and progression along the B-cell lineage. Ikaros targets accounted for one-half of all genes up-regulated during B-cell lineage specification in vivo, explaining the essential role of Ikaros in this process. Expression of the Ikaros paralogs Ikzf1 and Ikzf3 increases incrementally during B-cell progenitor differentiation, and, remarkably, inducible Ikaros expression in cycling pre-B cells was sufficient to drive transcriptional changes resembling the differentiation of cycling to resting pre-Bcells in vivo. The data suggest that Ikaros transcription factor dosage drives the progression of progenitors along a predetermined lineage by regulating multiple targets in key pathways, including pre-B­cell receptor signaling, cell cycle progression, and lymphocyte receptor rearrangement.Our approachmay be of general use to map the contribution of transcription factors to cell lineage commitment and differentiation.

Embryonic stem cell-derived hemangioblasts remain epigenetically plastic and require PRC1 to prevent neural gene expression.

Many lineage-specific developmental regulator genes are transcriptionally primed in embryonic stem (ES) cells; RNA Pol(II) is bound at their promoters but is prevented from productive elongation by the activity of polycomb repressive complexes (PRC) 1 and 2. This epigenetically poised state is thought to enable ES cells to rapidly execute multiple differentiation programs and is recognized by a simultaneous enrichment for trimethylation of lysine 4 and trimethylation of lysine 27 of histone H3 (bivalent chromatin) across promoter regions. Here we show that the chromatin profile of this important cohort of genes is progressively modified as ES cells differentiate toward blood-forming precursors. Surprisingly however, neural specifying genes, such as Nkx2-2, Nkx2-9, and Sox1, remain bivalent and primed even in committed hemangioblasts, as conditional deletion of PRC1 results in overt and inappropriate expression of neural genes in hemangioblasts. These data reinforce the importance of PRC1 for normal hematopoietic differentiation and reveal an unexpected epigenetic plasticity of mesoderm-committed hemangioblasts.

Neurofibromatosis type 1 and pregnancy complications: a population-based study.

OBJECTIVE: The objective of the study was to determine whether vascular and other complications are more common in pregnant women with neurofibromatosis type 1 (NF1). STUDY DESIGN: We performed a population-based retrospective cohort study using the US Nationwide Inpatient Sample, 1988-2009, defining a cohort of pregnancy-related hospitalizations with an associated diagnosis of NF1 and comparing it with the control group not associated with NF1. Multivariable logistic regression was used to adjust for suspected confounders. RESULTS: Among 19 million pregnancy-related admissions between 1988 and 2009, we identified 1553 associated with NF1 (prevalence 0.008%). A diagnosis of NF1 in delivering mothers was associated with gestational hypertension (adjusted odds ratio [AOR], 1.6, 95% confidence interval [CI], 1.2-2.0), preeclampsia (AOR, 2.8, 95% CI, 2.3-3.4), intrauterine growth restriction (AOR, 4.6, 95% CI, 3.7-5.6), cerebrovascular disease (OR, 8.1, 95% CI, 2.6-25.4), preterm labor (AOR, 1.6, 95% CI, 1.4-1.9), and cesarean delivery (AOR, 2.0, 95% CI, 1.8-2.3). Women with NF1 were not significantly more likely to have deep venous thrombosis/pulmonary embolism, acute cardiac events, or stillbirth or to die during their hospitalizations compared with the general obstetric population. CONCLUSION: NF1 was associated with increased maternal morbidity in pregnancy (including hypertensive and cerebrovascular complications) but not increased maternal mortality. Obstetricians should be aware of the potential for increased antenatal and peripartum complications among women with NF1.

A simple and novel method for RNA-seq library preparation of single cell cDNA analysis by hyperactive Tn5 transposase.

BACKGROUND: Deep sequencing of single cell-derived cDNAs offers novel insights into oncogenesis and embryogenesis. However, traditional library preparation for RNA-seq analysis requires multiple steps with consequent sample loss and stochastic variation at each step significantly affecting output. Thus, a simpler and better protocol is desirable. The recently developed hyperactive Tn5-mediated library preparation, which brings high quality libraries, is likely one of the solutions. RESULTS AND CONCLUSIONS: Here, we tested the applicability of hyperactive Tn5-mediated library preparation to deep sequencing of single cell cDNA, optimized the protocol, and compared it with the conventional method based on sonication. This new technique does not require any expensive or special equipment, which secures wider availability. A library was constructed from only 100 ng of cDNA, which enables the saving of precious specimens. Only a few steps of robust enzymatic reaction resulted in saved time, enabling more specimens to be prepared at once, and with a more reproducible size distribution among the different specimens. The obtained RNA-seq results were comparable to the conventional method. Thus, this Tn5-mediated preparation is applicable for anyone who aims to carry out deep sequencing for single cell cDNAs.

Klippel-Feil Syndrome with Cervical Diastematomyelia in an Adult with Extensive Cervicothoracic Fusions: Case Report and Review of the Literature.

Split cord malformation (SCM) is a developmental disorder that is usually symptomatic and diagnosed in childhood. The majority of these lesions are in the thoracic and lumbar spine, with only 1%-3% of cases found in the cervical spine. This is a case report of a 55-year-old female patient with an unremarkable medical history who presented with neck pain. Upon workup, she was found to have extensive developmental anomalies throughout her cervical and thoracic spine, including an incidentally found type 2 SCM and multiple autofused vertebrae. There are only 6 similar studies published in the literature. There was extensive facet degeneration in her cervical spine, which was suspected to be the etiology of her neck pain. This case illustrates the rare finding of asymptomatic adult cervical SCM and the likely significance of her autofused vertebrae causing accelerated symptomatic facet spondylosis.

Sex and race differences in mental health symptoms in juvenile justice: the MAYSI-2 national meta-analysis.

OBJECTIVE: Studies have suggested a high prevalence of mental health symptoms among youths in the juvenile justice system, with the highest prevalence among girls and whites compared to boys and other races. This multisite, archival study examined whether sex and race differences, when they exist, were consistent across U.S. juvenile justice programs. METHOD: Data included scores on the Massachusetts Youth Screening Instrument-Version 2 (MAYSI-2) for 70,423 youths from 283 juvenile justice probation, detention, or corrections programs. A meta-analytic technique investigated the consistency of effect sizes for sex and race/ethnic differences across sites in self-reported mental health problems; RESULTS: Across sites, girls on average were 1.8 (95% confidence interval 0.98-1.10) to 2.4 (95% confidence interval 2.38-2.48) times as likely as boys to have clinical elevations on all applicable MAYSI-2 scales except the Alcohol/Drug Use scale. On the Alcohol/Drug Use scale, a sex effect existed but only among youngeryouths. Whites were more likely to have clinical elevations than blacks or Hispanics; but surprisingly disparities varied across mental health categories and varied considerably across sites. CONCLUSION: At the aggregate level, 72% of girls and 63% of boys had a clinical elevation on at least one MAYSI-2 scale. Our meta-analytic technique indicated that the sex differences across sites were even larger than these numbers imply. Conversely and counter to existing evidence, race-related differences were generally small or nonexistent. Whites were more likely to have alcohol and drug problems and suicide ideation, but not more likely to have symptoms of depression, anxiety, or thought disturbance than blacks or Hispanics.

Differential subnuclear localization and replication timing of histone H3 lysine 9 methylation states.

Mono-, di-, and trimethylation of specific histone residues adds an additional level of complexity to the range of histone modifications that may contribute to a histone code. However, it has not been clear whether different methylated states reside stably at different chromatin sites or whether they represent dynamic intermediates at the same chromatin sites. Here, we have used recently developed antibodies that are highly specific for mono-, di-, and trimethylated lysine 9 of histone H3 (MeK9H3) to examine the subnuclear localization and replication timing of chromatin containing these epigenetic marks in mammalian cells. Me1K9H3 was largely restricted to early replicating, small punctate domains in the nuclear interior. Me2K9H3 was the predominant MeK9 epitope at the nuclear and nucleolar periphery and colocalized with sites of DNA synthesis primarily in mid-S phase. Me3K9H3 decorated late-replicating pericentric heterochromatin in mouse cells and sites of DAPI-dense intranuclear heterochromatin in human and hamster cells that replicated throughout S phase. Disruption of the Suv39h1,2 or G9a methyltransferases in murine embryonic stem cells resulted in a redistribution of methyl epitopes, but did not alter the overall spatiotemporal replication program. These results demonstrate that mono-, di-, and trimethylated states of K9H3 largely occupy distinct chromosome domains.

Postmortem Genetic Testing for Cardiac Ion Channelopathies in Stillbirths.

BACKGROUND: Although stillbirth is a significant health problem worldwide, the definitive cause of death remains elusive in many cases, despite detailed autopsy. In this study of partly explained and unexplained stillbirths, we used next-generation sequencing to examine an extended panel of 35 candidate genes known to be associated with ion channel disorders and sudden cardiac death. METHODS AND RESULTS: We examined tissue from 242 stillbirths (≥22 weeks), including those where no definite cause of death could be confirmed after a full autopsy. We obtained high-quality DNA from 70 cases, which were then sequenced for a custom panel of 35 genes, 12 for inherited long- and short-QT syndrome genes (LQT1-LQT12 and SQT1-3), and 23 additional candidate genes derived from genome-wide association studies. We examined the functional significance of a selected variant by patch-clamp electrophysiological recording. No predicted damaging variants were identified in KCNQ1 (LQT1) or KCNH2 (LQT2). A rare putative pathogenic variant was found in KCNJ2(LQT7) in 1 case, and several novel variants of uncertain significance were observed. The KCNJ2 variant (p. R40Q), when assessed by whole-cell patch clamp, affected the function of the channel. There was no significant evidence of enrichment of rare predicted damaging variants within any of the candidate genes. CONCLUSIONS: Although a causative link is unclear, 1 putative pathogenic and variants of uncertain significance variant resulting in cardiac channelopathies was identified in some cases of otherwise unexplained stillbirth, and these variants may have a role in fetal demise. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01120886.

Observing S-phase dynamics of histone modifications with fluorescently labeled antibodies.

Histone modifications are central to epigenetic regulation and must be reestablished with each round of DNA replication. Here we describe methods to localize these modifications within mammalian nuclei and to relate them to specific spatiotemporal patterns of DNA replication.

Safety and technical efficacy of over-the-wire balloons for the treatment of subarachnoid hemorrhage-induced cerebral vasospasm.

OBJECT: Over the past decade, low-pressure, flow-directed balloons have been replaced by over-the-wire balloons in the treatment of vasospasm induced by subarachnoid hemorrhage (SAH). The authors assess the procedural safety and technical efficacy of these newer devices. METHODS: Seventy-five patients who underwent 85 balloon angioplasty procedures for the treatment of SAH-induced vasospasm were identified from a prospective quality-assurance database. Medical records and angiographic reports were reviewed for evidence of procedural complications and technical efficacy. No vessel rupture or perforation occurred, but thromboembolic complications were noted in four (4.7%) of the 85 procedures. Balloon angioplasty was frequently attempted and successfully accomplished in the distal internal carotid (100%), proximal middle cerebral (94%), vertebral (73%), and basilar (88%) arteries. Severe narrowing was present in 89 proximal anterior cerebral arteries. Angioplasty was attempted in 41 of these vessels and was successful in only 14 (34%). In 19 of the 27 unsuccessful attempts, the balloon could not be advanced over the wire due to severe vasospasm or unfavorable vessel angle. Follow-up angiography in a subset of patients demonstrated that severe recurrent vasospasm occurred in 15 (13%) of 116 vessels studied after angioplasty. CONCLUSIONS: Over-the-wire balloons involve a low risk for vessel rupture. The anterior cerebral artery remains difficult to access and successfully treat with current devices. Further improvements in balloon design, such as smaller inflated diameters and better tracking, are necessary. Finally, thromboembolic complications remain an important concern, and severe vasospasm may recur after balloon angioplasty.

Single-Cell Expression Profiling Reveals a Dynamic State of Cardiac Precursor Cells in the Early Mouse Embryo.

In the early vertebrate embryo, cardiac progenitor/precursor cells (CPs) give rise to cardiac structures. Better understanding their biological character is critical to understand the heart development and to apply CPs for the clinical arena. However, our knowledge remains incomplete. With the use of single-cell expression profiling, we have now revealed rapid and dynamic changes in gene expression profiles of the embryonic CPs during the early phase after their segregation from the cardiac mesoderm. Progressively, the nascent mesodermal gene Mesp1 terminated, and Nkx2-5+/Tbx5+ population rapidly replaced the Tbx5low+ population as the expression of the cardiac genes Tbx5 and Nkx2-5 increased. At the Early Headfold stage, Tbx5-expressing CPs gradually showed a unique molecular signature with signs of cardiomyocyte differentiation. Lineage-tracing revealed a developmentally distinct characteristic of this population. They underwent progressive differentiation only towards the cardiomyocyte lineage corresponding to the first heart field rather than being maintained as a progenitor pool. More importantly, Tbx5 likely plays an important role in a transcriptional network to regulate the distinct character of the FHF via a positive feedback loop to activate the robust expression of Tbx5 in CPs. These data expands our knowledge on the behavior of CPs during the early phase of cardiac development, subsequently providing a platform for further study.

Clinical presentation and treatment considerations of a ruptured posterior spinal artery pseudoaneurysm.

Spinal artery pseudoaneurysms are rare vascular lesions with poorly defined natural history, diagnostic paradigms, and treatment strategies. We present a 68-year-old woman with severe back pain and left lower extremity weakness with spinal subarachnoid hemorrhage due to a ruptured T5 region posterior spinal artery pseudoaneurysm, and review issues related to radiologic diagnosis and endovascular and open neurosurgical interventions.

Common and distinct neural mechanisms of visual and tactile extinction: A large scale VBM study in sub-acute stroke.

Extinction is diagnosed when patients respond to a single contralesional item but fail to detect this item when an ipsilesional item is present concurrently. Extinction has been studied mainly in the visual modality but it occurs also in other sensory modalities (touch, audition) and hence can be considered a multisensory phenomenon. The functional and neuroanatomical relations between extinction in different modalities are poorly understood. Here, we used voxel-based mophometry (VBM) to examine the neuronal substrates of visual versus tactile extinction in a large group of sub-acute patients (n = 454) with strokes affecting different vascular territories. We found that extinction deficits in tactile and visual modalities were significantly correlated (r = 0.341; p < 0.01). Several lesions within the right hemisphere were linked to extinction including the inferior parietal lobule, the superior parietal lobule, the middle frontal and occipital gyri, while lesions involving the superior temporal gyrus, inferior temporal gyrus and putamen were associated with tactile extinction. Damage within the middle temporal gyrus and superior temporal sulcus was linked to both deficits. We conclude that extinction in different modalities emerges after damage to both common (supra-modal) and distinct (modality specific) brain regions, and that contrasting sites emerge after damage to different vascular territories. We discuss the implications for understanding extinction as a multisensory disorder.

Chemotherapy: present and future.

Vestibular schwannomas (VS) are among the most common benign tumors of the central nervous system. Bilateral VS are the hallmark of neurofibromatosis type II, commonly leading to complete deafness and cranial nerve deficits as a result of tumor progression or treatment with surgery or radiation. Effective medical therapies are needed to address tumor progression and treatment-related morbidity. This article reviews the standard therapies for VS, summarizes the molecular biology of these tumors, and describes potential targets for chemotherapeutic agents. The article also defines and recommends the use of specific clinical end points in future drug trials, describes previous and current experience with anti-VEGF and anti-EGFR agents, and delineates areas of future research.

Outcomes of hospitalization in pregnant women with CNS neoplasms: a population-based study.

Managing a CNS neoplasm during pregnancy presents complex challenges, and population-based studies are lacking. We designed a retrospective cohort study using the Nationwide Inpatient Sample (NIS) to investigate pregnancy outcomes in women with CNS neoplasms. We constructed a logistic regression model for maternal mortality, preterm labor, intrauterine growth restriction (IUGR), and Caesarean delivery, controlling for age, comorbidities, and demographic characteristics. We identified 379 malignant brain tumors, 437 benign brain tumors, and 44 spine tumors among 19 million pregnancy-related admissions from 1988 through 2009. Malignant brain tumors were associated with maternal mortality (odds ratio [OR], 143), preterm labor (OR, 3.4), and IUGR (OR, 2.9). Benign brain tumors were associated with preterm labor (OR, 2.3). A diagnosis of hyperemesis gravidarum was more common in malignant (OR, 2.2) and benign (OR, 2.8) brain tumors. Compared with the general population, Caesarean delivery was more frequent for malignant (OR, 6.4) and benign (OR, 2.8) brain tumors and spine tumors (OR, 3.9). Admission without delivery was more common for malignant (OR, 8.6) and benign (OR, 4.3) brain tumors and spine tumors (OR, 3.8; P < .05 for all outcomes). Thirty-three percent of all hospitalizations involved neurosurgical procedures, but pregnancy complications were not significantly more likely to occur in surgical patients. In conclusion, malignant brain tumors were associated with adverse pregnancy outcomes, and CNS neoplasms were associated with higher rates of Caesarean delivery. Additional research is needed to improve understanding of obstetric risk in these patients and to assist with treatment, counseling, and monitoring during delivery.