Lineage-Specific Functions of the Homeodomain Transcription Factor Pitx2 in Eye Development.

Numerous inductive patterning events occur in eye development. The periocular mesenchyme plays a role in these processes by patterning the optic stalk, corneal epithelium, and retinal pigmented epithelium during eye development, in addition to contributing cells to many non-neural tissues in the eye. The periocular mesenchyme includes cells from two embryonic lineages, the neural crest and mesoderm, which each form distinct cell types. The homeodomain transcription factor Pitx2 is required for normal eye development in both mice and humans, and mutations can lead to early onset glaucoma in humans. Pitx2 is expressed in both the neural crest and mesoderm lineages of the periocular mesenchyme, but the mechanisms of its function in each lineage were not known. To test the hypothesis that Pitx2 has unique functions in each lineage during eye development, lineage-specific knockout mice of Pitx2 in the neural crest and mesoderm were created using the Cre-lox system. Pitx2 in the neural crest is cell-autonomously required for anterior segment development, sclera formation and ocular blood vessel growth. Pitx2 also has non-cell autonomous functions in the neural crest in optic stalk development and RPE patterning. The defects in optic stalk development and ocular blood vessel growth represent two new potential mechanisms underlying the glaucoma seen in human patients with PITX2 mutations. In the mesoderm, Pitx2 is cell autonomously required for extraocular muscle precursor survival and non-cell autonomously required for optic fissure closure. Pitx2 function is also required in the mesoderm lineage for eyelid closure. Pitx2, not Pax7, regulates MRF expression in the extraocular muscles, and PITX2 can activate the Myod1 promoter through a novel sequence. This identifies distinct mechanisms of Pitx2 function in the two lineages of the periocular mesenchyme in the developing eye. These findings significantly expand the understanding of the functions of Pitx2 in eye development and its role in human disease.Ph.D.Cell and Developmental BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64671/1/alevans_1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/64671/2/alevans_2.pd

Pitx2 is an upstream activator of extraocular myogenesis and survival

AbstractThe transcription factors required to initiate myogenesis in branchial arch- and somite-derived muscles are known, but the comparable upstream factors required during extraocular muscle development have not been identified. We show Pax7 is dispensable for extraocular muscle formation, whereas Pitx2 is cell-autonomously required to prevent apoptosis of the extraocular muscle primordia. The survival requirement for Pitx2 is stage-dependent and ends following stable activation of genes for the muscle regulatory factors (e.g. Myf5, MyoD), which is reduced in the absence of Pitx2. Further, PITX2 binds and activates transcription of the Myf5 and MyoD promoters, indicating these genes are direct targets. Collectively, these data demonstrate that PITX2 is required at several steps in the development of extraocular muscles, acting first as an anti-apoptotic factor in pre-myogenic mesoderm, and subsequently to activate the myogenic program in these cells. Thus, Pitx2 is the first demonstrated upstream activator of myogenesis in the extraocular muscles

A quantitative model of normal Caenorhabditis elegans embryogenesis and its disruption after stress

AbstractThe invariant lineage of Caenorhabditis elegans has powerful potential for quantifying developmental variability in normal and stressed embryos. Previous studies of division timing by automated lineage tracing suggested that variability in cell cycle timing is low in younger embryos, but manual lineage tracing of specific lineages suggested that variability may increase for later divisions. We developed improved automated lineage tracing methods that allowroutine lineage tracing through the last round of embryonic cell divisions and we applied these methods to trace the lineage of 18 wild-type embryos. Cell cycle lengths, division axes and cell positions are remarkably consistent among these embryos at all stages, with only slight increase in variability later in development. The resulting quantitative 4-dimensional model of embryogenesis provides a powerful reference dataset to identify defects in mutants or in embryos that have experienced environmental perturbations. We also traced the lineages of embryos imaged at higher temperatures to quantify the decay in developmental robustness under temperature stress. Developmental variability increases modestly at 25°C compared with 22°C and dramatically at 26°C, and we identify homeotic transformations in a subset of embryos grown at 26°C. The deep lineage tracing methods provide a powerful tool for analysis of normal development, gene expression and mutants and we provide a graphical user interface to allow other researchers to explore the average behavior of arbitrary cells in a reference embryo

The Massive Star Content of NGC 3603

We investigate the massive star content of NGC 3603, the closest known giant H II region. We have obtained spectra of 26 stars in the central cluster using the Baade 6.5-m telescope (Magellan I). Of these 26 stars, 16 had no previous spectroscopy. We also obtained photometry of all of the stars with previous or new spectroscopy, primarily using archival HST ACS/HRC images. We use these data to derive an improved distance to the cluster, and to construct an H-R diagram for discussing the masses and ages of the massive star content of this cluster.Comment: Accepted by the Astronomical Journal. This revision updates the coordinates in Table 1 by (-0.18sec, +0.2") to place them on the UCAC2 syste

Effectiveness of the 2014 European Society of Cardiology guideline on sudden cardiac death in hypertrophic cardiomyopathy: a systematic review and meta-analysis.

Objective In 2014, the European Society of Cardiology (ESC) recommended the use of a novel risk prediction model (HCM Risk-SCD) to guide use of implantable cardioverter defibrillators (ICD) for the primary prevention of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM). We sought to determine the performance of HCM Risk-SCD by conducting a systematic review and meta-analysis of articles reporting on the prevalence of SCD within 5 years of evaluation in low, intermediate and high-risk patients as defined by the 2014 guidelines (predicted risk <4%, 4%–<6% and ≥6%, respectively). Methods The protocol was registered with PROSPERO (registration number: CRD42017064203). MEDLINE and manual searches for papers published from October 2014 to December 2017 were performed. Longitudinal, observational cohorts of unselected adult patients, without history of cardiac arrest were considered. The original HCM Risk-SCD development study was included a priori. Data were pooled using a random effects model. Results Six (0.9%) out of 653 independent publications identified by the initial search were included. The calculated 5-year risk of SCD was reported in 7291 individuals (70% low, 15% intermediate; 15% high risk) with 184 (2.5%) SCD endpoints within 5 years of baseline evaluation. Most SCD endpoints (68%) occurred in patients with an estimated 5-year risk of ≥4% who formed 30% of the total study cohort. Using the random effects method, the pooled prevalence of SCD endpoints was 1.01% (95% CI 0.52 to 1.61) in low-risk patients, 2.43% (95% CI 1.23 to 3.92) in intermediate and 8.4% (95% CI 6.68 to 10.25) in high-risk patients. Conclusions This meta-analysis demonstrates that HCM Risk-SCD provides accurate risk estimations that can be used to guide ICD therapy in accordance with the 2014 ESC guidelines. Registration number PROSPERO CRD42017064203;Pre-results.pre-print379 K

Signaling “cross-talk” is integrated by transcription factors in the development of the anterior segment in the eye

Extracellular signaling “cross-talk” between tissues is an important requirement for development of many organs yet the underlying mechanisms generally remain poorly understood. The anterior segment of the eye, which is constructed from four embryonic lineages, provides a unique opportunity to genetically dissect developmental processes such as signaling “cross-talk” without fear of inducing lethality. In the current review, we summarize recent data showing that PITX2, a homeodomain transcription factor, integrates retinoic acid and canonical Wnt/Β-catenin signaling during anterior segment development. Because the requirements for retinoic acid signaling, canonical Wnt/Β-catenin signaling, and PITX2 are not unique to the eye, this newly identified pathway may have relevance elsewhere during development and in tissue homeostasis. Developmental Dynamics 238:2149–2162, 2009. © 2009 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63590/1/22033_ftp.pd