The strong global dimension of piecewise hereditary algebras

Let T be a tilting object in a triangulated category equivalent to the bounded derived category of a hereditary abelian category with finite dimensional homomorphism spaces and split idempotents. This text investigates the strong global dimension, in the sense of Ringel, of the endomorphism algebra of T. This invariant is expressed using the infimum of the lengths of the sequences of tilting objects successively related by tilting mutations and where the last term is T and the endomorphism algebra of the first term is quasi-tilted. It is also expressed in terms of the hereditary abelian generating subcategories of the triangulated category.Comment: Final published version. After refereeing, historical considerations were added and the length of the article was reduced: Introduction and Section 1 were reformulated; Subsection 2.1 was moved to Section 1 (with an abridged proof); Subsection 3.2 was reformulated (with an abridged proof); The proof in A.5 was rewritten (now shorter); And minor rewording was processed throughout the articl

Sprouty2 mediated tuning of signalling is essential for somite myogenesis

Background: Negative regulators of signal transduction cascades play critical roles in controlling different aspects of normal embryonic development. Sprouty2 (Spry2) negatively regulates receptor tyrosine kinases (RTK) and FGF signalling and is important in differentiation, cell migration and proliferation. In vertebrate embryos, Spry2 is expressed in paraxial mesoderm and in forming somites. Expression is maintained in the myotome until late stages of somite differentiation. However, its role and mode of action during somite myogenesis is still unclear. Results: Here, we analysed chick Spry2 expression and showed that it overlaps with that of myogenic regulatory factors MyoD and Mgn. Targeted mis-expression of Spry2 led to inhibition of myogenesis, whilst its C-terminal domain led to an increased number of myogenic cells by stimulating cell proliferation. Conclusions: Spry2 is expressed in somite myotomes and its expression overlaps with myogenic regulatory factors. Overexpression and dominant-negative interference showed that Spry2 plays a crucial role in regulating chick myogenesis by fine tuning of FGF signaling through a negative feedback loop. We also propose that mir-23, mir-27 and mir-128 could be part of the negative feedback loop mechanism. Our analysis is the first to shed some light on in vivo Spry2 function during chick somite myogenesis

Mutations in KCTD1 Cause Scalp-Ear-Nipple Syndrome

Scalp-ear-nipple (SEN) syndrome is a rare, autosomal-dominant disorder characterized by cutis aplasia of the scalp; minor anomalies of the external ears, digits, and nails; and malformations of the breast. We used linkage analysis and exome sequencing of a multiplex family affected by SEN syndrome to identify potassium-channel tetramerization-domain-containing 1 (KCTD1) mutations that cause SEN syndrome. Evaluation of a total of ten families affected by SEN syndrome revealed KCTD1 missense mutations in each family tested. All of the mutations occurred in a KCTD1 region encoding a highly conserved bric-a-brac, tram track, and broad complex (BTB) domain that is required for transcriptional repressor activity. KCTD1 inhibits the transactivation of the transcription factor AP-2 alpha (TFAP2A) via its BTB domain, and mutations in TFAP2A cause cutis aplasia in individuals with branchiooculofacial syndrome (BOFS), suggesting a potential overlap in the pathogenesis of SEN syndrome and BOFS. the identification of KCTD1 mutations in SEN syndrome reveals a role for this BTB-domain-containing transcriptional repressor during ectodermal development.National Institutes of Health National Human Genome Research InstituteLife Sciences Discovery FundWashington Research FoundationMassachusetts Gen Hosp, Cutaneous Biol Res Ctr, Charlestown, MA 02129 USAUniv Washington, Dept Pediat, Seattle, WA 98195 USAUniv Washington, Dept Genome Sci, Seattle, WA 98195 USAUniv Western Sydney Macarthur, Sch Med, Campbelltown, NSW 2560, AustraliaGenet Learning Disabil Serv, Newcastle, NSW 2298, AustraliaJohns Hopkins Univ, Sch Med, McKusick Nathans Inst Genet Med, Baltimore, MD 21205 USAUniversidade Federal de São Paulo, Dept Morphol & Genet, Clin Genet Ctr, BR-04021001 São Paulo, BrazilPontificia Univ Catolica Parana, Dept Internal Med, BR-1155 Curitiba, Parana, BrazilWestern Gen Hosp, South East Scotland Clin Genet Serv, Edinburgh EH4 2XU, Midlothian, ScotlandUniv Florence, Dept Genet & Mol Med, I-50132 Florence, ItalyHop Necker Enfants Malad, Dept Genet, INSERM, U781, F-75015 Paris, FranceUniv Paris Descartes Sorbonne Paris Cite, Inst Imagine, F-75015 Paris, FranceHop Cote Nacre, CHU Caen, Serv Genet, F-14033 Caen 9, FranceUniv Connecticut, Ctr Hlth, Dept Reconstruct Sci, Farmington, CT 06030 USABoston Childrens Hosp, Dept Plast & Oral Surg, Boston, MA 02115 USATreuman Katz Ctr Pediat Bioeth, Seattle Childrens Res Inst, Seattle, WA 98101 USAUniversidade Federal de São Paulo, Dept Morphol & Genet, Clin Genet Ctr, BR-04021001 São Paulo, BrazilNational Institutes of Health National Human Genome Research Institute: 1U54HG006493National Institutes of Health National Human Genome Research Institute: 1RC2HG005608National Institutes of Health National Human Genome Research Institute: 5RO1HG004316Life Sciences Discovery Fund: 2065508Life Sciences Discovery Fund: 0905001Web of Scienc

Transcriptome analyses based on genetic screens for Pax3 myogenic targets in the mouse embryo

<p>Abstract</p> <p>Background</p> <p>Pax3 is a key upstream regulator of the onset of myogenesis, controlling progenitor cell survival and behaviour as well as entry into the myogenic programme. It functions in the dermomyotome of the somite from which skeletal muscle derives and in progenitor cell populations that migrate from the somite such as those of the limbs. Few Pax3 target genes have been identified. Identifying genes that lie genetically downstream of <it>Pax3 </it>is therefore an important endeavour in elucidating the myogenic gene regulatory network.</p> <p>Results</p> <p>We have undertaken a screen in the mouse embryo which employs a <it>Pax3^GFP</it>allele that permits isolation of Pax3 expressing cells by flow cytometry and a <it>Pax3^PAX3-FKHR</it>allele that encodes PAX3-FKHR in which the DNA binding domain of Pax3 is fused to the strong transcriptional activation domain of FKHR. This constitutes a gain of function allele that rescues the <it>Pax3 </it>mutant phenotype. Microarray comparisons were carried out between <it>Pax3^GFP/+</it>and <it>Pax3^{GFP/PAX3-FKHR}</it>preparations from the hypaxial dermomyotome of somites at E9.5 and forelimb buds at E10.5. A further transcriptome comparison between Pax3-GFP positive and negative cells identified sequences specific to myogenic progenitors in the forelimb buds. Potential Pax3 targets, based on changes in transcript levels on the gain of function genetic background, were validated by analysis on loss or partial loss of function <it>Pax3 </it>mutant backgrounds. Sequences that are up- or down-regulated in the presence of PAX3-FKHR are classified as somite only, somite and limb or limb only. The latter should not contain sequences from Pax3 positive neural crest cells which do not invade the limbs. Verification by whole mount <it>in situ </it>hybridisation distinguishes myogenic markers. Presentation of potential Pax3 target genes focuses on signalling pathways and on transcriptional regulation.</p> <p>Conclusions</p> <p>Pax3 orchestrates many of the signalling pathways implicated in the activation or repression of myogenesis by regulating effectors and also, notably, inhibitors of these pathways. Important transcriptional regulators of myogenesis are candidate Pax3 targets. Myogenic determination genes, such as <it>Myf5 </it>are controlled positively, whereas the effect of <it>Pax3 </it>on genes encoding inhibitors of myogenesis provides a potential brake on differentiation. In the progenitor cell population, <it>Pax7 </it>and also <it>Hdac5 </it>which is a potential repressor of <it>Foxc2</it>, are subject to positive control by <it>Pax3</it>.</p