"Self-regulation," a new facet of Hox genes' function

PMCID: PMC4482672[Background]: Precise temporal and spatial expression of the clustered Hox genes is essential for patterning the developing embryo. Temporal activation of Hox genes was shown to be cluster-autonomous. However, gene clustering appears dispensable for spatial colinear expression. Generally, a set of Hox genes expressed in a group of cells instructs these cells about their fate such that the differential expression of Hox genes results in morphological diversity. The spatial colinearity is considered to rely both on local and long-range cis regulation. [Results]: Here, we report on the global deregulation of HoxA and HoxD expression patterns upon inactivation of a subset of HOXA and HOXD proteins. [Conclusions]: Our data suggest the existence of a >self-regulation> mechanism, a process by which HOX proteins establish and/or maintain the spatial domains of the Hox gene family and we propose that the functionally dominant HOX proteins could contribute to generating the spatial parameters of Hox expression in a given tissue, i.e., HOX controlling the establishment of the ultimate HOX code.Grant sponsor: the Spanish Government; Grant number: BFU2011-24972; Grant sponsor: the Canadian Institutes for Health Research; Grant number: MOP-82880; Grant number: 126110. This work was supported by the Spanish Government to M.R. and by the Canadian Institutes for Health Research as well as the Canada Research Chair program to M.K. R.S was supported by a Formación Profesorado Universitario fellowship from the Spanish Ministry of Science and Innovation and currently supported by the Angelo Pizzagalli postdoctoral fellowship.Peer Reviewe

A BMP-Shh negative-feedback loop restricts Shhexpression during limb development

Normal patterning of tissues and organs requires the tight restriction of signaling molecules to well-defined organizing centers. In the limb bud, one of the main signaling centers is the zone of polarizing activity (ZPA) that controls growth and patterning through the production of sonic hedgehog (SHH). The appropriate temporal and spatial expression of Shh is crucial for normal limb bud patterning, because modifications, even if subtle, have important phenotypic consequences. However, although there is a lot of information about the factors that activate and maintain Shhexpression, much less is known about the mechanisms that restrict its expression to the ZPA. In this study, we show that BMP activity negatively regulates Shh transcription and that a BMP-Shhnegative-feedback loop serves to confine Shh expression. BMP-dependent downregulation of Shh is achieved by interfering with the FGF and Wnt signaling activities that maintain Shh expression. We also show that FGF induction of Shh requires protein synthesis and is mediated by the ERK1/2 MAPK transduction pathway. BMP gene expression in the posterior limb bud mesoderm is positively regulated by FGF signaling and finely regulated by an auto-regulatory loop. Our study emphasizes the intricacy of the crosstalk between the major signaling pathways in the posterior limb bud.Acknowledgements: We thank Kim Cooper, John Fallon, Cheryll Tickle, Miguel Torres and Mat Towers for critically reading the manuscript. We appreciate the excellent technical assistance of Marisa Junco and Dolores Delgado, Iñigo Casafont and members of the Piero Crespo and Ros laboratories for support. Supported by grant BFU2008-00397 from the Spanish Ministry of Education and Science. R.S. is a FPU fellow from the Spanish Ministry of Science and Innovation

A nanostructured Cu(II) coordination polymer based on alanine as a trifunctional mimic enzyme and efficient composite in the detection of Sphingobacteria

This research raises the potential use of coordination polymers as new useful materials in two essential research fields, allowing the obtaining of a new multiartificial enzyme with the capacity to inhibit the growth of bacteria resistance. The fine selection of the ligands allows the design of a new 2D coordination polymer (CP), with the formula [Cu2(IBA)2(OH2)4]n·6nH2O, by the combination of Cu (II) as the metal center with a pseudoamino acid (H2IBA = isophthaloyl bis β-alanine). Quantitative total X-ray fluorescence (TXRF) analyses show that the obtained CP can gradually release Cu (II) ions. Additionally, this CP can be nanoprocessed and transformed into a metal-organic gel (MOG) by using different Cu (II) salt concentrations and the application of ultrasounds. Considering its nanometric dimensions, the slow Cu (II) release and its simple processability, its performance as an artificial enzyme, and its antibacterial ability were explored. The results obtained show the first nanocoordination polymer acting as an artificial multienzyme (peroxidase, catalase, and superoxodismutase) exhibiting antibacterial activity in the presence of hydrogen peroxide, with selective behavior for three bacterium strains (S. spiritovirum, A. faecales, and B. cereus). Indeed, this CP shows a more robust inhibition capacity for Sphingobacterium. Going beyond that, as there are no comfortable and practically clinical tests capable of detecting the presence of Sphingobacteria, the compound can be easily embedded to form moldable gelatin that will facilitate the handling and low-cost commercial kit

Defects in memory B-cell and plasma cell subsets expressing different immunoglobulin-subclasses in patients with CVID and immunoglobulin subclass deficiencies

Background: Predominantly antibody deficiencies (PADs) are the most prevalent primary immunodeficiencies, but their B-cell defects and underlying genetic alterations remain largely unknown. Objective: We investigated patients with PADs for the distribution of 41 blood B-cell and plasma cell (PC) subsets, including subsets defined by expression of distinct immunoglobulin heavy chain subclasses. Methods: Blood samples from 139 patients with PADs, 61 patients with common variable immunodeficiency (CVID), 68 patients with selective IgA deficiency (IgAdef), 10 patients with IgG subclass deficiency with IgA deficiency, and 223 age matched control subjects were studied by using flow cytometry with EuroFlow immunoglobulin isotype staining. Patients were classified according to their B-cell and PC immune profile, and the obtained patient clusters were correlated with clinical manifestations of PADs. Results: Decreased counts of blood PCs, memory B cells (MB Cs), or both expressing distinct IgA and IgG subclasses were identified in all patients with PADs. In patients with IgAdef, B-cell defects were mainly restricted to surface membrane (sm)IgA(+) PCs and MBCs, with 2 clear subgroups showing strongly decreased numbers of smIgA(+) PCs with mild versus severe smIgA(+) MBC defects and higher frequencies of nonrespiratory tract infections, autoimmunity, and affected family members. Patients with IgG subclass deficiency with IgA deficiency and those with CVID showed defects in both smIgA(+) and smIgG(+) MBCs and PCs. Reduced numbers of switched PCs were systematically found in patients with CVID (absent in 98%), with 6 different defective MBC (and clinical) profiles: (1) profound decrease in MBC numbers; (2) defective CD27(+) MBCs with almost normal IgG(3)(+) MBCs; (3) absence of switched MBCs; and (4) presence of both unswitched and switched MBCs without and; (5) with IgG(2)(+) MBCs; and (6) with IgA(1)(+) MBCs. Conclusion: Distinct PAD defective B-cell patterns were identified that are associated with unique clinical profiles

A BMP-Shh negative-feedback loop restricts Shh expression during limb development

Normal patterning of tissues and organs requires the tight restriction of signaling molecules to well-defined organizing centers. In the limb bud, one of the main signaling centers is the zone of polarizing activity (ZPA) that controls growth and patterning through the production of sonic hedgehog (SHH). The appropriate temporal and spatial expression of Shh is crucial for normal limb bud patterning, because modifications, even if subtle, have important phenotypic consequences. However, although there is a lot of information about the factors that activate and maintain Shh expression, much less is known about the mechanisms that restrict its expression to the ZPA. In this study, we show that BMP activity negatively regulates Shh transcription and that a BMP-Shh negative-feedback loop serves to confine Shh expression. BMP-dependent downregulation of Shh is achieved by interfering with the FGF and Wnt signaling activities that maintain Shh expression. We also show that FGF induction of Shh requires protein synthesis and is mediated by the ERK1/2 MAPK transduction pathway. BMP gene expression in the posterior limb bud mesoderm is positively regulated by FGF signaling and finely regulated by an auto-regulatory loop. Our study emphasizes the intricacy of the crosstalk between the major signaling pathways in the posterior limb bud.Supported by grant BFU2008-00397 from the Spanish Ministry of Education and Science. R.S. is a FPU fellow from the Spanish Ministry of Science and Innovation.Peer Reviewe

How do we get a perfect complement of digits?

A crucial issue in limb development is how a correct set of precisely shaped digits forms in the digital plate. This process relies on patterning across the anterior-posterior axis of the limb bud, which is under the control of Sonic hedgehog emanating from the zone of polarizing activity. Recently, Sonic hedgehog function in the limb bud has been shown to have a dual character controlling both growth and patterning of the digital field. This finding has prompted the proposal of new models of how these two functions are achieved, and this will be discussed in this review. © 2008 Elsevier Ltd. All rights reserved.Supported by grant BFU2005-09309-CO2-01 from the Spanish Ministry of Education and Science.Peer Reviewe

Hoxd and Gli3 interactions modulate digit number in the amniote limb

During limb development, Sonic hedgehog (SHH) and HOX proteins are considered among the most important factors regulating digit number and identity. SHH signaling prevents the processing of GLI3 into a short form that functions as a strong transcriptional repressor. Gli3 mutant limbs are characterized by a severe polydactyly and associated ectopic anterior expression of 5′Hoxd genes. To genetically determine the involvement of 5′Hoxd genes in the polydactyly of Gli3 mutants, we have generated a compound mutant that simultaneously removes the three most 5′-located Hoxd genes and Gli3. Remarkably, the limbs that form in the absence of all four of these genes show the most severe polydactyly so far reported in the mouse. The analysis of gene expression performed in compound mutants allows us to propose that the increase in the number of digits is mediated by the gain in function of Hoxd10 and Hoxd9. Our results also support the notion that an adequate balance between positive and negative effects of different Hoxd genes is required for pentadactyly. © 2007 Elsevier Inc. All rights reserved.This work was supported by grant BFU2005-09309-CO2-01 from the Spanish Ministry of Education and Science. R.S. is a recipient of an FPU grant from the Spanish Ministry of Education and Science.Peer Reviewe

Análisis estructural de las prácticas de laboratorio de Biología

Realización de un estudio que permita ofrecer a los profesores de Ciencias una información a cerca del verdadero valor didáctico, alcance y eficacia de las prácticas de laboratorio, tal y como se desarrollan en la mayor parte de los centros educativos, y al mismo tiempo permita al grupo de investigación profundizar en la elaboración de un modelo acerca del papel que el laboratorio ha de desempeñar en el proceso de enseñanza. La muestra son 61 libros de texto de mayor difusión en los centros escolares de Cantabria, pertenecientes a un total de 17 empresas editoriales (24 libros de EGB, 29 de BUP y 8 de COU). Además se analizaron 26 libros de prácticas de laboratorio. Se han desarrollado dos vías de investigación: Un análisis lexicométrico literal del propio texto de las prácticas de laboratorio, tomando como variables independientes: los sustantivos, ya que constituyen el horizonte conceptual, y los verbos, que son las actividades que entrañan el conocimiento. Un análisis estructural, en el cual se consideraron las variables independientes: ciencia a la que se le asigna la práctica, objetivos que se pretenden, tema, nivel educativo a que se destina, y diferentes cuestiones a cerca del lugar para su realización, y tiempo estimado de duración de la misma. Realización de fichas a partir del muestreo de los libros. Análisis de los datos obtenidos de las prácticas de laboratorio existentes en los libros de texto con contenidos relacionados con la Biología. A partir de las fichas se han calculado frecuencias de repetición de los datos, cálculo de medias y de desviación estándar (tanto en el análisis estructural como lexicométrico). Además con el fin de demostrar que existe una relación entre las dos vías de investigación utilizadas, se ha hecho el estudio del coeficiente de correlación entre ambos análisis. Los resultados del análisis estructural son: 66 de las prácticas son complemento de la teoría, el 31,8 por ciento comprueban los conocimientos teóricos, el 2,2 tienen contenido propio e independiente; el 92 por ciento de las prácticas son totalmente cerradas, y sólo el 8 por ciento permiten iniciativa al alumno; la casi totalidad de las prácticas incluyen los conocimientos teóricos necesarios para su realización, sólo un 8 por ciento requieren búsqueda bibliográfica. Los resultados del análisis lexicométrico son: el 95 por ciento de los verbos referencian actividades de tipo instrumental, sólo el 1 por ciento indica actividades de tipo intelectual; el 88 por ciento de los verbos y el 96 por ciento de los sustantivos indican actividades de ejecución.CantabriaES

Hox genes regulate digit patterning by controlling the wavelength of a turing-type mechanism

The formation of repetitive structures (such as stripes) in nature is often consistent with a reaction-diffusion mechanism, or Turing model, of self-organizing systems. We used mouse genetics to analyze how digit patterning (an iterative digit/nondigit pattern) is generated. We showed that the progressive reduction in Hoxa13 and Hoxd11-Hoxd13 genes (hereafter referred to as distal Hox genes) from the Gli3-null background results in progressively more severe polydactyly, displaying thinner and densely packed digits. Combined with computer modeling, our results argue for a Turing-type mechanism underlying digit patterning, in which the dose of distal Hox genes modulates the digit period or wavelength. The phenotypic similarity with fish-fin endoskeleton patterns suggests that the pentadactyl state has been achieved through modification of an ancestral Turing-type mechanism.This work was supported by grant BFU2011-24972 from the Spanish Ministry of Science and Innovation to M. A. R. and by grant MOP-82880 from the Canadian Institutes of Health Research to M. K. R. S. was supported by a Formacion Profesorado Universitario fellowship from the Spanish Ministry of Science and Innovation; L. M. was supported by a fellowship from the EMBL-CRG Systems Biology Program.Peer Reviewe

Decoupling the function of Hox and Shh in developing limb reveals multiple inputs of Hox genes on limb growth

Limb development relies on an exquisite coordination between growth and patterning, but the underlying mechanisms remain elusive. Anterior-posterior and proximal-distal specification initiates in early limb bud concomitantly with the proliferative expansion of limb cells. Previous studies have shown that limb bud growth initially relies on fibroblast growth factors (FGFs) produced in the apical ectodermal ridge (AER-FGFs), the maintenance of which relies on a positive-feedback loop involving sonic hedgehog (Shh) and the BMP antagonist gremlin 1 (Grem1). The positive cross-regulation between Shh and the HoxA and HoxD clustered genes identified an indirect effect of Hox genes on the maintenance of AER-FGFs but the respective function of Shh and Hox genes in this process remains unknown. Here, by uncoupling Hox and Shh function, we show that HoxA and HoxD genes are required for proper AER-FGFs expression, independently of their function in controlling Shh expression. In addition, we provide evidence that the Hoxdependent control of AER-FGF expression is achieved through the regulation of key mesenchymal signals, namely Grem1 and Fgf10, ensuring proper epithelial-mesenchymal interactions. Notably, HoxA and HoxD genes contribute to both the initial activation of Grem1 and the subsequent anterior expansion of its expression domain. We propose that the intricate interactions between Hox genes and the FGF and Shh signaling pathways act as a molecular network that ensures proper limb bud growth and patterning, probably contributing to the coordination of these two processes. © 2013. Published by The Company of Biologists Ltd.This work was supported by the Canadian Institute of Health Research [CIHR-82880 to M.K.], the Canada Research Chairs program (to M.K.) and the Spanish Ministry of Science and Innovation [BFU2011-24972 to M.A.R.]. R.S. was supported by the Angelo Pizzagalli post-doctoral fellowship, D.G. was supported by a post-doctoral fellowship from the Fonds de la Recherche en Santé du Québec and M.S. was supported by a pre-doctoral fellowship from the Molecular Biology program of the University of Montreal.Peer Reviewe