Cell proliferation and Notch signaling coordinate the formation of epithelial folds in the Drosophila leg.

The formation of complex three-dimensional organs during development requires precise coordination between patterning networks and mechanical forces. In particular, tissue folding is a crucial process that relies on a combination of local and tissue-wide mechanical forces. Here, we investigate the contribution of cell proliferation to epithelial morphogenesis using the Drosophila leg tarsal folds as a model. We reveal that tissue-wide compression forces generated by cell proliferation, in coordination with the Notch signaling pathway, are essential for the formation of epithelial folds in precise locations along the proximo-distal axis of the leg. As cell numbers increase, compressive stresses arise, promoting the folding of the epithelium and reinforcing the apical constriction of invaginating cells. Additionally, the Notch target dysfusion plays a key function specifying the location of the folds, through the apical accumulation of F-actin and the apico-basal shortening of invaginating cells. These findings provide new insights into the intricate mechanisms involved in epithelial morphogenesis, highlighting the crucial role of tissue-wide forces in shaping a three-dimensional organ in a reproducible manner.

In vivo analysis of the evolutionary conserved BTD-box domain of Sp1 and Btd during Drosophila development.

The Sp family of transcription factors plays important functions during development and disease. An evolutionary conserved role for some Sp family members is the control of limb development. The family is characterized by the presence of three C2H2-type zinc fingers and an adjacent 10 aa region with an unknown function called the Buttonhead (BTD) box. The presence of this BTD-box in all Sp family members identified from arthropods to vertebrates, suggests that it plays an essential role during development. However, despite its conservation, the in vivo function of the BTD-box has never been studied. In this work, we have generated specific BTD-box deletion alleles for the Drosophila Sp family members Sp1 and buttonhead (btd) using gene editing tools and analyzed its role during development. Unexpectedly, btd and Sp1 mutant alleles that lack the BTD-box are viable and have almost normal appendages. However, in a sensitized background the requirement of this domain to fully regulate some of Sp1 and Btd target genes is revealed. Furthermore, we have also identified a novel Sp1 role promoting leg vs antenna identity through the repression of spineless (ss) expression in the leg, a function that also depends on the Sp1 BTD-box.

Role of Notch Signaling in Leg Development in Drosophila melanogaster.

Notch pathway plays diverse and fundamental roles during animal development. One of the most relevant, which arises directly from its unique mode of activation, is the specification of cell fates and tissue boundaries. The development of the leg of Drosophila melanogaster is a fine example of this Notch function, as it is required to specify the fate of the cells that will eventually form the leg joints, the flexible structures that separate the different segments of the adult leg. Notch activity is accurately activated and maintained at the distal end of each segment in response to the proximo-distal patterning gene network of the developing leg. Region-specific downstream targets of Notch in turn regulate the formation of the different types of joints. We discuss recent findings that shed light on the molecular and cellular mechanisms that are ultimately governed by Notch to achieve epithelial fold and joint morphogenesis. Finally, we briefly summarize the role that Notch plays in inducing the nonautonomous growth of the leg. Overall, this book chapter aims to highlight leg development as a useful model to study how patterning information is translated into specific cell behaviors that shape the final form of an adult organ.

New Records and Range Extensions for Birds from the Western Slope of the Eastern Andes, Santander, Colombia / Nuevos registros y ampliación de distribución de aves en la vertiente occidental, cordillera oriental, santander, colombia

RESUMEN Las aves de la vertiente occidental de la Cordillera Oriental en Santander han sido poco estudiadas. La Serranía de los Yariguíes y zonas aledañas, al norte del municipio de El Peñón, han sido muestreados en la última década con nuevas subespecies descritas y ampliaciones de distribución. Estudiamos las aves de la parte alta del municipio de El Peñón entre los 2750 a 2850 m s.n.m. durante ocho días de campo en agosto de 2016, mediante captura con redes de niebla y observaciones visuales y auditivas en bosques de roble. Registramos 77 especies de aves pertenecientes a 13 órdenes y 29 familias. La familia mejor representada fue Tyrannidae (Atrapamoscas) con 12 especies, seguida por Trochilidae (Colibríes) con nueve y Thraupidae (Fruteros y afines) con ocho. Registramos la ampliación de distribución geográfica para la endémica Pyrrhyra calliptera para el flanco occidental de la Cordillera Oriental, la segunda localidad para Macroagelaius subalaris para este flanco y al sur de los registros conocidos de la Serranía de los Yariguíes, ampliaciones menores o confirmación de presencia para 18 especies y otras 11 poco conocidas para este flanco. Casi el 45 % de los individuos capturados presentaron indicios de actividad reproductiva (parches de incubación o gónadas desarrolladas). Así mismo, 50 % de los individuos se encontraban mudando el plumaje, donde 15 % presentaron solapamiento entre muda y reproducción. Aunque comparte especies con los bosques al norte y sur, los bosques de roble remanentes están en buen estado e inmersos entre ecosistemas cársticos poco conocidos.

ABSTRACT Birds from the western slope of the East Andean Cordillera at Santander have been little studied. Serranía de los Yariguies and nearby areas, just north of El Peñon, have been studied in the last decade with new subspecies described and new range extensions. We studied birds from oak forests from the upper part of the municipality of El Peñon between 2750 and 2850 m a.s.l during eight field days during August 2016. Surveys included vocal and visual observations and mist netting. We report 77 species belonging to 13 different Orders and 29 Families. The best-represented family was Tyrannidae (Flycatchers) with 12 species, followed by Trochilidae (Hummingbirds) with nine and Thraupidae (fruit eaters and allies) with eight. Mayor range extensions were made for the endemic Pyrrhura calliptera - Brown-breasted Parakeet from the eastern to the western flack, confirmed a second locality for Macroagelaius subalaris-Colombian Mountain Grackle south of previously known Serranía de los Yariguies, minor range extensions or confirmed presence records for 18 species and new information for 11 poorly known species for this flank. Almost 45 % of all captured individuals showed reproductive activity (brood patches or developed gonads). 50 % of individuals were molting feathers, where 15 % showed some overlap between reproduction and molt. Even though species are shared with other forests to the north and south, the remnant oak forests are in good condition and immersed in karst ecosystems poorly known.

Illustrated and online catalog of the type specimens of birds (Class: Aves) in the Ornithological Collection at the Instituto de Investigación de Recursos Biológicos Alexander von Humboldt (IAvH-A), Colombia.

The catalog of type specimens of birds deposited in the Bird Collection of Instituto de Investigación de Recursos Biológicos Alexander von Humboldt (IAvH-A) is presented. The list includes 10 specimens representing two holotypes and eight paratypes of three nominal species and five nominal subspecies. Three specimens also have tissues deposited in the Tissue Collection of the Instituto Humboldt (IAvH-CT). Corrections, additions, and updated information of the original descriptions and geographic locations are included as individual remarks for each catalog number and a gallery of photographs of each specimen is provided. An online version of the catalog is available at: http://colecciones.humboldt.org.co/catalogos/tiposaves.

The transcription factor Dysfusion promotes fold and joint morphogenesis through regulation of Rho1.

The mechanisms that control tissue patterning and cell behavior are extensively studied separately, but much less is known about how these two processes are coordinated. Here we show that the Drosophila transcription factor Dysfusion (Dysf) directs leg epithelial folding and joint formation through the regulation of Rho1 activity. We found that Dysf-induced Rho1 activity promotes apical constriction specifically in folding epithelial cells. Here we show that downregulation of Rho1 or its downstream effectors cause defects in fold and joint formation. In addition, Rho1 and its effectors are sufficient to induce the formation of epithelial folds when misexpressed in a flat epithelium. Furthermore, as apoptotic cells can actively control tissue remodeling, we analyzed the role of cell death in the formation of tarsal folds and its relation to Rho1 activity. Surprisingly, we found no defects in this process when apoptosis is inhibited. Our results highlight the coordination between a patterning transcription factor and the cellular processes that cause the cell shape changes necessary to sculpt a flat epithelium into a three dimensional structure.

Specification and Patterning of Drosophila Appendages.

Appendages are external projections of the body that serve the animal for locomotion, feeding, or environment exploration. The appendages of the fruit fly Drosophilamelanogaster are derived from the imaginal discs, epithelial sac-like structures specified in the embryo that grow and pattern during larva development. In the last decades, genetic and developmental studies in the fruit fly have provided extensive knowledge regarding the mechanisms that direct the formation of the appendages. Importantly, many of the signaling pathways and patterning genes identified and characterized in Drosophila have similar functions during vertebrate appendage development. In this review, we will summarize the genetic and molecular mechanisms that lead to the specification of appendage primordia in the embryo and their posterior patterning during imaginal disc development. The identification of the regulatory logic underlying appendage specification in Drosophila suggests that the evolutionary origin of the insect wing is, in part, related to the development of ventral appendages.

NEST AND CHICKS OF Pseudoscops clamator (AVES: STRIGIDAE) IN THE HIGHLAND PLATEAU OF THE SABANA DE BOGOTÁ, COLOMBIA / Nido y polluelos de Pseudoscops clamator (AVES: STRIGIDAE) en el altiplano de la sabana de Bogotá, Colombia

ABSTRACT The Striped Owl (Pseudoscops clamator) has a wide geographic distribution despite that there is scarce information on its reproductive biology. In this study, we present the first published nesting records of P. clamator for Colombia. We provide data on its nesting habits and reproductive biology from observations between April and May 2013 of a nest found in a plantation of Eucalyptus globulus in Cajicá, Cundinamarca, Colombia. The ground nest is similar to those described from Argentina, Brazil, and Suriname; with a clutch of two where only one chick survived and left the nest after 25-30 days. We found in the owl diet, Brazilian guinea pig (Cavia aperea) and Eared Dove (Zenaida auriculata). Little is known about other species predated by the Striped Owl or whether this species has more than one reproductive cycle in the Bogotá highland plateau. Future studies should further examine these aspects to assess the possibilities for expansion of P. clamator in the Bogotá highland plateau.

RESUMEN El búho rayado (Pseudoscops clamator) tiene amplia distribución geográfica, y a pesar de ello la información sobre su biología reproductiva es dispersa. En este estudio presentamos el primer registro de nido de P. clamator para Colombia. Brindamos datos sobre su anidación y reproducción, basados en observaciones de un nido encontrado en una plantación de Eucalyptus globulus entre abril y mayo de 2013 en Cajicá, Cundinamarca, Colombia. El nido encontrado sobre el suelo es similar a otros previamente descritos en Argentina, Brasil y Surinam, con una nidada de dos individuos, donde sólo sobrevivió un polluelo que dejó el nido luego de 25 a 30 días de nacido. Encontramos en la dieta del búho, curíes (Cavia aperea) y paloma sabanera (Zenaida auriculaya). Poco se conoce sobre otras especies que son depredadas por el búho rayado o si esta especie presenta más de un ciclo reproductivo al año en la Sabana de Bogotá. Estos aspectos deben ser examinados en futuros estudios para evaluar las posibilidades de expansión de P. clamator en la Sabana de Bogotá.

The evolutionarily conserved transcription factor Sp1 controls appendage growth through Notch signaling.

The appendages of arthropods and vertebrates are not homologous structures, although the underlying genetic mechanisms that pattern them are highly conserved. Members of the Sp family of transcription factors are expressed in the developing limbs and their function is required for limb growth in both insects and chordates. Despite the fundamental and conserved role that these transcription factors play during appendage development, their target genes and the mechanisms by which they participate in control limb growth are mostly unknown. We analyzed here the individual contributions of two Drosophila Sp members, buttonhead (btd) and Sp1, during leg development. We show that Sp1 plays a more prominent role controlling leg growth than does btd We identified a regulatory function of Sp1 in Notch signaling, and performed a genome-wide transcriptome analysis to identify other potential Sp1 target genes contributing to leg growth. Our data suggest a mechanism by which the Sp factors control appendage growth through the Notch signaling.

The bHLH-PAS transcription factor dysfusion regulates tarsal joint formation in response to Notch activity during drosophila leg development.

A characteristic of all arthropods is the presence of flexible structures called joints that connect all leg segments. Drosophila legs include two types of joints: the proximal or "true" joints that are motile due to the presence of muscle attachment and the distal joints that lack musculature. These joints are not only morphologically, functionally and evolutionarily different, but also the morphogenetic program that forms them is distinct. Development of both proximal and distal joints requires Notch activity; however, it is still unknown how this pathway can control the development of such homologous although distinct structures. Here we show that the bHLH-PAS transcription factor encoded by the gene dysfusion (dys), is expressed and absolutely required for tarsal joint development while it is dispensable for proximal joints. In the presumptive tarsal joints, Dys regulates the expression of the pro-apoptotic genes reaper and head involution defective and the expression of the RhoGTPases modulators, RhoGEf2 and RhoGap71E, thus directing key morphogenetic events required for tarsal joint development. When ectopically expressed, dys is able to induce some aspects of the morphogenetic program necessary for distal joint development such as fold formation and programmed cell death. This novel Dys function depends on its obligated partner Tango to activate the transcription of target genes. We also identified a dedicated dys cis-regulatory module that regulates dys expression in the tarsal presumptive leg joints through direct Su(H) binding. All these data place dys as a key player downstream of Notch, directing distal versus proximal joint morphogenesis.

A comprehensive multilocus phylogeny for the wood-warblers and a revised classification of the Parulidae (Aves).

The birds in the family Parulidae-commonly termed the New World warblers or wood-warblers-are a classic model radiation for studies of ecological and behavioral differentiation. Although the monophyly of a 'core' wood-warbler clade is well established, no phylogenetic hypothesis for this group has included a full sampling of wood-warbler species diversity. We used parsimony, maximum likelihood, and Bayesian methods to reconstruct relationships among all genera and nearly all wood-warbler species, based on a matrix of mitochondrial DNA (5840 nucleotides) and nuclear DNA (6 loci, 4602 nucleotides) characters. The resulting phylogenetic hypotheses provide a highly congruent picture of wood-warbler relationships, and indicate that the traditional generic classification of these birds recognizes many non-monophyletic groups. We recommend a revised taxonomy in which each of 14 genera (Seiurus, Helmitheros, Mniotilta, Limnothlypis, Protonotaria, Parkesia, Vermivora, Oreothlypis, Geothlypis, Setophaga, Myioborus, Cardellina, Basileuterus, Myiothlypis) corresponds to a well-supported clade; these nomenclatural changes also involve subsuming a number of well-known, traditional wood-warbler genera (Catharopeza, Dendroica, Ergaticus, Euthlypis, Leucopeza, Oporornis, Parula, Phaeothlypis, Wilsonia). We provide a summary phylogenetic hypothesis that will be broadly applicable to investigations of the historical biogeography, processes of diversification, and evolution of trait variation in this well studied avian group.