We also CanFly! The 2nd MexFly drosophila research conference

ABSTRACT

The 2nd Mexican Drosophila Research Conference (MexFly) took place on June 30th and July 1st, 2016 in Mexico City, at the Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav). Principal investigators, postdocs, students, and technicians from Drosophila labs across Mexico attended. The guest speaker was Chris Rushlow from New York University, who presented work on Zelda, a key transcriptional activator of the early zygotic genome. Here we provide a brief report of the meeting, which sketches the present landscape of Drosophila research in Mexico. We also provide a brief historical note on one of the pioneers of the field in this country, Victor Salceda, personally trained by Theodosius Dobzhansky. Salceda presented at the meeting an update of his collaborative project with Dobzhansky on the distribution of Drosophila pseudoobscura chromosomal inversions, initiated over forty years ago.

KEYWORDS:

• genetics
• developmental biology
• evolutionary biology
• systems biology
• toxicology
• metal physiology

Theodosius Dobzhansky's fly-collecting trips in Mexico and Guatemala in the late 1930s contributed to the advisory role he offered three decades later in setting up the first Drosophila laboratory in Mexico.

“The Genetics and Radiobiology Program, founded by de Garay in 1960… was fundamental to the development of genetics in Mexico… One of the young scientists sent for training abroad was Victor Salceda. In 1965 he spent 2 y at Dobzhansky's laboratory at Rockefeller University in New York…. Upon his return to Mexico, and following Dobzhansky's suggestion, Salceda proposed to de Garay that he continue with Dobzhansky's collections of D. pseudoobscura in Mexico, seeking more fully to describe and understand the patterns of geographic distribution of the third chromosome inversion polymorphisms. Salceda's training at Rockefeller University had prepared him to recognize these inversions, and thus he was well prepared to lead the Mexican scientists who would participate in the project.”^{1, p984;*}

Salceda, now a researcher at the National Institute for Nuclear Research of Mexico (ININ), was one of the sixty participants that attended the 2nd MexFly Drosophila Meeting held at the Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav) in Mexico City on June 30 – July 1, 2016. He contributed a lecture where he described the continuation of work he initiated with Dobzhansky nearly 50 y ago^4,5 (Fig. 1). The variation in relative frequencies of third chromosome inversions was analyzed during 1974–2000 in three populations of Drosophila pseudoobscura (Amecameca, Tulancingo and Zirahuén). Fifteen chromosomal re-arrangements were observed in total, of which five were prevalent. Differences between the populations and cyclic patterns of dominant inversions were noted with periods of 4–5 y.⁴

Figure 1. Victor Salceda (left) and Theodosius Dobzhansky (right) during fly collecting trips in 1974 on the outskirts of the Popocatépetl volcano (A) and Michoacán (B). Photos are courtesy of Victor Salceda.

Figure 2. Group photograph of participants at the 2nd MexFly meeting. At the center of the photo in the first row is Victor Salceda. Second from right is Chris Rushlow, who was our invited speaker. The meeting's closing lecture was given by Juan Riesgo (tallest man on the front row). Photo is courtesy of Angel Marín.

In 2001, Juan Riesgo Escovar, a group leader at the Neurobiology Institute of the National Autonomous University of Mexico (UNAM) organized a small fly conference at an Hacienda near the city of Queretaro. This first fly meeting gathered about 20 attendees, most of them affiliated with the UNAM. Since then, the Drosophila community in Mexico has grown dramatically – we could say that the community is in its larval stage! In the past 5 y, Cinvestav recruited three Drosophila researchers as principal investigators (PIs); the authors, working at its main campus in Mexico City, and Teri Markow from Cinvestav's National Laboratory of Genomics for Biodiversity (LANGEBIO) located in Irapuato, a small city from the central State, Guanajuato. It was natural then, that we came up to propose the main campus of Cinvestav, in the northern part of Mexico City, as the venue for a second Drosophila meeting in Mexico (Fig. 2). For this meeting, we set ourselves three goals: (1) Reach out all Drosophila labs working in Mexico; (2) Secure institutional funding to support the attendance of as many students and postdocs as possible; and (3) Honor Victor Salceda and the history of Drosophila research in Mexico.

The name MexFly responded to the acronym pioneered by Canadian colleagues.⁶ The MexFly meeting had a two-day format, starting with a keynote lecture by Chris Rushlow, from New York University, who spoke about her work on the Zelda (Zld) transcription factor,⁷ whose binding to blastoderm-active enhancers is predictive of enhancer function.⁸ Zld binds to patterning genes before they become active suggesting that Zld may function as a pioneer factor. The early Drosophila embryo is patterned by a ventral-to-dorsal nuclear gradient of the transcription factor, Dorsal, that establishes different gene expression patterns in a concentration-dependent manner.^9,10 Changing the number of Zld binding sites in Dorsal moprhogen target enhancers without changing the Dorsal binding sites, can alter the transcriptional response.¹¹ Thus, the differential effects of Dorsal concentrations on its target genes can depend on their differential sensitivity to the uniform factor Zld. Chris Rushlow further hypothesized that Zld binding displaces and/or precludes nucleosome formation over enhancer regions, thus potentiating the activity of transcription factors by increasing accessibility to their cognate binding sites. She presented results obtained in collaboration with the Zeitlinger lab assessing Dorsal binding and nucleosome occupancy in wild-type and zld mutant embryos showing that Zld lowers the (intrinsically high) nucleosome barrier at enhancers, thereby allowing other transcription factors to bind and activate gene expression.¹² In this way, Zld plays a key pioneer role during zygotic genome activation in Drosophila.

Unlike other meetings where most talks are given by PIs, at the 2nd MexFly meeting we asked the PIs to propose one or two students/postdocs to represent the work in their laboratories. Thus, most talks were given by students/postdocs, providing to most of them, a first opportunity to speak about their work in a formal setting. In addition, a poster session was also held, so other students were able to share their results and get feedback from their peers. All talks and posters were presented in English.

Students from Teri Markow's lab presented work on cactophilic Drosophila,¹³ including Karina López Olmos on the evolution of Glutathione-S-Transferase D1 in these species, Alejandra Pérez Leaños on the distribution of mites in nature,¹⁴ Nestor Nazario Yepiz on differential responses of ecologically diverse species to diets differing in sugar and protein, and Cynthia Castro Vargas on incipient speciation in Drosophila aldrichi.

Members of Mario Zurita's lab from the Institute of Biotechnology of the UNAM (IBT-UNAM) in Cuernavaca shared work on early embryonic transcription.¹⁵ Joselyn Chávez Fuentes, in collaboration with Viviana Valadez Graham, showed a novel role for the dAtrx ATPase chromatin remodeling complex in telomeric maintenance, while Alyeri Bucio Méndez presented studies on the regulation of the translation of a bicistronic mRNA in Drosophila melanogaster encoding for proteins that function in different complexes with the TFIIH transcription factor and the SWR1 chromatin remodeling complex. Saraí Valerio Cabrera presented confocal imaging of embryos expressing Cdk7, Mat1, and Cyclin H (the Cdk activating kinase components of the TFIIH) fused to fluorescent proteins and also RNA interference of Cdk7, which resulted in mitotic defects and retarded development, although surprisingly not in lethality.

From the laboratory of Marcos Nahmad that focuses on systems-biology approaches to developmental biology,¹⁶ Maria del Carmen Andrés Barrera presented unpublished work on wing morphogenesis and Luis Manuel Muñoz Nava presented a poster on the spatio-temporal quantification of the Vestigial gradient in the Drosophila wing disc.

The Missirlis lab uses the fly to study the function of metals in biology.^17,18 Posters were from Carlos Tejeda Guzmán describing the storage mechanism for zinc ions in Malpighian tubules, Johana Vásquez Procopio on the intestinal proteome of a manganese-depleted fly, while Abraham Rosas-Arellano (who represented also the Austral University of Chile at the meeting) described an antibody enhancer solution (hydrogen peroxide, glycine, triton-X and tween-20), which results in improved immunofluorescence imaging.¹⁹

Angel Carvajal Oliveros presented shared work from the Enrique Reynaud (IBT-UNAM) and Veronica Narvaez-Padilla (University Autonomous of Morelos) labs on the effects of nicotine on the central nervous system of flies.²⁰ Nicotine toxicity also featured in Brenda Gómez Loza's poster, from the group led by Maria Eugenia Heres-Pulido at the Iztacala campus of the UNAM, with Irma Dueñas García reporting on the modulation of nitroquinoline-1-oxide genotoxicity by cotreatments with lycopene, resveratrol, vitamin C with or without ferrous sulfate using the wing spot test.²¹

América Castañeda Sortibrán from the UNAM's Faculty of Sciences demonstrated genotoxicity of the herbicide clomazone using an improved version of the same assay where in addition to the standard basal metabolic capability cross, a high bioactivation cross with constitutive overexpression of P450 enzymes was employed. The results suggested that the current classification of clomasone as a non-mutagenic pesticide should be revised. Ricardo Peraza Vega from the same group, headed by Rosario Rodríguez Arnaiz, described a new comet assay using cells from the wing imaginal discs of Drosophila larvae to test the toxicity of another herbicide, diuron, which causes DNA breaks observable on the comet assay that could be related to the mutation and recombination events obtained with the classic wing-spot test.²²

The Diana Reséndez-Pérez lab from the University Autonomous of Nuevo Leon in Monterrey presented novel work on the regulation of Antennapedia (Antp).²³ Asking how different Hox genes acquire their specificity despite their similar DNA homeodomain preferences, Claudia Altamirano Torres showed a physical interaction between Antp and TFIIE-β, implicating this protein-protein interaction during antenna specification in development. Jannet Salinas Hernández analyzed Antp regulation by micro-RNAs and specifically showed that miR-304 recognized target sites in the Antp 3′ untranslated region, reduced endogenous expression of Antp and affected homeotic antenna transformation.

The Mexican fly, Anastrepha ludens, could not be absent from this event: Ximena Gutiérrez Ramos from the University of Veracruz presented the expression pattern of zld in this native-of-Mexico fly species.

Finally, Juan Riesgo Escovar presented the closing lecture of the meeting speaking about his work on aaquetzalli (aqz) and chem, two different vital genes (named after fan in the Aztec language Nahuatl and boat in the Maya language, respectively) that are required for epithelial polarity in the embryo.²⁴ In aqz, the earliest phenotype was seen during formation of the nervous system, as the differentiation between neuroblasts and epidermoblasts was disrupted. In chem, the distribution of several subapical and basolateral membrane proteins (Crumbs, Coracle, Armadillo) was affected leading to disrupted lateral and salivary gland epithelia. Thus, loss-of-function mutations in either aqz or chem lead to disrupted epithelia.

The next MexFly meeting is being scheduled for 2018 in Cuernavaca. For the 2nd MexFly, the organizers were fortunate to receive a generous grant from the Cinvestav that covered travel and accommodation costs for all the students who participated at the event and enabled us to invite our international speaker. The challenge we pass on to the IBT-UNAM is how to secure the funding for extending the invitation to students and postdocs from Mexico working abroad with the best-studied multicellular genetic model system available to experimental biologists. If you are reading this and thinking of joining us for the 3rd MexFly Meeting, stay put, we would love to see you in Cuernavaca in 2018!

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.

Acknowledgments

The organizers wish to acknowledge Cinvestav and in particular Ricardo Felix, who, in the capacity of the Academic Secretary, approved funding for this event. The meeting ran smoothly thanks to the generous help on the ground by Andrea Salazar, Luz María Buendía Rangel, Beatriz Osorio, Benjamín Muñoz Ramirez, and Jose Luis Fernandez.

Notes

* For a concise history of the institutionalization of genetics in Mexico, which rightly included an experimental Drosophila research laboratory led by Rodolfo Félix Estrada, see references 2 and 3.