title: rst transcriptional activity influences kirre mRNA concentration in the Drosophila pupal retina during the final steps of ommatidial patterning.
abstract: BACKGROUND
  Drosophila retinal architecture is laid down between 24-48 hours after puparium formation, when some of the still uncommitted interommatidial cells (IOCs) are recruited to become secondary and tertiary pigment cells while the remaining ones undergo apoptosis. This choice between survival and death requires the product of the roughest (rst) gene, an immunoglobulin superfamily transmembrane glycoprotein involved in a wide range of developmental processes. Both temporal misexpression of Rst and truncation of the protein intracytoplasmic domain, lead to severe defects in which IOCs either remain mostly undifferentiated and die late and erratically or, instead, differentiate into extra pigment cells. Intriguingly, mutants not expressing wild type protein often have normal or very mild rough eyes.
  
  
  RESULTS
  By using quantitative real time PCR to examine rst transcriptional dynamics in the pupal retina, both in wild type and mutant alleles we showed that tightly regulated temporal changes in rst transcriptional rate underlie its proper function during the final steps of eye patterning. Furthermore we demonstrated that the unexpected wild type eye phenotype of mutants with low or no rst expression correlates with an upregulation in the mRNA levels of the rst paralogue kin-of-irre (kirre), which seems able to substitute for rst function in this process, similarly to their role in myoblast fusion. This compensatory upregulation of kirre mRNA levels could be directly induced in wild type pupa upon RNAi-mediated silencing of rst, indicating that expression of both genes is also coordinately regulated in physiological conditions.
  
  
  CONCLUSIONS
  These findings suggest a general mechanism by which rst and kirre expression could be fine tuned to optimize their redundant roles during development and provide a clearer picture of how the specification of survival and apoptotic fates by differential cell adhesion during the final steps of retinal morphogenesis in insects are controlled at the transcriptional level.
authors.affiliation: Departmento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Maiaro Cabral Rosa
authors.initials: MC
authors.lastname: Machado
authors.forename: Shirlei
authors.initials: S
authors.lastname: Octacilio-Silva
authors.forename: Mara Silvia A
authors.initials: MS
authors.lastname: Costa
authors.forename: Ricardo Guelerman P
authors.initials: RG
authors.lastname: Ramos
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005123:Eye / Q000254:growth & development / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D009024:Morphogenesis; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D011679:Pupa / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012160:Retina / Q000254:growth & development / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D015816:Cell Adhesion Molecules, Neuronal; D029721:Drosophila Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C413082:kirre protein, Drosophila; C085209:rst protein, Drosophila