RESUMEN
The human PITX3 gene encodes a bicoid-like homeodomain transcription factor associated with a variety of congenital ocular conditions, including anterior segment dysgenesis, Peter's anomaly, and cataracts. We identified a zebrafish pitx3 gene encoding a protein (Pitx3) that possesses 63% amino acid identity with human PITX3. The zebrafish pitx3 gene encompasses approximately 16.5kb on chromosome 13 and consists of four exons, which is similar to the genomic organization of other pitx genes. Expression of the zebrafish pitx3 gene was studied by in situ mRNA hybridization and RT-PCR. The pitx3 transcripts were detected throughout development with the greatest level of expression occurring in the developing lens and brain at 24hpf. In adults, the highest expression was detected in the eye. Morpholinos were used to knockdown expression of the Pitx3 protein and a control morpholino that contains five mismatched bases was used to confirm the specificity of the phenotypes. The morphants had small eyes, misshapen heads and reduced jaws and fins relative to controls. The morphants exhibited abnormalities in lens development and their retinas contained pyknotic nuclei accompanied by a reduction in the number of cells in different neuronal classes. This suggests the lens is required for retinal development or Pitx3 has an unexpected role in retinal cell differentiation or survival. These results demonstrate zebrafish pitx3 represents a true ortholog of the human PITX3 gene and the general function of the Pitx3 protein in lens development is conserved between mammals and the teleost fish.
Asunto(s)
Proteínas de Homeodominio/metabolismo , Cristalino/embriología , Cristalino/metabolismo , Retina/embriología , Retina/metabolismo , Proteínas de Pez Cebra/metabolismo , Pez Cebra/embriología , Pez Cebra/metabolismo , Actinas/metabolismo , Secuencia de Aminoácidos , Animales , Animales Modificados Genéticamente , Clonación Molecular , Embrión no Mamífero/embriología , Embrión no Mamífero/metabolismo , Regulación del Desarrollo de la Expresión Génica/genética , Proteínas de Homeodominio/química , Proteínas de Homeodominio/genética , Humanos , Inmunohistoquímica , Datos de Secuencia Molecular , Fenotipo , Alineación de Secuencia , Pez Cebra/genética , Proteínas de Pez Cebra/química , Proteínas de Pez Cebra/genéticaRESUMEN
The effect of nutritional stress on phenotypical and genetic variation was examined for five morphological traits (thorax length, wing length, sternopleural chaeta number, abdominal chaeta number and arista branch number) in 30 isofemale lines of Drosophila melanogaster. Phenotypical variation of all traits except sternopleural chaeta number and fluctuating asymmetry of all bilateral traits were significantly higher in flies reared under poor feeding conditions. Estimates of isofemale line heritability (coefficients of intraclass correlation) did not show a consistent pattern among traits. However, additive genetic variance was generally higher in poor feeding conditions in all traits except sternopleural chaeta number, although these differences were not statistically significant. Similarly, estimates of evolvability were higher under nutritional stress for all traits except sternopleural chaeta number. These results suggest that nutritional stress increases the expression of genetic variation for some morphological traits in Drosophila and, in this respect, is similar to the effects of temperature stress studied previously.
Asunto(s)
Fenómenos Fisiológicos Nutricionales de los Animales , Drosophila melanogaster/genética , Variación Genética , Análisis de Varianza , Animales , Femenino , Genotipo , Necesidades Nutricionales , Fenotipo , TemperaturaRESUMEN
The effect of temperature, nutrition, and density stresses on phenotypic and genetic variation in morphological traits (thorax length, wing length, number of sternopleural and abdominal bristles, and number of arista branches) was examined in Drosophila melanogaster. In addition, the effect of stress on developmental stability measured as fluctuation asymmetry of bilateral traits was analyzed. All of the stresses were shown to increase phenotypic variation and fluctuating asymmetry of bilateral traits. Genetic variation of morphometric traits estimated using the isofemale line technique was higher under stressful than under normal conditions. Biotic and abiotic stresses were similar in their effect on phenotypic and genetic variation. The effect of stress on variability of morphometric traits was generally higher than on that of meristic traits. Possible causes of the increase of genetic variation under stress are discussed.
Asunto(s)
Fenómenos Fisiológicos Nutricionales de los Animales , Drosophila melanogaster/anatomía & histología , Dinámica Poblacional , Animales , Drosophila melanogaster/genética , Femenino , Variación Genética , Fenotipo , TemperaturaRESUMEN
Effect of high larval density in Drosophila melanogaster cultures on the phenotypic and genetic variation of morphological traits (thorax length, wing length, and number of stempoleural bristles) and on the stability of development (estimated as the fluctuating asymmetry of bilateral traits) was studied. The fluctuating asymmetry of both bilateral traits was higher at high than at low larval density. An increase in phenotypic variation at a high as compared to low density was demonstrated. However, no increase in genetic variation at a high density was revealed.
