Changes in protein synthetic activity in early Drosophila embryos mutant for the segmentation gene Krüppel

Analyzing the stability of gene expression using a simple reaction-diffusion model in an early Drosophila embryo

In all complex organisms, the precise levels and timing of gene expression controls vital biological processes. In higher eukaryotes, including the fruit fly Drosophila melanogaster, the complex molecular control of transcription (the synthesis of RNA from DNA) and translation (the synthesis of proteins from RNA) events driving this gene expression are not fully understood. In particular, for Drosophila melanogaster, there is a plethora of experimental data, including quantitative measurements of both RNA and protein concentrations, but the precise mechanisms that control the dynamics of gene expression during early development and the processes which lead to steady-state levels of certain proteins remain elusive. This study analyzes a current mathematical modeling approach in an attempt to better understand the long-term behavior of gene regulation. The model is a modified reaction-diffusion equation which has been previously employed in predicting gene expression levels and studying the relative contributions of transcription and translation events to protein abundance [10,11,24]. Here, we use Matrix Algebra and Analysis techniques to study the stability of the gene expression system and analyze equilibria, using very general assumptions regarding the parameter values incorporated into the model. We prove that, given realistic biological parameter values, the system will result in a unique, stable equilibrium solution. Additionally, we give an example of this long-term behavior using the model alongside actual experimental data obtained from Drosophila embryos.

Protein mutations revealed by two-dimensional electrophoresis

High-resolution two-dimensional electrophoresis (2DE) can resolve many hundreds of proteins present in complex mixtures depending on the method of detection. These proteins can be characterised qualitatively, with respect to their electrophoretic mobilities (i.e. charge and apparent molecular mass) and quantitatively, using densitometry, to determine their amounts. There has been a widespread application of 2DE in the analysis and characterisation of protein mutations for a range of organisms. This review presents examples of the use of 2DE to study naturally occurring protein mutations and polymorphisms as well as the characterisation of induced protein mutations in prokaryotes and eukaryotes. Examples are presented to illustrate the use of 2DE to detect mutations affecting the electrophoretic mobility and biosynthesis of individual proteins as well as mutations leading to global alterations in cellular protein synthesis. The advantages and disadvantages of 2DE in the detection of protein mutations are discussed.

Gene expression patterns in the black blowfly (Phormia regina) as revealed by two-dimensional electrophoresis of proteins. I. Developmental stage-specific and sex-specific differences

The black blowfly, Phormia regina, has been implicated in human myiasis and as a contact vector of viral and bacterial diseases present in carrion to which female flies are attracted for egg deposition. Inbred strains of P. regina are an excellent model system for studying gene expression in the developmental stages of such holometabolous dipteran parasites. However, information regarding gene and protein expression patterns in P. regina is limited. We used ISO-DALT high-resolution, two-dimensional electrophoresis with silver staining to establish fundamental protein maps for examination of the stage-specific gene expression patterns in the 615 most abundant proteins of the eggs, first- and third-instar larvae, pupae, and male and female adults. We also used a differential extraction technique to identify the major cuticular proteins of the adults. The results show 48 clearly identifiable stage-specific and sex-specific proteins. Thus, approximately 8% of the most abundant proteins exhibit developmental changes. These analyses serve as an initial data base for further studies of ontogenetic regulation, organellar origin, and physiologic function of the stage-specific proteins in the life cycle of these opportunistically parasitic dipterans.