Question

Pretend you are trying to establish a specific species of mosquito as a model organism in order to design more effective pesticides. After sequencing the genome of Culiseta longiareolata, you uncover a gene that has a 54% sequence similarity to the oskar gene in the fruit fly Drosophila melanogaster. To begin determining if the oskar-like gene in the mosquito has a similar function to its potential homolog in the fruit fly, you’ve decided to first test if the oskar-like gene is a morphogen. How would you begin testing whether oskar-like is a morphogen? In your response, be sure to include which technique(s) you would use and your predicted result(s).

Answer 1

Ans: Morphogens are signaling molecules produced by genes if these homologs present across the insects with a similar activity, the genes termed as morphogen genes. If the signaling molecules produced by genes which are showing some percentage of homology in different species across the insects or any other animal we can term those genes as morphogens.

The first step towards identifying and analyzing a morphogen is to determine whether a signaling molecule fulfills the criteria required to qualify as a morphogen, i.e. whether the molecule induces distinct cellular responses in a concentration-dependent manner and whether it acts directly on cells at a distance from its source.

In the question oskar are maternal effect genes of Drosophila. Its mRNA is having dual charecteristics of both coding and noncoding functions.

As an mRNA, oskar encodes a protein required for embryonic patterning and germ cell formation. Other than this absence of mRNA (not its protein product) disrupts formation of the karyosome and blocks progression through oogenesis. It shows that loss of oskar mRNA also affects the distribution of regulatory proteins, relaxing their association with large RNPs within the germline, and allowing them to accumulate in the somatic follicle cells. These noncoding functions of the oskar mRNA are mediated by multiple sequence elements with distinct roles. One role, provided by numerous binding sites in two distinct regions of the oskar 3' UTR, was to sequester the translational regulator Bruno (Bru), which itself controlled translation of oskar mRNA. This defined a novel regulatory circuit, with Bru restricting the activity of oskar, and oskar in turn restricting the activity of Bru. Other functional elements, which did not bind Bru and were positioned close to the 3' end of the RNA, acted in the oocyte and were essential. Despite the different roles played by the different types of elements contributing to RNA function, mutation of any led to accumulation of the germline regulatory factors in the follicle cells.

Now coming to the mosquito Oskar like gene having 54% sequence similarity to the oskar gene in the fruit fly Drosophila. Take this Oskar like gene from mosquito and clone in to the Drosophila, which is a mutant for oskar gene (or create a mutant by removing oskar gene) express and study mosquitos mRNA and also its translational protein product. If it shows some of the characteristics (at least 50%) of oskar like activity (oskar effects in drosophila discussed in the above paragraph) in the development of drsophila, then it can be considered as the morphogen for the drosophila gene ‘oskar’. One more methodology can be isolate oskar like gene mRNA or translational protein products from the developing mosquito and inject in to the developing drosophila mutant for oskar and see the effects on drosophila development.