A group of researchers from the Council of Scientific and Industrial Research (CSIR), New Delhi, Centre for Cellular and Molecular Biology (CCMB), Hyderabad, and the Tata Institute for Genetics and Society (TIGS), Bengaluru, have established a novel method of studying the nuclear matrix of the fruit fly (Drosophila melanogaster) without removing the nucleus from the embryo of the fruit fly. This method allows comparative study of nuclear matrix in different cells within the embryo, giving a boost for fruit fly genetics. In this regard, two papers have been published in two journals, Nucleus and Molecular and Cell Proteomics.
Fruit Fly
Fruit fly is a species of fly, which continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution. The fruit fly is typically used in research, due to its rapid life cycle, relatively simple genetics with only four pairs of chromosomes, and large number of offspring per-generation.
Nuclear Matrix and Study of Nucleus
Nuclear matrix is a scaffolding that helps package the genome differently in different types of cells. This scaffolding or nuclear matrix is typically made of polymeric biomaterials that provide the structural support for cell attachment and subsequent tissue development.
To study nuclear matrix, nucleus is taken out and the DNA is removed biochemically. Thereafter, the nucleus is treated with an enzyme that digests all the DNA. In the end, the nucleus is washed with a solution of high salt concentration so that the viable DNA proteins or protein-protein interactions are removed. As a result, a fibrous meshwork of proteins remains, known as the nuclear matrix which creates the architecture in which the genome is packaged.
Every cell that makes up an organism contains a copy of its genome. This genome in the nucleus is embedded and protected by nuclear matrix which provides access for the regulation of different genes in different cells. So, studying the nuclear matrix helps in better studying how precisely development progresses, every time a new individual is born.
Working of Human Genome
Human body consists of around 220 different types of cells. However, all the cells contain identical genomes. For instance, the same genome sequence works differently in different cells, such as in neurons, it works for thinking; in the liver, it works for the body metabolism; in the intestine, it works for digestion, and so on. Hence, it is packaged differently in different types of cells.
The different ways, in which the genome is folded and packaged in different types of cells, could be studied with the example of proteases which are enzymes that digest proteins, and are active in the intestine. The intestine contains a lining that prevents these enzymes from digesting the proteins present there, so that the intestine could be protected. The same enzymes are also present in the brain cells. If the enzymes were allowed to be active, they would digest the brain cells which do not have the protective epithelium causing disaster to brain. Hence, the genome, despite carrying all the genetic material, is packaged such that some genetic material is hidden and is never seen by transcription machinery. It means the 220 different kinds of cells in human body have identical genomes packaged in 220 different ways.
In Situ Nuclear Matrix Preparation
According to the researchers, the new method treats the nuclei within the embryo itself, known as in situ nuclear matrix preparation. For this purpose, they collected embryos which were between zero and 16 hours old. They then performed the in situ nuclear matrix preparation with these embryos and imaged them. The researchers found out that some embryos are in very early developmental stages—they are made up of nuclei only, or are just making a mono layer of nuclei across the embryos or have gone through differentiation. This entire array is made available in one single preparation through imaging.
Significance of the Study
So far, the researchers have worked in this area by tracking single molecules such as DNA-binding regulatory proteins, typically, studying one at a time. This will prove to be beneficial for the study of mitotic waves, stages of cell cycle, early dividing embryos, or late embryogenesis. The study will also open the field of fruit fly genetics to study nuclear architecture using genetic and cell biology approaches, restricted only to biochemical approaches, earlier.
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