The purpose of this study is to gain an understanding of the fos B gene and it's neurological effects on the behavior of mice through the analysis of "A Defect in Nurturing in Mice Lacking the Immediate Early Gene fos B" appearing in the July 26 issue of Cell. Through various chemical and behavioral tests it is found that fos B mothers demonstrate an inability to nurture their young. It was shown that the lack of expression of the fos B gene in certain areas of the brain was the probable cause of the lack of the nurturing response in the mutant mice.
Immediate Early Genes (IEGs)
When the central nervous system of an organism receives a stimulus, such as light, visual images, odors, etc., programs of gene expression are initiated. This expression of genes can start within minutes of receipt of the stimulus, and last for many hours in certain parts of the brain. The very first genes to be expressed are called the Immediate Early Genes. These genes can be transcribed almost immediately without the formation of new proteins.
fos B: A Member of the fos Family
The fos B gene belongs to a group of genes known as the fos family. The fos family has four members: c-fos, fos B, fra-1, and fra-2. The members of the fos family work in conjunction with a group called the Jun family. The protein that is produced as a result of fos gene expression can be dimerized with Jun prodeits utilizing a leucine zipper domain. This unit then binds to a certain region of DNA.
The fos family of genes are expressed during a variety of adaptive neural responses. It has been found that fos related proteins are activated in areas of the nervous system that are needed for nurturing behavior.
Creating a fos B lacking Population
In order to test the effect of the fos B gene, mice lacking the gene were needed. Using recombinant DNA techniques, scientists were able to create a population of mice in which the gene was knocked out.
Scientists injected PGK-neo into plasmids used to transvect embryonic stem cells from mice. PGK-neo is a neomycin resistance gene which makes cells resistant to cell killing by both neomycin and gangcyclovir. Using this trait, these cells could then be isolated. Gangcyclovir and neomycin, when phosphorized become toxic to cells, thus killing these cells. As a result the resistant cells become isolated. These cells are then injected into blastosises from pregnant albino mice. These mice give birth to agouti pups heterozygous for the fos B gene. These mice are then bred together, thus producing some offspring that are homozygous recessive for the fos B gene.
Using blotting techniques the homozygous recessive mice were separated from the other pups. Blotting is a process when samples are cut using a restriction enzyme (Southern blot utilizes DNA, western blots use proteins, and northern blots use mRNA). These resultant fragments are separated by gel electrolysis. Thus it is possible to identify the mice lacking the fos B...