A Review of Expression in Aneuploid Drosophila S2 Cells
Donald McIntyre
July 17, 2014
A Review of Expression in Aneuploid Drosophila S2 Cells
Introduction
When you are missing copies of a gene or chromosome it can lead to cancers, miss carriages or disease
susceptibility. Zhang, Malone, Powell, Spana, MacAlpine, and Oliver (2010) examined the gene
expression in Drosophila cells with different types of gross copy number changes that are typical with
cancers. Most somatic cells are diploid with haploid restricted to post-meiotic cells. Chromosomal
aneuploidy happens when chromosome are lost or duplicated. A segmental aneuploidy can happen
when there are deletions, duplications, and unbalanced translocations. Examples of cells that are like
aneuploidy are human cancer cells. Most tumors are diploid or tetraploid that either has extra or lost
chromosomes.
Aneuploidy is sometime going to take place in a scale of genome balance, for us to understand
the way aneuploidy worked requires more studies and experimental understanding of how the result
and the general control of all gene. The Drosophila S2 tissue was used as a systematic genome-wide
segmental and aneuploidy study. The study identified 5 different tests that included segmental
aneuploidy in S2 cells, Genome-wide compensation, X chromosome, MLS complex, and a genome-wide
sublinear expression response to gene dose Zhang et al (2010).
Methods/Materials
To perform the study the authors used cell strains and media for the Drosophila S2 cells. The S2
DNA cells were extracted using a genomic DNA kit. The cDNA was synthesized by a reverse transcriptase
using mRNA fragments as a template. The data was compiled into the Firecrest and Bustard application
program Zhang et al (2010).
Results
Next generation sequencing and comparative genome hybridization was utilized to determine the
aneuploidy in S2 cells. The results found that S2 cells exhibit large regions of segmental aneuploidy
which showed an extra or lost copy. The results suggest that S2 cells are aneuploidy but are a stable
genotype. The data suggest that S2 cells are aneuploidy but are a stable genotype. The genome-wide
compensation results indicated that there are dosage compensation is genome-wide and not just on the
X chromosomes. S2 cells expressed two copies of the X chromosome and four copies of the autosome
genes. MLS is bound to certain expressed genes and there is a relationship between expression levels
and dosage compensation. The MSL is a feed-forward multiplier causing a fixed-fold effect on the X
chromosome expression no matter the number of genes that were copied. The genome-wide sublinear
expression response to gene dose the data suggested that the X chromosome is subjected to dosage
compensation based on the actual gene dose Zhang et al (2010).
Discussion
The information that was calculated allowed the authors to formulate two hypotheses. The first
hypothesis states that the expression of autosomes will remain the same and the expression of the X
chromosome is decreased by half after RNAi treatment. The second hypothesis states that the
expressions of autosomes are increased by 2 fold after the RNAi treatment and the X chromosome will
stay the same. Genes come in sets of two in diploid organisms. Where there are extra or missing copies
of genes it will cause an imbalance that may cause cancer. One of the responses was universal and tries
to correct copy number changes. On the X chromosome it tries to increase the expression regardless of
the gene dose. This study identifies the importance of balance in gene expression for cells to function
Zhang et al (2010).
Reference
Zhang, L., Malone, J., Powell, S., Periwal, V., Spana, E., MacAlpine, D., & Oliver, B. “Expression in
Aneuploid Drosophila S2 Cells.” PLoS Biology February 2010: 1-12 Web 20 June 2014