Download Using a novel toxicogenetic screen in human haploid cells to identify

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Technical Title
A Functional Genetic Screen in Human Haploid Cells to Identify Genes Involved in Susceptibility to Chemical
Exposure
LayTitle
Finding the genes which confer sensitivity to formaldehyde and other toxic chemicals
Authors (Note superscript to identify author institution in the next field)
Hua Shen1, Martyn T. Smith1,2, Luoping Zhang1
Institutions
1
Division of Environmental Health Sciences, School of Public Health,
University of California, Berkeley, CA 94720; 2Institute of the Environment, University of California, Berkeley,
CA 94720
Technical Abstract (250 word limit) - 244 words in this sample
Functional genetic screening systems have been successfully applied to study susceptibility to chemical
toxicity. However, some approaches have certain limitations, including the relevance to humans of yeast
mutant screen findings and incomplete gene knock-out and off-target effects of RNA interference. Human
haploid cell models hold promise for overcoming some of these limitations as an induced gene mutation can
result in a clear phenotype due to the absence of a second gene copy. We recently developed a more
efficient semi-solid medium based screening platform that employs a human haploid cell mutant library
(KBM7-Mu) to identify genes that modulate susceptibility to chemical exposures. Compared to the liquid
medium-based approach, our method allows for simultaneously screening and generating mutant colonies
from cells resistant to the chemical of interest. This shortens the entire screening process by approximately
3 weeks and decreases the rate of false positives. Using this new approach, we identified 11 human genes
that confer the resistance to formaldehyde (FA), a known human leukemogen. Among these genes, GOT1
(Glutamic-oxaloacetic transaminase 1) and M1AP (Meiosis 1 Associated Protein) were confirmed in two
independent screening experiments. GOT1 and M1AP mutant KBM7 cells showed significant resistance to
FA-induced toxicity compared to wild type cells (KBM7-Wt), suggesting that GOT1 and M1AP are involved in
susceptibility to FA toxicity. They further demonstrate the broad applicability of this optimized approach to
screen genetic susceptibility to toxic chemicals, identify novel susceptibility genes, and gain insight into
potential mechanisms of toxicity of chemical exposures.
Lay Abstract (250 word limit) - 250 words in this sample
We know that people differ in their sensitivity to the toxic effects of chemicals. However, we do not know
which individuals will be more susceptible. Many of the biological pathways leading to toxic effects involve
genes, which are part of the body’s DNA. Genes produce proteins that can start or stop biological
processes relevant to toxic effects. This is called “gene expression” and it varies a lot. This variation can
be because of differences in the genes themselves or in diet and chemical exposures, among other factors.
These differences can contribute to greater susceptibility to chemical exposures. We have limited
information about which genes contribute to greater susceptibility to toxic chemicals. To determine this, we
improved a method using human cells to screen for genes that confer susceptibility to chemical agents. The
human “cell line” employed was modified to have one set of genes, rather than the usual two sets (one from
the mother and one from the father). We screened for genes that contribute to susceptibility to
formaldehyde, which is in resins and adhesives added to everything from paper napkins to carpeting.
Formaldehyde is an irritant and causes cancer in humans and laboratory animals. We identified 11 genes
as potentially causing susceptibility to formaldehyde. We confirmed two of these in additional experiments.
The genes are GOT1 (Glutamic-oxaloacetic transaminase 1) and M1AP (Meiosis 1 Associated Protein). We
don’t know how these genes confer susceptibility. Additional studies in human populations and in cell
cultures are needed to discover how this works.