In humans, for example, a gene that causes a genetic disease may produce severe symptoms in one patient but mild symptoms in another. Paaby et al.'s findings serve as a reminder that the effect of a mutation depends on other DNA sequences in the organism. How this affected the embryo, and whether or not it was able to survive, was due in large part to the naturally-occurring genetic variation in other genes in these worms. interrupted the activity of specific genes that embryos need in order to develop. The experiments show that populations of worms harbor a lot of genetic variation that affects how they tolerate the loss of an important gene. adapted a genetics technique called a ‘modifier screen’ to study how genetic variation affects the development of a roundworm known as Caenorhabditis elegans. Within the same species, there is genetic variation in the DNA that programs embryogenesis, but it is not clear what effect this variation has on how the embryo develops. The process by which an embryo forms (which is called embryogenesis) follows a precisely controlled series of events. Some of these mutations may have a positive or negative effect on the ability of the organisms to survive and reproduce, but others may have no effect at all. These mutations may be passed on to these individuals' offspring, who in turn pass them on to their descendants.
This ‘genetic variation’ is due to random changes in the DNA-known as mutations-that occur among individuals. Individuals of the same species have similar, but generally not identical, DNA sequences. Our findings demonstrate the extent of conditional functionality in complex trait architecture. Phenotypes were mediated by many modifiers, indicating high polygenicity, but the alleles tend to act very specifically, indicating low pleiotropy. Each perturbation revealed CGV, indicating that wild-type genomes harbor myriad genetic modifiers that may have little effect individually but which in aggregate can dramatically influence penetrance.
Here, we adapted a classical modifier screen to interrogate the alleles segregating in natural populations of Caenorhabditis elegans: we induced gene knockdowns and used quantitative genetic methodology to examine how segregating variants modify the penetrance of embryonic lethality. Its essentiality may favor the accumulation of cryptic genetic variation (CGV) that has no effect in the wild-type but that enhances or suppresses the effects of rare disruptions to gene function.
Embryogenesis is an essential and stereotypic process that nevertheless evolves among species.
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