Gene Variants Linked to Educational Attainment

Gene Variants Linked to Educational Attainment

  7:49:00 AM    Science Lover

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A multi-national team of researchers has identified genetic markers that predict educational attainment by pooling data from more than 125,000 individuals in the United States, Australia, and 13 western European countries.

A multi-national team of researchers has identified genetic markers that predict educational attainment by pooling data from more than 125,000 individuals in the United States, Australia, and 13 western European countries. (Credit: © Tom Wang / Fotolia)

The study, which appears in the journal Science, was conducted by the Social Science Genetic Association Consortium (SSGAC), which includes researchers at NYU, Erasmus University, Cornell University, Harvard University, the University of Bristol, and the University of Queensland, among other institutions.

The SSGAC conducted what is called a genome-wide association study (GWAS) to explore the link between genetic variation and educational attainment -- the number of years of schooling completed by an individual and whether he or she graduated college. In a GWAS, researchers test hundreds of thousands of genetic markers for association with some characteristics such as a disease, trait or life outcome.

Because the sample included people from different countries -- where markers for schooling vary significantly -- the research team adopted the International Standard Classification of Education (ISCED) scale, which is a commonly used method for establishing a uniform measure of educational attainment across cohorts.

Anticipating that very large samples would be required to credibly detect genetic associations, the SSGAC researchers assembled a total sample size more than 10 times larger than any previous genetic study of any social-scientific outcome. The team examined associations between educational attainment and genetic variants called single-nucleotide polymorphisms, or SNPs, which are tiny changes at a single location in a person's genetic code.

The study found that the genetic markers with the strongest effects on educational attainment could each only explain two one-hundredths of a percentage point (0.02 percent). To put that figure into perspective, it is known from earlier research that the SNP with the largest effect on human height accounts for about 0.40 percent of the variation.

Combining the two million examined SNPs, the SSGAC researchers were able to explain about 2 percent of the variation in educational attainment across individuals, and anticipate that this figure will rise as larger samples become available.

"We hope that our findings will eventually be useful for understanding biological processes underlying learning, memory, reading disabilities and cognitive decline in the elderly," said co-author Daniel Benjamin, a behavioral economist at Cornell who is a co-director of the SSGAC.

"Another contribution of our study is that it will strengthen the methodological foundations of social-science genetics," said David Cesarini, an NYU assistant professor at the Center for Experimental Social Science and the Center for Neuroeconomics, who also co-directs the SSGAC. "We used 125,000 individuals to conduct this study. Previous studies used far smaller samples, sometimes as small as 100 individuals and rarely more than 10,000. These small samples make sense under the assumption that individual genes have large effects. However, if genes have small effects, as our study shows, then sample sizes need to be very large to produce robust findings that will reliably replicate in other samples."

The researchers were careful to note that they have not discovered "the gene for education" or that these findings somehow imply that a person's educational attainment is determined at birth.

"For most outcomes that we study as social scientists, genetic influences are likely to operate through environmental channels that are modifiable," explained NYU sociologist Dalton Conley, one of the study's co-authors who also serves on the Advisory Board of the SSGAC. "We have now taken a small but important first step toward identifying the specific genetic variants that predict educational attainment. Armed with this knowledge, we can now begin to examine how other factors -- including public policy, parental roles, and economic status -- dampen or amplify genetic effects and ultimately devise better remedies to bolster educational outcomes." 

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Sexual Plant Reproduction: Male and Female Parts 'Talk' in the Same Way as Do Cells in Your Brain

Sexual Plant Reproduction: Male and Female Parts 'Talk' in the Same Way as Do Cells in Your Brain

  9:38:00 AM    Science Lover

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A team of researchers at the Instituto Gulbenkian de Ciência (IGC), Portugal, discovered that pollen, the organ that contains the plant male gametes, communicate with the pistil, their female counterpart, using a mechanism commonly observed in the nervous system of animals. This study not only reveals a new mechanism which underlies reproduction in plants, but also opens an exciting new avenue in the study of how cell-cell communication is conserved between animals and plants.

This is a microscope image of the pollen grains germinating 
at the stigma of the weed Arabidopsis Thaliana. 
(Credit: Jose Feijo / Instituto Gulbenkian de Ciencia)

 

The research was recently published in Science Express of the journal Science.

For many years biologist have observed regular oscillations in several parameters that control growth of pollen tubes, such as pH (concentration of proton ions) and calcium ions, but the actual molecular channels that control these oscillations and their physiological output have remained elusive. Led by José Feijó, group leader at the IGC and Professor at Lisbon University, this international team have now discovered that the oscillations of calcium ions in the growing pollen tubes of tobacco and the Arabidopsis plant are facilitated by channels called Glutamate receptors-like (GLRs), and that these channels are opened by, amongst other components, a rare aminoacid, D-serine (D-Ser). Both D-Ser and GLRs are key molecular players in cell-cell communication in the animal central nervous systems, at various levels: they play a central role in memory and learning processes in the brain, and have been implicated in a wide range of neurodegenerative diseases such as multiple sclerosis, Alzheimer, Huntington's disease and others. And now, surprisingly, they also have a role in reproduction of plants.

Working in the IGC laboratories, the team used an extensive combination of genetic, pharmacologic and electrophysiological techniques to reveal the role of glutamate receptor-like (GLRs) genes and D-serine in pollen grains, and their physiological impact on plant reproduction. In proving that GLRs are calcium channels, the team also solved two long-standing riddles in plant biology: the molecular nature of calcium channels in the outer membrane of plant cells, a central question in plant physiology elusive for more than 20 years, and what are the functions of GLRs genes in plants, a fact that has puzzled biologists ever since the first genome of the model plant Arabidopsis was sequenced.

Plant reproduction is a complex and highly coordinated process. Pollen grains, which contain the plants' male gametes (sperm cells), are carried from the male organ of the flower (the stamen) to the female organ (the pistil). Here the pollen germinates and grows a pollen tube, which extends and is guided to the ovary, where it releases the sperm. The sperm fuse with the egg cells, giving rise to an embryo, part of the seed.

In this study, the researchers showed that impairing the GLR functions in male gametes leads to partial male sterility: fewer seeds are produced by the plant, and the pollen tubes are abnormal. Furthermore, D-serine activates the GLRs on the tips of pollen tubes, allowing calcium ions to flow into the tube. They took their research a step further demonstrating that D-serine is indeed produced in the female sexual organs, and that absence of D-serine in these organs also leads to deformed pollen tubes. Together, these findings strongly suggest that D-serine, produced in the female sexual organs may have a role in guiding pollen tubes to their final target.

José Feijó says, "Pollen tubes are a model system for cellular tip-growth, a process common to fission yeast, filamentous fungi, the root hairs of plants and nerve cells. Our findings, implicating analogous genes in growth processes in both plants and animals, underscores how evolution re-uses successful mechanisms, over and over again. We feel that our research, performed in Arabidopsis and tobacco, now opens doors for the study of conserved cell-cell communication processes, across plant and animals species."

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