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Genomics In The Journals: Dec 6, 2012

NEW YORK (GenomeWeb News) – In Nature Genetics, members of the Early Growth Genetics Consortium have presented evidence for an overlap between genetic loci influencing birth weight — a trait that reflects growth in utero — and metabolically-related features that manifest themselves in adulthood, such as height or type 2 diabetes risk.

The shared genetic features were uncovered through the team's multi-stage meta-analysis involving tens of thousands of Europeans assessed through previous studies. Using that approach, researchers uncovered seven loci linked to birth weight, including four not detected in the past. Two of these birth weight-associated regions had past ties to adult height, they noted, two more to type 2 diabetes, and a fifth to blood pressure in adults.

"Our findings add to the growing evidence that events during early growth in the womb can have a significant impact on our health as adults," the University of Oxford's Mark McCarthy, co-senior author on the paper, said in a statement.

"However, these genes tell only part of the story," he added. "It's important that we understand how much is down to genetics and how much is due to the environment in which we grow so that we can target efforts to prevent disease later in life."

The average human genome contains an estimated 400 damaging variants and two disease-related mutations, according to an American Journal of Human Genetics paper by members of the 1000 Genomes Project consortium.

From low-coverage genome sequence data representing 179 apparently healthy individuals assessed for the pilot stage of the 1000 Genomes Project, coupled with database information on variants known or suspected to be deleterious, the team estimated that each of our genomes contains some 281 to 515 missense substitutions. They are also home to a slew of SNPs that could confer elevated disease risk, it seems, and between 40 and 110 variants are believed to cause disease based on their inclusion in the Human Gene Mutation Database. Moreover, researchers explain, an average of 40 to 85 missense substitutions and three to 24 disease-causing variants are found in the more damaging homozygous form, in which both versions of a given allele are potentially risky.

"We now know that normal healthy people can possess many damaged or even completely inactivated proteins without any noticeable impact on their health," co-author David Cooper, a medical genetics researcher with Cardiff University, said in a statement.

"It is extremely difficult to predict the clinical consequences of a given genetic variant," he explained, "but databases such as [the Human Gene Mutation Database] promise to come into their own as we enter the new era of personalized medicine."

A Current Biology study suggests that the diverse Romani populations living in Europe today are descendants of a group that lived in north or northwest India around 1,500 years ago.

Researchers from Spain, the Netherlands, and elsewhere relied on information at more than 800,000 SNPs across the genomes of 152 individuals from 13 Romani groups in Europe to reconstruct the Romani people's past. Their results indicate that, as a group, present-day European Romani individuals are not most closely related to the European populations that left their mark on Romani language patterns. Instead, the team explains, an ancestral Romani group appears to have started off in India, moving into Europe by way of the Balkans an estimated 900 years ago, and then mixing with various European populations.

"From a genome-wide perspective, Romani people share a common and unique history that consists of two elements: the roots in northwestern India and the admixture with non-Romani Europeans accumulating with different magnitudes during the out-of-India migration across Europe," Erasmus University's Manfred Kayser, one of the study's senior authors, said in a statement.

A team from the US and France tallies up the genes participating in mutagenic DNA repair networks in Escherichia coli for a study in Science.

The researchers used an insertional mutagenesis screen in E. coli to find potential contributors to stress-induced mutagenesis pathways. The search uncovered 77 new genes belonging to networks behind mutagenic DNA repair — a process that uses error-prone polymerase enzymes and other mechanisms to elevate the chance of mutation when cells face double-strand DNA breaks during stressful situations. That brings the total set of known mutagenic repair network genes up to at least 93, study authors say, explaining that many of these genes feed in to three main pathways that seem to sense and respond to stress.

"It's a resounding confirmation of the regulation of mutagenesis by stress responses," senior author Susan Rosenberg, a molecular and human genetics researchers with Baylor College of Medicine, said in a statement, "which causes mutations specifically when cells are maladapted to their environment — when mutations might allow the cell to adapt."

Genomics In The Journals is a weekly feature pointing readers to select, recently published articles involving genomics and related research.

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