Obesity is one of the biggest concerns of the American population. In 2007-2008, 34% of adults over 20 years old had been diagnosed with obesity. One of the mysteries of obesity is locating the genes responsible for it and understanding its inheritance. We all know that obesity is mostly caused by the environment, and we know there is a genetic component involved, but we do not clearly understand it. A paper was published in 2010 that discussed rare variants discovered in early onset obese patients. Since researchers knew obesity was heritable, they wanted to investigate the copy number variation to obesity in Caucasian patients who were diagnosed with early onset obesity. They first found that early onset obesity is associated with rare number variants causing rare developmental disease, such as autism and mental retardation. They discovered a large chromosomal deletion about 500 kilobases on chromosome 16p11.2, and these deletions were occurring very rarely at <1%. The 16p11.2 region of the chromosome is involved in many genes, but there is a gene that has been involved in leptin and insulin signaling called SH2B1. They found a delayed and exaggerated insulin secretion in patients who have a SH2B1 deletion. In Gene-wide association studies, they identified common single nucleotide polymorphisms (SNPs) near the SH2B1 locus which were associated with Body Mass Index (BMI). After gathering all the data, researchers proposed a mechanism to explain why the deletions are a more frequent source of loss of function at SH2B1 loci; they believe this could occur through a segmental duplication of 16p11.2 by non-allelic homologous recombination. This paper sheds light on a topic that has been very difficult to understand for a very long time.
Bochukova et al. “Large, rare chromosomal deletions associated with severe early-onset obesity.” Nature 463, 666-670.
Centers for Disease Control and Prevention. http://www.cdc.gov/nchs/fastats/overwt.htm
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