Featured Research

from universities, journals, and other organizations

Genomic 'hotspots' offer clues to causes of autism, other disorders

Date:
December 20, 2012
Source:
University of California - San Diego
Summary:
Scientists have discovered that "random" mutations in the genome are not quite so random after all. Their study shows that the DNA sequence in some regions of the human genome is quite volatile and can mutate ten times more frequently than the rest of the genome.

Spontaneous mutations in the germline are a significant factor influencing genetic risk for autism spectrum disorders (ASDs). Using whole-genome sequencing of autism families, Michaelson et al. (pp. 1431–1442) determine the intrinsic characteristics of the genome that influence regional mutation rates and quantify the effect of paternal age on global mutation rate. Mutation rates vary widely throughout the genome, and regional hypermutation emerges as a factor determining the contribution of individual genes to risk for ASD and other disorders in the population.
Credit: Michaelson et al., Cell. Artwork by Evgeny Buryat Onutchin

An international team, led by researchers from the University of California, San Diego School of Medicine, has discovered that "random" mutations in the genome are not quite so random after all. Their study, to be published in the journal Cell on December 21, shows that the DNA sequence in some regions of the human genome is quite volatile and can mutate ten times more frequently than the rest of the genome. Genes that are linked to autism and a variety of other disorders have a particularly strong tendency to mutate.

Clusters of mutations or "hotspots" are not unique to the autism genome but instead are an intrinsic characteristic of the human genome, according to principal investigator Jonathan Sebat, PhD, professor of psychiatry and cellular and molecule medicine, and chief of the Beyster Center for Molecular Genomics of Neuropsychiatric Diseases at UC San Diego.

"Our findings provide some insights into the underlying basis of autism -- that, surprisingly, the genome is not shy about tinkering with its important genes" said Sebat. "To the contrary, disease-causing genes tend to be hypermutable."

Sebat and collaborators from Rady Children's Hospital-San Diego and BGI genome center in China sequenced the complete genomes of identical twins with autism spectrum disorder and their parents. When they compared the genomes of the twins to the genomes of their parents, the scientists identified many "germline" mutations (genetic variants that were present in both twins but not present in their mother or father).

Nearly 600 germline mutations -- out of a total of 6 billion base pairs -- were detected in the 10 pairs of identical twins sequenced in the study. An average of 60 mutations was detected in each child.

"The total number of mutations that we found was not surprising," said Sebat, "it's exactly what we would expect based on the normal human mutation rate." What the authors did find surprising was that mutations tended to cluster in certain regions of the genome. When the scientists looked carefully at the sites of mutation, they were able to determine the reasons why some genomic regions are "hot" while other regions are cold.

"Mutability could be explained by intrinsic properties of the genome," said UC San Diego postdoctoral researcher Jacob Michaelson, lead author of the study. "We could accurately predict the mutation rate of a gene based on the local DNA sequence and its chromatin structure, meaning the way that the DNA is packaged."

The researchers also observed some remarkable examples of mutation clustering in an individual child, where a shower of mutations occurred all at once. "When multiple mutations occur in the same place, such an event has a greater chance of disrupting a gene," said Michaelson.

The researchers surmised that hypermutable genes could be relevant to disease. When they predicted the mutation rates for genes, the authors found that genes that have been linked to autism were more mutable than the average gene, suggesting that some of the genetic culprits that contribute to autism are mutation hotspots.

The authors observed a similar trend for other disease genes. Genes associated with dominant disorders tended to be highly mutable, while mutation rates were lower for genes associated with complex traits.

"We plan to focus on these mutation hotspots in our future studies," said Sebat. "Sequencing these regions in larger numbers of patients could enable us to identify more of the genetic risk factors for autism."


Story Source:

The above story is based on materials provided by University of California - San Diego. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jacob J. Michaelson, Yujian Shi, Madhusudan Gujral, Hancheng Zheng, Dheeraj Malhotra, Xin Jin, Minghan Jian, Guangming Liu, Douglas Greer, Abhishek Bhandari, Wenting Wu, Roser Corominas, Áine Peoples, Amnon Koren, Athurva Gore, Shuli Kang, Guan Ning Lin, Jasper Estabillo, Therese Gadomski, Balvindar Singh, Kun Zhang, Natacha Akshoomoff, Christina Corsello, Steven McCarroll, Lilia M. Iakoucheva, Yingrui Li, Jun Wang, Jonathan Sebat. Whole-Genome Sequencing in Autism Identifies Hot Spots for De Novo Germline Mutation. Cell, 2012; 151 (7): 1431 DOI: 10.1016/j.cell.2012.11.019

Cite This Page:

University of California - San Diego. "Genomic 'hotspots' offer clues to causes of autism, other disorders." ScienceDaily. ScienceDaily, 20 December 2012. <www.sciencedaily.com/releases/2012/12/121220143516.htm>.
University of California - San Diego. (2012, December 20). Genomic 'hotspots' offer clues to causes of autism, other disorders. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2012/12/121220143516.htm
University of California - San Diego. "Genomic 'hotspots' offer clues to causes of autism, other disorders." ScienceDaily. www.sciencedaily.com/releases/2012/12/121220143516.htm (accessed July 25, 2014).

Share This




More Health & Medicine News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

New Painkiller Designed To Discourage Abuse: Will It Work?

New Painkiller Designed To Discourage Abuse: Will It Work?

Newsy (July 24, 2014) — The FDA approved Targiniq ER on Wednesday, a painkiller designed to keep users from abusing it. Like any new medication, however, it has doubters. Video provided by Newsy
Powered by NewsLook.com
Doctor At Forefront Of Fighting Ebola Outbreak Gets Ebola

Doctor At Forefront Of Fighting Ebola Outbreak Gets Ebola

Newsy (July 24, 2014) — Sheik Umar Khan has treated many of the people infected in the Ebola outbreak, and now he's become one of them. Video provided by Newsy
Powered by NewsLook.com
Condemned Man's US Execution Takes Nearly Two Hours

Condemned Man's US Execution Takes Nearly Two Hours

AFP (July 24, 2014) — America's death penalty debate raged Thursday after it took nearly two hours for Arizona to execute a prisoner who lost a Supreme Court battle challenging the experimental lethal drug cocktail. Duration: 00:55 Video provided by AFP
Powered by NewsLook.com
Can Watching TV Make You Feel Like A Failure?

Can Watching TV Make You Feel Like A Failure?

Newsy (July 24, 2014) — A study by German researchers claims watching TV while you're stressed out can make you feel guilty and like a failure. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:  

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile iPhone Android Web
          Follow Facebook Twitter Google+
          Subscribe RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins