The study, ... confirms that genes connected to regulating the brain chemical dopamine are involved in schizophrenia, as predicted. But so are genes involved in the immune system, and several associated with heavy smoking.
"Some are very familiar genes expressed in nerve cells, and some are results where you scratch your head and you know you have more work to do" to understand their role in schizophrenia, said Steven Hyman, director of the Stanley Center for Psychiatric Research at the Broad Institute of MIT and Harvard, which helped lead the study.
That doesn't mean that schizophrenia is caused by inflammation or cigarettes. Genes may play one role in the immune system and another in the brain, for instance, Hyman said.
"Most importantly, the goal is not to end up with a list of genes, but with novel treatments," Hyman said via e-mail. To that end, he said, another member of theStanley Institute, former Merck executive Ed Scolnick, has developed a program to discover new drugs through combining genetics, stem cell work and neurobiological data, Hyman said.
At this point, the identification of the 108 schizophrenia genes in the new study means much more to scientists than to patients. Patients will start to benefit, Hyman said, when scientists — and hopefully drug companies — use the genes to identify targets for drug treatments.
"In some sense, it's already giving us clues to the biology of this disease that ultimately will be exploitable to understand what is going wrong in the brain and most importantly for very much needed new treatments," Hyman said.
This isn't the first time that researchers have considered a link between the immune system and schizophrenia. Smaller genetic studies have hinted at a connection. People with schizophrenia often have signs of inflammation in their bloodstream, and relatives of those with autoimmune disorders have as much as 45% increased risk of developing schizophrenia, said Consuelo Walss Bass, an associate professor at theUniversity of Texas Health Science Center in Houston.
The new study removes any doubt about the connection.
The genome-wide association study, or GWAS, looked for genes that were common across many of the 150,000 participants, nearly 37,000 of whom had the disease. The large number — and overrepresentation of those with schizophrenia — was crucial for scientists to see the contributions of multiple genes, each of which only contributes a little bit to schizophrenia.
About 1% of Americans have schizophrenia, a brain disorder that can lead to agitation, hearing voices and terrifying paranoia.
Studying so many patients requires the collaboration of many scientists and doctors, and is a "huge achievement," said Marcus Munafò, a professor of Biological Psychology at the University of Bristol in the United Kingdom, who wrote a commentary about the new study in
Nature.
Most common diseases are the result of many genes interacting. GWAS studies help researchers identify genes that are important to a particular condition but may not be obvious in terms of function.
It's not clear yet why the genes associated with smoking are involved with schizophrenia, Munafò said, but knowing that they are could help researchers identify whether smoking actually increases risk, for instance, or whether there are lifestyle changes people could make to reduce their chances of getting schizophrenia, he said.
Because the study is so large, it's pretty certain that any gene that showed up in the study plays a significant role in schizophrenia, but not every gene important to the condition has been identified yet.
"Now we have 108 pieces, but maybe it's a 1,000-piece puzzle, so we have a long way to go," Hyman said.
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Scientists have long known that schizophrenia runs in families. The illness occurs in 1 percent of the general population, but it occurs in 10 percent of people who have a first-degree relative with the disorder, such as a parent, brother, or sister. People who have second-degree relatives (aunts, uncles, grandparents, or cousins) with the disease also develop schizophrenia more often than the general population. The risk is highest for an identical twin of a person with schizophrenia. He or she has a 40 to 65 percent chance of developing the disorder.
We inherit our genes from both parents. Scientists believe several genes are associated with an increased risk of schizophrenia, but that no gene causes the disease by itself. In fact, recent research has found that people with schizophrenia tend to have higher rates of rare genetic mutations. These genetic differences involve hundreds of different genes and probably disrupt brain development.
Witches did not pop up in Salem, a witch trial, with its roots in economics and religion popped up.
Because genetic make-up accounts for about 40 percent of the chance of a man being homosexual, besides, those with elements of the homosexual genotype and (and do) reproduce.
You do not understand any genetics beyond a simple Mendelian model, and even there you fail to factor in dominant and recessive considerations.