Researchers have grown patients’ skin cells into neurons to discover what goes wrong in the brain in Timothy Syndrome which can potentially hold clues to aautism.

Researchers funded by the National Institutes of Health used a cutting edge “disease-in-a-dish” technology to find clues on how autism miswires the brain by using a new technology called induced pluripotent stem cells, iPSCs.

The researchers explained that they “first converted skin cells from Timothy Syndrome patients into stem cells and then coaxed these to differentiate into neurons.”

Most children with Timothy Syndrome show symptoms of autism spectrum disorder along with a constellation of physical problems, the authors wrote, with abnormalities including changes in the composition of cells in the cortex, the largest brain structure in humans, and of neurons that secrete two key chemical messengers.

The authors noted that neurons that make long-distance connections between the brain's hemispheres tended to be in short supply.

Although Timothy Syndrome patients show symptoms of autism spectrum disorder, unlike most cases of autism, Timothy syndrome is known to be caused by a single genetic mutation.

"Studying the consequences of a single mutation, compared to multiple genes with small effects, vastly simplifies the task of pinpointing causal mechanisms," said Ricardo Dolmetsch, Ph.D., of Stanford University, National Institute of Mental Health (NIMH) grantee who led the study.

"Unlike animal research, the cutting-edge technology employed in this study makes it possible to pinpoint molecular defects in a patient's own brain cells," said NIMH Director Thomas R. Insel, M.D. "It also offers a way to screen more rapidly for medications that act on the disordered process."

The mutation in Timothy Syndrome caused by a tiny glitch in the gene that codes for a calcium channel protein in cell membranes results in “too much calcium entering cells, causing a tell-tale set of abnormalities throughout the body.”

The authors explain that “proper functioning of the calcium channel is known to be particularly critical for proper heart rhythm” and that many patients “die in childhood of arrhythmias, but its role in brain cells was less well understood.”

So Dolmetsch and his colleagues came together to learn more by using the new iPSCs technology.

Observations across multiple iPSC lines proved "remarkable reproducibility" and individuals confirmed that the technique can reveal defects in neuronal differentiation, “such as whether cells assume the correct identity as the brain gets wired-up in early development.”

Researchers explained that fewer neurons from Timothy Syndrome patients became neurons of the lower layers of the cortex and more became upper layer neurons, compared to those from controls.

“The lower layer cells that remained were more likely to be the kind that project to areas below the cortex,” the NIMH said in a statement. “In contrast, there were fewer-than-normal neurons equipped to form a structure, called the corpus callosum, which makes possible communications between the left and right hemispheres.”

Parallel studies of mice with the same genetic mutation found in Timothy syndrome patients showed many of these defects as well, which supports the link between the mutation and the developmental abnormalities.

The authors said that several genes previously implicated in autism were among hundreds found to be expressed abnormally in Timothy Syndrome neurons and that excess cellular calcium levels also caused an overproduction of neurons that make key chemical messengers, secreting 3.5 times more norepinephrine and 2.3 times more dopamine than control neurons.

“Addition of a drug that blocks the calcium channel reversed the abnormalities in cultured neurons, reducing the proportion of catecholamine-secreting cells by 68 percent,” the NIMH said.

Timothy Syndrome patient iPSCs were similar to those in Rett Syndrome, another single gene disorder that often includes autism-like symptoms.

The study suggests that disorders on the autism spectrum affect multiple stages in early brain development.

"Most of these abnormalities are consistent with other emerging evidence that ASDs arise from defects in connectivity between cortex areas and show decreased size of the corpus callosum," said Dolmetsch.

"Our study reveals how these might be traceable to specific mechanisms set in motion by poor regulation of cellular calcium. It also demonstrates that neurons derived from iPSCs can be used to identify the cellular basis of a neurodevelopmental disorder."

Dolmetsch said the mechanisms identified in this study may become potential targets for developing new therapies for Timothy Syndrome and may also provide insights into the neural basis of deficits in other forms of autism.