Insight into underlying causes of seizure disorder in babies

Date:
August 3, 2021
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
Researchers report that infantile spasms, a rare but serious seizure
disorder in babies, appear to be the result of a molecular pathway
gone awry. In their study of a mouse model of the disorder, the
researchers discovered that genetic mutations associated with the
disease impair a pathway that is involved in building new synapses
in the hippocampus, a brain region essential to learning and memory.



FULL STORY ========================================================================== Researchers report that infantile spasms, a rare but serious seizure
disorder in babies, appear to be the result of a molecular pathway gone
awry. In their study of a mouse model of the disorder, the researchers discovered that genetic mutations associated with the disease impair a
pathway that is involved in building new synapses in the hippocampus,
a brain region essential to learning and memory.


==========================================================================
The findings, described in the journal EMBO Reports, also detail the
use of a potential therapeutic intervention to address some of the developmental problems that are often associated with infantile spasms.

"We are trying to understand the reasons behind learning and memory disabilities in patients with infantile spasms," said Nien-Pei Tsai,
a professor of molecular and integrative physiology at the University
of Illinois Urbana-Champaign who led the study with U. of I. research
scientist Kwan Young Lee. Tsai is a faculty member in the Beckman
Institute for Advanced Science and Technology at the U. of I.

While infantile spasms often disappear by the age of 4 or 5, long-term developmental problems affecting memory and learning persist, Tsai said.

"The learning and memory deficits are long-lasting and the patients often require assistance at school," he said. "This tells us that the seizures
and the learning defects are likely caused by different issues in the
brain, but no one really knows how." Previous research has found that infantile spasms are often associated with mutations in a gene known as Nedd4-2, which codes for a protein called a ligase that regulates the excitability of neurons, Tsai said.



==========================================================================
"To study the role of this gene, we used mice in which Nedd4-2 is
selectively removed from the brain as a model to mimic patients with
impaired Nedd4-2," he said.

The researchers conducted behavioral and physiological experiments in
mice with impaired Nedd4-2 ligase function and in mice with normal
function. They also looked at how a lack of the ligase affected
biochemical pathways in mouse neurons grown in cell culture.

They found that male mice lacking adequate Nedd4-2 ligase levels in the hippocampus were impaired in their ability to learn and remember. This disability was associated with problems in the structure of excitatory synapses, which carry electrical signals between neurons, in the
hippocampus.

The researchers focused on neurons in the hippocampus because this brain
region plays a key role in converting short-term memory to long-term
memory.

Their experiments showed that a lack of Nedd4-2 in the hippocampus
disrupted a pathway that regulates the growth of filaments, called actin,
that support the formation of cellular structures such as synapses. Cells lacking adequate levels of the ligase experienced the destruction of
these filaments and had fewer excitatory synapses in the hippocampus.

"Synapses need structural support to sustain their functions and
integrity," Tsai said. "Actin, which is one of the critical structural components in a cell, is made up of monomers that can attach to one
another to form polymers.

When the actin polymers are formed in synapses, the synapses become
stronger.

This process is critical for learning and memory." When the team exposed
mice lacking adequate Nedd4-2 levels to a drug compound that mimics the activity of the ligase in the brain, the mice appeared to regain some
of their lost hippocampal-dependent memory. The same compound restored hippocampal excitatory neurons in cell culture, the researchers found.

"Because we showed that some of the learning and memory issues associated
with infantile spasms can be improved by a synthetic peptide in animals,
it means that one day we may be able to medically enhance learning and
memory of patients who carry mutations in this Nedd4-2 gene," Tsai said.

The National Institutes of Health and the Brain and Behavior Research Foundation supported this research.

========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Original written by Diana Yates. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Kwan Young Lee, Jiuhe Zhu, Cathryn A Cutia, Catherine A
Christian‐Hinman, Justin S Rhodes, Nien‐Pei
Tsai. Infantile spasms‐linked Nedd4‐2 mediates
hippocampal plasticity and learning via cofilin signaling. EMBO
reports, 2021; DOI: 10.15252/ embr.202152645 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210803121339.htm

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