October 30, 2020

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Taiwanese researchers discover link between gene and rare brain disorder

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MALFORMATION: One of the causes of lissencephaly is mutation of the CEP85L gene, which might...

MALFORMATION:
One of the causes of lissencephaly is mutation of the CEP85L gene, which might not be hereditary, a researcher said, urging prenatal controls

  • By Lee I-chia / Staff reporter

Researchers yesterday said that they have identified a gene that is an important cause for posterior predominant lissencephaly, a rare brain disorder.

Kaohsiung Chang Gung Memorial Hospital’s Department of Neurology Epilepsy Section director Tsai Meng-han (蔡孟翰) said that the brain normally has folds, or gyri, which correlate with specific cognitive abilities.

However, people with lissencephaly have gyral malformations that cause parts or the entire surface of their brains to appear smooth, which gives the disorder its name, meaning “smooth brain.”

Lissencephaly is a rare brain malformation caused by gene mutations, with an incidence rate of about 12 per million among newborns, he said, adding that there are an estimated 300 cases in Taiwan.

The life expectancy of most people with lissencephaly is about two years, Tsai said.

Those who grow older have severe intellectual disability, remaining at the intellectual ability of an infant aged three to six months old, he said, adding that they also have delayed development, intractable epilepsy, poor or absent speech, difficulty swallowing and inability to walk.

Researchers had identified more than 20 types of genes linked to lissencephaly, with mutations in the LIS1 gene found on chromosome 17 being the most common cause of posterior predominant lissencephaly, but the cause of about 60 percent of the other cases remain unknown, Tsai said.

A 20-year-old man identified as “Hsiao Yo” was found to have speech and developmental delay when he was a child, he said.

He began having seizures at age three and was diagnosed with epilepsy at age eight, Tsai said.

He was later diagnosed with lissencephaly following a magnetic resonance imaging examination at the hospital, he said.

Tsai said that his medical team cooperated with Linkou Chang Gung Memorial Hospital and used next-generation sequencing technology to screen for gene mutations.

They found that the spontaneous mutation of the Centrosomal Protein 85 Like (CEP85L) gene was an important cause for posterior predominant lissencephaly.

Hsiao Yo’s parents did not have the CEP85L gene mutation, so it was a spontaneous mutation, he said, adding that the team was the first to find the association between the gene and lissencephaly.

The team cooperated with research teams in Australia, Malaysia and the US, and found 12 other people with lissencephaly who also have the CEP85L gene mutation, he added.

Tsai said they also worked with another team led by Tsai Jin-wu (蔡金吾), a professor at National Yang-Ming University’s Institute of Brain Science, and found that knockdown of the CEP85l gene causes a neuronal migration defect in mice.

Parents of people with lissencephaly are often puzzled as to why their children have the condition when they do not have a family history of it, and the study shows that the disorder is caused by spontaneous gene mutation, Tsai Meng-han said.

The CEP85L gene can be included in prenatal genetic screening tests to detect lissencephaly in fetuses, he added.

The study was published in the scientific journal Neuron in April.

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