birth defects

Found gene linked to severe birth defects

U. LEEDS (UK)—Scientists have identified the genetic cause of an inherited condition that leads to severe fetal abnormalities in the brain, eyes, and kidneys.

The discovery should allow couples at risk of conceiving babies with the profoundly disabling Meckel-Gruber and Joubert syndromes to be identified beforehand through genetic screening and may ultimately lead to treatments for more common related disorders, such as spina bifida and polycystic kidney disease.

The findings show how the disease gene stops cells’ finger-like antennae or ‘cilia’ from detecting and relaying information, researchers say.

The paper is published in Nature Genetics.

“By understanding the science behind this relatively rare condition, we can gain insight into other developmental conditions that are less serious but far more frequent,” says University of Leeds professor Colin Johnson. “Spina bifida, for example, is one of the most common birth defects, affecting in one in every 1,000 children.”

Meckel-Gruber and Joubert syndromes are part of a wider family of disorders known as ‘ciliopathies’—so-called because the cilia are not working as they should and do not respond properly to signals.

The lack of communication can prevent the neural tube from developing correctly in growing embryos, leading to abnormalities in the brain.

Affected embryos can also develop abnormalities in the eyes, extra fingers or toes, and multiple cysts in their kidneys. Defects are often only picked up on a 12-week ultrasound scan.

To find the gene responsible for Meckel-Gruber and Joubert syndromes, researchers examined DNA from families with a history of the disorder, from skin cells donated by patients, and from cells grown in the laboratory.

They also studied zebrafish, which have very visible embryos.

The work identified a previously unknown gene—TMEM216—as a cause of Meckel-Gruber and Joubert syndromes. They also showed that the faulty TMEM216 gene stopped cells from making a protein that is needed for signaling.

Because Meckel-Gruber and Joubert syndromes are recessive genetic disorders, only couples who both have a copy of the disease gene are at risk of conceiving babies with these birth defects.

The condition is more common in certain close-knit populations where the gene has been passed down from generation to generation.

“Accurate genetic testing for TMEM216 will be particularly important for families throughout the world that have a history of ciliopathies caused by mutations to this gene,” Johnson says.

“Now that we have identified a gene that causes Meckel-Gruber syndrome and Joubert syndrome, the role of particular signalling pathways whilst the embryo is developing can also be more clearly understood,” he adds.

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