Scientists have discovered the primary mechanism¹ by which thalidomide causes malformed limbs in developing embryos².

科学家已发现在胚胎发育过程中由萨立多胺所引发的畸形肢体的初步原因。

Thalidomide affects limb and ear development in embryos

This side-effect was recognised after thousands of affected³ children were born to mothers who had been prescribed（规定，开药方） the drug for morning sickness.

Research in the journal Science reveals that thalidomide（萨立多胺） binds⁴ to and renders（提出，放弃） inactive the protein cereblon（小脑） , which is very important in limb formation.

This finding could help the development of safer thalidomide-like drugs.

'Unknown mechanism'

Thalidomide can be effective in the treatment of certain cancers and leprosy（麻风） , but its infamous⁵（无耻的，邪恶的） side-effect, which is known as teratogenicity（致畸性） , mean that for women its use remains⁶ risky⁷ and controversial.

Medical researchers would therefore like to develop drugs that mimic⁸（模仿） the action of thalidomide, but do not affect limb development.

The research team, led by Takumi Ito from the Tokyo Institute of Technology in Japan, managed to isolate⁹ the negative effects of this "potentially useful" drug.

They set out to discover which target molecules¹¹（分子，微粒） thalidomide bound to in the body. They did this using tiny beads¹² that extracted each individual molecule¹⁰ the drug bound to.

The scientists confirmed their conclusion by using genetic¹³ techniques to reduce the production of the cereblon protein in developing zebrafish and chick embryos（胚胎，晶胚） .

The embryos with reduced cereblon had similar developmental defects to those that were treated with thalidomide.

"We [have shown] that cereblon... is a primary target of thalidomide teratogenicity," the researchers wrote in their Science article.

Dr Ito told BBC News: "Although the mechanism for the teratogenic effect was made clear, the mechanism for its therapeutic¹⁴ effects remains unknown.

"[If we want to develop] a new drug devoid¹⁵ of（缺乏） teratogenic activity, it is important to understand [this] mechanism... this is what we are heading for."