Biallelic mutations in the 3' exonuclease TOE1 cause pontocerebellar hypoplasia and uncover a role in snRNA processing.

Deadenylases are best known for degrading the poly(A) tail during mRNA decay. The deadenylase family has expanded throughout evolution and, in mammals, consists of 12 Mg2+-dependent 3'-end RNases with substrate specificity that is mostly unknown. Pontocerebellar hypoplasia type 7 (PCH7) is a unique recessive syndrome characterized by neurodegeneration and ambiguous genitalia. We studied 12 human families with PCH7, uncovering biallelic, loss-of-function mutations in TOE1, which encodes an unconventional deadenylase. toe1-morphant zebrafish displayed midbrain and hindbrain degeneration, modeling PCH-like structural defects in vivo. Surprisingly, we found that TOE1 associated with small nuclear RNAs (snRNAs) incompletely processed spliceosomal. These pre-snRNAs contained 3' genome-encoded tails often followed by post-transcriptionally added adenosines. Human cells with reduced levels of TOE1 accumulated 3'-end-extended pre-snRNAs, and the immunoisolated TOE1 complex was sufficient for 3'-end maturation of snRNAs. Our findings identify the cause of a neurodegenerative syndrome linked to snRNA maturation and uncover a key factor involved in the processing of snRNA 3' ends.

Citation

Rea M Lardelli, Ashleigh E Schaffer, Veerle R C Eggens, Maha S Zaki, Stephanie Grainger, Shashank Sathe, Eric L Van Nostrand, Zinayida Schlachetzki, Basak Rosti, Naiara Akizu, Eric Scott, Jennifer L Silhavy, Laura Dean Heckman, Rasim Ozgur Rosti, Esra Dikoglu, Anne Gregor, Alicia Guemez-Gamboa, Damir Musaev, Rohit Mande, Ari Widjaja, Tim L Shaw, Sebastian Markmiller, Isaac Marin-Valencia, Justin H Davies, Linda de Meirleir, Hulya Kayserili, Umut Altunoglu, Mary Louise Freckmann, Linda Warwick, David Chitayat, Susan Blaser, Ahmet Okay Çağlayan, Kaya Bilguvar, Huseyin Per, Christina Fagerberg, Henrik T Christesen, Maria Kibaek, Kimberly A Aldinger, David Manchester, Naomichi Matsumoto, Kazuhiro Muramatsu, Hirotomo Saitsu, Masaaki Shiina, Kazuhiro Ogata, Nicola Foulds, William B Dobyns, Neil C Chi, David Traver, Luigina Spaccini, Stefania Maria Bova, Stacey B Gabriel, Murat Gunel, Enza Maria Valente, Marie-Cecile Nassogne, Eric J Bennett, Gene W Yeo, Frank Baas, Jens Lykke-Andersen, Joseph G Gleeson. Biallelic mutations in the 3' exonuclease TOE1 cause pontocerebellar hypoplasia and uncover a role in snRNA processing. Nature genetics. 2017 Mar;49(3):457-464

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PMID: 28092684

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