Mutations in the histone methyltransferase gene KMT2B cause complex early-onset dystonia

Esther Meyer, Keren J Carss, Julia Rankin, John M E Nichols, Detelina Grozeva, Agnel P Joseph, Niccolo E Mencacci, Apostolos Papandreou, Joanne Ng, Serena Barral, Adeline Ngoh, Hilla Ben-Pazi, Michel A Willemsen, David Arkadir, Angela Barnicoat, Hagai Bergman, Sanjay Bhate, Amber Boys, Niklas Darin, Nicola Foulds, Nicholas Gutowski, Alison Hills, Henry Houlden, Jane A Hurst, Zvi Israel, Margaret Kaminska, Patricia Limousin, Daniel Lumsden, Shane McKee, Shibalik Misra, Shekeeb S Mohammed, Vasiliki Nakou, Joost Nicolai, Magnus Nilsson, Hardev Pall, Kathryn J Peall, Gregory B Peters, Prab Prabhakar, Miriam S Reuter, Patrick Rump, Reeval Segel, Margje Sinnema, Martin Smith, Peter Turnpenny, Susan M White, Dagmar Wieczorek, Sarah Wiethoff, Brian T Wilson, Gidon Winter, Christopher Wragg, Simon Pope, Simon J H Heales, Deborah Morrogh, Alan Pittman, Lucinda J Carr, Belen Perez-Dueñas, Jean-Pierre Lin, Andre Reis, William A Gahl, Camilo Toro, Kailash P Bhatia, Nicholas W Wood, Erik-Jan Kamsteeg, Wui K Chong, Paul Gissen, Maya Topf, Russell C Dale, Jonathan R Chubb, F Lucy Raymond, Manju A Kurian

Histone lysine methylation, mediated by mixed-lineage leukemia (MLL) proteins, is now known to be critical in the regulation of gene expression, genomic stability, cell cycle and nuclear architecture. Despite MLL proteins being postulated as essential for normal development, little is known about the specific functions of the different MLL lysine methyltransferases. Here we report heterozygous variants in the gene KMT2B (also known as MLL4) in 27 unrelated individuals with a complex progressive childhood-onset dystonia, often associated with a typical facial appearance and characteristic brain magnetic resonance imaging findings. Over time, the majority of affected individuals developed prominent cervical, cranial and laryngeal dystonia. Marked clinical benefit, including the restoration of independent ambulation in some cases, was observed following deep brain stimulation (DBS). These findings highlight a clinically recognizable and potentially treatable form of genetic dystonia, demonstrating the crucial role of KMT2B in the physiological control of voluntary movement.