This is what you should know about KCNT1 – a 2015 update

Dual phenotypes. When KCNT1 was first described as a gene for Migrating Partial Seizures of Infancy in 2012, it wasn’t just a novel gene for epileptic encephalopathies. In parallel, the same gene was found to underlie a novel subtype of autosomal dominant nocturnal frontal lobe epilepsies (ADNFLE). At the time, this left us scratching our heads how a gene could cause such distinct, but entirely separate phenotypes. In a recent publication in Epilepsia, Møller and collaborators revisit the phenotypic spectrum of KCNT1. They find that both phenotypes can occur within a single family and that KCNT1 mutations can result in other phenotypes, adding to the mystery of KCNT1. Continue reading

These are the top 10 epilepsy genes of 2014

Top 10. 2014 has been a very productive year in epilepsy gene discovery and with our final blog post this year, we wanted to provide a brief overview of what has been pertinent this year. From the multitude of novel genes identified this year, here are the 10 most relevant findings – including some genes that you probably didn’t expect. Continue reading

WWOX, spinocerebellar ataxia, neurodegeneration, and epilepsy

Exomes. Massive parallel sequencing technologies are ideally suited to identify the genetic basis of monogenic disorders, particularly recessive diseases. In a recent publication in the Orphanet Journal of Rare Disease, Abdel-Salam and collaborators identify a homozygous mutation in WWOX in a family with epileptic encephalopathy and neurodegeneration. Their study highlights the issues of how to interpret recessive gene findings spanning different phenotypes identified in the era of exome sequencing. Continue reading

SLC25A22, migrating seizures and mitochrondial glutamate deficiency

MPSI. Migrating partial seizures of infancy (MPSI) are a catastrophic form of infantile epilepsy that was entirely unexplained until de novo mutations in KCNT1 were identified in a subset of sporadic cases in 2012. For familial MPSI, however, the genetic basis remained unknown. In a recent publication in Annals of Neurology, Poduri and collaborators identify mutations in SCL25A22 in a family with recessive MPSI. Their study sheds light on the genetic basis of catastrophic epilepsies and the phenotypic range of mitochondrial glutamate starvation. Continue reading

QARS mutations, tRNA, and neurodegeneration with migrating seizures

Q for glutamine. Transfer RNAs (tRNAs) are small adaptor molecules that match a nucleotide sequence to a given amino acid during protein translation. After unloading their amino acid payload, tRNAs are recharged with new amino acids through specific tRNA synthetases. Q is the official letter for the amino acid glutamine, and its respective tRNA synthetase is glutaminyl-tRNA synthetase (QARS). In a recent publication in the American Journal of Human Genetics, Zhang and colleagues identify compound heterozygous mutations in the QARS gene in two families with progressive microcephaly, neurodegeneration, and intractable, early-onset epilepsy. Interestingly, in at least two probands, the seizures are described as migrating partial seizures reminiscent of Malignant Migrating Partial Seizures of Infancy (MMPSI) due to mutations in KCNT1. The disease mechanism, however, appears to be entirely different. Continue reading