Three novel aspects about epilepsy gene panels

Gene panels. Epilepsy gene panels have emerged as the first line genetic test for most suspected genetic epilepsies. Gene panels for childhood epilepsies are among the most common genetic tests ordered in a pediatric setting. While the role of gene panel testing is well established, the ideal design of gene panels remains an ongoing issue. A recent publication in the Journal of Medical Genetics provides additional evidence for the role of gene panel analysis in patients with genetic epilepsies. There are three aspects of this study that are particularly noteworthy. Continue reading

What’s new with KCNT1 – a 2016 update

Continued expansion of the KCNT1 phenotype. In 2012, de novo heterozygous KCNT1 variants were first described in six individuals with migrating partial seizures of infancy (MPSI) (Barcia et al, 2012). In the same edition of Nature Genetics, Heron and colleagues (2012) described 3 families with frontal lobe epilepsy with prominent psychiatric features were also identified to have heterozygous disease-causing variants in KCNT1. Within the last 5 years, de novo and inherited heterozygous KCNT1 variants have been found in a number of patients with MPSI and ADNFLE. Yet, there have been no clear genotype-phenotype correlations established. Recently, several studies have identified KCNT1 variants in patients with other types of epilepsy. Keep reading to learn more about the expansion of the KCNT1-associated epilepsy phenotype. Continue reading

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

Beyond the Ion Channel – and back

Where do all the ion channels come from? I would like to start off with a brief commentary about the current state of gene discovery in human epilepsy. Some of our readers rightfully took offense to my previous statement that gene discovery in epilepsy it over – quite the contrary is true, and I apologize for any confusion that I may have caused. Gene discovery in epilepsy is one of the few areas of human genetics with an ongoing, rapid sequence of gene discovery with a tremendous translational potential. But we also need to reconsider the name of this blog – we are far from being beyond the ion channel. The ion channel concept has made a remarkable return in human epilepsy genetics. Let’s find out why. Continue reading

The OMIM epileptic encephalopathy genes – a 2014 review

EIEE1-19. Online Mendelian Inheritance in Man (OMIM) is one of the most frequently accessed online databases for information on genetic disorders. Genes for epileptic encephalopathies are organized within a phenotypic series entitled Early Infantile Epileptic Encephalopathy (EIEE). The EIEE phenotypic series currently lists 19 genes (EIEE1-19). Let’s review the evidence for these genes as of 2014. 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