Monday, October 12, 2020

CUX2 mutation

Inspired by a patient

Barington M, Risom L, Ek J, Uldall P, Ostergaard E. A recurrent de novo CUX2 missense variant associated with intellectual disability, seizures, and autism spectrum disorder. Eur J Hum Genet. 2018 Sep;26(9):1388-1391. doi: 10.1038/s41431-018-0184-5. Epub 2018 May 24. PMID: 29795476; PMCID: PMC6117349.


In most patients with intellectual disability (ID), the etiology is unknown, but lately several de novo variants have been associated with ID. One of the involved genes, CUX2, has twice been reported to be affected by a de novo variant c.1768G>A; p.(Glu590Lys) in patients with ID or epileptic encephalopathy. CUX2 is expressed primarily in nervous tissues where it may act as a transcription factor involved in neural specification. Here we describe a third case who was diagnosed with epilepsy including general and myoclonic seizures, moderate to severe cognitive disability, and infantile autism. The patient was heterozygous for the c.1768G>A; p.(Glu590Lys) variant in CUX2 identified by whole exome sequencing. These findings strongly suggest a causal impact of this variant and add to our understanding of a subset of patients with ID, seizures, and autism spectrum disorder as well as suggest an important role for the CUX2 gene in human brain function.

Chatron N, Møller RS, Champaigne NL, Schneider AL, Kuechler A, Labalme A, Simonet T, Baggett L, Bardel C, Kamsteeg EJ, Pfundt R, Romano C, Aronsson J, Alberti A, Vinci M, Miranda MJ, Lacroix A, Marjanovic D, des Portes V, Edery P, Wieczorek D, Gardella E, Scheffer IE, Mefford H, Sanlaville D, Carvill GL, Lesca G. The epilepsy phenotypic spectrum associated with a recurrent CUX2 variant. Ann Neurol. 2018 May;83(5):926-934. doi: 10.1002/ana.25222. Epub 2018 Apr 30. PMID: 29630738; PMCID: PMC6021218.


Objective: Cut homeodomain transcription factor CUX2 plays an important role in dendrite branching, spine development, and synapse formation in layer II to III neurons of the cerebral cortex. We identify a recurrent de novo CUX2 p.Glu590Lys as a novel genetic cause for developmental and epileptic encephalopathy (DEE). 

Methods: The de novo p.Glu590Lys variant was identified by whole-exome sequencing (n = 5) or targeted gene panel (n = 4). We performed electroclinical and imaging phenotyping on all patients. 

Results: The cohort comprised 7 males and 2 females. Mean age at study was 13 years (0.5-21.0). Median age at seizure onset was 6 months (2 months to 9 years). Seizure types at onset were myoclonic, atypical absence with myoclonic components, and focal seizures. Epileptiform activity on electroencephalogram was seen in 8 cases: generalized polyspike-wave (6) or multifocal discharges (2). Seizures were drug resistant in 7 or controlled with valproate (2). Six patients had a DEE: myoclonic DEE (3), Lennox-Gastaut syndrome (2), and West syndrome (1). Two had a static encephalopathy and genetic generalized epilepsy, including absence epilepsy in 1. One infant had multifocal epilepsy. Eight had severe cognitive impairment, with autistic features in 6. The p.Glu590Lys variant affects a highly conserved glutamine residue in the CUT domain predicted to interfere with CUX2 binding to DNA targets during neuronal development. 

Interpretation: Patients with CUX2 p.Glu590Lys display a distinctive phenotypic spectrum, which is predominantly generalized epilepsy, with infantile-onset myoclonic DEE at the severe end and generalized epilepsy with severe static developmental encephalopathy at the milder end of the spectrum.

Pfisterer U, Petukhov V, Demharter S, Meichsner J, Thompson JJ, Batiuk MY, Martinez AA, Vasistha NA, Thakur A, Mikkelsen J, Adorjan I, Pinborg LH, Pers TH, von Engelhardt J, Kharchenko PV, Khodosevich K. Identification of epilepsy-associated neuronal subtypes and gene expression underlying epileptogenesis. Nat Commun. 2020 Oct 7;11(1):5038. doi: 10.1038/s41467-020-18752-7. PMID: 33028830.


Epilepsy is one of the most common neurological disorders, yet its pathophysiology is poorly understood due to the high complexity of affected neuronal circuits. To identify dysfunctional neuronal subtypes underlying seizure activity in the human brain, we have performed single-nucleus transcriptomics analysis of >110,000 neuronal transcriptomes derived from temporal cortex samples of multiple temporal lobe epilepsy and non-epileptic subjects. We found that the largest transcriptomic changes occur in distinct neuronal subtypes from several families of principal neurons (L5-6_Fezf2 and L2-3_Cux2) and GABAergic interneurons (Sst and Pvalb), whereas other subtypes in the same families were less affected. Furthermore, the subtypes with the largest epilepsy-related transcriptomic changes may belong to the same circuit, since we observed coordinated transcriptomic shifts across these subtypes. Glutamate signaling exhibited one of the strongest dysregulations in epilepsy, highlighted by layer-wise transcriptional changes in multiple glutamate receptor genes and strong upregulation of genes coding for AMPA receptor auxiliary subunits. Overall, our data reveal a neuronal subtype-specific molecular phenotype of epilepsy.

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