TY - JOUR
T1 - Alternative splicing potentiates dysfunction of early-onset epileptic encephalopathy SCN2A variants
AU - Thompson, Christopher H.
AU - Ben-Shalom, Roy
AU - Bender, Kevin J.
AU - George, Alfred L.
N1 - Funding Information:
This work was funded in part by grants from the National Institutes of Health (U54-NS108874), grants from the Simons Foundation Autism Research Initiative to A.L. George Jr. and K.J. Bender (513133 to K.J. Bender), and a generous gift from the Davee Foundation. The authors declare no competing financial interests.
Publisher Copyright:
© 2020 Thompson et al.
PY - 2020/3/2
Y1 - 2020/3/2
N2 - Epileptic encephalopathies are severe forms of infantile-onset epilepsy often complicated by severe neurodevelopmental impairments. Some forms of early-onset epileptic encephalopathy (EOEE) have been associated with variants in SCN2A, which encodes the brain voltage-gated sodium channel NaV1.2. Many voltage-gated sodium channel genes, including SCN2A, undergo developmentally regulated mRNA splicing. The early onset of these disorders suggests that developmentally regulated alternative splicing of NaV1.2 may be an important consideration when elucidating the pathophysiological consequences of epilepsy-associated variants. We hypothesized that EOEE-associated NaV1.2 variants would exhibit greater dysfunction in a splice isoform that is prominently expressed during early development. We engineered five EOEE-associated NaV1.2 variants (T236S, E999K, S1336Y, T1623N, and R1882Q) into the adult and neonatal splice isoforms of NaV1.2 and performed whole-cell voltage clamp to elucidate their functional properties. All variants exhibited functional defects that could enhance neuronal excitability. Three of the five variants (T236S, E999K, and S1336Y) exhibited greater dysfunction in the neonatal isoform compared with those observed in the adult isoform. Computational modeling of a developing cortical pyramidal neuron indicated that T236S, E999K, S1336Y, and R1882Q showed hyperexcitability preferentially in immature neurons. These results suggest that both splice isoform and neuronal developmental stage influence how EOEE-associated NaV1.2 variants affect neuronal excitability.
AB - Epileptic encephalopathies are severe forms of infantile-onset epilepsy often complicated by severe neurodevelopmental impairments. Some forms of early-onset epileptic encephalopathy (EOEE) have been associated with variants in SCN2A, which encodes the brain voltage-gated sodium channel NaV1.2. Many voltage-gated sodium channel genes, including SCN2A, undergo developmentally regulated mRNA splicing. The early onset of these disorders suggests that developmentally regulated alternative splicing of NaV1.2 may be an important consideration when elucidating the pathophysiological consequences of epilepsy-associated variants. We hypothesized that EOEE-associated NaV1.2 variants would exhibit greater dysfunction in a splice isoform that is prominently expressed during early development. We engineered five EOEE-associated NaV1.2 variants (T236S, E999K, S1336Y, T1623N, and R1882Q) into the adult and neonatal splice isoforms of NaV1.2 and performed whole-cell voltage clamp to elucidate their functional properties. All variants exhibited functional defects that could enhance neuronal excitability. Three of the five variants (T236S, E999K, and S1336Y) exhibited greater dysfunction in the neonatal isoform compared with those observed in the adult isoform. Computational modeling of a developing cortical pyramidal neuron indicated that T236S, E999K, S1336Y, and R1882Q showed hyperexcitability preferentially in immature neurons. These results suggest that both splice isoform and neuronal developmental stage influence how EOEE-associated NaV1.2 variants affect neuronal excitability.
UR - http://www.scopus.com/inward/record.url?scp=85078687845&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85078687845&partnerID=8YFLogxK
U2 - 10.1085/JGP.201912442
DO - 10.1085/JGP.201912442
M3 - Article
C2 - 31995133
AN - SCOPUS:85078687845
VL - 152
JO - Journal of General Physiology
JF - Journal of General Physiology
SN - 0022-1295
IS - 3
M1 - 201912442
ER -