Deletion of the betaine-GABA transporter (BGT1; slc6a12) gene does not affect seizure thresholds of adult mice

A C Lehre; N M Rowley; Y Zhou; S Holmseth; C Guo; T Holen; R Hua; P Laake; A M Olofsson; I Poblete-Naredo; D A Rusakov; Karsten Kirkegaard Madsen; Rasmus Prætorius Clausen; Arne Schousboe; H Steve White; N C Danbolt

doi:10.1016/j.eplepsyres.2011.02.014

Deletion of the betaine-GABA transporter (BGT1; slc6a12) gene does not affect seizure thresholds of adult mice

A C Lehre, N M Rowley, Y Zhou, S Holmseth, C Guo, T Holen, R Hua, P Laake, A M Olofsson, I Poblete-Naredo, D A Rusakov, Karsten Kirkegaard Madsen, Rasmus Prætorius Clausen, Arne Schousboe, H Steve White, N C Danbolt

56 Citations (Scopus)

Abstract

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian brain. Once released, it is removed from the extracellular space by cellular uptake catalyzed by GABA transporter proteins. Four GABA transporters (GAT1, GAT2, GAT3 and BGT1) have been identified. Inhibition of the GAT1 by the clinically available anti-epileptic drug tiagabine has been an effective strategy for the treatment of some patients with partial seizures. Recently, the investigational drug EF1502, which inhibits both GAT1 and BGT1, was found to exert an anti-convulsant action synergistic to that of tiagabine, supposedly due to inhibition of BGT1. The present study addresses the role of BGT1 in seizure control and the effect of EF1502 by developing and exploring a new mouse line lacking exons 3-5 of the BGT1 (slc6a12) gene. The deletion of this sequence abolishes the expression of BGT1 mRNA. However, homozygous BGT1-deficient mice have normal development and show seizure susceptibility indistinguishable from that in wild-type mice in a variety of seizure threshold models including: corneal kindling, the minimal clonic and minimal tonic extension seizure threshold tests, the 6Hz seizure threshold test, and the i.v. pentylenetetrazol threshold test. We confirm that BGT1 mRNA is present in the brain, but find that the levels are several hundred times lower than those of GAT1 mRNA; possibly explaining the apparent lack of phenotype. In conclusion, the present results do not support a role for BGT1 in the control of seizure susceptibility and cannot provide a mechanistic understanding of the synergism that has been previously reported with tiagabine and EF1502.

Original language	English
Journal	Epilepsy Research
Volume	95
Issue number	1-2
Pages (from-to)	70-81
ISSN	0920-1211
DOIs	https://doi.org/10.1016/j.eplepsyres.2011.02.014
Publication status	Published - 1 Jun 2011

Keywords

Former Faculty of Pharmaceutical Sciences

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10.1016/j.eplepsyres.2011.02.014

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Lehre, A. C., Rowley, N. M., Zhou, Y., Holmseth, S., Guo, C., Holen, T., Hua, R., Laake, P., Olofsson, A. M., Poblete-Naredo, I., Rusakov, D. A., Madsen, K. K., Clausen, R. P., Schousboe, A., White, H. S., & Danbolt, N. C. (2011). Deletion of the betaine-GABA transporter (BGT1; slc6a12) gene does not affect seizure thresholds of adult mice. Epilepsy Research, 95(1-2), 70-81. https://doi.org/10.1016/j.eplepsyres.2011.02.014

Lehre, AC, Rowley, NM, Zhou, Y, Holmseth, S, Guo, C, Holen, T, Hua, R, Laake, P, Olofsson, AM, Poblete-Naredo, I, Rusakov, DA, Madsen, KK, Clausen, RP , Schousboe, A, White, HS & Danbolt, NC 2011, 'Deletion of the betaine-GABA transporter (BGT1; slc6a12) gene does not affect seizure thresholds of adult mice', Epilepsy Research, vol. 95, no. 1-2, pp. 70-81. https://doi.org/10.1016/j.eplepsyres.2011.02.014

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title = "Deletion of the betaine-GABA transporter (BGT1; slc6a12) gene does not affect seizure thresholds of adult mice",

abstract = "Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian brain. Once released, it is removed from the extracellular space by cellular uptake catalyzed by GABA transporter proteins. Four GABA transporters (GAT1, GAT2, GAT3 and BGT1) have been identified. Inhibition of the GAT1 by the clinically available anti-epileptic drug tiagabine has been an effective strategy for the treatment of some patients with partial seizures. Recently, the investigational drug EF1502, which inhibits both GAT1 and BGT1, was found to exert an anti-convulsant action synergistic to that of tiagabine, supposedly due to inhibition of BGT1. The present study addresses the role of BGT1 in seizure control and the effect of EF1502 by developing and exploring a new mouse line lacking exons 3-5 of the BGT1 (slc6a12) gene. The deletion of this sequence abolishes the expression of BGT1 mRNA. However, homozygous BGT1-deficient mice have normal development and show seizure susceptibility indistinguishable from that in wild-type mice in a variety of seizure threshold models including: corneal kindling, the minimal clonic and minimal tonic extension seizure threshold tests, the 6Hz seizure threshold test, and the i.v. pentylenetetrazol threshold test. We confirm that BGT1 mRNA is present in the brain, but find that the levels are several hundred times lower than those of GAT1 mRNA; possibly explaining the apparent lack of phenotype. In conclusion, the present results do not support a role for BGT1 in the control of seizure susceptibility and cannot provide a mechanistic understanding of the synergism that has been previously reported with tiagabine and EF1502.",

keywords = "Former Faculty of Pharmaceutical Sciences",

author = "Lehre, {A C} and Rowley, {N M} and Y Zhou and S Holmseth and C Guo and T Holen and R Hua and P Laake and Olofsson, {A M} and I Poblete-Naredo and Rusakov, {D A} and Madsen, {Karsten Kirkegaard} and Clausen, {Rasmus Pr{\ae}torius} and Arne Schousboe and White, {H Steve} and Danbolt, {N C}",

note = "Keywords: GABA uptake, epilepsy, betaine-GABA transporter, SLC6A12, conditional knockout, EF1502",

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doi = "10.1016/j.eplepsyres.2011.02.014",

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T1 - Deletion of the betaine-GABA transporter (BGT1; slc6a12) gene does not affect seizure thresholds of adult mice

AU - Lehre, A C

AU - Rowley, N M

AU - Zhou, Y

AU - Holmseth, S

AU - Guo, C

AU - Holen, T

AU - Hua, R

AU - Laake, P

AU - Olofsson, A M

AU - Poblete-Naredo, I

AU - Rusakov, D A

AU - Madsen, Karsten Kirkegaard

AU - Clausen, Rasmus Prætorius

AU - Schousboe, Arne

AU - White, H Steve

AU - Danbolt, N C

N1 - Keywords: GABA uptake, epilepsy, betaine-GABA transporter, SLC6A12, conditional knockout, EF1502

PY - 2011/6/1

Y1 - 2011/6/1

N2 - Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian brain. Once released, it is removed from the extracellular space by cellular uptake catalyzed by GABA transporter proteins. Four GABA transporters (GAT1, GAT2, GAT3 and BGT1) have been identified. Inhibition of the GAT1 by the clinically available anti-epileptic drug tiagabine has been an effective strategy for the treatment of some patients with partial seizures. Recently, the investigational drug EF1502, which inhibits both GAT1 and BGT1, was found to exert an anti-convulsant action synergistic to that of tiagabine, supposedly due to inhibition of BGT1. The present study addresses the role of BGT1 in seizure control and the effect of EF1502 by developing and exploring a new mouse line lacking exons 3-5 of the BGT1 (slc6a12) gene. The deletion of this sequence abolishes the expression of BGT1 mRNA. However, homozygous BGT1-deficient mice have normal development and show seizure susceptibility indistinguishable from that in wild-type mice in a variety of seizure threshold models including: corneal kindling, the minimal clonic and minimal tonic extension seizure threshold tests, the 6Hz seizure threshold test, and the i.v. pentylenetetrazol threshold test. We confirm that BGT1 mRNA is present in the brain, but find that the levels are several hundred times lower than those of GAT1 mRNA; possibly explaining the apparent lack of phenotype. In conclusion, the present results do not support a role for BGT1 in the control of seizure susceptibility and cannot provide a mechanistic understanding of the synergism that has been previously reported with tiagabine and EF1502.

AB - Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian brain. Once released, it is removed from the extracellular space by cellular uptake catalyzed by GABA transporter proteins. Four GABA transporters (GAT1, GAT2, GAT3 and BGT1) have been identified. Inhibition of the GAT1 by the clinically available anti-epileptic drug tiagabine has been an effective strategy for the treatment of some patients with partial seizures. Recently, the investigational drug EF1502, which inhibits both GAT1 and BGT1, was found to exert an anti-convulsant action synergistic to that of tiagabine, supposedly due to inhibition of BGT1. The present study addresses the role of BGT1 in seizure control and the effect of EF1502 by developing and exploring a new mouse line lacking exons 3-5 of the BGT1 (slc6a12) gene. The deletion of this sequence abolishes the expression of BGT1 mRNA. However, homozygous BGT1-deficient mice have normal development and show seizure susceptibility indistinguishable from that in wild-type mice in a variety of seizure threshold models including: corneal kindling, the minimal clonic and minimal tonic extension seizure threshold tests, the 6Hz seizure threshold test, and the i.v. pentylenetetrazol threshold test. We confirm that BGT1 mRNA is present in the brain, but find that the levels are several hundred times lower than those of GAT1 mRNA; possibly explaining the apparent lack of phenotype. In conclusion, the present results do not support a role for BGT1 in the control of seizure susceptibility and cannot provide a mechanistic understanding of the synergism that has been previously reported with tiagabine and EF1502.

KW - Former Faculty of Pharmaceutical Sciences

U2 - 10.1016/j.eplepsyres.2011.02.014

DO - 10.1016/j.eplepsyres.2011.02.014

M3 - Journal article

C2 - 21459558

SN - 0920-1211

VL - 95

SP - 70

EP - 81

JO - Journal of Epilepsy

JF - Journal of Epilepsy

IS - 1-2

ER -

Deletion of the betaine-GABA transporter (BGT1; slc6a12) gene does not affect seizure thresholds of adult mice

Abstract

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