Pinggera Alexandra, Lieb Andreas, Benedetti Bruno, Lampert Michaela, Monteleone Stefania, Liedl Klaus R, Tuluc Petronel, Striessnig Jörg
Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
Institute of General, Inorganic and Theoretical Chemistry, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
Biol Psychiatry. 2015 May 1;77(9):816-22. doi: 10.1016/j.biopsych.2014.11.020. Epub 2014 Dec 8.
Cav1.3 voltage-gated L-type calcium channels (LTCCs) are part of postsynaptic neuronal signaling networks. They play a key role in brain function, including fear memory and emotional and drug-taking behaviors. A whole-exome sequencing study identified a de novo mutation, p.A749G, in Cav1.3 α1-subunits (CACNA1D), the second main LTCC in the brain, as 1 of 62 high risk-conferring mutations in a cohort of patients with autism and intellectual disability. We screened all published genetic information available from whole-exome sequencing studies and identified a second de novo CACNA1D mutation, p.G407R. Both mutations are present only in the probands and not in their unaffected parents or siblings.
We functionally expressed both mutations in tsA-201 cells to study their functional consequences using whole-cell patch-clamp.
The mutations p.A749G and p.G407R caused dramatic changes in channel gating by shifting (~15 mV) the voltage dependence for steady-state activation and inactivation to more negative voltages (p.A749G) or by pronounced slowing of current inactivation during depolarizing stimuli (p.G407R). In both cases, these changes are compatible with a gain-of-function phenotype.
Our data, together with the discovery that Cav1.3 gain-of-function causes primary aldosteronism with seizures, neurologic abnormalities, and intellectual disability, suggest that Cav1.3 gain-of-function mutations confer a major part of the risk for autism in the two probands and may even cause the disease. Our findings have immediate clinical relevance because blockers of LTCCs are available for therapeutic attempts in affected individuals. Patients should also be explored for other symptoms likely resulting from Cav1.3 hyperactivity, in particular, primary aldosteronism.
Cav1.3电压门控L型钙通道（LTCCs）是突触后神经元信号网络的一部分。它们在大脑功能中起关键作用，包括恐惧记忆、情绪和药物成瘾行为行为。一项全外显子组测序研究在大脑中第二主要的LTCC即Cav1.3α1亚基（CACNA1D）中鉴定出一个新生突变p.A749G，该突变是自闭症和智力残疾患者队列中62个高风险突变之一。我们筛选了全外显子组测序研究中所有已发表的遗传信息，并鉴定出第二个新生的CACNA1D突变p.G407R。这两个突变仅存在于先证者中，而不存在于其未受影响的父母或兄弟姐妹中。
我们在tsA-201细胞中功能性表达这两个突变，使用全细胞膜片钳技术研究其功能后果。
p.A749G和p.G407R突变导致通道门控发生显著变化，通过将稳态激活和失活的电压依赖性向更负的电压方向移动（约15 mV）（p.A749G），或通过在去极化刺激期间电流失活明显减慢（p.G407R）。在这两种情况下，这些变化都与功能获得性表型一致。
我们的数据，以及Cav1.3功能获得导致原发性醛固酮增多症伴癫痫发作、神经异常和智力残疾的发现，表明Cav1.3功能获得性突变在这两个先证者中赋予了自闭症的主要风险，甚至可能导致该疾病。我们的发现具有直接的临床相关性，因为LTCC阻滞剂可用于对受影响个体进行治疗尝试。还应探索患者是否存在可能由Cav1.3功能亢进导致的其他症状，特别是原发性醛固酮增多症。
