Université libre de Bruxelles (ULB), Hôpital Universitaire de Bruxelles (H.U.B), Hôpital Universitaire des Enfants Reine Fabiola (HUDERF), Paediatric Endocrinology Unit, Avenue J.J. Crocq 15, 1020 Bruxelles, Belgium.
Division of Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, 3010 Bern, Switzerland.
Eur J Endocrinol. 2024 Aug 5;191(2):144-155. doi: 10.1093/ejendo/lvae090.
Adrenal cortisol production occurs through a biosynthetic pathway which depend on NADH and NADPH for energy supply. The mitochondrial respiratory chain and the reactive oxygen species (ROS) detoxification system are therefore important for steroidogenesis. Mitochondrial dysfunction leading to oxidative stress has been implicated in the pathogenesis of several adrenal conditions. Nonetheless, only very few patients with variants in one gene of the ROS detoxification system, Thioredoxin Reductase 2 (TXNRD2), have been described with variable phenotypes.
Clinical, genetic, structural, and functional characterization of a novel, biallelic TXNRD2 splice variant.
On human biomaterial, we performed whole exome sequencing to identify and RNA analysis to characterize the specific TXNRD2 splice variant. Amino acid conservation analysis and protein structure modeling were performed in silico. Using patient's fibroblast-derived human induced pluripotent stem cells, we generated adrenal-like cells (iALC) to study the impact of wild-type (WT) and mutant TXNRD2 on adrenal steroidogenesis and ROS production.
The patient had a complex phenotype of primary adrenal insufficiency (PAI), combined with genital, ophthalmological, and neurological features. He carried a homozygous splice variant c.1348-1G > T in TXNRD2 which leads to a shorter protein lacking the C-terminus and thereby affecting homodimerization and flavin adenine dinucleotide binding. Patient-derived iALC showed a loss of cortisol production with overall diminished adrenal steroidogenesis, while ROS production was significantly increased.
Lack of TXNRD2 activity for mitochondrial ROS detoxification affects adrenal steroidogenesis and predominantly cortisol production.
肾上腺皮质醇的产生是通过一个生物合成途径进行的，该途径依赖于 NADH 和 NADPH 提供能量。因此，线粒体呼吸链和活性氧（ROS）解毒系统对类固醇生成很重要。导致氧化应激的线粒体功能障碍已被认为与几种肾上腺疾病的发病机制有关。尽管如此，只有极少数患有 ROS 解毒系统中一个基因（硫氧还蛋白还原酶 2（TXNRD2））变异的患者具有不同的表型。
对一种新型的 TXNRD2 剪接变体进行临床、遗传、结构和功能特征分析。
在人类生物材料上，我们进行了全外显子组测序以鉴定和 RNA 分析以表征特定的 TXNRD2 剪接变体。在计算机上进行了氨基酸保守性分析和蛋白质结构建模。使用患者的成纤维细胞衍生的人诱导多能干细胞（hiPSC），我们生成了肾上腺样细胞（iALC），以研究野生型（WT）和突变型 TXNRD2 对肾上腺类固醇生成和 ROS 产生的影响。
患者表现为原发性肾上腺功能不全（PAI）的复杂表型，伴有生殖、眼科和神经系统特征。他携带 TXNRD2 的纯合剪接变体 c.1348-1G > T，导致缺少 C 末端的较短蛋白质，从而影响同源二聚化和黄素腺嘌呤二核苷酸结合。源自患者的 iALC 显示皮质醇产生减少，整体肾上腺类固醇生成减少，而 ROS 产生显著增加。
缺乏 TXNRD2 活性以进行线粒体 ROS 解毒会影响肾上腺类固醇生成，主要是皮质醇生成。
