NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Department of Neuropediatrics, Charité-Universitätsmedizin Berlin, Berlin, Germany.
J Med Genet. 2019 Mar;56(3):164-175. doi: 10.1136/jmedgenet-2018-105711. Epub 2018 Nov 28.
Very long-chain fatty acids (VLCFAs) are essential for functioning of biological membranes. ELOVL fatty acid elongase 1 catalyses elongation of saturated and monounsaturated C22-C26-VLCFAs. We studied two patients with a dominant mutation. Independently, Kutkowska-Kaźmierczak had investigated the same patients and found the same mutation. We extended our study towards additional biochemical, functional, and therapeutic aspects.
We did mutation screening by whole exome sequencing. RNA-sequencing was performed in patient and control fibroblasts. Ceramide and sphingomyelin levels were measured by LC-MS/MS. ELOVL1 activity was determined by a stable isotope-labelled [C]malonyl-CoA elongation assay. ELOVL1 expression patterns were investigated by immunofluorescence, hybridisation and RT-qPCR. As treatment option, we investigated VLCFA loading of fibroblasts.
Both patients carried an identical heterozygous mutation (c.494C>T, NM_001256399; p.S165F) not deriving from a founder allele. Patients suffered from epidermal hyperproliferation and increased keratinisation (ichthyosis). Hypomyelination of the central white matter explained spastic paraplegia and central nystagmus, while optic atrophy was causative for reduction of peripheral vision and visual acuity. The mutation abrogated ELOVL1 enzymatic activity and reduced ≥C24 ceramides and sphingomyelins in patient cells. Fibroblast loading with C22:0-VLCFAs increased C24:0-ceramides and sphingomyelins. We found competitive inhibition for ceramide and sphingomyelin synthesis between saturated and monounsaturated VLCFAs. Transcriptome analysis revealed upregulation of modules involved in epidermal development and keratinisation, and downregulation of genes for neurodevelopment, myelination, and synaptogenesis. Many regulated genes carried consensus proliferator-activated receptor (PPAR)α and PPARγ binding motifs in their 5'-regions.
A dominant mutation causes a neuro-ichthyotic disorder possibly amenable to treatment with PPAR-modulating drugs.
长链脂肪酸（VLCFAs）对生物膜的功能至关重要。ELOVL 脂肪酸延长酶 1 催化饱和和单不饱和 C22-C26-VLCFAs 的延长。我们研究了两位携带显性突变的患者。Kutkowska-Kaźmierczak 独立地研究了相同的患者，并发现了相同的突变。我们扩展了我们的研究，以涵盖其他生化、功能和治疗方面。
我们通过全外显子组测序进行突变筛选。在患者和对照成纤维细胞中进行 RNA 测序。通过 LC-MS/MS 测量神经酰胺和神经鞘磷脂的水平。通过稳定同位素标记的 [C]丙二酰 CoA 延伸测定法测定 ELOVL1 活性。通过免疫荧光、杂交和 RT-qPCR 研究 ELOVL1 表达模式。作为治疗选择，我们研究了成纤维细胞的 VLCFA 加载。
两位患者均携带相同的杂合突变（c.494C>T，NM_001256399; p.S165F），并非来自一个创始等位基因。患者患有表皮过度增生和角化过度（鱼鳞癣）。中枢白质的髓鞘形成不良解释了痉挛性截瘫和中央眼球震颤，而视神经萎缩导致周边视力和视力下降。该突变使 ELOVL1 酶活性丧失，并降低了患者细胞中的≥C24 神经酰胺和神经鞘磷脂。成纤维细胞加载 C22:0-VLCFAs 增加了 C24:0-神经酰胺和神经鞘磷脂。我们发现饱和和单不饱和 VLCFAs 之间的神经酰胺和神经鞘磷脂合成存在竞争抑制。转录组分析显示，与表皮发育和角化相关的模块上调，与神经发育、髓鞘形成和突触发生相关的基因下调。许多受调控的基因在其 5'-区域携带公认的过氧化物酶体增殖物激活受体（PPAR）α和 PPARγ 结合基序。
显性突变导致神经鱼鳞癣障碍，可能适合用 PPAR 调节药物治疗。
