Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Nagoya 4678601, Japan.
Department of Cell Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya 4678601, Japan.
Brain. 2024 Nov 4;147(11):3949-3967. doi: 10.1093/brain/awae185.
Patatin-like phospholipase domain-containing lipase 8 (PNPLA8), one of the calcium-independent phospholipase A2 enzymes, is involved in various physiological processes through the maintenance of membrane phospholipids. Biallelic variants in PNPLA8 have been associated with a range of paediatric neurodegenerative disorders. However, the phenotypic spectrum, genotype-phenotype correlations and the underlying mechanisms are poorly understood. Here, we newly identified 14 individuals from 12 unrelated families with biallelic ultra-rare variants in PNPLA8 presenting with a wide phenotypic spectrum of clinical features. Analysis of the clinical features of current and previously reported individuals (25 affected individuals across 20 families) showed that PNPLA8-related neurological diseases manifest as a continuum ranging from variable developmental and/or degenerative epileptic-dyskinetic encephalopathy to childhood-onset neurodegeneration. We found that complete loss of PNPLA8 was associated with the more profound end of the spectrum, with congenital microcephaly. Using cerebral organoids generated from human induced pluripotent stem cells, we found that loss of PNPLA8 led to developmental defects by reducing the number of basal radial glial cells and upper-layer neurons. Spatial transcriptomics revealed that loss of PNPLA8 altered the fate specification of apical radial glial cells, as reflected by the enrichment of gene sets related to the cell cycle, basal radial glial cells and neural differentiation. Neural progenitor cells lacking PNPLA8 showed a reduced amount of lysophosphatidic acid, lysophosphatidylethanolamine and phosphatidic acid. The reduced number of basal radial glial cells in patient-derived cerebral organoids was rescued, in part, by the addition of lysophosphatidic acid. Our data suggest that PNPLA8 is crucial to meet phospholipid synthetic needs and to produce abundant basal radial glial cells in human brain development.
载脂蛋白样磷脂酶域包含脂酶 8（PNPLA8）是钙非依赖性磷脂酶 A2 酶之一，通过维持膜磷脂参与各种生理过程。PNPLA8 的双等位基因变异与一系列儿科神经退行性疾病有关。然而，表型谱、基因型-表型相关性和潜在机制尚不清楚。在这里，我们从 12 个无关的家庭中发现了 14 个个体，他们具有双等位基因超罕见的 PNPLA8 变异，表现出广泛的临床特征表型谱。对当前和以前报道的个体（20 个家庭中的 25 个受影响个体）的临床特征进行分析表明，PNPLA8 相关的神经疾病表现为从可变发育和/或退行性癫痫性运动障碍到儿童期发病的神经变性的连续谱。我们发现，PNPLA8 的完全缺失与更为严重的表型谱相关，表现为先天性小头畸形。使用源自人类诱导多能干细胞的大脑类器官，我们发现 PNPLA8 的缺失通过减少基底放射状胶质细胞和上皮层神经元的数量导致发育缺陷。空间转录组学揭示，PNPLA8 的缺失改变了顶壁放射状胶质细胞的命运特化，这反映在与细胞周期、基底放射状胶质细胞和神经分化相关的基因集的富集上。缺乏 PNPLA8 的神经祖细胞表现出较少的溶血磷脂酸、溶血磷脂酰乙醇胺和磷脂酸。患者来源的大脑类器官中基底放射状胶质细胞数量减少，部分通过添加溶血磷脂酸得到挽救。我们的数据表明，PNPLA8 对于满足磷脂合成需求和在人类大脑发育中产生丰富的基底放射状胶质细胞至关重要。
