Gabillard-Lefort Claudie, Martinez Caroline Silveira, Gueguen Naïg, Desquiret-Dumas Valérie, Wery Méline, Legoff Louis, Guimier Anne, Rondeau Sophie, Barcia Giulia, Barnerias Christine, Cogne Benjamin, Besnard Thomas, Lorino Elsa, Douglas Jessica, Bodamer Olaf, Vetro Annalisa, Guerrini Renzo, Balestrini Simona, Conti Valerio, Siri Laura, Chevrollier Arnaud, Bris Céline, Colin Estelle, Procaccio Vincent, Prunier-Mirebeau Delphine, Lenaers Guy, Khiati Salim, Nizon Mathilde, Baris Olivier R
University of Angers, MitoLab, Unité MITOVASC, UMR CNRS 6015, INSERM U1083, SFR ICAT, University Hospital of Angers, Angers, France.
University of Angers, MitoLab, Unité MITOVASC, UMR CNRS 6015, INSERM U1083, SFR ICAT, University Hospital of Angers, Angers, France; Departments of Biochemistry and Molecular Biology, University Hospital of Angers, Angers, France.
Am J Hum Genet. 2025 Jul 3;112(7):1711-1721. doi: 10.1016/j.ajhg.2025.05.004. Epub 2025 May 30.
We identified via exome sequencing bi-allelic variants in TM2D3 in four affected individuals from four unrelated families with overlapping clinical presentations, including microcephaly, severe global developmental delay with absent speech, autistic features, heart malformation, and dysmorphic facial features. TM2D3 encodes a transmembrane protein present in many tissues, with a higher abundance in the central nervous system, but little is known about its function and cell localization. Here, by using chemical and genetically encoded probes in SNB75 cells, we show that TM2D3 is an endoplasmic reticulum (ER) protein. Further analysis on SNB75 TM2D3-knockout cells as well as skin fibroblasts from affected individuals harboring the recurrent c.503G>A (p.Gly168Asp) allele revealed an impact of TM2D3 on ER-stress response, with dysregulated expression of ATF4, HSPA5, and DDIT3. Transmission electron microscopy highlighted ER swelling as well as unexpected secondary mitochondrial alterations including increased length, cristae width, and ER-mitochondria distance. To gain further insights into the pathomechanisms at play, we performed RNA sequencing from the fibroblasts of the three individuals harboring the p.Gly168Asp variant and four available parents and disclosed 21 differentially expressed genes, including genes coding for extracellular matrix components involved in the migration of neuronal precursors. Altogether, these clinical and experimental data show that bi-allelic TM2D3 variants underlie a severe syndromic neurodevelopmental disorder linked to exacerbated ER-stress sensitivity, secondary mitochondrial alterations, and altered extracellular matrix gene expression.
我们通过外显子组测序，在来自四个不相关家庭的四名患病个体中鉴定出TM2D3基因的双等位基因变异，这些个体具有重叠的临床表现，包括小头畸形、严重的全面发育迟缓且无语言能力、自闭症特征、心脏畸形和面部畸形特征。TM2D3编码一种存在于许多组织中的跨膜蛋白，在中枢神经系统中丰度较高，但其功能和细胞定位知之甚少。在这里，我们通过在SNB75细胞中使用化学和基因编码探针，表明TM2D3是一种内质网（ER）蛋白。对携带复发性c.503G>A（p.Gly168Asp）等位基因的患病个体的SNB75 TM2D3基因敲除细胞以及皮肤成纤维细胞的进一步分析显示，TM2D3对内质网应激反应有影响，ATF4、HSPA5和DDIT3的表达失调。透射电子显微镜突出显示内质网肿胀以及意想不到的继发性线粒体改变，包括长度增加、嵴宽度增加和内质网与线粒体距离增加。为了进一步深入了解其中的发病机制，我们对三名携带p.Gly168Asp变异的个体及其四名可获得的父母的成纤维细胞进行了RNA测序，发现了21个差异表达基因，包括编码参与神经元前体迁移的细胞外基质成分的基因。总之，这些临床和实验数据表明，双等位基因TM2D3变异是一种严重的综合征性神经发育障碍的基础，该障碍与内质网应激敏感性加剧、继发性线粒体改变以及细胞外基质基因表达改变有关。
