1. Loss of UGP2 in brain leads to a severe epileptic encephalopathy, emphasizing that bi-allelic isoform-specific start-loss mutations of essential genes can cause genetic diseases
- Author
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Nuzhat Rana, Edwin H. Jacobs, Ehsan Ghayoor Karimiani, Amber Begtrup, Jozef Hertecant, Evita Medici-van den Herik, Mohammad Doosti, Gouri Rao Passi, Mohammadreza Dehghani, Tjakko J. van Ham, Mariya Kozenko, Laila AlQuait, Mohammad Yahya Vahidi Mehrjardi, Dilek Colak, Herma C. van der Linde, Henry Houlden, Eleonora Aronica, Huma Arshad Cheema, Jennefer N. Kohler, Namik Kaya, Krishna Kumar Kandaswamy, Salem Alwadaee, Maysoon Alsagob, Woutje M. Berdowski, Zaynab Khazaei, Renjith Mani, Faisal Al Azri, Amna Al Futaisi, Stephanie Efthymiou, Majid Mojarrad, Aida M. Bertoli-Avella, Murat Gunel, Tahsin Stefan Barakat, Wilfred F. J. van IJcken, Kristin G. Monaghan, Rebecca I. Torene, Atieh Eslahi, Fathiya Al Murshedi, Khalid Awartani, Peter Bauer, Muddathir H. Hamad, Kyle Retterer, Reza Maroofian, Rawan Almass, Erik-Jan Kamsteeg, Serdar Coskun, Jonathan A. Bernstein, Elena Perenthaler, Anita Nikoncuk, Mohammed A. AlMuhaizea, Jana Vandrovcova, Anas M. Dababo, Soheil Yousefi, Fateme Massinaei Darmiyan, Mustafa A. Salih, Lauren Brick, A. Gulhan Ercan-Sencicek, Futwan Al-Mohanna, Ivan Čapo, Faisal Zafar, Khaled O. Alahmadi, Marjon van Slegtenhorst, Walter G. de Valk, Mazhor Al-Dosary, Wafa Qubbaj, Alice S. Brooks, Mehrnaz Ghazvini, Paul van den Berg, Darija Putar, Clinical Genetics, Cell biology, Neurology, Pathology, ANS - Cellular & Molecular Mechanisms, APH - Aging & Later Life, and APH - Mental Health
- Subjects
Gene isoform ,Protein isoform ,Male ,Microcephaly ,Recurrent mutation ,UTP-Glucose-1-Phosphate Uridylyltransferase ,UGP2 ,medicine.disease_cause ,Sensory disorders Donders Center for Medical Neuroscience [Radboudumc 12] ,Pathology and Forensic Medicine ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,0302 clinical medicine ,epileptic encephalopathy ,ATG mutations ,start-loss mutation ,genetics ,whole exome sequencing ,microcephaly ,recurrent mutation ,founder mutation ,essential gene ,medicine ,Genetics ,Missense mutation ,Animals ,Humans ,Allele ,Founder mutation ,Zebrafish ,Exome sequencing ,030304 developmental biology ,0303 health sciences ,Mutation ,Original Paper ,Brain Diseases ,Genes, Essential ,biology ,Epileptic encephalopathy ,Whole exome sequencing ,Infant ,biology.organism_classification ,medicine.disease ,3. Good health ,Pedigree ,Start-loss mutation ,Essential gene ,Child, Preschool ,Female ,Neurology (clinical) ,Epileptic Syndromes ,030217 neurology & neurosurgery - Abstract
Developmental and/or epileptic encephalopathies (DEEs) are a group of devastating genetic disorders, resulting in early-onset, therapy-resistant seizures and developmental delay. Here we report on 22 individuals from 15 families presenting with a severe form of intractable epilepsy, severe developmental delay, progressive microcephaly, visual disturbance and similar minor dysmorphisms. Whole exome sequencing identified a recurrent, homozygous variant (chr2:64083454A > G) in the essential UDP-glucose pyrophosphorylase (UGP2) gene in all probands. This rare variant results in a tolerable Met12Val missense change of the longer UGP2 protein isoform but causes a disruption of the start codon of the shorter isoform, which is predominant in brain. We show that the absence of the shorter isoform leads to a reduction of functional UGP2 enzyme in neural stem cells, leading to altered glycogen metabolism, upregulated unfolded protein response and premature neuronal differentiation, as modeled during pluripotent stem cell differentiation in vitro. In contrast, the complete lack of all UGP2 isoforms leads to differentiation defects in multiple lineages in human cells. Reduced expression of Ugp2a/Ugp2b in vivo in zebrafish mimics visual disturbance and mutant animals show a behavioral phenotype. Our study identifies a recurrent start codon mutation in UGP2 as a cause of a novel autosomal recessive DEE syndrome. Importantly, it also shows that isoform-specific start-loss mutations causing expression loss of a tissue-relevant isoform of an essential protein can cause a genetic disease, even when an organism-wide protein absence is incompatible with life. We provide additional examples where a similar disease mechanism applies. Electronic supplementary material The online version of this article (10.1007/s00401-019-02109-6) contains supplementary material, which is available to authorized users.
- Published
- 2020