Biallelic variants in <i>HPDL</i> cause pure and complicated hereditary spastic paraplegia
Manuela Wiessner, Reza Maroofian, Meng-Yuan Ni, Andrea Pedroni, Juliane Müller, Rolf Stucka, Christian Beetz, Stéphanie Efthymiou, Filippo M. Santorelli, Ahmed Alfares, Changlian Zhu, Anna Uhrová Mészárosová, Elham Alehabib, Somayeh Bakhtiari, Andreas Janecke, María Gabriela Otero, Jin Yun Helen Chen, James T. Peterson, Tim M. Strom, Peter De Jonghe, Tine Deconinck, Willem De Ridder, Jonathan De Winter, Rossella Pasquariello, Ivana Ricca, Majid Alfadhel, Bart P.C. van de Warrenburg, R Portier, Carsten Bergmann, Saghar Ghasemi Firouzabadi, Sheng Chih Jin, Kaya Bilgüvar, Sherifa A. Hamed, Mohammed Abdelhameed, Nourelhoda A. Haridy, Shazia Maqbool, Fatima Rahman, Najwa Anwar, Jenny Carmichael, Alistair T. Pagnamenta, Nick W Wood, Frédéric Tran Mau‐Them, Tobias B. Haack, Maja Di Rocco, Isabella Ceccherini, Michele Iacomino, Federico Zara, Vincenzo Salpietro, Marcello Scala, Marta Rusmini, Yiran Xu, Yinghong Wang, Yasuhiro Suzuki, Kishin Koh, Haitian Nan, Hiroyuki Ishiura, Shoji Tsuji, Laëtitia Lambert, Emmanuelle Schmitt, Elodie Lacaze, Hanna Küpper, David Dredge, Cara Skraban, Amy Goldstein, Mary Willis, Katheryn Grand, John M. Graham, Richard A. Lewis, Francisca Millan, Özgür Duman, Nihal Olgaç Dündar, Gökhan Uyanık, Lüdger Schöls, Peter Nürnberg, Gudrun Nürnberg, Andrea Català-Bordes, Pavel Seeman, Martin Kuchař, Hossein Darvish, Adriana Rebelo, Filipa Bouçanova, Jean‐Jacques Médard, Roman Chrast, Michaela Auer‐Grumbach, Fowzan S. Alkuraya, Hanan E. Shamseldin, Saeed Al Tala, Jamileh Rezazadeh Varaghchi, Maryam Najafi, Selina Deschner, Dieter Gläser, Wolfgang Hüttel, Michael C. Kruer, Erik-Jan Kamsteeg, Yoshihisa Takiyama, Stephan Züchner, Jonathan Baets, Matthis Synofzik, Rebecca Schüle, Rita Horváth
Abstract
Human 4-hydroxyphenylpyruvate dioxygenase-like (HPDL) is a putative iron-containing non-heme oxygenase of unknown specificity and biological significance. We report 25 families containing 34 individuals with neurological disease associated with biallelic HPDL variants. Phenotypes ranged from juvenile-onset pure hereditary spastic paraplegia to infantile-onset spasticity and global developmental delays, sometimes complicated by episodes of neurological and respiratory decompensation. Variants included bona fide pathogenic truncating changes, although most were missense substitutions. Functionality of variants could not be determined directly as the enzymatic specificity of HPDL is unknown; however, when HPDL missense substitutions were introduced into 4-hydroxyphenylpyruvate dioxygenase (HPPD, an HPDL orthologue), they impaired the ability of HPPD to convert 4-hydroxyphenylpyruvate into homogentisate. Moreover, three additional sets of experiments provided evidence for a role of HPDL in the nervous system and further supported its link to neurological disease: (i) HPDL was expressed in the nervous system and expression increased during neural differentiation; (ii) knockdown of zebrafish hpdl led to abnormal motor behaviour, replicating aspects of the human disease; and (iii) HPDL localized to mitochondria, consistent with mitochondrial disease that is often associated with neurological manifestations. Our findings suggest that biallelic HPDL variants cause a syndrome varying from juvenile-onset pure hereditary spastic paraplegia to infantile-onset spastic tetraplegia associated with global developmental delays.