Browsing by Author "Zaki, Maha S."

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    The clinical and genetic spectrum of inherited glycosylphosphatidylinositol deficiency disorders
    (Oxford University Press, 2024) Sidpra, Jai; Sudhakar, Sniya; Biswas, Asthik; Massey, Flavia; Turchetti, Valentina; Lau, Tracy; Cook, Edward; Alvi, Javeria Raza; Elbendary, Hasnaa M.; Jewell, Jerry L.; Riva, Antonella; Orsini, Alessandro; Vignoli, Aglaia; Federico, Zara; Rosenblum, Jessica; Schoonjans, An-Sofie; de Wachter, Matthias; Alvarez, Ignacio Delgado; Felipe-Rucián, Ana; Haridy, Nourelhoda A.; Haider, Shahzad; Zaman, Mashaya; Banu, Selina; Anwaar, Najwa; Rahman, Fatima; Maqbool, Shazia; Yadav, Rashmi; Salpietro, Vincenzo; Maroofian, Reza; Patel, Rajan; Radhakrishnan, Rupa; Prabhu, Sanjay P.; Lichtenbelt, Klaske; Stewart, Helen; Murakami, Yoshiko; Löbel, Ulrike; D'Arco, Felice; Wakeling, Emma; Jones, Wendy; Hay, Eleanor; Bhate, Sanjay; Jacques, Thomas S.; Mirsky, David M.; Whitehead, Matthew T.; Zaki, Maha S.; Sultan, Tipu; Striano, Pasquale; Jansen, Anna C.; Lequin, Maarten; de Vries, Linda S.; Severino, Mariasavina; Edmondson, Andrew C.; Menzies, Lara; Campeau, Philippe M.; Houlden, Henry; McTague, Amy; Efthymiou, Stephanie; Mankad, Kshitij; Radiology and Imaging Sciences, School of Medicine
    Inherited glycosylphosphatidylinositol deficiency disorders (IGDs) are a group of rare multisystem disorders arising from pathogenic variants in glycosylphosphatidylinositol anchor pathway (GPI-AP) genes. Despite associating 24 of at least 31 GPI-AP genes with human neurogenetic disease, prior reports are limited to single genes without consideration of the GPI-AP as a whole and with limited natural history data. In this multinational retrospective observational study, we systematically analyse the molecular spectrum, phenotypic characteristics and natural history of 83 individuals from 75 unique families with IGDs, including 70 newly reported individuals; the largest single cohort to date. Core clinical features were developmental delay or intellectual disability (DD/ID, 90%), seizures (83%), hypotonia (72%) and motor symptoms (64%). Prognostic and biologically significant neuroimaging features included cerebral atrophy (75%), cerebellar atrophy (60%), callosal anomalies (57%) and symmetric restricted diffusion of the central tegmental tracts (60%). Sixty-one individuals had multisystem involvement including gastrointestinal (66%), cardiac (19%) and renal (14%) anomalies. Though dysmorphic features were appreciated in 82%, no single dysmorphic feature had a prevalence >30%, indicating substantial phenotypic heterogeneity. Follow-up data were available for all individuals, 15 of whom were deceased at the time of writing. Median age at seizure onset was 6 months. Individuals with variants in synthesis stage genes of the GPI-AP exhibited a significantly shorter time to seizure onset than individuals with variants in transamidase and remodelling stage genes of the GPI-AP (P = 0.046). Forty individuals had intractable epilepsy. The majority of individuals experienced delayed or absent speech (95%), motor delay with non-ambulance (64%), and severe-to-profound DD/ID (59%). Individuals with a developmental epileptic encephalopathy (51%) were at greater risk of intractable epilepsy (P = 0.003), non-ambulance (P = 0.035), ongoing enteral feeds (P < 0.001) and cortical visual impairment (P = 0.007). Serial neuroimaging showed progressive cerebral volume loss in 87.5% and progressive cerebellar atrophy in 70.8%, indicating a neurodegenerative process. Genetic analyses identified 93 unique variants (106 total), including 22 novel variants. Exploratory analyses of genotype-phenotype correlations using unsupervised hierarchical clustering identified novel genotypic predictors of clinical phenotype and long-term outcome with meaningful implications for management. In summary, we expand both the mild and severe phenotypic extremities of the IGDs, provide insights into their neurological basis, and vitally, enable meaningful genetic counselling for affected individuals and their families.
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    UBR7 functions with UBR5 in the Notch signaling pathway and is involved in a neurodevelopmental syndrome with epilepsy, ptosis, and hypothyroidism
    (Cell Press, 2021-01-07) Li, Chunmei; Beauregard-Lacroix, Eliane; Kondratev, Christine; Rousseau, Justine; Heo, Ah Jung; Neas, Katherine; Graham, Brett H.; Rosenfeld, Jill A.; Bacino, Carlos A.; Wagner, Matias; Wenzel, Maren; Al Mutairi, Fuad; Al Deiab, Hamad; Gleeson, Joseph G.; Stanley, Valentina; Zaki, Maha S.; Kwon, Yong Tae; Leroux, Michel R.; Campeau, Philippe M.; Medical and Molecular Genetics, School of Medicine
    The ubiquitin-proteasome system facilitates the degradation of unstable or damaged proteins. UBR1-7, which are members of hundreds of E3 ubiquitin ligases, recognize and regulate the half-life of specific proteins on the basis of their N-terminal sequences ("N-end rule"). In seven individuals with intellectual disability, epilepsy, ptosis, hypothyroidism, and genital anomalies, we uncovered bi-allelic variants in UBR7. Their phenotype differs significantly from that of Johanson-Blizzard syndrome (JBS), which is caused by bi-allelic variants in UBR1, notably by the presence of epilepsy and the absence of exocrine pancreatic insufficiency and hypoplasia of nasal alae. While the mechanistic etiology of JBS remains uncertain, mutation of both Ubr1 and Ubr2 in the mouse or of the C. elegans UBR5 ortholog results in Notch signaling defects. Consistent with a potential role in Notch signaling, C. elegans ubr-7 expression partially overlaps with that of ubr-5, including in neurons, as well as the distal tip cell that plays a crucial role in signaling to germline stem cells via the Notch signaling pathway. Analysis of ubr-5 and ubr-7 single mutants and double mutants revealed genetic interactions with the Notch receptor gene glp-1 that influenced development and embryo formation. Collectively, our findings further implicate the UBR protein family and the Notch signaling pathway in a neurodevelopmental syndrome with epilepsy, ptosis, and hypothyroidism that differs from JBS. Further studies exploring a potential role in histone regulation are warranted given clinical overlap with KAT6B disorders and the interaction of UBR7 and UBR5 with histones.