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Indellicato R, Domenighini R, Malagolini N, Cereda A, Mamoli D, Pezzani L, Iascone M, dall'Olio F, Trinchera M. A novel nonsense and inactivating variant of ST3GAL3 in two infant siblings suffering severe epilepsy and expressing circulating CA19.9. Glycobiology 2020; 30:95-104. [PMID: 31584066 DOI: 10.1093/glycob/cwz079] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Revised: 09/09/2019] [Accepted: 09/24/2019] [Indexed: 01/06/2023] Open
Abstract
Three missense variants of ST3GAL3 are known to be responsible for a congenital disorder of glycosylation determining a neurodevelopmental disorder (intellectual disability/epileptic encephalopathy). Here we report a novel nonsense variant, p.Y220*, in two dichorionic infant twins presenting a picture of epileptic encephalopathy with impaired neuromotor development. Upon expression in HEK-293T cells, the variant appears totally devoid of enzymatic activity in vitro, apparently accumulated with respect to the wild-type or the missense variants, as detected by western blot, and in large part properly localized in the Golgi apparatus, as assessed by confocal microscopy. Both patients were found to efficiently express the CA19.9 antigen in the serum despite the total loss of ST3GAL3 activity, which thus appears replaceable from other ST3GALs in the synthesis of the sialyl-Lewis a epitope. Kinetic studies of ST3GAL3 revealed a strong preference for lactotetraosylceramide as acceptor and gangliotetraosylceramide was also efficiently utilized in vitro. Moreover, the p.A13D missense variant, the one maintaining residual sialyltransferase activity, was found to have much lower affinity for all suitable substrates than the wild-type enzyme with an overall catalytic efficiency almost negligible. Altogether the present data suggest that the apparent redundancy of ST3GALs deduced from knock-out mouse models only partially exists in humans. In fact, our patients lacking ST3GAL3 activity synthesize the CA19.9 epitope sialyl-Lewis a, but not all glycans necessary for fine brain functions, where the role of minor gangliosides deserves further attention.
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Affiliation(s)
- Rossella Indellicato
- Department of Health Sciences, San Paolo Hospital, University of Milan, via Antonio di Rudinì 8, 20142 Milano, Italy
| | - Ruben Domenighini
- Department of Health Sciences, San Paolo Hospital, University of Milan, via Antonio di Rudinì 8, 20142 Milano, Italy
| | - Nadia Malagolini
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, via San Giacomo 14, 40126 Bologna, Italy
| | - Anna Cereda
- Department of Pediatrics, ASST Papa Giovanni XXIII, via OMS 1, 24127 Bergamo, Italy
| | - Daniela Mamoli
- Neuropsichiatria infantile, ASST Papa Giovanni XXIII, via OMS 1, 24127 Bergamo, Italy
| | - Lidia Pezzani
- Laboratory of Medical Genetics, ASST Papa Giovanni XXIII, via OMS 1, 24127 Bergamo, Italy
| | - Maria Iascone
- Laboratory of Medical Genetics, ASST Papa Giovanni XXIII, via OMS 1, 24127 Bergamo, Italy
| | - Fabio dall'Olio
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, via San Giacomo 14, 40126 Bologna, Italy
| | - Marco Trinchera
- Department of Medicine and Surgery (DMC), University of Insubria, via JH Dunant 5, 21100 Varese, Italy
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Trinchera M, Parini R, Indellicato R, Domenighini R, dall'Olio F. Diseases of ganglioside biosynthesis: An expanding group of congenital disorders of glycosylation. Mol Genet Metab 2018; 124:230-237. [PMID: 29983310 DOI: 10.1016/j.ymgme.2018.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 06/27/2018] [Accepted: 06/27/2018] [Indexed: 10/28/2022]
Abstract
Among the numerous congenital disorders of glycosylation concerning glycoproteins, only a single mutation in ganglioside biosynthesis had been reported until a few years ago: one in the ST3GAL5 gene, encoding GM3 synthase. More recently, additional mutations in the same gene were reported, together with several distinct mutations in the B4GALNT1 gene, encoding GM2/GD2/GA2 synthase. Patients suffering from ST3GAL5 deficiency present a devastating syndrome characterized by early onset and dramatic neurological and cognitive impairment, sometimes associated with dyspigmentation and an increased blood lactate concentration. On the other hand, B4GALNT1 mutations give rise to a form of complicated hereditary spastic paraplegia (HSP), previously referred to as HSP26. It is characterized by the late onset of lower limb weakness and mild to moderate intellectual impairment, which is usually not progressive. In addition to the most typical signs, some patients present ocular and endocrine signs, pes cavus, and psychiatric illness. Since the nineties, mice lacking genes for single glycosyltransferases involved in ganglioside biosynthesis, including ST3GAL5 and B4GALNT1, were created and studied. The resulting phenotypes were frequently mild or very mild, so double knock-out animals were created to effectively study the function of gangliosides. The main clinical and biochemical features of patients suffering from GM3 synthase or GM2/GD2/GA2 synthase deficiency, compared with the phenotypes described in mice that are null for single or multiple glycosyltransferase genes, provide suggestions to improve the recognition of novel mutations and potentially related disorders.
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Affiliation(s)
- Marco Trinchera
- Department of Medicine and Surgery (DMC), University of Insubria, 21100 Varese, Italy.
| | - Rossella Parini
- Pediatric Unit, Fondazione MBBM, San Gerardo Hospital, 20900 Monza, Italy
| | - Rossella Indellicato
- Department of Health Sciences, San Paolo Hospital, University of Milan, 20142 Milano, Italy
| | - Ruben Domenighini
- Department of Health Sciences, San Paolo Hospital, University of Milan, 20142 Milano, Italy
| | - Fabio dall'Olio
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, 40126 Bologna, Italy
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