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RSRC1 loss-of-function variants cause mild to moderate autosomal recessive intellectual disability

Scala M, Mojarrad M, Riazuddin S, Brigatti KW, Ammous Z, Cohen JS, Hosny H, Usmani MA, Shahzad M, Riazuddin S, Stanley V, Eslahi A, Person RE, Elbendary HM, Comi AM, Poskitt L, Salpietro V, Genomics QS, Rosenfeld JA, Williams KB, Marafi D, Xia F, Biderman Waberski M, Zaki MS, Gleeson J, Puffenberger E, Houlden H, Maroofian R.

Brain. 2020 Apr 1;143(4):e31. doi: 10.1093/brain/awaa070. NO ABSTRACT PMID:32227164 | PMC:PMC7174030 | DOI:10.1093/brain/awaa070

April 1, 2020

Bi-allelic Variants in the GPI Transamidase Subunit PIGK Cause a Neurodevelopmental Syndrome with Hypotonia, Cerebellar Atrophy, and Epilepsy

Nguyen TTM, Murakami Y, Mobilio S, Niceta M, Zampino G, Philippe C, Moutton S, Zaki MS, James KN, Musaev D, Mu W, Baranano K, Nance JR, Rosenfeld JA, Braverman N, Ciolfi A, Millan F, Person RE, Bruel AL, Thauvin-Robinet C, Ververi A, DeVile C, Male A, Efthymiou S, Maroofian R, Houlden H, Maqbool S, Rahman F, Baratang NV, Rousseau J, St-Denis A, Elrick MJ, Anselm I, Rodan LH, Tartaglia M, Gleeson J, Kinoshita T, Campeau PM.

Am J Hum Genet. 2020 Apr 2;106(4):484-495. doi: 10.1016/j.ajhg.2020.03.001. Epub 2020 Mar 26. ABSTRACT Glycosylphosphatidylinositol (GPI)-anchored proteins are critical for embryogenesis, neurogenesis, and cell signaling. Variants in several genes participating in GPI biosynthesis and processing lead to decreased cell surface presence of GPI-anchored proteins (GPI-APs) and cause inherited GPI deficiency disorders (IGDs). In this report, we describe 12 individuals from nine unrelated families with 10 different bi-allelic PIGK variants. PIGK encodes a component of the GPI transamidase complex, which attaches the GPI anchor to proteins. Clinical features found in most individuals include global developmental delay and/or intellectual disability, hypotonia, cerebellar ataxia, cerebellar atrophy, and facial dysmorphisms. The majority of the individuals have epilepsy. Two individuals have slightly decreased levels of serum alkaline phosphatase, while eight do not. Flow cytometric analysis of blood and fibroblasts from affected individuals showed decreased cell surface presence of GPI-APs. The overexpression of wild-type (WT) PIGK in fibroblasts rescued the levels of cell surface GPI-APs. In a knockout cell line, transfection with WT PIGK also rescued the GPI-AP levels, but transfection with the two tested mutant variants did not. Our study not only expands the clinical and known genetic spectrum of IGDs, but it also expands the genetic differential diagnosis for cerebellar atrophy. Given the fact that cerebellar atrophy is seen in other IGDs, flow cytometry for GPI-APs should be considered in the work-ups of individuals presenting this feature. PMID:32220290 | PMC:PMC7118585 | DOI:10.1016/j.ajhg.2020.03.001

March 30, 2020


Dystonia-Ataxia with early handwriting deterioration in COQ8A mutation carriers: A case series and literature review

Galosi S, Barca E, Carrozzo R, Schirinzi T, Quinzii CM, Lieto M, Vasco G, Zanni G, Di Nottia M, Galatolo D, Filla A, Bertini E, Santorelli FM, Leuzzi V, Haas R, Hirano M, Friedman J.

Parkinsonism Relat Disord. 2019 Nov;68:8-16. doi: 10.1016/j.parkreldis.2019.09.015. Epub 2019 Sep 28.


Cerebellar ataxia is a hallmark of coenzyme Q10 (CoQ10) deficiency associated with COQ8A mutations. We present four patients, one with novel COQ8A pathogenic variants all with early, prominent handwriting impairment, dystonia and only mild ataxia. To better define the phenotypic spectrum and course of COQ8A disease, we review the clinical presentation and evolution in 47 reported cases. Individuals with COQ8A mutation display great clinical variability and unpredictable responses to CoQ10 supplementation. Onset is typically during infancy or childhood with ataxic features associated with developmental delay or regression. When disease onset is later in life, first symptoms can include: incoordination, epilepsy, tremor, and deterioration of writing. The natural history is characterized by a progression to a multisystem brain disease dominated by ataxia, with disease severity inversely correlated with age at onset. Six previously reported cases share with ours, a clinical phenotype characterized by slowly progressive or static writing difficulties, focal dystonia, and speech disorder, with only minimal ataxia. The combination of writing difficulty, dystonia and ataxia is a distinctive constellation that is reminiscent of a previously described clinical entity called Dystonia Ataxia Syndrome (DYTCA) and is an important clinical indicator of COQ8A mutations, even when ataxia is mild or absent.

PMID:31621627 | DOI:10.1016/j.parkreldis.2019.09.015

October 18, 2019
Genetic Neurologic DiseaseNeurogenomics


Paroxysmal motor disorders: expanding phenotypes lead to coalescing genotypes

Zima L, Ceulemans S, Reiner G, Galosi S, Chen D, Sahagian M, Haas RH, Hyland K, Friedman J.

Ann Clin Transl Neurol. 2018 Jul 17;5(8):996-1010. doi: 10.1002/acn3.597. eCollection 2018 Aug.


Paroxysmal movement disorders encompass varied motor phenomena. Less recognized features and wide phenotypic and genotypic heterogeneity are impediments to straightforward molecular diagnosis. We describe a family with episodic ataxia type 1, initially mis-characterized as paroxysmal dystonia to illustrate this diagnostic challenge. We summarize clinical features in affected individuals to highlight underappreciated aspects and provide comprehensive phenotypic description of the rare familial KCNA1 mutation. Delayed diagnosis in this family is emblematic of the broader challenge of diagnosing other paroxysmal motor disorders. We summarize genotypic and phenotypic overlap and provide a suggested diagnostic algorithm for approaching patients with these conditions.

PMID:30128325 | PMC:PMC6093839 | DOI:10.1002/acn3.597

August 22, 2018
Genetic Neurologic DiseaseNeurogenomics

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