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Umano A, Fang K, Qu Z, Scaglione JB, Altinok S, Treadway CJ, Wick ET, Paulakonis E, Karunanayake C, Chou S, Bardakjian TM, Gonzalez-Alegre P, Page RC, Schisler JC, Brown NG, Yan D, Scaglione KM. The molecular basis of spinocerebellar ataxia type 48 caused by a de novo mutation in the ubiquitin ligase CHIP. J Biol Chem 2022; 298:101899. [PMID: 35398354 PMCID: PMC9097460 DOI: 10.1016/j.jbc.2022.101899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/24/2022] [Accepted: 03/28/2022] [Indexed: 11/25/2022] Open
Abstract
The spinocerebellar ataxias (SCAs) are a class of incurable diseases characterized by degeneration of the cerebellum that results in movement disorder. Recently, a new heritable form of SCA, spinocerebellar ataxia type 48 (SCA48), was attributed to dominant mutations in STIP1 homology and U box-containing 1 (STUB1); however, little is known about how these mutations cause SCA48. STUB1 encodes for the protein C terminus of Hsc70 interacting protein (CHIP), an E3 ubiquitin ligase. CHIP is known to regulate proteostasis by recruiting chaperones via a N-terminal tetratricopeptide repeat domain and recruiting E2 ubiquitin-conjugating enzymes via a C-terminal U-box domain. These interactions allow CHIP to mediate the ubiquitination of chaperone-bound, misfolded proteins to promote their degradation via the proteasome. Here we have identified a novel, de novo mutation in STUB1 in a patient with SCA48 encoding for an A52G point mutation in the tetratricopeptide repeat domain of CHIP. Utilizing an array of biophysical, biochemical, and cellular assays, we demonstrate that the CHIPA52G point mutant retains E3-ligase activity but has decreased affinity for chaperones. We further show that this mutant decreases cellular fitness in response to certain cellular stressors and induces neurodegeneration in a transgenic Caenorhabditis elegans model of SCA48. Together, our data identify the A52G mutant as a cause of SCA48 and provide molecular insight into how mutations in STUB1 cause SCA48.
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Affiliation(s)
- A Umano
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - K Fang
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - Z Qu
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - J B Scaglione
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - S Altinok
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - C J Treadway
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - E T Wick
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - E Paulakonis
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - C Karunanayake
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
| | - S Chou
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - T M Bardakjian
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - P Gonzalez-Alegre
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - R C Page
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
| | - J C Schisler
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - N G Brown
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - D Yan
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - K M Scaglione
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA; Department of Neurology, Duke University, Durham, North Carolina, USA; Duke Center for Neurodegeneration and Neurotherapeutics, Duke University, Durham, North Carolina, USA.
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Schilter KF, Reis LM, Schneider A, Bardakjian TM, Abdul-Rahman O, Kozel BA, Zimmerman HH, Broeckel U, Semina EV. Whole-genome copy number variation analysis in anophthalmia and microphthalmia. Clin Genet 2013; 84:473-81. [PMID: 23701296 DOI: 10.1111/cge.12202] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [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: 02/24/2013] [Revised: 05/17/2013] [Accepted: 05/17/2013] [Indexed: 01/19/2023]
Abstract
Anophthalmia/microphthalmia (A/M) represent severe developmental ocular malformations. Currently, mutations in known genes explain less than 40% of A/M cases. We performed whole-genome copy number variation analysis in 60 patients affected with isolated or syndromic A/M. Pathogenic deletions of 3q26 (SOX2) were identified in four independent patients with syndromic microphthalmia. Other variants of interest included regions with a known role in human disease (likely pathogenic) as well as novel rearrangements (uncertain significance). A 2.2-Mb duplication of 3q29 in a patient with non-syndromic anophthalmia and an 877-kb duplication of 11p13 (PAX6) and a 1.4-Mb deletion of 17q11.2 (NF1) in two independent probands with syndromic microphthalmia and other ocular defects were identified; while ocular anomalies have been previously associated with 3q29 duplications, PAX6 duplications, and NF1 mutations in some cases, the ocular phenotypes observed here are more severe than previously reported. Three novel regions of possible interest included a 2q14.2 duplication which cosegregated with microphthalmia/microcornea and congenital cataracts in one family, and 2q21 and 15q26 duplications in two additional cases; each of these regions contains genes that are active during vertebrate ocular development. Overall, this study identified causative copy number mutations and regions with a possible role in ocular disease in 17% of A/M cases.
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Affiliation(s)
- K F Schilter
- Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, WI, USA; Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
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Ng WY, Pasutto F, Bardakjian TM, Wilson MJ, Watson G, Schneider A, Mackey DA, Grigg JR, Zenker M, Jamieson RV. A puzzle over several decades: eye anomalies with FRAS1 and STRA6 mutations in the same family. Clin Genet 2012; 83:162-8. [PMID: 22283518 DOI: 10.1111/j.1399-0004.2012.01851.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Fraser syndrome (FS) and microphthalmia syndromic 9 (MCOPS9) are autosomal recessive conditions with distinct, and some overlapping features affecting the ocular, respiratory and cardiac systems. Mutations in FRAS1 and FREM2 occur in FS, and mutations in STRA6 occur in MCOPS9. We report two sibships, in the same family, where four deceased offspring had ocular, respiratory and cardiac abnormalities. Two sibs with microphthalmia had syndactyly and laryngeal stenosis, suggesting a clinical diagnosis of FS. Our results indicate that they were compound heterozygotes for novel FRAS1 mutations, p.Cys729Phe and p.Leu3813Pro. The other two sibs, first cousins to the first sib pair, had anophthalmia, lung hypoplasia and cardiac anomalies, suggesting a retrospective diagnosis of MCOPS9. Our results indicate compound heterozygous STRA6 mutations, a novel frameshift leading to p.Tyr18* and a p.Thr644Met mutation. The one surviving individual from these sibships is heterozygous for the p.Tyr18*STRA6 mutation and has bilateral ocular colobomata and microphthalmia. This work emphasises the need for careful phenotypic characterisation to determine genes for assessment in ocular syndromic conditions. It also indicates that heterozygous STRA6 mutations may rarely contribute to microphthalmia and coloboma.
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Affiliation(s)
- W Y Ng
- Eye Genetics Research Group, Children's Medical Research Institute, The Children's Hospital at Westmead, Save Sight Institute, Sydney, Australia
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