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BMC Med Genet. 2017 Dec 13;18(1):147. doi: 10.1186/s12881-017-0508-2.

A donor splice site mutation in CISD2 generates multiple truncated, non-functional isoforms in Wolfram syndrome type 2 patients.

Author information

1
Cardiovascular Research Unit, IRCCS MultiMedica, Via G. Fantoli 16/15, 20138, Milan, Italy. monica.cattaneo@multimedica.it.
2
Cardiovascular Research Unit, IRCCS MultiMedica, Via G. Fantoli 16/15, 20138, Milan, Italy.
3
Diabetes Endocrine and Metabolic Diseases Unit, IRCCS MultiMedica, 20099 Sesto San Giovanni, Milan, Italy.
4
IRCCS Centro Cardiologico Monzino Diabetes, Endocrine and Metabolic Diseases Unit, 20138, Milan, Italy.
5
Department of Molecular Medicine, University of Pavia, 27100, Pavia, Italy.
6
Department of Medicine and Surgery, University of Salerno, 84084, Salerno, Italy.
7
Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) and Centro de Investigación Biomedica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Barcelona, Spain.

Abstract

BACKGROUND:

Mutations in the gene that encodes CDGSH iron sulfur domain 2 (CISD2) are causative of Wolfram syndrome type 2 (WFS2), a rare autosomal recessive neurodegenerative disorder mainly characterized by diabetes mellitus, optic atrophy, peptic ulcer bleeding and defective platelet aggregation. Four mutations in the CISD2 gene have been reported. Among these mutations, the homozygous c.103 + 1G > A substitution was identified in the donor splice site of intron 1 in two Italian sisters and was predicted to cause a exon 1 to be skipped.

METHODS:

Here, we employed molecular assays to characterize the c.103 + 1G > A mutation using the patient's peripheral blood mononuclear cells (PBMCs). 5'-RACE coupled with RT-PCR were used to analyse the effect of the c.103 + 1G > A mutation on mRNA splicing. Western blot analysis was used to analyse the consequences of the CISD2 mutation on the encoded protein.

RESULTS:

We demonstrated that the c.103 + 1G > A mutation functionally impaired mRNA splicing, producing multiple splice variants characterized by the whole or partial absence of exon 1, which introduced amino acid changes and a premature stop. The affected mRNAs resulted in either predicted targets for nonsense mRNA decay (NMD) or non-functional isoforms.

CONCLUSIONS:

We concluded that the c.103 + 1G > A mutation resulted in the loss of functional CISD2 protein in the two Italian WFS2 patients.

KEYWORDS:

CISD2; Non functional isoforms; Nonsense-mediated mRNA decay; Wolfram syndrome type 2; mRNA splicing

PMID:
29237418
PMCID:
PMC5729406
DOI:
10.1186/s12881-017-0508-2
[Indexed for MEDLINE]
Free PMC Article

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