A novel mutation in DDR2 causing spondylo-meta-epiphyseal dysplasia with short limbs and abnormal calcifications (SMED-SL) results in defective intra-cellular trafficking

Adila Al-Kindi, Praseetha Kizhakkedath, Huifang Xu, Anne John, Abeer A. Sayegh, Anuradha Ganesh, Maha Al-Awadi, Lamya Al-Anbouri, Lihadh Al-Gazali, Birgit Leitinger, Bassam R. Ali

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Abstract

Background: The rare autosomal genetic disorder, Spondylo-meta-epiphyseal dysplasia with short limbs and abnormal calcifications (SMED-SL), is reported to be caused by missense or splice site mutations in the human discoidin domain receptor 2 (DDR2) gene. Previously our group has established that trafficking defects and loss of ligand binding are the underlying cellular mechanisms of several SMED-SL causing mutations. Here we report the clinical characteristics of two siblings of consanguineous marriage with suspected SMED-SL and identification of a novel disease-causing mutation in the DDR2 gene.Methods: Clinical evaluation and radiography were performed to evaluate the patients. All the coding exons and splice sites of the DDR2 gene were sequenced by Sanger sequencing. Subcellular localization of the mutated DDR2 protein was determined by confocal microscopy, deglycosylation assay and Western blotting. DDR2 activity was measured by collagen activation and Western analysis.Results: In addition to the typical features of SMED-SL, one of the patients has an eye phenotype including visual impairment due to optic atrophy. DNA sequencing revealed a novel homozygous dinucleotide deletion mutation (c.2468_2469delCT) on exon 18 of the DDR2 gene in both patients. The mutation resulted in a frameshift leading to an amino acid change at position S823 and a predicted premature termination of translation (p.S823Cfs*2). Subcellular localization of the mutant protein was analyzed in mammalian cell lines, and it was found to be largely retained in the endoplasmic reticulum (ER), which was further supported by its N-glycosylation profile. In keeping with its cellular mis-localization, the mutant protein was found to be deficient in collagen-induced receptor activation, suggesting protein trafficking defects as the major cellular mechanism underlying the loss of DDR2 function in our patients.Conclusions: Our results indicate that the novel mutation results in defective trafficking of the DDR2 protein leading to loss of function and disease. This confirms our previous findings that DDR2 missense mutations occurring at the kinase domain result in retention of the mutant protein in the ER.

Original languageEnglish
Article number42
JournalBMC Medical Genetics
Volume15
Issue number1
DOIs
Publication statusPublished - Apr 11 2014

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Extremities
Mutation
Mutant Proteins
Endoplasmic Reticulum
Genes
Exons
Collagen Receptors
Activation Analysis
Discoidin Domain Receptor 2
Optic Atrophy
Inborn Genetic Diseases
Sequence Deletion
Vision Disorders
Protein Transport
Missense Mutation
Marriage
DNA Sequence Analysis
Glycosylation
Confocal Microscopy
Radiography

Keywords

  • DDR2
  • ERAD
  • Optic atrophy
  • SMED-SL
  • Spondylo-meta-epiphyseal dysplasia
  • Trafficking defect

ASJC Scopus subject areas

  • Genetics(clinical)
  • Genetics

Cite this

A novel mutation in DDR2 causing spondylo-meta-epiphyseal dysplasia with short limbs and abnormal calcifications (SMED-SL) results in defective intra-cellular trafficking. / Al-Kindi, Adila; Kizhakkedath, Praseetha; Xu, Huifang; John, Anne; Sayegh, Abeer A.; Ganesh, Anuradha; Al-Awadi, Maha; Al-Anbouri, Lamya; Al-Gazali, Lihadh; Leitinger, Birgit; Ali, Bassam R.

In: BMC Medical Genetics, Vol. 15, No. 1, 42, 11.04.2014.

Research output: Contribution to journalArticle

Al-Kindi, Adila ; Kizhakkedath, Praseetha ; Xu, Huifang ; John, Anne ; Sayegh, Abeer A. ; Ganesh, Anuradha ; Al-Awadi, Maha ; Al-Anbouri, Lamya ; Al-Gazali, Lihadh ; Leitinger, Birgit ; Ali, Bassam R. / A novel mutation in DDR2 causing spondylo-meta-epiphyseal dysplasia with short limbs and abnormal calcifications (SMED-SL) results in defective intra-cellular trafficking. In: BMC Medical Genetics. 2014 ; Vol. 15, No. 1.
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abstract = "Background: The rare autosomal genetic disorder, Spondylo-meta-epiphyseal dysplasia with short limbs and abnormal calcifications (SMED-SL), is reported to be caused by missense or splice site mutations in the human discoidin domain receptor 2 (DDR2) gene. Previously our group has established that trafficking defects and loss of ligand binding are the underlying cellular mechanisms of several SMED-SL causing mutations. Here we report the clinical characteristics of two siblings of consanguineous marriage with suspected SMED-SL and identification of a novel disease-causing mutation in the DDR2 gene.Methods: Clinical evaluation and radiography were performed to evaluate the patients. All the coding exons and splice sites of the DDR2 gene were sequenced by Sanger sequencing. Subcellular localization of the mutated DDR2 protein was determined by confocal microscopy, deglycosylation assay and Western blotting. DDR2 activity was measured by collagen activation and Western analysis.Results: In addition to the typical features of SMED-SL, one of the patients has an eye phenotype including visual impairment due to optic atrophy. DNA sequencing revealed a novel homozygous dinucleotide deletion mutation (c.2468_2469delCT) on exon 18 of the DDR2 gene in both patients. The mutation resulted in a frameshift leading to an amino acid change at position S823 and a predicted premature termination of translation (p.S823Cfs*2). Subcellular localization of the mutant protein was analyzed in mammalian cell lines, and it was found to be largely retained in the endoplasmic reticulum (ER), which was further supported by its N-glycosylation profile. In keeping with its cellular mis-localization, the mutant protein was found to be deficient in collagen-induced receptor activation, suggesting protein trafficking defects as the major cellular mechanism underlying the loss of DDR2 function in our patients.Conclusions: Our results indicate that the novel mutation results in defective trafficking of the DDR2 protein leading to loss of function and disease. This confirms our previous findings that DDR2 missense mutations occurring at the kinase domain result in retention of the mutant protein in the ER.",
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AU - Xu, Huifang

AU - John, Anne

AU - Sayegh, Abeer A.

AU - Ganesh, Anuradha

AU - Al-Awadi, Maha

AU - Al-Anbouri, Lamya

AU - Al-Gazali, Lihadh

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