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Open Access Research article

A canine model of Cohen syndrome: Trapped Neutrophil Syndrome

Jeremy R Shearman12 and Alan N Wilton13*

Author Affiliations

1 School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia

2 National Center for Genetic Engineering and Biotechnology, 113 Phahonyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailand

3 Clive and Vera Ramaciotti Centre for Gene Function Analysis, University of New South Wales, Sydney, NSW 2052, Australia

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BMC Genomics 2011, 12:258  doi:10.1186/1471-2164-12-258

Published: 23 May 2011

Abstract

Background

Trapped Neutrophil Syndrome (TNS) is a common autosomal recessive neutropenia in Border collie dogs.

Results

We used a candidate gene approach and linkage analysis to show that the causative gene for TNS is VPS13B. We chose VPS13B as a candidate because of similarities in clinical signs between TNS and Cohen syndrome, in human, such as neutropenia and a typical facial dysmorphism. Linkage analysis using microsatellites close to VPS13B showed positive linkage of the region to TNS. We sequenced each of the 63 exons of VPS13B in affected and control dogs and found that the causative mutation in Border collies is a 4 bp deletion in exon 19 of the largest transcript that results in premature truncation of the protein. Cohen syndrome patients present with mental retardation in 99% of cases, but learning disabilities featured in less than half of TNS affected dogs. It has been implied that loss of the alternate transcript of VPS13B in the human brain utilising an alternate exon, 28, may cause mental retardation. Mice cannot be used to test this hypothesis as they do not express the alternate exon. We show that dogs do express alternate transcripts in the brain utilising an alternate exon homologous to human exon 28.

Conclusion

Dogs can be used as a model organism to explore the function of the alternately spliced transcript of VPS13B in the brain. TNS in Border collies is the first animal model for Cohen syndrome and can be used to study the disease aetiology.

Keywords:
Trapped Neutrophil Syndrome; Cohen Syndrome; neutropenia; vesicle transport; expression; vesicle protein sorting 13 B; VPS13B; dog