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Becker D, Minor KM, Letko A, Ekenstedt KJ, Jagannathan V, Leeb T, Shelton GD, Mickelson JR, Drögemüller C. A GJA9 frameshift variant is associated with polyneuropathy in Leonberger dogs. BMC Genomics 2017; 18:662. [PMID: 28841859 PMCID: PMC5574090 DOI: 10.1186/s12864-017-4081-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 08/21/2017] [Indexed: 01/15/2023] Open
Abstract
Background Many inherited polyneuropathies (PN) observed in dogs have clinical similarities to the genetically heterogeneous group of Charcot-Marie-Tooth (CMT) peripheral neuropathies in humans. The canine disorders collectively show a variable expression of progressive clinical signs and ages of onset, and different breed prevalences. Previously in the Leonberger breed, a variant highly associated with a juvenile-onset PN was identified in the canine orthologue of a CMT-associated gene. As this deletion in ARHGEF10 (termed LPN1) does not explain all cases, PN in this breed may encompass variants in several genes with similar clinical and histopathological features. Results A genome-wide comparison of 173 k SNP genotypes of 176 cases, excluding dogs homozygous for the ARHGEF10 variant, and 138 controls, was carried out to detect further PN-associated variants. A single suggestive significant association signal on CFA15 was found. The genome of a PN-affected Leonberger homozygous for the associated haplotype was sequenced and variants in the 7.7 Mb sized critical interval were identified. These variants were filtered against a database of variants observed in 202 genomes of various dog breeds and 3 wolves, and 6 private variants in protein-coding genes, all in complete linkage disequilibrium, plus 92 non-coding variants were revealed. Five of the coding variants were predicted to have low or moderate effect on the encoded protein, whereas a 2 bp deletion in GJA9 results in a frameshift of high impact. GJA9 encodes connexin 59, a connexin gap junction family protein, and belongs to a group of CMT-associated genes that have emerged as important components of peripheral myelinated nerve fibers. The association between the GJA9 variant and PN was confirmed in an independent cohort of 296 cases and 312 controls. Population studies showed a dominant mode of inheritance, an average age of onset of approximately 6 years, and incomplete penetrance. Conclusions This GJA9 variant represents a highly probable candidate variant for another form of PN in Leonberger dogs, which we have designated LPN2, and a new candidate gene for CMT disease. To date, approximately every third PN-diagnosed Leonberger dog can be explained by the ARHGEF10 or GJA9 variants, and we assume that additional genetic heterogeneity in this condition exists in the breed. Electronic supplementary material The online version of this article (10.1186/s12864-017-4081-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Doreen Becker
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3001, Bern, Switzerland
| | - Katie M Minor
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, 55108, USA
| | - Anna Letko
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3001, Bern, Switzerland
| | - Kari J Ekenstedt
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, 55108, USA.,Department of Basic Medical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Vidhya Jagannathan
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3001, Bern, Switzerland
| | - Tosso Leeb
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3001, Bern, Switzerland
| | - G Diane Shelton
- Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California, 92093, USA
| | - James R Mickelson
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, 55108, USA
| | - Cord Drögemüller
- Institute of Genetics, Vetsuisse Faculty, University of Bern, 3001, Bern, Switzerland.
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Trosko JE, Lenz HJ. What roles do colon stem cells and gap junctions play in the left and right location of origin of colorectal cancers? J Cell Commun Signal 2017; 11:79-87. [PMID: 28220297 PMCID: PMC5362582 DOI: 10.1007/s12079-017-0381-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 02/02/2017] [Indexed: 12/15/2022] Open
Abstract
This "Commentary" examines an important clinical observation that right-sided colorectal cancers appear less treatable than the left-sided cancers. The concepts of (a) the "initiation/promotion/progression" process, (b) the stem cell hypothesis, (c) the role gap junctional intercellular communication, (d) cancer cells lacking GJIC either because of the non-expression of connexin genes or of non-functional gap junction proteins, and (e) the role of the microbiome in promoting initiated colon stem cells to divide symmetrically or asymmetrically are examined to find an explanation. It has been speculated that "embryonic-like" lesions in the ascending colon are initiated stem cells, promoted via symmetrical cell division, while the polyp-type lesions in the descending colon are initiated stem cells stimulated to divide asymmetrically. To test this hypothesis, experiments could be designed to examine if right-sided lesions might express Oct4A and ABCG2 genes but not any connexin genes, whereas the left-sided lesions might express a connexin gene, but not Oct4A or the ABCG2 genes. Treatment of the right sided lesions might include transcriptional regulators, whereas the left-sided lesions would need to restore the posttranslational status of the connexin proteins.
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Affiliation(s)
- James E Trosko
- Department Pediatrics and Human Development, College of Human Medicine, Michigan State University, 1129 Farm Lane, East Lansing, MI, 48824, USA.
| | - Heinz-Josef Lenz
- University of California Norris Comprehensive Cancer Center, Los Angeles, CA, USA
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