Submitted on January 21, 2009
Revised on March 17, 2009
Accepted on April 6, 2009
Genetic Dissection Reveals Diabetes Loci Proximal to the Gimap5 Lymphopenia Gene
Jessica M. Fuller1*, Marika Bogdani2, Terry D. Tupling3, Richard A. Jensen3, Ranae Pefley3, Sahar Manavi3, Laura Cort4, Elizabeth P. Blankenhorn4, John P. Mordes5, Ake Lernmark6, and Anne E Kwitek7
1 Diabetes and Celiac Unit, Lund University
2 Pacific Northwest Research Institute
3 University of Washington
4 Drexel University College of Medicine
5 University of Massachusetts Medical School
6 Diabetes and Celiac Unit, Lund University,
7 University of Iowa
* To whom correspondence should be addressed. E-mail: jfuller{at}u.washington.edu.
Congenic DRF.f/f rats are protected from type 1 diabetes (T1D) by 34 Mb of F344 DNA introgressed proximal to the Gimap5 lymphopenia gene. To dissect the genetic factor(s) that confer protection from T1D in the DRF.f/f rat line, DRF.f/f rats were crossed to inbred BBDR or DR.lyp/lyp rats to generate congenic sublines that were genotyped, monitored for T1D and positional candidate genes sequenced. All (100%) DR.lyp/lyp rats developed T1D by 83 days of age. Reduction of the DRF.f/f F344 DNA fragment by 26 Mb (42.52 Mb-68.51 Mb) retained complete T1D protection. Further dissection revealed that a 2 Mb interval of F344 DNA (67.41-70.17 Mb) (Region 1) resulted in 47% protection and significantly delayed onset (p<0.001 compared to DR.lyp/lyp). Retaining <1 Mb of F344 DNA at the distal end (76.49-76.83 Mb) (Region 2) resulted in 28% protection and also delayed onset (p<0.001 compared to DR.lyp/lyp). Comparative analysis of diabetes frequency in the DRF.f/f congenic sublines further refined the RNO4 Region 1 interval to approximately 670 Kb and Region 2 to the 340 Kb proximal to Gimap5. All congenic DRF.f/f sublines were prone to low-grade pancreatic mononuclear cell infiltration around ducts and vessels but less than 20% of islets in non-diabetic rats showed islet infiltration. Coding sequence analysis revealed TCR V
8E, 12 and 13 as candidate genes in Region 1 and Znf467 and Atp6v0e2 as candidate genes in Region 2. Our results show that spontaneous T1D is controlled by at least two genetic loci 7 Mb apart on rat chromosome 4.
