1. ¹The Robert H Smith Institute of Plant Sciences & Genetics, The Hebrew University of Jerusalem, Rehovot 76100, Israel
2. ²Department of Medicine-C, Barzilai Medical Center, Ashkelon 78306, Israel
3. ³The Authority for Research Animals, The Hebrew University of Jerusalem, Israel
4. ⁴Institute of Evolution, University of Haifa, Mt. Carmel, Haifa 31905, Israel
5. ⁵Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA
6. ⁶Diabetes Research Center, Hadassah University Hospital, Jerusalem 91120, Israel
7. ⁷Department of Human Genetics, Hadassah Medical Center, Jerusalem 91120, Israel
8. ⁸Pulmonary Institute, Assaf Harofeh Medical Center, PO Beer Yaacov, Zerifin 70300, Israel
9. ⁹Institute of Horticulture, ARO-Volcani Center, PO Box 6, Bet-Dagan 50250, Israel

Correspondence: J Hillel, The Robert H Smith Institute of Plant Sciences & Genetics, The Hebrew University of Jerusalem, Rehovot 76100, Israel. E-mail: Hillel@agri.huji.ac.il

Received 23 July 2004; Accepted 13 April 2005; Published online 1 June 2005.

Abstract

We investigated the mode of inheritance of nutritionally induced diabetes in the desert gerbil Psammomys obesus (sand rat), following transfer from low-energy (LE) to high-energy (HE) diet which induces hyperglycaemia. Psammomys selected for high or low blood glucose level were used as two parental lines. A first backcross generation (BC₁) was formed by crossing F₁ males with females of the diabetes-prone line. The resulting 232 BC₁ progeny were assessed for blood glucose. All progeny were weaned at 3 weeks of age (week 0), and their weekly assessment of blood glucose levels proceeded until week 9 after weaning, with all progeny maintained on HE diet. At weeks 1 to 9 post weaning, a clear bimodal distribution statistically different from unimodal distribution of blood glucose was observed, normoglycaemic and hyperglycaemic at a 1:1 ratio. This ratio is expected at the first backcross generation for traits controlled by a single dominant gene. From week 0 (prior to the transfer to HE diet) till week 8, the hyperglycaemic individuals were significantly heavier (4–17%) than the normoglycaemic ones. The bimodal blood glucose distribution in BC₁ generation, with about equal frequencies in each mode, strongly suggests that a single major gene affects the transition from normo- to hyperglycaemia. The wide range of blood glucose values among the hyperglycaemic individuals (180 to 500 mg/dl) indicates that several genes and environmental factors influence the extent of hyperglycaemia. The diabetes-resistant allele appears to be dominant; the estimate for dominance ratio is 0.97.