Identification of chromosomal region(s) influencing tooth root development in mouse

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In human, the fused root of the second molar or third molar in the lower jaw is known as gutter-shaped root (GSR). Many investigators have reported the morphological features of this anomaly, but its cause is not known. It has been reported that C57L/J mice are one of the most useful models for studying its cause ; the incidence rate of GSR is known to be about 90-100%. A classic genetic study on the cause of GSR in C57L/J mice was reported to suggest that a genetic factor with autosomal-dominant inheritance affected the development of mouse GSR, and that a few genes were involved. Recently, we demonstrated that micro-CT is a very useful tool to quantify mouse GSR as a quantitative trait. The purpose of this study was to identify the major candidate chromosome and to detect the region that would include the candidate gene causing GSR in the C57L/J mice. N2 backcross [(C57L X AKR)F1 X AKR] mice were obtained by mating the mice in our laboratory. Interval mapping that was one of the QTL analysis was performed with the used of MapManager QTXb11. Chromosome(s) 6, 7 and 8 were selected as candidate bearing the gene causing the tooth root anomaly in mouse. The high significant linkage was found at D6Mit230 on chromosome 6, and other significant linkages were found around D7Mit105 on chromosome and D8Mit65 on chromosome 8. These results suggest that the major gene(s) responsible for mouse root formation are located in these regions.