Mapping of a candidate gene for the absence of third molars in EL/mice

(1)牙胚发育的组织学观察取5、7、10日龄的EL/kw（对照组）和EL/sea（突变组）小鼠的下颌骨，用布因氏固定液固定24小时，14%EDTA脱钙1周，脱水，石蜡包埋。切片用苏木精和伊红染色，并在光学显微镜下观察。5<rd>日龄时，EL/sea的第3磨牙（M3）牙胚发育比EL/kw慢。然而，牙冠形态发生进展正常。在7日龄时发现M3牙胚畸形，在EL/sea中观察到M3牙胚发育停滞。出生后10天，EL/sea组牙胚几乎消失，EL/kw组牙胚发育正常。(2)M3的免疫组织化学将组织在4℃下在4%多聚甲醛中固定过夜，并在12.5%EDTA中脱钙。它们被脱水了，包在石蜡里。在5、7和10日龄的EL/kw中。Lef 1在M3的牙胚和周围细胞中表达。另一方面，在EL/sea小鼠中，Lef 1的表达随5、7和10日龄而变化。在7日龄的EL/海小鼠，强烈的Lef 1的表达中检测到的M3的牙胚。在5日龄和10日龄，Lef 1表达几乎完全下调.在5、7和10日龄的EL/kw和EL/sea小鼠中，EGF的表达没有观察到显著差异。结果表明，Lef 1基因可能在抑制M3的生殖发育中起重要作用。

(1) Histological findings for the tooth germ developmentThe mandibles obtained from the EL/kw (control mouse) and EL/sea (mutant mouse) mice at 5, 7.10 days of age were in Bouin's fixtative for 24h, decalcified in 14% EDTA for 1 week, dehydrated, and then embedded in paraffin. The section were stained with hematoxylin and eosin, and observed under a light microscope. The development of the 3^<rd> morlar (M3) tooth germ of EL/sea was slower than EL/kw at 5 days of age. However, tooth crown morphogenesis was progressing normally. The malformation of the M3 tooth germ was found on 7 days of age and arrest of M3 tooth germ development was observed in EL/sea. When it was the ten days after birth, the tooth germ almost disappeared in EL/sea, compared with normal development in EL/kw.(2) Immunohistochemistry for the M3The tissues were fixed in 4% paraformaldehyde at 4℃ overnight, and decalcified in 12.5% EDTA. They were dehydrated, embedded in paraffin. In EL/kw of 5, 7 and 10 days of age. Lef 1 was expressed in a tooth germ of M3 and the surrounding cells. On the other hand, the expression of Lef 1 was varied by 5, 7 and 10 days of age in EL/sea mice. In 7-day-old EL/sea mice, strong Lef 1 expression was detected in the tooth germ of M3. In both 5 and 10 days of age, Lef 1 expression was down regulated almost completely. In both EL/kw and EL/sea mice of 5, 7 and 10 days of age, there were observed no significant differences in the expression of EGF. From the result, it was suggested that Lef 1 may play an important role in arrest of the germ development of M3.