Elbow knee synostosis (Eks):: a new mutation on mouse Chromosome 14
Elbow knee synostosis (Eks):: a new mutation on mouse Chromosome 14
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DOI：
10.1007/s00335-001-2143-6
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发表时间：
2002-07-01
期刊：
影响因子：
2.5
通讯作者：
Koseki, H
中科院分区：
文献类型：
--
作者：
Murakami, H;Okawa, A;Koseki, H
我们的转基因品系在 C57BL/6J 和 DBA/2J 混合背景上产生了一种新的自发小鼠突变体，其具有扭尾。 Yoshida 等人。 1996）。最初的育种实验表明，这种骨骼缺陷是可遗传的，并且与转基因位点分离。这种突变是通过杂合突变体之间的同胞交配得以维持的。由于尾巴弯曲，这种突变预计会导致骨骼异常。这导致我们进行射线照相检查。事实上，在所有受影响的杂合子中都发现了肘关节融合和膝关节发育不良（图 1）。随着小鼠的成熟，膝关节最终融合（图 1D、E）。根据这些骨骼表型，我们将这种突变命名为肘膝关节骨性连接（Eks）。与野生型同窝小鼠相比，Eks 杂合子表现出生长迟缓，但最终会赶上生长。这种生长迟缓可能是由于肘关节僵硬而导致食物摄入困难。受影响最严重的杂合子通常是矮个子，并且经常在断奶时死亡。大多数 Eks 杂合子行走顺利，因为关节缺陷仅限于肘部和膝盖。首先，我们通过将 Eks 杂合子与 C57BL/6J 小鼠杂交来检查 Eks 突变的外显率。这种交配产生了正常和受影响的后代，比例为 1:1 (45:47)，如 6 周龄小鼠的放射线检查所示（图 1）。在后代 H. Murakami 中没有观察到性别比例差异，未发表的观察结果）。这些结果表明 Eks 是一种具有完全外显率的常染色体显性突变。杂合突变体的生育力在雌性和雄性中均正常。通过杂合子杂交获得的新生儿推定 Eks 纯合突变体表现出缩短的四肢和尾巴。这些幼崽通常是活着出生的。然而，它们不会蠕动，表现出痛苦的呼吸和发绀，并在出生后几天内死亡。事实上，通过使用近端微卫星标记 D14Mit15 进行基因型分析，那些表现出比杂合子更强的骨骼改变的幼崽最终被证明是纯合突变体，如下所述。纯合子、杂合子和野生型子代的数量分别为19、44和19。这意味着 Eks 是半显性突变。比较纯合子、杂合子和野生型新生小鼠的骨骼异常。在 Eks 纯合子中，肘关节完全缺失，而分隔肱骨和尺骨的关节软骨却存在（图 2A、D、E）。膝关节的形成在纯合子中也受到类似的影响（图2J）。纯合子的预期肱骨、桡骨和尺骨比杂合子和野生型的短和厚得多（图2A、B、C）。纯合子中股骨、腓骨和胫骨也受到类似影响（图 2J、K、L）。在杂合子中，肘关节融合也很明显，但比纯合子中的融合程度要低得多，纯合子中分离肱骨和桡骨的关节软骨丢失，肱骨和桡骨融合（图 2B、F、G）。 Eks 纯合子的骨骼缺陷也见于颅面区域和脊柱（图 3）。纯合头骨的侧视图揭示了其异常形状，表现为高额头和由于鼻骨和前上颌骨缩短而导致的中面部发育不全（图3A、B、C、D）。背面观还显示冠状缝和矢状缝的过早融合以及眼睛间隔较宽，这可能导致眼球突出（图 3C、D）。除了颅面改变外，在 Eks 纯合子中也可重复看到次级腭裂和颞骨肥大……
A new spontaneous mouse mutant with kinky tail arose from our transgenic line on a C57BL/6J and DBA/2J mixed background Yoshida et al. 1996). Initial breeding experiments revealed that this skeletal defect is heritable and segregated from the transgenic locus. This mutation was maintained by sib mating between heterozygous mutants. Because of the kinky tail, this mutation was expected to cause skeletal abnormalities. This led us to perform radiographic examination. Indeed, elbow joint fusion and knee joint dysplasia were found in all of affected heterozygotes Fig. 1). The knee joints eventually fused as the mice matured Fig. 1D, E). On the basis of these skeletal phenotypes, we named this mutation Elbow knee synostosis Eks). Eks heterozygotes exhibit retarded growth compared with wild-type littermates, but eventually catch up in growth. This growth retardation might be due to difficulty in food intake because of the stiff elbow joints. The most severely affected heterozygotes are usually runts and often die around the time of weaning. Most Eks heterozygotes walk smoothly because the joint defects are restricted to the elbows and knees. First, we examined the penetrance of the Eks mutation by crossing Eks heterozygotes with C57BL/6J mice. This mating resulted in normal and affected offspring in a ratio of 1: 1 45: 47) as revealed by radiographic examination of 6-week-old mice Fig. 1). No sex ratio difference was observed in the progeny H. Murakami, unpublished observations). These results imply that Eks is an autosomal dominant mutation with full penetrance. The fertility of heterozygous mutants was normal in both females and males. Newborn presumptive Eks homozygous mutants obtained by crossing heterozygotes exhibited shortened limbs and tails. These pups were usually born alive; however, they did not creep, exhibited agonal breathing and cyanosis, and died within a few days of birth. Indeed, those pups exhibiting stronger skeletal alterations than heterozygotes eventually turned out to be homozygous mutants by genotype analysis with a proximal microsatellite marker, D14Mit15, as described below. The number of homozygous, heterozygous, and wildtype offspring of heterozygous matings were 19, 44, and 19, respectively. This implies that Eks is a semidominant mutation. Skeletal abnormalities of newborn mice were compared among homozygotes, heterozygotes, and wild type. In Eks homozygotes, the elbow joints were totally absent, while joint cartilage separating the humerus and ulna was present Fig. 2A, D, E). The formation of the knee joint was similarly affected in homozygotes Fig. 2J). The prospective humerus, radius, and ulna of homozygotes were much shorter and thicker than those of heterozygotes and wild type Fig. 2A, B, C). The femur, fibula, and tibia were similarly affected in homozygotes Fig. 2J, K, L). In heterozygotes, elbow joint fusion was also evident, but was much less extensive than in homozygotes, where joint cartilage separating the humerus and radius was lost and the humerus and radius were fused Fig. 2B, F, G). Skeletal defects in Eks homozygotes were also seen in the craniofacial region and the vertebral column Fig. 3). A lateral view of the homozygous skull reveals its abnormal shape as manifested by tall forehead and mid-face hypoplasia due to shortened nasal bones and premaxilla Fig. 3A, B, C, D). A dorsal view also shows premature fusions of the coronal and sagittal sutures and widely spaced eyes, which might result in proptosis Fig. 3C, D). In addition to the craniofacial alterations, a cleft in the secondary palate and hypertrophy of the temporal bones were reproducibly seen in Eks homozygotes …