Physiology and Bosch Institute, University of Sydney, Sydney, Australia.
Anatomy and Histology and Bosch Institute, University of Sydney, Sydney, Australia.
J Neuromuscul Dis. 2017;4(2):159-164. doi: 10.3233/JND-160197.
The L25 mouse line was generated by random genomic insertion of a lens-specific transgene. Inbreeding of L25 hemizygotes revealed an unanticipated spastic phenotype in the hind limbs.
The goals were to characterize the motor phenotype in the L25 mice and to map the transgene insert site within the mouse genome.
Six pairs of L25+/- mice were repeatedly mated. Beginning at weaning, all progeny were inspected for body weight and motor signs twice weekly until they displayed predefined ethical criteria for termination. The transgene insert site was determined by whole genome sequencing. Western blotting was used to compare the expression levels of beta-IV spectrin protein in the brain.
Matings of hemizygous L25+/- × L25+/- mice yielded 20% (29/148) affected weanlings, identified by an abnormal retraction of the hind limbs when lifted by the tail, and a fine tremor. Affected mice were less mobile and grew more slowly than wild-type littermates. All affected mice required termination due to >15% loss of body weight (50% survival age 92 days). At the endpoint, mice showed varying degrees of spastic paresis or spastic paralysis localised to the hind limbs. Motor endplates remained fully innervated. Genome sequencing confirmed that the transgene was inserted in the locus of βIV spectrin of L25 mice. Western blotting indicated that this random insertion had greatly reduced the expression of βIV spectrin protein in the affected L25 mice.
The results confirm the importance of βIV spectrin for maintaining central motor pathway control of the hind limbs, and provide a developmental time course for the phenotype.
L25 鼠系是通过随机基因组插入一个晶状体特异性转基因而产生的。L25 半合子的近交揭示了后肢中一种意外的痉挛表型。
目标是描述 L25 小鼠的运动表型，并在小鼠基因组中定位转基因插入位点。
六对 L25+/- 小鼠反复交配。从断奶开始，每周两次检查所有后代的体重和运动迹象，直到它们显示出预定的伦理终止标准。转基因插入位点通过全基因组测序确定。Western blot 用于比较大脑中β-IV spectrin 蛋白的表达水平。
半合子 L25+/-×L25+/- 小鼠的交配产生了 20%（29/148）受影响的断奶幼鼠，其特征是尾巴提起时后肢异常缩回和细微震颤。受影响的小鼠比野生型同窝仔移动性差，生长速度慢。所有受影响的小鼠因体重损失超过 15%（50%的存活年龄为 92 天）而需要终止。在终点时，小鼠表现出不同程度的痉挛性轻瘫或痉挛性瘫痪，局限于后肢。运动终板保持完全神经支配。基因组测序证实转基因插入到 L25 小鼠的βIV spectrin 基因座中。Western blot 表明，这种随机插入大大降低了受影响的 L25 小鼠中βIV spectrin 蛋白的表达。
结果证实了βIV spectrin 对于维持后肢中枢运动通路控制的重要性，并提供了表型的发育时间过程。
