Spontaneous pre-axial polydactyly in Swiss mice

ABSTRACT: Spontaneous polydactyly has been described in several species, but only one report about it in Swiss mice. The aim of the current study was to report the spontaneous occurrence of pre-axial polydactyly in Swiss mice. Clinical examination showed one extra toe laterally to the first digit, in the plantar region, alopecia in the back, altered face growth anatomy and changed perineal region anatomy. Pre-axial polydactyly in the tibial side, fused metatarsals and Y-shaped free phalanges were evidenced in the radiographic images. Pre-axial polydactyly observed in the plantar region differed from that in reports on albino Swiss mice with post-axial polydactyly (Po/Po+) phenotype featured by one extra toe in the ulnar side of one, or both, front limbs, which is the dominant feature. The observed findings highlight the importance of both clinical examinations and close attention by professionals involved in rodents’ breeding on physical changes resulting from different causes, including the genetic ones, since they reveal mutations and, sometimes, new biomodels.

摘要：自发性多指（趾）畸形（spontaneous polydactyly）已在多个物种中被报道，但目前仅见1篇关于瑞士小鼠（Swiss mice）的相关研究报告。本研究旨在报告瑞士小鼠中轴前多指（趾）畸形（pre-axial polydactyly）的自发发生情况。临床检查显示，受试个体跖侧区域的第一趾外侧存在额外趾，背部出现脱毛，面部生长解剖结构异常，会阴区解剖结构亦发生改变。X线影像学检查可见胫骨侧轴前多指（趾）畸形、跖骨融合以及Y形游离趾骨。本次观察到的跖侧轴前多指（趾）畸形，与此前报道的携带轴后多指（趾）畸形（post-axial polydactyly，Po/Po+）表型的白化瑞士小鼠存在显著差异——该表型以单侧或双侧前肢尺骨侧存在额外趾为核心特征，且呈显性遗传。本次观察结果凸显了双重重要性：一是临床检查的必要性，二是啮齿类动物繁育从业者需密切关注各类诱因（包括遗传因素）引发的机体形态变化，此类变化可揭示基因突变，有时还可催生全新的生物模型。