Bickelmann Constanze, van der Vos Wessel, de Bakker Merijn A G, Jiménez Rafael, Maas Saskia, Sánchez-Villagra Marcelo R
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115, Berlin, Germany.
Paläontologisches Institut und Museum, University of Zurich, Karl-Schmid-Strasse 4, 8006 , Zurich, Switzerland.
Evol Dev. 2017 Jan;19(1):3-8. doi: 10.1111/ede.12216.
Fossorial talpid moles use their limbs predominantly for digging, which explains their highly specialized anatomy. The humerus is particularly short and dorsoventrally rotated, with broadened distal and proximal parts where muscles attach and which facilitate powerful abductive movements. The radius and ulna are exceptionally robust and short. The ulna has an expanded olecranon process. The femur is generalized, but the fused tibia-fibula complex is short and robust. To understand the developmental bases of these specializations, we studied expression patterns of four 5' Hox genes in the fossorial Iberian mole (Talpa occidentalis). These genes are known to play major roles in patterning the developing limb skeleton in the mouse, with which comparisons were made (Mus musculus, C57BL/6Jico strain). We find that HoxA9 expression is spatially expanded in the developing stylopodial area in the mole forelimb, compared to the less specialized mouse forelimb and mole hind limb. HoxD9 expression does not extend into the thoracic body wall in the mole forelimb in contrast to the mouse, and is also reduced in the presumptive zeugopodium in mole forelimb, compared to mouse. Expression of HoxD11 is upregulated in the mole in the postaxial area of the hind limb zeugopod, compared to the mouse. On the other hand, HoxD13 is downregulated in the postaxial zeugopodial area in the forelimb of the mole, compared to the mouse. The differences in the expression patterns of these 5' Hox genes between Talpa and Mus are an indication of the developmental changes going hand in hand with anatomical digging adaptations in the mole adult.
穴居的鼹形鼠主要用它们的四肢挖掘，这就解释了它们高度特化的解剖结构。肱骨特别短，并且在背腹方向上旋转，其远端和近端变宽，此处是肌肉附着的部位，有助于有力的外展运动。桡骨和尺骨异常粗壮且短小。尺骨有一个扩大的鹰嘴突。股骨结构一般，但融合的胫腓骨复合体短而粗壮。为了了解这些特化的发育基础，我们研究了四种5’Hox基因在穴居的伊比利亚鼹鼠（Talpa occidentalis）中的表达模式。已知这些基因在小鼠发育中的肢体骨骼模式形成中起主要作用，并与小鼠（小家鼠，C57BL/6Jico品系）进行了比较。我们发现，与不太特化的小鼠前肢和鼹鼠后肢相比，HoxA9在鼹鼠前肢发育中的肢体近端区域的表达在空间上有所扩展。与小鼠相比，HoxD9在鼹鼠前肢中不延伸到胸壁，并且在鼹鼠前肢的假定中肢区域的表达也减少。与小鼠相比，HoxD11在鼹鼠后肢中肢的轴后区域的表达上调。另一方面，与小鼠相比，HoxD13在鼹鼠前肢的轴后中肢区域下调。Talpa和Mus之间这些5’Hox基因表达模式的差异表明，发育变化与成年鼹鼠的解剖学挖掘适应性密切相关。
