Rudimentary claws and pigmented nail-like structures on the distal tips of the digits of Wnt7a mutant mice: Wnt7A suppresses nail-like structure development in mice.
BACKGROUND
As Wnt7a mutant mice exhibit double ventral structures in the digits of autopods, it has been accepted that dorsal-ventral identity in limb development is regulated by the Wnt7a signal. The most important evidence for this was the presence of surface pads, typical characteristics of ventral structures, on the dorsal side of digital tips and at the base of digits and their pigmentation.


METHODS
The morphologic features of the appendages on the distal tips of digits were inspected in the fore- and hindlimbs of mice having a different Wnt7a mutation. The digital structures were examined macroscopically and histologically.


RESULTS
The Wnt7a homozygous mutant mice with defects in postaxial digits had rudimentary claws or claws and pigmented nail-like structures, instead of dorsal pads, on the distal digital tips and hairs on the dorsal surface of the digits of fore- and hindlimbs. Furthermore, pigmented ectopic nail-like structures but not pads were also present on the dorsal surface of the base of digits. Double ventral structures were observed in the bones and tendons, excluding pads in digital areas.


CONCLUSIONS
These findings suggest that Wnt7a is not necessarily an exclusive dorsalizing signal to the dorsal ectoderm of the digital areas of autopods. Rather, the Wnt7a signal may participate in suppression of the development of pigmented nail-like structures in normal limb development. This means that even rodents, a species lower than primates in the evolution from claws to nails, have molecular potential to develop cutaneous appendages similar to nails at their location.
Kimura
Sumiko
S
Congenital Anomaly Research center, Kyoto University, Japan. skimura2428@gmail.com <skimura2428@gmail.com>
Saitsu
Hirotomo
H
Schaumann
Blanka A
BA
Shiota
Kohei
K
Matsumoto
Naomichi
N
Ishibashi
Makoto
M
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D005260:Female; D006720:Homozygote; D006724:Hoof and Claw / Q000254:growth & development*; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D009154:Mutation; D051153:Wnt Proteins / Q000235:genetics / Q000502:physiology*
D017931:DNA Primers; D051153:Wnt Proteins; C490508:Wnt7a protein, mouse