Table 2.

Typical phenotypes of three talpid mutants in the limb bud.

	talpid2	talpid3	HMM mutant
Ptch1 expression	Expanded to the anterior border (Caruccio et al., 1999)	Uniformly expressed at very low level throughout mesenchyme (Lewis et al., 1999)	Similar to talpid3
ZPA graft	–	High level Ptch1 was induced (Lewis et al., 1999)	Ptch1 was not Induced
Anterior graft	Induced digit duplication without Shh expression (Caruccio et al., 1999)	Ptch1 was induced (Lewis et al., 1999)	–
Bmp2 expression	Expanded throughout AP axis (Caruccio et al., 1999)	Uniformly expressed under the AER along the AP axis (Francis-West et al., 1995)	Downregulated
Hoxd13 expression	Expanded throughout AP axis (Rodriguez et al., 1996)	Expressed in the anterior mesenchyme (Francis-West et al., 1995)	Expressed only at the posterior side as same as wild-type
Primary cilia	Disrupted (Chang et al., 2014)	Lack of primary cilia (Bangs et al., 2011)	Exist
Responsible gene	C2CD3	KIAA0586	not identified
Gli3 expression	Expanded to the posterior side (Caruccio et al., 1999)	Expanded to the posterior side (Lewis et al., 1999)	Similar to talpid2 and talpid3
GLI3 protein	Functional high GLI3A expression(Chang et al., 2014)	No functional high GLI3A expression (Davey et al., 2006)	No functional high GLI3A expression
Gli1 expression	Expanded to the antetior side (Caruccio et al., 1999)	Expressed very weakly throughout the limb except distally under the AER (Lewis et al., 1999)	Similar to talpid3
SHH protein	–	Wide spreaded than normal (Davey et al., 2006)	Expressed as same as wild-type
Skeletal pattern	Short broad radius and narrower ulna (Dvorak and Fallon, 1992)	Radius and ulna were fused (Ede and Kelly, 1964)	Indistinguishable same size of short radius and ulna
	Claw was formed in the leg (Litingtung et al., 2002)	Claw was not observed due to severe syndactyly (Bangs et al., 2011)	Claw was formed in some leg digits