Billy A. Watson and Kerby C. Oberg
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limb development in humans as a consequence of deficiency/mutations in
these receptors are well known and include Apert syndrome (FGFR2
mutation), Crouzon syndrome (FGFR2 mutation), Pfeiffer syndrome (FGFR1
and 2 mutations), achondroplasia (FGFR3 mutation), and thanatophoric
dysplasia (FGFR3 mutation) (Toriello et al., 2008).
Figure 1. Early limb development and axis organization. A) Illustration of a human
embryo at Carnegie stage 12 (~ 4 weeks gestation) showing an emerging upper limb
bud. B) Evidence suggests that Hox genes establish upper limb position and polarity.
C-E) Molecular pathways involved in forelimb initiation and patterning along the
proximal-distal axis (C), anterior-posterior axis (D), and dorsal-ventral axis. Apical
ectodermal ridge (AER) (orange), Pr – proximal, Di-distal, Ant(Rad)-anterior/radial,
Post(Uln)-posterior/ulnar, zone of polarizing activity (ZPA) (dark purple), Do-dorsal,
Ve-ventral, dorsal ectoderm and mesoderm (green). From Oberg et al., (Oberg et al.,
2014) with permission.