Differential expression of the two closely related LIM-class homeobox genes LH-2A and LH-2B during limb development.
We have isolated the chicken homeobox genes LH-2A and LH-2B encoding two related LIM domain-containing homeodomain proteins and examined the expression pattern during chick limb development. LH-2A is most closely related to human and rat LH-2, while LH-2B is less conserved. Although both LH-2A and LH-2B are expressed in the limb mesenchyme throughout stage 16 to stage 32, LH-2A transcripts are detectable in the distal limb bud and LH-2B transcripts are detectable in the anterior limb bud. Signals from the apical ectodermal ridge positively regulate LH-2A expression, since removal of the apical ectoderm resulted in the rapid reduction of LH-2A expression in the distal limb mesenchyme. Ectopic expression of the sonic hedgehog gene in the anterior margin of the limb bud resulted in the rapid reduction of LH-2B expression accompanying respecification of the positional value to the posterior phenotype. These results suggest that LH-2A and LH-2B play important roles in the determination and specification of the proximal-distal and anterior-posterior positional values, respectively.
Nohno
T
T
Department of Molecular Biology, Department of Biochemistry I, Kawasaki Medical School, 577 Matsushima, Kurashiki, 701-01, Japan. nohno@bcc.kawasaki-m.ac.jp
Kawakami
Y
Y
Wada
N
N
Ishikawa
T
T
Ohuchi
H
H
Noji
S
S
D000595:Amino Acid Sequence; D000818:Animals; D002642:Chick Embryo; D005121:Extremities / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D060850:LIM-Homeodomain Proteins; D008969:Molecular Sequence Data; D051381:Rats; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics*
D018398:Homeodomain Proteins; C489783:LHX2 protein, human; D060850:LIM-Homeodomain Proteins; C086922:LIM-homeodomain protein LH-2; C079093:Lhx2 protein, rat; D014157:Transcription Factors