Portal de Periódicos da CAPES

Morphological Diversity of the Avian Foot Is Related with the Pattern ofmsxGene Expression in the Developing Autopod

1998; Elsevier BV; Volume: 196; Issue: 1 Linguagem: Inglês

10.1006/dbio.1997.8843

1095-564X

Y. Gañán, D. Macías, Ricardo D. Basco, Ramón Merino, Juan M. Hurlé,

dental development and anomalies

The formation of the digits in amniota embryos is accompanied by apoptotic cell death of the interdigital mesoderm triggered through BMP signaling. Differences in the intensity of this apoptotic process account for the establishment of the different morphological types of feet observed in amniota (i.e., free-digits, webbed digits, lobulated digits). The molecular basis accounting for the differential pattern of interdigital cell death remains uncertain since the reduction of cell death in species with webbed digits is not accompanied by a parallel reduction in the pattern of expression ofbmpgenes in the interdigital regions. In this study we show that the duck interdigital web mesoderm exhibits an attenuated response to both BMP-induced apoptosis and TGFβ-induced chondrogenesis in comparison with species with free digits. The attenuated response to these signals is accompanied by a reduced pattern of expression ofmsx-1andmsx-2genes. Local application of FGF in the duck interdigit expands the domain ofmsx-2expression but not the domain ofmsx-1expression. This change in the expression ofmsx-2is followed by a parallel increase in spontaneous and exogenous BMP-induced interdigital cell death, while the chondrogenic response to TGFβs is unchanged. The regression of AER, as deduced by the pattern of extinction offgf-8expression, takes place in a similar fashion in the chick and duck regardless of the differences in interdigital cell death andmsxgene expression. Implantation of BMP-beads in the distal limb mesoderm induces AER regression in both the chick and duck. This finding suggests an additional role for BMPs in the physiological regression of the AER. It is proposed that the formation of webbed vs free-digit feet in amniota results from a premature differentiation of the interdigital mesoderm into connective tissue caused by a reduced expression ofmsxgenes in the developing autopod.