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Presenting Author(s) Juan José Sanz-Ezquerro
Abstract Title Digit morphogenesis and tip formation.
Full author List Jesús Chamorro and Juan José Sanz-Ezquerro
Text of abstract

Digits are the last skeletal structures to be formed during limb development. Formation of digits starts with condensation of mesenchymal cells to establish chondrogenic digital rays. These then grow and segment to form phalanges and joints. Finally, the distalmost phalange or tip is generated.

Digit identity, which is defined by the number and shape of phalanges, is determined along the antero-posterior axis. Positional information clues from the polarising region at early limb bud stages are translated later on into signalling interactions that coordinate digit morphogenesis. Digit primordia have thus some plasticity and modulation of Fgf signalling from the AER, BMP signalling from the interdigital spaces and Ihh signalling from condensations seems essential for proper digit formation. However, our understanding of the process is still limited at the molecular and cellular levels, including how joint periodicity is established and how the tip of digits form, which seems to depend on a special programme.

We had previously shown that application of Shh to interdigits leads to maintenance of Fgf8 expression in the AER and elongation of the penultimate phalange of digits. This happens with the induction of a new joint and phalange but maintaining a normal tip.

Here we have analysed the possible involvement of endogenous hedgehog and BMP signalling (including BMP antagonists) in the maintenance of Fgf8 expression and AER activity. Also, to gain insight into the process of phalange and particularly tip formation, we have mapped, by DiI labelling at different stages of normal chick autopod development, the contribution of cells from distal mesenchyme to phalanges. The chondrogenic potential of isolated distal mesenchyme from digit primordia has also been evaluated by tissue transplantation. Finally, we intend to use differential expression analyses with cDNA microarrays with the aim of identifying new genes specifically involved in tip formation.
Which session is your work most relevant to: Limb patterning