Regulation of Sox9 by Sonic Hedgehog (Shh) is essential for patterning and formation of tracheal cartilage.

We report that Sonic Hedgehog (Shh) regulates both formation and patterning of tracheal cartilage by controlling the expression pattern and level of the chondrogenic gene, Sox9. In Shh(-/-) tracheo-esophageal tubes, Sox9 expression is transient and not restricted ventrally to the site of chondrogenesis, and is absent at the time of chondrogenesis, resulting in the failure of tracheal cartilage formation. Inhibition of Hedgehog signalling with cyclopamine in tracheal cultures prevents tracheal cartilage formation, while treatment of Shh(-/-) tracheal explant with exogenous Shh peptide rescues cartilage formation.

A simple in vitro culture system for tracheal cartilage development.

Semi-circular tracheal cartilage is a critical determinant of maintaining architectural integrity of the respiratory airway. The current effort to understand the morphogenesis of tracheal cartilage is challenged by the lack of appropriate model systems. Here we report an in vitro tracheal cartilage system using embryonic tracheal–lung explants to recapitulate in vivo tracheal cartilage developmental processes.

The role of Shh transcription activator Gli2 in chick cloacal development.

Patterning and differentiation along the dorsal-ventral (D-V) axis lead to cloacal partitioning into ventral urinary and dorsal alimentary tracts in most mammals, but not birds and fish. We previously reported that the major activator of Sonic hedgehog (Shh) signaling transcription factor Gli2 plays an essential role in cloacal partitioning along the D-V axis in a mouse model. Here, we report that chick cloacal patterning and differentiation is along the anterior-posterior axis.

DeltaNp63 plays an anti-apoptotic role in ventral bladder development.

The bladder, the largest smooth-muscle organ in the human body, is responsible for urine storage and micturition. P63, a homolog of the p53 tumor-suppressor gene, is essential for the development of all stratified epithelia, including the bladder urothelium. The N-terminal truncated isoform of p63, DeltaNp63, is known to have anti-apoptotic characteristics.