[Molecular basis of the primary ciliary dyskinesias]

The primary ciliary dyskinesias (PCD) are rare diseases characterised by infection of the airways due to impaired muco-ciliary clearance. Half the patients have situs inversus making up Kartagener's syndrome.

Primary cilia play a role in development. In the adult ciliated cells occur mainly in the airways and the genital tract. The axoneme, the internal structure of the cilia, is made up of a central pair of microtubules surrounded by peripheral doublets carrying the inner and outer dynein arms. These multiprotein complexes are composed of chains of dynein whose ATPase activity is the basis of ciliary movement. Structural and functional abnormalities of the respiratory ciliated cells are the cause of PCD, diseases that are heterogeneous at both the genetic and ultrastructural levels.

There are more than two hundred axonemal proteins. The synthesis and assembly of these proteins are controlled by transcription factors and intraflagellar transport molecules respectively. The genes that code for these proteins are as numerous as candidate genes for PCD.

To date only two dynein genes, DNA11 and DNAH5, have been implicated and only in individuals suffering from PCD with absence of outer dynein arms.