Progressive tooth pattern changes in Cilk1-deficient mice depending on Hedgehog signaling

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Primary cilia are sensory organelles crucial for developmental signaling pathways like Hedgehog (Hh).
• Hh pathway dysregulation is linked to abnormal tooth development, including supernumerary teeth and molar fusion.
• Cilk1 kinase is vital for ciliary transport, and its loss causes ciliopathies, but its role in tooth development is unknown.

Purpose of the Study:

• To investigate the function of Cilk1 in mammalian tooth development.
• To elucidate the role of Cilk1-mediated ciliary transport in Hedgehog signaling during odontogenesis.
• To understand how Cilk1 deficiency impacts tooth patterning and morphology.

Main Methods:

• Analysis of Cilk1 expression in developing mouse molars.
• Generation and phenotypic analysis of Cilk1-deficient mice.
• Assessment of ciliary dynamics and Hedgehog signaling pathway activity (e.g., Ptch1, Sostdc1 expression).
• Examination of tooth morphology and patterning in wild-type and mutant mice, including compound mutants.

Main Results:

• Cilk1 is expressed in developing molar epithelium and mesenchyme.
• Cilk1 deficiency alters ciliary dynamics (reduced frequency, increased length) and downregulates Hh target genes.
• Loss of Cilk1 leads to diastemal supernumerary teeth formation.
• Compounded Hh signaling suppression results in enlarged diastemal supernumerary teeth and molar fusion.

Conclusions:

• Cilk1 is essential for normal tooth development by regulating ciliary function and Hh signaling.
• Altered Hh signaling levels, influenced by Cilk1, progressively affect tooth patterning, from supernumerary tooth induction to molar fusion.
• This study identifies a novel role for Cilk1 in controlling tooth morphology through a gradient-dependent Hh signaling mechanism.