Structural Analysis Implicates CASK-Liprin-α2 Interaction in Cerebellar Granular Cell Death in MICPCH Syndrome

Area of Science:

• Neuroscience
• Genetics
• Developmental Biology

Background:

• Microcephaly with pontine and cerebellar hypoplasia (MICPCH) syndrome is a neurodevelopmental disorder linked to the CASK gene.
• The precise molecular mechanisms underlying CASK deficiency-induced cerebellar hypoplasia are not fully understood.

Purpose of the Study:

• To investigate the molecular mechanisms of CASK deficiency in cerebellar hypoplasia using a mouse model.
• To identify the specific CASK domains essential for cerebellar granule cell survival.

Main Methods:

• Utilized CASK knockout (KO) mice and cultured cerebellar granule (CG) cells.
• Employed lentiviral rescue experiments with wild-type and mutant CASK constructs.
• Performed machine learning-based structural analysis (AlphaFold 2.2) of CASK mutations.

Main Results:

• Female CASK KO mice exhibited progressive cerebellar hypoplasia mirroring MICPCH syndrome.
• CASK KO CG cells demonstrated cell death, which was rescued by wild-type CASK.
• CaMK, PDZ, and SH3 domains, but not L27 or guanylate kinase domains, were vital for CG cell survival.
• Human patient-derived CaMK domain mutations in CASK failed to rescue CG cell death and were predicted to disrupt Liprin-α2 binding.

Conclusions:

• The CaMK domain of CASK is essential for cerebellar granule cell survival.
• Disruption of the CASK-Liprin-α2 interaction via CaMK domain mutations may contribute to cerebellar hypoplasia in MICPCH syndrome.