SMPD4-mediated sphingolipid metabolism regulates brain and primary cilia development

Area of Science:

• Genetics
• Neuroscience
• Cell Biology

Background:

• Genetic variants in sphingolipid biosynthesis genes are linked to human brain disorders.
• Mutations in the SMPD4 gene, encoding a neutral sphingomyelinase, lead to severe developmental brain malformations like microcephaly and cerebellar hypoplasia.

Purpose of the Study:

• To elucidate the disease mechanism of SMPD4 in human brain development.
• To investigate the role of SMPD4-produced ceramide in primary cilia formation and cellular signaling.

Main Methods:

• Development of a novel mouse model for SMPD4 deficiency.
• Analysis of human induced pluripotent stem cells (hiPSCs) lacking SMPD4.
• Assessment of primary cilia length and Purkinje cell development in mouse models and hiPSCs.

Main Results:

• The mouse model exhibited cerebellar hypoplasia due to impaired Purkinje cell development.
• SMPD4-deficient hiPSCs showed neural progenitor cell death and shortened primary cilia.
• Supplementation with exogenous ceramide rescued the primary cilia defect in hiPSCs.

Conclusions:

• SMPD4-mediated ceramide production is critical for the development of primary cilia.
• Disruption of SMPD4 impacts neural progenitor cells and Purkinje neuron development, leading to brain malformations.
• Ceramide is essential for normal human brain development, with SMPD4 playing a key role in its early biosynthesis.