Sphingomyelin lipidosis in a cat: Golgi studies

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Neuronal storage disorders, often caused by lysosomal enzyme deficiencies, lead to metabolic alterations and cellular storage.
• Aberrant neurite growth and meganeurite formation are observed in various neuronal storage disorders.
• Previous studies have identified specific neurite abnormalities in gangliosidoses and feline models of alpha-mannosidosis and mucopolysaccharidosis type 1.

Purpose of the Study:

• To investigate the alterations in neuronal geometry in a feline model of sphingomyelin lipidosis.
• To characterize the specific changes in neuron morphology, particularly at the axon hillock-initial segment region.

Main Methods:

• Utilized Golgi staining technique to impregnate neurons in various brain regions of a feline model.
• Examined neurons in the cerebral cortex, basal ganglia, amygdala, thalamus, and cerebellum.
• Analyzed cell type specificity and regional distribution of observed neuronal alterations.

Main Results:

• Identified conspicuous enlargements (meganeurites) at the axon hillock-initial segment region in many neurons.
• Observed sprouting of secondary neuritic processes from the axon hillock-initial segment, resembling small dendrites.
• Demonstrated cell type-specific changes, with some neurons showing normal morphology, somatic enlargement, or degeneration, while others exhibited dendritic thinning and spine loss.

Conclusions:

• Sphingomyelin lipidosis induces aberrant neurite growth and meganeurite formation in specific feline neurons.
• The observed axon hillock-associated neurite growth in mature neurons is a novel finding for sphingomyelin lipidosis, previously seen only in specific other storage disorders.
• These findings contribute to understanding the spectrum of neuronal pathology in lysosomal storage diseases.