Meganeurites and other aberrant processes of neurons in feline GM1-gangliosidosis: a Golgi study.

Golgi studies were carried out on neurons in several forebrain structures of young adult mutant cats with inherited beta-galactosidase deficiency and neurobehavioral deterioration due to GM1-ganglioside storage disease. Meganeurites similar to those observed in several human gangliosidoses were present on small and medium pyramidal neurons, granule cells of the fascia dentata and spiny neurons of the caudate nucleus. Large and giant pyramidal cells of the motor cortex exhibited prominent somatic spines but lacked meganeurites. Cortical non-pyramidal neurons and aspiny caudate cells were relatively normal in appearance although they showed variable increases in cell body diameter. The range of morphological alterations in different types of cortical neurons in feline GM1-gangliosidosis was identical to that found in human ganglioside storage diseases. Neurite outgrowth from meganeurites was particularly prominent in the feline mutant. The extensive proliferation of neurites confined to meganeurites indicates that the latter have growth properties typical of embryonic neuronal elements. The demonstration of neurite outgrowth from meganeurites of mature cortical neurons in feline GM1-gangliosidosis suggests a possible role for gangliosides in neurite formation during neuronal differentiation and synaptogenesis.