GM1 enhances the association of neuron-specific MAP2 with actin in MAP2-transfected 3T3 cells

Dopamine and serotonin alterations by Hizikia fusiformis extracts under in vitro cortical primary neuronal cell cultures

BACKGROUND/OBJECTIVES

Hizikia fusiformis (HF) is a class of brown seaweeds whose active ingredients exert central nervous system protective effects, such as neuroprotection; however, the underlying mechanisms remain unknown. Given that dopamine (DA) and serotonin (5HT) are two major neurotransmitters involved in various psychiatric disorders and neuronal growth in early neurodevelopmental processes, we investigated whether HF extract could modulate the molecular expression associated with DA and 5HT transmission as well as the structural formation of neurons.

MATERIALS/METHODS

In vitro cell cultures were prepared from cerebral cortical neurons obtained from CD-1 mice on embryonic day 14. Cultured cells were treated with 0.1, 1.0, or 10.0 μg/mL of HT extract for 24 h, followed by fluorescence immunostaining for DA and 5HT-related receptors and transporters and some neuronal structural formation-associated molecules.

RESULTS

HF extract dose-dependently upregulated the expression levels of selective DA and 5HT receptors, and downregulated the levels of DA and 5HT transporters. Moreover, HF extract increased the neurofilament light chain expression.

CONCLUSION

These results suggest that HF may modulate DA and 5HT transmission, thereby affecting neurodevelopment.

Cytoskeletal microdifferentiation: a mechanism for organizing morphological plasticity in dendrites

Experimental evidence suggests that microfilaments and microtubules play contrasting roles in regulating the balance between motility and stability in neuronal structures. Actin-containing microfilaments are associated with structural plasticity, both during development when their dynamic activity drives the exploratory activity of growth cones and after circuit formation when the actin-rich dendritic spines of excitatory synapses retain a capacity for rapid changes in morphology. By contrast, microtubules predominate in axonal and dendritic processes, which appear to be morphologically relatively more stable. To compare the cytoplasmic distributions and dynamics of microfilaments and microtubules we made time-lapse recordings of actin or the microtubule-associated protein 2 tagged with green fluorescent protein in neurons growing in dispersed culture or in tissue slices from transgenic mice. The results complement existing evidence indicating that the high concentrations of actin present in dendritic spines is a specialization for morphological plasticity. By contrast, microtubule-associated protein 2 is limited to the shafts of dendrites where time-lapse recordings show little evidence for dynamic activity. A parallel exists between the partitioning of microfilaments and microtubules in motile and stable domains of growing processes during development and between dendrite shafts and spines at excitatory synapses in established neuronal circuits. These data thus suggest a mechanism, conserved through development and adulthood, in which the differential dynamics of actin and microtubules determine the plasticity of neuronal structures.

Expression of microtubule-associated protein 2 in benign and malignant melanocytes: implications for differentiation and progression of cutaneous melanoma

Cutaneous melanocytic neoplasms are known to acquire variable characteristics of neural crest differentiation. Melanocytic nevus cells in the dermis and desmoplastic melanomas often display characteristics of nerve sheath differentiation. The extent and nature of neuronal differentiation characteristics displayed by primary and metastatic melanoma cells are not well understood. Here, we describe induction of a juvenile isoform of microtubule-associated protein 2 (MAP-2c) in cultured metastatic melanoma cells by the differentiation inducer hexamethylene bisacetamide. Up-regulation of this MAP-2 isoform, a marker for immature neurons, is accompanied by extended dendritic morphology and down-regulation of tyrosinase-related protein 1 (TYRP1/gp75), a melanocyte differentiation marker. In a panel of cell lines that represent melanoma tumor progression, MAP-2c mRNA and the corresponding approximately 70-kd protein could be detected predominantly in primary melanomas. Immunohistochemical analysis of 61 benign and malignant melanocytic lesions showed abundant expression of MAP-2 protein in melanocytic nevi and in the in situ and invasive components of primary melanoma, but only focal heterogeneous expression in a few metastatic melanomas. In contrast, MAP-2-positive dermal nevus cells and the invasive cells of primary melanomas were TYRP1-negative. This reciprocal staining pattern in vivo is similar to the in vitro observation that induction of the neuronal marker MAP-2 in metastatic melanoma cells is accompanied by selective extinction of the melanocytic marker TYRP1. Our data show that neoplastic melanocytes, particularly at early stages, retain the plasticity to express the neuron-specific marker MAP-2. These observations are consistent with the premise that both benign and malignant melanocytes in the dermis can express markers of neuronal differentiation.