Depolarization differentially affects the secretory and migratory properties of two cell lines of immortalized luteinizing hormone‐releasing hormone (LHRH) neurons

Abstract

In this report we studied and compared the biochemical and the electrophysiological characteristics of two cell lines (GT1-7 and GN11) of immortalized mouse LHRH-expressing neurons and the correlation with their maturational stage and migratory activity. In fact, previous results indicated that GN11, but not GT1-7, cells exhibit an elevated motility in vitro. The results show that the two cell lines differ in terms of immunoreactivity for tyrosine hydroxylase and nestin as well as of production and release of 3,4-dihydroxyphenylalanine (DOPA) and of intracellular distribution and release of the LHRH. Patch-clamp recordings in GN11 cells, reveal the presence of a single inward rectifier K+ current indicative of an immature neuronal phenotype (neither firing nor electrical activity). In contrast, as known from previous studies, GT1-7 cells show the characteristics of mature LHRH neurons with a high electrical activity characterized by spontaneous firing and excitatory postsynaptic potentials. K+-induced depolarization induces in GT1-7 cells, but not in GN11 cells, a strong increase in the release of LHRH in the culture medium. However, depolarization of GN11 cells significantly decreases their chemomigratory response. In conclusion, these results indicate that GT1-7 and GN11 cells show different biochemical and electrophysiological characteristics and are representative of mature and immature LHRH neurons, respectively. The early stage of maturation of GN11 cells, as well as the low electrical activity detected in these cells, appears to correlate with their migratory activity in vitro.

Developmental Regulation of Gonadotropin-releasing Hormone Gene Expression by the MSX and DLX Homeodomain Protein Families

“…Neuronal Cell Lines-Characterization of the GT1-7 and GN11 or NLT cell lines suggests that the GT1-7 cells represent a differentiated, mature GnRH neuron while the GN11 or NLT cells mimic the immature, migratory stages of GnRH neuron development (12)(13)(14)(15). Previous findings suggest that GnRH expression itself is involved in furthering the commitment and migratory state of the GnRH neurons (11).…”

“…The generation of immortalized GnRH neuronal cell lines, the GT1-7, GN11, and NLT cells, has provided cellular model systems in which to study GnRH (12,13). Whereas the murine hypothalamic cell line, GT1-7, exhibits key characteristics of a mature, fully differentiated GnRHexpressing neuron, the GN11 and NLT cell lines are migratory in culture and suggested to represent immature GnRH neurons (12)(13)(14)(15). Studies with these two models have been invaluable for identifying the protein transcription factor complexes that facilitate expression of GnRH.…”

REST levels affect the functional expression of voltage dependent calcium channels and the migratory activity in immortalized GnRH neurons

“…voltage dependent channels [18,19]; more recently, however, expression of the transcript of P/Q type VDCCs has been reported [22]. For this reason, we reexamined VDCCs expression and functionality in both control and silenced cells, using a calcium imaging approach.…”

“…2), pointing to a role of REST in the control of the migratory properties of this cell line. For comparison, migratory activity was also evaluated in GT1-7 cells, considered to show a low migratory potential [18], in the same conditions as above (three experiments; Fig. 2).…”

“…The steps of their development are recapitulated in two immortalised cell lines that have been obtained by genetically targeted tumorigenesis: GN11 cells [17] have been isolated from a murine olfactory bulb tumour; they exhibit an immature neuronal phenotype, with high proliferative and migratory activity, and have been regarded as electrically non-excitable [18,19]. In contrast GT1-7 cells [20], obtained from a hypothalamic tumour, represent post-migratory GnRH neurons, and show the relevant properties of a mature phenotype: neurite growth, excitability and hormone release [18].…”