Cell Differentiation of Gonadotropin-Releasing Hormone Neurons and Alternative RNA Splicing of the Gonadotropin-Releasing Hormone Transcript

Abstract

Two different, yet related issues regarding gonadotropin-releasing hormone (GnRH), i.e. the development and differentiation of hypothalamic GnRH neurons and the alternative RNA splicing of GnRH gene transcripts, are addressed in the present review. Using the immortalized GnRH-producing GT1 cell line, we found that activation of protein kinase C (PKC) with 12-O-tetradecanoylphorbol-13-acetate induces morphological and functional differentiation of these neurons. Specific isoforms of PKC are involved in neurite growth, cell migration and synaptic contacts and involve different signaling pathways. Using an in vitro splicing assay with HeLa nuclear extract, we found that excision of the first intron of the GnRH primary transcript is attenuated in non-GnRH-producing cells, but not in GnRH-producing cells such as GT1. This attenuation was relieved by exonic splicing enhancers located in the GnRH exons 3 and 4. Interestingly, addition of nuclear extract derived from GT1 cells further increased the excision rate of intron A, indicating that GnRH neurons contain trans-acting splicing factors. Extensive biochemical analysis indicates that Tra2α, a serine/arginine-rich RNA-binding protein, and other cofactors are likely involved in mediating neuron-specific excision of intron A from the GnRH primary transcript. An understanding of the GnRH neuron-specific splicing machinery provides critical insight into the molecular mechanism of GnRH gene regulation and consequently of mammalian reproductive development.

Postnatal expression of V2 vasopressin receptor splice variants in the rat cerebellum

“…6C). Similar findings have been reported in other cell systems and might reflect differences in the gene transcription or/and RNA processing rates (Choe et al, 2003; Yue et al, 2006). On the basis of our PCR studies and previous studies on the expression of the mRNAs encoding V 2a and V 2b (Firsov et al 1994, and Sarmiento et al 2004) we estimated that the relative expression of these transcripts remains constant throughout the postnatal development of the cerebellum (Fig.…”

Studies of oxytocin and vasopressin gene expression in the rat hypothalamus using exon- and intron-specific probes

“…Previous investigators have cautioned that the presence of stable intermediates in multipleintron genes could confound interpretations of the relationship of hnRNA to transcription vs. to varying pre-mRNA processing rates (18,25). Evidence for persistent hnRNA intermediates, whose rates appear to be regulated, has been reported for specific biological systems (11,21,25,45). We do not know whether the pre-mRNA processing rates of either the OT or VP primary transcripts undergo changes under the experimental conditions that we have studied nor is there evidence to suggest that this is occurring for either peptide gene.…”