Unlike other members of the EGF family, Nrg-1 is subject to extensive alternative splicing, giving rise to a rich and diverse number of distinct peptides.
7 It is now appreciated that these peptides with very distinct functions are all produced from a single gene, Nrg-1. 1 Originally, the individual Nrgs were variously described as 1) a ligand for the oncogene ErbB2 2 3 4 2) a glial growth factor 5 6 or 3) a factor that stimulates acetylcholine receptor synthesis in muscle. Neuregulins (Nrg) are paracrine, autocrine, and juxtacrine signaling peptides that belong to the epidermal growth factor (EGF) family. Finally, there was a preference of exon usage that varied by location in the cornea and this pattern changed when cells were placed into culture. These domains are known to direct ligand/receptor interaction and the trafficking, processing, and release of Nrg-1 from the cell. This altered the predicted coding sequence in three domains of Nrg-1. Eight distinct forms of Nrg-1 were expressed in the adult human cornea that differ by the alternate use of four exons. qPCR suggested that epithelial cells and stromal cells produce equivalent levels of Nrg-1, but distinct variants were present that differ in proportion with each source of RNA.Ĭonclusions. RT-PCR and Western blot analyses demonstrated that Nrg-1 and its receptor are expressed in adult corneal tissue and cultured cells derived from this tissue. Finally, the receptor family known to interact with Nrg-1 was examined to confirm its expression in corneal tissue. A combination of fluorescent primers, restriction endonucleases, and image analysis was used to determine the proportion of each splice variant. Quantitative real-time polymerase chain reactions (qPCR) were performed to determine the overall levels of Nrg-1.
RNA was purified from isolated corneal epithelium, corneal stroma, and primary cultures of both epithelial cells and stromal fibroblasts. After sequencing, the likely exon/intron structure was determined by comparison to genomic sequence. cDNA for Nrg-1 was obtained by direct amplification of RNA isolated from human corneal cell cultures. To determine whether neuregulin 1 (Nrg-1) is expressed in the normal adult human cornea.
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