Rescue of pituitary function in a mouse model of isolated growth hormone deficiency type II by RNA interference

Splicing mutations in the human GH (hGH) gene (GH-1) that cause skipping of exon 3 result in a form of GH deficiency termed isolated GH deficiency type II (IGHD II). The GH-1 gene contains five exons; constitutive splicing produces the wild-type 22-kDa hormone, whereas skipping of exon 3 results in transcripts encoding a 17.5-kDa isoform that acts as a dominant-negative to block secretion of the wild-type hormone. Common characteristics of IGHD II include short stature due to impaired bone elongation, growth, and, in severe cases, anterior pituitary hypoplasia. Typically, IGHD II is treated by sc delivery of hGH, which can rescue stature but, unfortunately, does not inhibit pituitary hypoplasia. Direct destruction of transcripts encoding the dominant-negative 17.5-kDa isoform should both rescue stature and prevent hypoplasia. Here, we have used delivery of short hairpin RNAs to rescue a murine model of IGHD II by specifically targeting transcripts encoding the 17.5-kDa isoform using RNA interference. To our knowledge, this is the first example where a short hairpin RNA has been expressed to specifically degrade an incorrectly spliced transcript and rescue a dominant-negative disease phenotype in vivo.