Exon splice enhancer mutation (GH-E32A) causes autosomal dominant growth hormone deficiency.
OBJECTIVE
Alteration of exon splice enhancers (ESE) may cause autosomal dominant GH deficiency (IGHD II). Disruption analysis of a (GAA) (n) ESE motif within exon 3 by introducing single-base mutations has shown that single nucleotide mutations within ESE1 affect pre-mRNA splicing.


METHODS
Confirming the laboratory-derived data, a heterozygous splice enhancer mutation in exon 3 (exon 3 + 2 A-->C) coding for GH-E32A mutation of the GH-1 gene was found in two independent pedigrees, causing familial IGHD II. Because different ESE mutations have a variable impact on splicing of exon 3 of GH and therefore on the expression of the 17.5-kDa GH mutant form, the GH-E32A was studied at the cellular level.


RESULTS
The splicing of GH-E32A, assessed at the protein level, produced significantly increased amounts of 17.5-kDa GH isoform (55% of total GH protein) when compared with the wt-GH. AtT-20 cells coexpressing both wt-GH and GH-E32A presented a significant reduction in cell proliferation as well as GH production after forskolin stimulation when compared with the cells expressing wt-GH. These results were complemented with confocal microscopy analysis, which revealed a significant reduction of the GH-E32A-derived isoform colocalized with secretory granules, compared with wt-GH.


CONCLUSIONS
GH-E32A mutation found within ESE1 weakens recognition of exon 3 directly, and therefore, an increased production of the exon 3-skipped 17.5-kDa GH isoform in relation to the 22-kDa, wt-GH isoform was found. The GH-E32A mutant altered stimulated GH production as well as cell proliferation, causing IGHD II.
Petkovic
Vibor
V
Department of Pediatric Endocrinology, Diabetology, and Metabolism, Inselspital, University Children's Hospital, CH-3010 Bern, Switzerland.
Lochmatter
Didier
D
Turton
James
J
Clayton
Peter E
PE
Trainer
Peter J
PJ
Dattani
Mehul T
MT
Eblé
Andrée
A
Robinson
Iain C
IC
Flück
Christa E
CE
Mullis
Primus E
PE
D000293:Adolescent; D000328:Adult; D015153:Blotting, Western; D001827:Body Height; D049109:Cell Proliferation; D002470:Cell Survival / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D025063:Chromosome Disorders / Q000235:genetics*; D005576:Colforsin / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D005091:Exons / Q000235:genetics*; D005260:Female; D005799:Genes, Dominant / Q000235:genetics; D005822:Genetic Vectors / Q000235:genetics; D006056:Golgi Apparatus / Q000648:ultrastructure; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D009154:Mutation / Q000502:physiology*; D010375:Pedigree; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D022142:Secretory Vesicles / Q000648:ultrastructure
D020033:Protein Isoforms; D012333:RNA, Messenger; D019382:Human Growth Hormone; D005576:Colforsin