title: The growth hormone receptor (GHR) c.899dupC mutation functions as a dominant negative: insights into the pathophysiology of intracellular GHR defects.
abstract: BACKGROUND
  GH insensitivity (GHI) is a condition characterized by pronounced IGF-I deficiency and severe short stature. We previously identified a novel compound heterozygous GH receptor (GHR) mutation, GHR:p.R229H/c.899dupC, in a patient presenting with GHI. The heterozygous p.R229H (prepeptide) variant was previously associated with GHI despite a lack of adequate functional studies. The novel heterozygous GHR:c.899dupC variant affects the critical JAK2-binding Box 1 region of the GHR intracellular domain; the duplication predicted a frameshift and early protein termination.
  
  
  OBJECTIVE
  The individual and synergistic effect(s) of the p.R229H and c.899dupC mutations on GHR function(s) were evaluated in reconstitution studies.
  
  
  RESULTS
  The recombinant human GHR (hGHR):p.R229H variant was readily expressed, and unexpectedly, GH-induced signal transducer and activator of transcription 5b (STAT5b) phosphorylation was comparable to that induced by wild-type hGHR. The truncated, immunodetected hGHR:c.899dupC variant, in contrast, was unresponsive to GH. To mimic a compound heterozygous state, the two variants were coexpressed, and strikingly, the presence of the hGHR:c.899dupC effectively abolished the GH-induced STAT5b activities that were observed with hGHR:p.R229H alone. Furthermore, hGHR:c.899dupC dose-dependently reduced the GH-induced STAT5b activities associated with hGHR:p.R229H. This dominant negative effect was also observed when hGHR:c.899dupC was coexpressed with wild-type hGHR.
  
  
  CONCLUSIONS
  The p.R229H variant, contrary to an earlier report, appeared to function like wild-type GHR and, therefore, is unlikely to cause GHI. The c.899dupC variant is a novel dominant negative mutation that disrupted normal GHR signaling and is the cause for the GHI phenotype of the reported patient.
authors: Department of Pediatrics, CDRCP, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239-3098, USA. derrm@ohsu.edu
authors: Michael A
authors: MA
authors: Derr
authors: Javier
authors: J
authors: Aisenberg
authors: Peng
authors: P
authors: Fang
authors: Yardena
authors: Y
authors: Tenenbaum-Rakover
authors: Ron G
authors: RG
authors: Rosenfeld
authors: Vivian
authors: V
authors: Hwa
mesh_terms: D057809:HEK293 Cells; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000172:deficiency*; D046150:Laron Syndrome / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation / Q000235:genetics; D011986:Receptors, Somatotropin / Q000235:genetics* / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics
chemical_list: D011986:Receptors, Somatotropin; D050799:STAT5 Transcription Factor; D007334:Insulin-Like Growth Factor I