A common polymorphism of the growth hormone receptor is associated with increased responsiveness to growth hormone Nature Genetics, July 2004 Christine Dos Santos, Laurent Essioux, Cécile Teinturier, Mäité Tauber, Vincent Goffin & Pierre Bougnères

Outline Introduction Growth Hormone Receptor (GHR) Allellic differences in growth rate Relevance of findings

Growth Hormone Therapy Growth hormone therapy may be necessary for some of the population Where does normal pathway deviate in response to growth hormone?

Growth Hormone Pathway Image taken from BioCarta.com

Growth Hormone Pathway Problems associated with pathway Lack of growth hormone production Problems with the growth hormone receptor (GHR) Downstream components GHR and downstream components are obvious choices for study on problems associated with growth hormone sensitivity Image taken from BioCarta.com

Growth Hormone Receptor Transmembrane protein Coded for by 9 exons 246aa extracellular domain (exons 3-7) Single transmembrane domain Single cytoplasmic domain Dimer formation

Growth Hormone Receptor Variant allele d3-GHR Isoform lacking exon 3 Exon 3 codes for 22aa Conserved in mammalian species important role in protein function Possible loss of glycosylation site Difference in receptor domain due to change in highly conserved amino acid at end of exon 2 Dominant over full length isoform

Isoform Response to GH Children chosen with normal growth hormone levels Short for Gestational Age (SGA) – small birth size Idiopathic Short Stature (ISS) – normal birth size, slow growth

Data Collection Growth rate monitored for first two years of hormone administration Individuals tested for GHR genotype Only subjects of European origin used in study Response to growth hormone measured

Response to GH

Response to GH Striking increase in response to GH in children carrying at least one d3-GHR allele

Linear Regression Model GHR genotype has a significant effect on growth acceleration (P<10-6 for first year, P<0.005 for second year) Nine other tested polymorphisms had no correlation

Activities of GHR and d3-GHR Transfected 293 HEK fibroblasts with full length GHR, d3-GHR, or GHR/d3-GHR LHRE-luciferase assay used Cells exposed to varying GH levels Consistent higher induction of reporter construct by d3-GHR (~30%) GH levels used were low to ensure in vivo relevance

Relevance Recent recombinant GH use approved by FDA and ERA for children Genotyping for a single polymorphism can be carried out efficiently Personalized dose regimen can reduce costs and improve treatment success Half of people of European descent are heterozygous or homozygous for d3-GHR

Conclusion Individuals with d3-GHR isoform have ~twice the growth rate in response to GH as homozygous GHR subjects This isoform is present at high levels in the human population (~50%) Efficient cost effective genotyping can lead to improved treatment regimens for patients

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