An activating mutation in the kinase homology domain of the natriuretic peptide receptor-2 causes extremely tall stature without skeletal deformities.
BACKGROUND
C-type natriuretic peptide (CNP)/natriuretic peptide receptor 2 (NPR2) signaling is essential for long bone growth. Enhanced CNP production caused by chromosomal translocations results in tall stature, a Marfanoid phenotype, and skeletal abnormalities. A similar phenotype was described in a family with an activating NPR2 mutation within the guanylyl cyclase domain.


METHODS
Here we describe an extremely tall male without skeletal deformities, with a novel NPR2 mutation (p.Arg655Cys) located in the kinase homology domain.


OBJECTIVE
The objective of the study was to investigate the functional and structural effects of the NPR2 mutation.


METHODS
Guanylyl cyclase activities of wild-type vs mutant NPR2 were analyzed in transfected human embryonic kidney 293 cells and in skin fibroblasts. The former were also used to study possible interactions between both isoforms. Homology modeling was performed to understand the molecular impact of the mutation.


RESULTS
CNP-stimulated cGMP production by the mutant NPR2 was markedly increased in patient skin fibroblasts and transfected human embryonic kidney 293 cells. The stimulatory effects of ATP on CNP-dependent guanylyl cyclase activity were augmented, suggesting that this novel mutation enhances both the responsiveness of NPR2 to CNP and its allosteric modulation/stabilization by ATP. Coimmunoprecipitation showed that wild-type and mutant NPR2 can form stable heterodimers, suggesting a dominant-positive effect. In accordance with augmented endogenous receptor activity, plasma N-terminal pro-CNP (a marker of CNP production in tissues) was reduced in the proband.


CONCLUSIONS
We report the first activating mutation within the kinase homology domain of NPR2, resulting in extremely tall stature. Our observations emphasize the important role of this domain in the regulation of guanylyl cyclase activity and bone growth in response to CNP.
MD, PhD, Department of Paediatrics, Leiden University Medical Centre, Postbus 9600, 2300 RC Leiden, The Netherlands. s.e.hannema@lumc.nl.
Sabine E
SE
Hannema
Hermine A
HA
van Duyvenvoorde
Thomas
T
Premsler
Ruey-Bing
RB
Yang
Thomas D
TD
Mueller
Birgit
B
Gassner
Heike
H
Oberwinkler
Ferdinand
F
Roelfsema
Gijs W E
GW
Santen
Timothy
T
Prickett
Sarina G
SG
Kant
Annemieke J M H
AJ
Verkerk
André G
AG
Uitterlinden
Eric
E
Espiner
Claudia A L
CA
Ruivenkamp
Wilma
W
Oostdijk
Alberto M
AM
Pereira
Monique
M
Losekoot
Michaela
M
Kuhn
Jan M
JM
Wit
D019943:Amino Acid Substitution; D001827:Body Height; D001846:Bone Development; D001848:Bone Diseases, Developmental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020134:Catalytic Domain; D004789:Enzyme Activation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D017461:Receptors, Atrial Natriuretic Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000099242:Atrial Natriuretic Factor Receptor B
D017461:Receptors, Atrial Natriuretic Factor; D000099242:Atrial Natriuretic Factor Receptor B