A cluster of translocation breakpoints in 2q37 is associated with overexpression of NPPC in patients with a similar overgrowth phenotype.
ABSTRACT Overexpression of the C-type natriuretic peptide, encoded by the NPPC gene in 2q37.1, was recently reported in a patient presenting an overgrowth phenotype and a balanced t(2;7)(q37.1;q21.3) translocation. We present clinical, cytogenetic, and molecular data from two additional patients carrying balanced translocations involving the same 2q37.1 chromosome band and chromosomes 8 and 13, respectively. The clinical phenotype of these patients is very similar to the first patient described. In addition to the overgrowth syndrome, there is evidence of generalized cartilage dysplasia. In these two new cases, we found overexpression of NPPC, confirming that this unusual overgrowth phenotype in humans is due to the overexpression of this gene. The involvement of three different chromosomes and a cluster of breakpoints around the NPPC gene suggests that the overexpression of this gene in translocation patients could be due to its separation from a negative regulatory element located on chromosome 2, which would constitute a previously undescribed mutational mechanism.
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ABSTRACT: The signal pathway of the C-type natriuretic (CNP) and its receptor, natriuretic peptide receptor 2 (NPR2) is involved in the longitudinal growth of long bones. Loss of function mutations at NPR2 cause acromesomelic dysplasia, type Maroteaux, while overproduction of CNP by chromosomal translocation and a gain-of-function mutation at NPR2 have been reported to be responsible for an overgrowth syndrome in three cases and one family, respectively. We identified a four-generation family with an overgrowth syndrome characterized by tall stature, macrodactyly of the great toes, scoliosis, coxa valga and slipped capital femoral epiphysis, similar to those previously reported in association with CNP/NPR2 overactivity. The serum level of amino-terminal proCNP was normal in the proband. A novel missense mutation of NPR2, c.1462G>C (p.Ala488Pro) was found to co-segregate with the phenotype in this family. In vitro transfection assay of the mutant NPR2 revealed overactivity of the mutant receptor at baseline as well as with the ligand. This overgrowth syndrome caused by a gain-of-function mutation at NPR2 should be differentiated from Marfan or related syndromes, and may be categorized along with the overgrowth syndrome caused by overproduction of CNP due to its phenotypical similarity as overgrowth CNP/NPR2 signalopathy. © 2013 Wiley Periodicals, Inc.American Journal of Medical Genetics Part A 11/2013; · 2.30 Impact Factor
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ABSTRACT: Achondroplasia (ACH), the most common form of dwarfism, is an inherited autosomal-dominant chondrodysplasia caused by a gain-of-function mutation in fibroblast-growth-factor-receptor 3 (FGFR3). C-type natriuretic peptide (CNP) antagonizes FGFR3 downstream signaling by inhibiting the pathway of mitogen-activated protein kinase (MAPK). Here, we report the pharmacological activity of a 39 amino acid CNP analog (BMN 111) with an extended plasma half-life due to its resistance to neutral-endopeptidase (NEP) digestion. In ACH human growth-plate chondrocytes, we demonstrated a decrease in the phosphorylation of extracellular-signal-regulated kinases 1 and 2, confirming that this CNP analog inhibits fibroblast-growth-factor-mediated MAPK activation. Concomitantly, we analyzed the phenotype of Fgfr3(Y367C/+) mice and showed the presence of ACH-related clinical features in this mouse model. We found that in Fgfr3(Y367C/+) mice, treatment with this CNP analog led to a significant recovery of bone growth. We observed an increase in the axial and appendicular skeleton lengths, and improvements in dwarfism-related clinical features included flattening of the skull, reduced crossbite, straightening of the tibias and femurs, and correction of the growth-plate defect. Thus, our results provide the proof of concept that BMN 111, a NEP-resistant CNP analog, might benefit individuals with ACH and hypochondroplasia.The American Journal of Human Genetics 11/2012; · 11.20 Impact Factor
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ABSTRACT: Coordinated bone growth is controlled by numerous mechanisms which are only partially understood because of the involvement of many hormones and local regulators. The C-type Natriuretic Peptide (CNP), encoded by NPPC gene located on chromosome 2q37.1, is a molecule that regulates endochondral ossification of the cartilaginous growth plate and influences longitudinal bone growth. Two independent studies have described three patients with a Marfan-like phenotype presenting a de novo balanced translocation involving the same chromosomal region 2q37.1 and overexpression of NPPC. We report on two partially overlapping interstitial 2q37 deletions identified by array CGH. The two patients showed opposite phenotypes characterized by short stature and skeletal overgrowth, respectively. The patient with short stature presented a 2q37 deletion causing the loss of one copy of the NPPC gene and the truncation of the DIS3L2 gene with normal CNP plasma concentration. The deletion identified in the patient with a Marfan-like phenotype interrupted the DIS3L2 gene without involving the NPPC gene. In addition, a strongly elevated CNP plasma concentration was found in this patient. A possible role of NPPC as causative of the two opposite phenotypes is discussed in this study.PLoS ONE 06/2013; 8(6):e66048. · 3.53 Impact Factor