Abstract
Functionally activating mutations in fibroblast growth factor receptor 3 (FGFR3) can cause four types of autosomal dominant skeletal dysplasia with short-limbed dwarfism that include the mildest phenotype, hypochondroplasia (HCH). A novel mutation (c.805A>T, p.S269C) was identified in a Japanese infant with HCH through direct sequencing of all FGFR3 exons and exon/intron boundaries. This mutation creates an additional cysteine residue in the extracellular region of FGFR3 that results in the functional activation of FGFR3.
Introduction
Functionally activating mutations of fibroblast growth factor receptor 3 (FGFR3) can cause four types of autosomal dominant skeletal dysplasia with short-limbed dwarfism: thanatophoric dysplasia (TD; OMIN187600) I and II, achondroplasia (ACH; OMIM100800), and hypochondroplasia (HCH; OMIM146000). Individuals with TD usually die after birth from respiratory distress due to pulmonary hypoplasia, and ACH and HCH are the most common genetic forms of dwarfism in children and adults1.
The features of ACH include a short stature caused by rhizomelic shortening of the limbs, characteristic faces with frontal bossing and midface hypoplasia, exaggerated lumbar lordosis, limited elbow extension, genu varum, and trident hands. By contrast, HCH is characterized by a short-limbed short stature, lumbar lordosis, short and broad bones, and caudal narrowing of the interpediculate distance of the lumbar spine. HCH results in milder phenotypes than ACH but has a broader spectrum of phenotypes that occasionally overlap with those of patients with ACH and normal individuals of short stature.
FGFR3 encodes a member of the FGFR subfamily of tyrosine kinase (TK) receptors. The four FGFR members share a common organization that is composed of three extracellular immunoglobulin-like loops (Ig I–III), one hydrophobic transmembrane (TM) domain, and two cytoplasmic TK sub-domains (TK1 and TK2) that are related to its catalytic activity. While more than 98% of patients with ACH have a recurrent p.G380R substitution in the TM domain of the receptor2, approximately 70% of patients with HCH have a recurrent p.N540K substitution in the cytoplasmic TK1 domain3. In this report, we describe a novel p.S269C mutation in FGFR3 that was identified in an infant with HCH. This mutation creates an additional cysteine residue in the extracellular region of FGFR3 that results in its functional activation.
The patient was a boy born to nonconsanguineous Japanese parents with a birth weight and height of 2.6 kg and 45.5 cm, respectively, after 38 weeks of gestation. At birth, his father was 52 years of age and his mother was 43 years of age. He was referred to us at the age of 6 months and exhibited growth failure with a weight and height of 6.6 kg and 59.5 cm (−3.5 SD), respectively. His head circumference was 42.7 cm, which was within the normal range. His facial appearance was not peculiar, and he did not have triangular hands. An X-ray of the patient revealed short, broad, and hypoplastic iliac bones that were reminiscent of HCH. Following the clinical diagnosis of HCH, the patient continued to exhibit stunted growth. At the age of 2 years, skeletal X-ray findings revealed broad, long, and hypoplastic iliac bones, but caudal narrowing of the interpediculate distance of the lumbar spine was not observed (Fig. 1 a and b).
A genetic diagnosis was then performed with genomic DNA isolated from the whole blood of the patient and his parents and indicated an absence of the common recurrent mutations responsible for HCH and ACH (i.e., p.N540K and p.G380R, respectively). Subsequently, all 18 exons and exon/intron boundaries of FGFR3 were amplified via polymerase chain reaction and then directly sequenced. The results revealed that the patient was heterozygous for the c.805A>T (p.S269C) mutation. The parents were not carriers of this missense mutation; thus, c.805A>T was a de novo mutation in FGFR3 in the patient (Fig. 2). This study was approved by the Institutional Review Board and Ethical Committee of Akita University Graduate School of Medicine. Written informed consent was obtained from the parents of the patient.
After the initial discovery of mutations in FGFR3 in cases of ACH, other FGFR3 gene mutations were subsequently discovered in cases of TD and HCH. A recurrent mutation in FGFR3, i.e., p.G380R, was found to be responsible for more than 98% of ACH cases2, whereas missense mutations that create cysteine residues in the extracellular domain of FGFR3 have been found to be responsible for TD1.
Regarding HCH, a recurrent mutation, i.e., p.N540, in the intracellular TK1 domain was determined to be responsible for approximately 70% of HCH cases3. Subsequently, 19 missense mutations have been reported as frequent minor mutations in HCH. Of these mutations, 10 (p.S84L4, p.R200C4, p.N262H4, p.G268C4, p.Y278C4, p.L324V5, p.L324H6, p.N328I7, p.G342C8, and p.S348C9) are located in the extracellular region of FGFR3, six (p.M528I10, p.I538V11, p.N540S12, p.N540T13, p.K650N14, and p.K650Q14) are located in the intracellular region of FGFR3, and three (p.G380K15, which is also responsible for AHC, p.V381E4, and p.F384L10) are located in the TM region of FGFR3. In this report, we identified a novel FGFR3 mutation that was responsible for HCH, i.e., p.S269C, which is located in the extracellular region of FGFR3 (Fig. 3). Among the mutations in FGFR3 that have been identified thus far, those responsible for HCH are distributed along a wide genomic region of FGFR3. Thus, it is essential to sequence the entire FGFR3 gene to make a genetic diagnosis of skeletal dysplasia with a short-limbed short stature, even if patients do not have the common mutations in FGFR3.
Notably, six of the mutations responsible for HCH are a result of an additional cysteine residue in the extracellular region of FGFR3. FGFR3 regulates a variety of biological functions, including cell proliferation, migration, and differentiation1. Upon ligand binding, FGFR3 dimerizes, which results in controlled activation of a specific signal transduction pathway. Some representative mutations in FGFR3 that are responsible for TD and ACH have been biochemically studied to determine their effects on the induction and stabilization of FGFR3 dimerization16,17. Each of the mutations studied thus far has been demonstrated to increase the propensity for FGFR3 dimerization to some degree. The three mutations that create an additional cysteine residue in the extracellular region of FGFR3, i.e., p.G370C, p.S371C, and p.Y373C, are commonly found in patients with TD and have been biochemically analyzed and demonstrated to induce disulfide-mediated receptor dimerization and constitutive activation18,19. Thus, we speculate that the mutations that are responsible for HCH that create a cysteine residue may elicit constitutive activation of FGFR3 through the formation of an abnormal disulfide bond in a manner similar to the activation of FGFR3, which is associated with the common mutations responsible for TD.
HGV Database
The relevant data from this Data Report are hosted at the Human Genome Variation Database at https://doi.org/10.6084/m9.figshare.hgv.1920.
References
Horton, W. A., Hall, J. G. & Hecht, J. T. Achondroplasia. Lancet 370, 162–172 (2007).
Bellus, G. A. et al. Achondroplasia is defined by recurrent G380R mutations of FGFR3. Am. J. Hum. Genet. 56, 368–373 (1995).
Bellus, G. A. et al. A recurrent mutation in the tyrosine kinase domain of fibroblast growth factor receptor 3 causes hypochondroplasia. Nat. Genet. 10, 357–359 (1995).
Heuertz, S. et al. Novel FGFR3 mutations creating cysteine residues in the extracellular domain of the receptor cause achondroplasia or severe forms of hypochondroplasia. Eur. J. Hum. Genet. 14, 1240–1247 (2006).
Saito, T. et al. Radiological clues to the early diagnosis of hypochondroplasia in the neonatal period: report of two patients. Am. J. Med. Genet. 158A, 630–634 (2012).
Nagahara, K. et al. Japanese familial case of hypochondroplasia with a novel mutation in FGFR3. Clin. Pediatr. Endocrinol. 25, 103–106 (2016).
Winterpacht, A. et al. A novel mutation in FGFR-3 disrupts a putative N-glycosylation site and results in hypochondroplasia. Physiol. Genom. 2, 9–12 (2000).
Wang, H. et al. A novel missense mutation of FGFR3 in a Chinese female and her fetus with hypochondroplasia by next-generation sequencing. Clin. Chim. Acta 423, 62–65 (2013).
Couser, N. L. et al. Mild achondroplasia/hypochondroplasia with acanthosis nigricans, normal development, and a p.Ser348Cys FGFR3 mutation. Am. J. Med. Genet. 9999, 1–5 (2017).
Kant, S. G. et al. A novel variant of FGFR3 causes proportionate short stature. Eur. J. Endocrinol. 172, 763–770 (2015).
Grigelioniene, G. et al. A novel missense mutation Ile538Val in the fibroblast growth factor receptor 3 in hypochondroplasia. Hum. Mutat. 11, 333 (1998).
Mortier, G. et al. Clinical and radiological features of a family with hypochondroplasia owing to a novel Asn540Ser mutation in the fibroblast growth factor receptor 3 gene. J. Med. Genet. 37, 220–224 (2000).
Deutz-Terlouw, P. P., Losekoot, M., Aalfs, C. M., Hennekam, R. C. M. & Bakker, E. Asn540Thr substitution in the fibroblast growth factor receptor 3 tyrosine kinase domain causing hypochondroplasia. Hum. Mutat. 11, S62–S65 (1998).
Bellus, G. A. et al. Distinct missense mutations of the FGFR3 lys650 codon modulate receptor kinase activation and the severity of the skeletal dysplasia phenotype. Am. J. Hum. Genet. 67, 1411–1421 (2000).
Santos, H. G., Almeida, M., Fernandes, H. & Wilkie, A. Clinical hypochondroplasia in a family caused by a heterozygous double mutation in FGFR3 encoding GLY380LYS. Am. J. Med. Genet. A 143A, 355–359 (2007).
Monsonego-Ornan, E., Adar, R., Feferman, T., Segev, O. & Yayon, A. The transmembrane mutation G380R in fibroblast growth factor receptor 3 uncouples ligand-mediated receptor activation from down-regulation. Mol. Cell. Biol. 20, 516–522 (2000).
Lievens, P. M. J., Mutinelli, C., Baynes, D. & Liboi, E. The kinase activity of fibroblast growth factor receptor 3 with activation loop mutations affects receptor trafficking and signaling. J. Biol. Chem. 279, 43254–43260 (2004).
Adar, R., Monsonego-Ornan, E., David, P. & Yayon, A. Differential activation of cysteine-substitution mutants of fibroblast growth factor receptor 3 is determined by cysteine localization. J. Bone Miner. Res. 17, 860–868 (2002).
You, M. et al. Effect of pathogenic cysteine mutations on FGFR3 transmembrane domain dimerization in detergents and lipid bilayers. Biochemistry 46, 11039–11046 (2007).
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Additional information
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, and provide a link to the Creative Commons license. You do not have permission under this license to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, http://creativecommons.org/licenses/by-nc-nd/4.0/.
About this article
Cite this article
Takahashi, I., Kondo, D., Oyama, C. et al. A novel S269C mutation in fibroblast growth factor receptor 3 in a Japanese child with hypochondroplasia. Hum Genome Var 5, 1 (2018). https://doi.org/10.1038/s41439-018-0001-2
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41439-018-0001-2