Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Case Reports
. 2000 Dec;67(6):1411-21.
doi: 10.1086/316892. Epub 2000 Oct 27.

Distinct missense mutations of the FGFR3 lys650 codon modulate receptor kinase activation and the severity of the skeletal dysplasia phenotype

G A Bellus  1 , E B Spector, P W Speiser, C A Weaver, A T Garber, C R Bryke, J Israel, S S Rosengren, M K Webster, D J Donoghue, C A Francomano
Affiliations
Case Reports

Distinct missense mutations of the FGFR3 lys650 codon modulate receptor kinase activation and the severity of the skeletal dysplasia phenotype

G A Bellus et al. Am J Hum Genet. 2000 Dec.

Abstract

The fibroblast growth factor-receptor 3 (FGFR3) Lys650 codon is located within a critical region of the tyrosine kinase-domain activation loop. Two missense mutations in this codon are known to result in strong constitutive activation of the FGFR3 tyrosine kinase and cause three different skeletal dysplasia syndromes-thanatophoric dysplasia type II (TD2) (A1948G [Lys650Glu]) and SADDAN (severe achondroplasia with developmental delay and acanthosis nigricans) syndrome and thanatophoric dysplasia type I (TD1) (both due to A1949T [Lys650Met]). Other mutations within the FGFR3 tyrosine kinase domain (e.g., C1620A or C1620G [both resulting in Asn540Lys]) are known to cause hypochondroplasia, a relatively common but milder skeletal dysplasia. In 90 individuals with suspected clinical diagnoses of hypochondroplasia who do not have Asn540Lys mutations, we screened for mutations, in FGFR3 exon 15, that would disrupt a unique BbsI restriction site that includes the Lys650 codon. We report here the discovery of three novel mutations (G1950T and G1950C [both resulting in Lys650Asn] and A1948C [Lys650Gln]) occurring in six individuals from five families. Several physical and radiological features of these individuals were significantly milder than those in individuals with the Asn540Lys mutations. The Lys650Asn/Gln mutations result in constitutive activation of the FGFR3 tyrosine kinase but to a lesser degree than that observed with the Lys540Glu and Lys650Met mutations. These results demonstrate that different amino acid substitutions at the FGFR3 Lys650 codon can result in several different skeletal dysplasia phenotypes.

PubMed Disclaimer

Figures

Figure 1
Figure 1
BbsI digestion and DNA sequencing of FGFR3 exon 15 PCR products. A, BbsI digestion of exon 15 PCR products for four families. The mutant allele is not digested in affected individuals. Lane M, 100-bp DNA-ladder standard. B, Automated DNA sequencing, which reveals the presence of a heterozygous G1950C/K650N mutation in patient 1 (top) and a heterozygous G1950T/K650N in patient 4 (middle). Patients 2, 3, and 6 were also found to have G1950C/K650N mutations (data not shown). Control sequence (bottom) is depicted with theBbsI restriction site underlined. Sequencing autoradiography of patient 5 (left gel) shows the presence of a heterozygous A1948C/K650Q mutation (arrow) not seen in the control (right gel).
Figure 2
Figure 2
Photographs of patients. Note the mild shortening of the arms and normal facial appearance in patient 1, who has G1950C (Lys650Asn) and is shown at age 15 years (A–D), whereas patient 4, who has G1950T (Lys650Asn) and is shown at age 15 mo (E and F), and patient 5, who has A1948C (Lys650Gln) and is shown at age 20 mo (G), have more-prominent dysmorphic facial features.
Figure 3
Figure 3
Radiographs of patients. The skull radiograph of patient 4 at age 15 mo (A) exhibits macrocephaly and frontal bossing, whereas that of patient 6 at age 2 years (B) is less disproportionate. AP spines of patient 3 at age 39 years (C) and of patient 5 at age 18 mo (E) show some widening of the interpediculate distances (i.e., width of the spinal canal), proceeding from L1 to L4, although this is less than normal. Shortening of the lumbar pedicles as seen in the lateral spine views (i.e., depth of spinal canal) is observed in patient 3 at age 39 years (D) but is less severe in patient 5 at age 18 mo (F). The pelvis of patient 4 at age 15 mo (G) is relatively normal, except for shortened femoral necks, whereas patient 5 at age 18 mo (H) shows shortening of the femoral necks and narrowing of the greater sciatic notch.
Figure 4
Figure 4
Radiographs and photographs of extremities. In patient 3 at age 39 years (A), patient 1 at age 13 years (B), and patient 4 at age 15 mo (C), the fibula:tibia length ratio is close to normal. There is moderately exaggerated flaring of the distal femoral and proximal tibial metaphyses in the younger patient (C). There is mild to moderate shortening of the metacarpals and phalanges in patient 1 at age 15 years (D and F), which is more pronounced in patient 4 at age 15 mo E and G).
Figure 5
Figure 5
MCP. The lengths of the metacarpals and phalanges were measured on the basis of radiographs of the hands of each patient, and Z scores were determined according to the method of Poznanski (1984); the average Z score for each metacarpal (mc1–mc5) and phalanx (pp1–pp5, mp2–mp5, and dp1–dp5) is shown.• = FGFR3 Lys650Asn/Gln (n=6); ▪ = FGFR3 Asn540Lys (n=9) (Prinster et al. 1998); ▴ = radiologically confirmed hypochondroplasia (n=21) (Hall and Spranger 1979). The range in Z scores for each bone is shown for the patients with Lys650Asn/Gln mutations.
Figure 6
Figure 6
Autophosphorylation of FGFR3 cDNA mutant constructs. FGFR3 cDNA constructs comprising all of the possible amino acid substitutions resulting from single nucleotide changes of the Lys650 codon were synthesized and transfected into NIH 3T3 cells. FGFR3 was immunoprecipitated from cell lysates and incubated with [32P]-ATP in an autophosphorylation assay. Equal amounts of immunoprecipitate (lower panel) were then separated by gel electrophoresis and were exposed to x-ray film. The locations of molecular-weight markers (in kD) are shown on the left. The relative activity of the mutations, compared with that in the wild type, was determined by densitometry and is as follows: K650R, 1.5×; K650N, 3.7×; K650Q, 4.9×; K650T, 3.1×; K650E, 9.6×; and K650M, 18.1×.
Figure 7
Figure 7
FGFR3 hypochondroplasia mutations. A schematic of the FGFR3 protein is shown, and the areas within the three exons where hypochondroplasia missense mutations occur are shown in greater detail. The nucleotide substitutions are shown above, and the amino acid substitutions are shown below; for comparison, the mutations causing TD2 and SADDAN syndrome are also shown.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

Electronic-Database Information

    1. Online Mendelian Inheritance in Man (OMIM), http://www.ncbi.nlm.nih.gov/Omim (for hypochondroplasia [MIM 146000])

References

    1. Baker KM, Olson DS, Harding CO, Pauli RM (1997) Long-term survival in typical type 1 thanatophoric dysplasia. Am J Med Genet 70:427–436 - PubMed
    1. Beals RK (1969) Hypochondroplasia: a report of five kindreds. J Bone Joint Surg Am 51-A:728–736 - PubMed
    1. Bellus GA, Bamshad MJ, Przylepa K, Dorst J, Lee RR, Hurko O, Jabs EW, Curry CJ, Wilcox WR, Lachman RS, Rimoin DL, Francomano CA (1999) Severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN): phenotypic analysis of a new skeletal dysplasia caused by the fibroblast growth factor receptor 3 Lys650Met mutation. Am J Med Genet 85:53–65 - PubMed
    1. Bellus GA, Hefferon TW, Ortiz de Luna RI, Hecht JT, Horton WA, Machado M, Kaitila, McIntosh I, Francomano CA (1995a) Achondroplasia is defined by recurrent G380R mutations of FGFR3. Am J Hum Genet 56:368–373 - PMC - PubMed
    1. Bellus GA, McIntosh I, Smith EA, Ayslworth AS, Kaitila I, Horton WA, Greenhaw, FA, Hecht JT, Francomano CA (1995b) A recurrent mutation in the tyrosine kinase domain of fibroblast growth factor receptor 3 causes hypochondroplasia. Nat Genet 10:357–359 - PubMed

Publication types

MeSH terms

LinkOut - more resources