Deformed Skull Morphology Is Caused by the Combined Effects of the Maldevelopment of Calvarias, Cranial Base and Brain in FGFR2-P253R Mice Mimicking Human Apert Syndrome.

Apert syndrome (AS) is a common genetic syndrome in humans characterized with craniosynostosis. Apert patients and mouse models showed abnormalities in sutures, cranial base and brain, that may all be involved in the pathogenesis of skull malformation of Apert syndrome. To distinguish the differential roles of these components of head in the pathogenesis of the abnormal skull morphology of AS, we generated mouse strains specifically expressing mutant FGFR2 in chondrocytes, osteoblasts, and progenitor cells of central nervous system (CNS) by crossing Fgfr2+/P253R-Neo mice with Col2a1-Cre, Osteocalcin-Cre (OC-Cre), and Nestin-Cre mice, respectively. We then quantitatively analyzed the skull and brain morphology of these mutant mice by micro-CT and micro-MRI using Euclidean distance matrix analysis (EDMA). Skulls of Col2a1-Fgfr2+/P253R mice showed Apert syndrome-like dysmorphology, such as shortened skull dimensions along the rostrocaudal axis, shortened nasal bone, and evidently advanced ossification of cranial base synchondroses. The OC-Fgfr2+/P253R mice showed malformation in face at 8-week stage. Nestin-Fgfr2+/P253R mice exhibited increased dorsoventral height and rostrocaudal length on the caudal skull and brain at 8 weeks. Our study indicates that the abnormal skull morphology of AS is caused by the combined effects of the maldevelopment in calvarias, cranial base, and brain tissue. These findings further deepen our knowledge about the pathogenesis of the abnormal skull morphology of AS, and provide new clues for the further analyses of skull phenotypes and clinical management of AS.

Rapid detection of de novo P253R mutation in FGFR2 using uncultured amniocytes in a pregnancy affected by polyhydramnios, Blake's pouch cyst, and Apert syndrome.

OBJECTIVE: To present prenatal ultrasound and molecular genetic diagnosis of Apert syndrome. CASE REPORT: A 30-year-old, gravida 3, para 2 woman was referred for genetic counseling at 32 weeks of gestation because of polyhydramnios and craniofacial and digital abnormalities in the fetus. She had undergone amniocentesis at 18 weeks of gestation because of maternal anxiety. Results of amniocentesis revealed a karyotype of 46,XX. A prenatal ultrasound at 32 weeks of gestation revealed a female fetus with a fetal biometry equivalent to 32 weeks, polyhydramnios with an increased amniotic fluid index of 26.1 cm, frontal bossing, midface hypoplasia, hypertelorism, Blake's pouch cyst with an apparent posterior fossa cyst in communication with the fourth ventricle on axial images, digital fusion, and bilateral syndactyly of the hands and feet. A DNA testing for the FGFR2 gene was immediately performed using uncultured amniocytes obtained by repeated amniocentesis, which revealed a heterozygous c.758C>G, CCT>CGT transversion leading to a p.Pro253Arg (P253R) mutation in the FGFR2 gene. Subsequently, a diagnosis of Apert syndrome was made. Molecular analysis of the FGFR2 gene in the parents did not reveal such a mutation. The fetus postnatally manifested frontal bossing, midface hypoplasia, and bilateral syndactyly of the hands (mitten hands) and feet. CONCLUSION: Prenatal diagnosis of polyhydramnios, frontal bossing, and midface hypoplasia associated with brain and digital abnormalities should include a differential diagnosis of Apert syndrome. A molecular analysis of FGFR2 using uncultured amniocytes is useful for rapid confirmation of Apert syndrome at prenatal diagnosis.

Análisis genotípico de 11 pacientes colombianos con Síndrome de Apert / Genotypic analysis of 11 Colombian Apert syndrome patients

Antecedentes. El síndrome de Apert (SA) es una de las craneosinostosis sindrómicas más severas que afecta el neuro y viscerocraneo y además presenta alteraciones multisistémicas con repercusiones en aspectos físicos (aspecto general y talla baja), sensoriales (hipoacusia y trastornos visuales), cognoscitivos (retardo mental o trastornos del aprendizaje) y de inclusión laboral (sindactilia severa en manos y pies). Su etiología es la mutación del receptor 2 del factor de crecimiento fibroblástico (FGFR2) y se hereda de forma autosómica dominante. Materiales y métodos. Se analizaron clínica y molecularmente 11 pacientes con sospecha de SA. Se realizó estudio mutacional mediante RFLP para el gen FGFR2. Resultados. Se confirmaron molecularmente los 11 pacientes con SA, cuyas edades oscilaron desde los 0 a 32 años. Todos los pacientes presentaron el fenotipo clásico. Se encontró un 63.6% de pacientes con la mutación S252W y 36.4% con P253R. Discusión. De los pacientes analizados, llamo la atención la presencia de talla baja y RM/RGD en algunos de ellos. Desde el punto de vista genotípico, las frecuencias mutacionales para S252W y P253R no mostraron diferencias con relación a lo reportado mundialmente. Aunque no se disponen de datos de la incidencia de esta patología a nivel local, este estudio podría ser el primer acercamiento para fines epidemiológicos en Colombia.

Background. Apert Syndrome (AS) is one of the most severe syndromic craniosynostosis affecting neuro and viscerocranium and presenting with multisystemic anomalies altering physical aspects (general looks and short stature), sensorineural aspects (deafness and visual problems), cognitive development (mental retardation or trouble learning) and work inclusion (severe syndactyly in hands and feet). Its aetiology relies on mutation of the Fibroblast Growth Factor Receptor type 2 (FGFR2) gene, inherited by an autosomal dominant path. Materials and methods. 11 patients with suspicion of AS were clinically evaluated and molecularly tested for mutations in FGFR2 by RFLP. Results. Patients with AS from 0 to 32 years old were analized for mutations in FGFR2 gene. All of them had the classical phenotype of the disease. 63.6% of the patients had the S252W mutation while 36.4% had the P253R mutation. Discussion. Of all patients enrolled in this study it is notwworthy that some of them had short stature, while others had mental retardation or global development delay. Mutational frequencies for S252W and P253R did not show difference according to what has been reported worldwide. Although there is no data about the incidence of this disease locally, this study could be a first approach to its epidemiology in Colombia.

A Case of Apert Syndrome with a P253R Mutation on FGFR2 Exon VIII

Apert syndrome is a rare congenital anomaly characterized by craniofacial malformations and severe symmetrical syndactyly of fingers and toes. This syndrome is caused by a genetic mutation; the S253 mutation is common, though the P253R mutation is not as frequent. Common symptoms include skeletal malformations, poor joint mobility, eye and ear problems, cleft palate, and orthodontic and other dental problems. We report a case of an infant with the common morphological features of Apert syndrome. Interestingly, she was found to have the P253R mutation in FGFR2 exon VIII, which has been less commonly observed in Korea. A brief review of the literature is included.