Differential Expression of Fibroblast Growth Factor Receptors in Human Digital Development Suggests Common Pathogenesis in Complex Acrosyndactyly and Craniosynostosis:

The natural history of patients treated for FGFR3-associated (Muenke-type) craniosynostosis

BACKGROUND

Muenke-type craniosynostosis is defined as fibroblast growth factor receptor 3 (FGFR3)-associated coronal craniosynostosis with or without mental retardation. With complementary genetic information, more precise diagnosis and long-term functional outcome of cranial vault remodeling in affected patients can be studied, and additional distinct features of Muenke syndrome can now be investigated. This study was undertaken to assess craniofacial growth and long-term functional outcome in patients with Muenke-type craniosynostosis.

METHODS

A chart review of all FGFR3 patients at The Children's Hospital of Philadelphia who had undergone cranial vault remodeling for unicoronal or bicoronal synostosis (n = 16) was performed. Need for reoperation, midface surgery, and functional corrections were assessed. Audiology and orthodontic records were reviewed.

RESULTS

All patients underwent cranial remodeling during infancy. Repeated intracranial surgery was performed or is currently scheduled for aesthetic reasons only (n = 7). Sexual dimorphism with male preponderance in FGFR3 unicoronal synostosis was detected. Despite dental crowding amenable to palatal expansion in patients with bicoronal synostosis, significant midface hypoplasia was not observed. Sensorineural hearing loss with a distinctive pattern was present in all patients who had undergone audiology testing.

CONCLUSIONS

Patients with FGFR3-associated craniosynostosis demonstrate a sexual dimorphism, with a male preponderance for unicoronal synostosis. A secondary major intracranial procedure is required for recurrent supraorbital retrusion in at least 43 percent of patients. A secondary or tertiary extracranial forehead contouring procedure should be anticipated in nearly all patients. No patient required any midface correctional procedure. These patients demonstrate characteristic bilateral, symmetric, low- to mid-frequency sensorineural hearing loss.

TGF-beta1, FGF-2, and receptor mRNA expression in suture mesenchyme and dura versus underlying brain in fusing and nonfusing mouse cranial sutures

Recent studies have supported a functional role for the transforming growth factor beta-1 (TGF-beta1) and fibro-blast growth factor 2 (FGF-2) signaling cascades in the process of mouse cranial suture fusion. TGF-beta1 and FGF-2 protein expression have been shown to be elevated in the fusing posterior frontal suture versus the nonfusing sagittal suture. The authors evaluated simultaneous mRNA expression of TGF-beta1 and its R1 receptor and FGF-2 and its R2 receptor during mouse cranial suture fusion. They evaluated the suture mesenchyme-dura complex separately from the underlying brain to determine whether there is tissue-specific biologic activity (i.e., brain versus suture mesenchyme-dura) for each cytokine and receptor. Data were collected from 150 male CD-1 mice studied over five time periods from postnatal days 22 to 45. They utilized reverse-transcriptase polymerase chain reaction as a means to detect TGF-beta1, TGF-beta receptor 1 (TGF-betaR1), FGF-2, and FGF receptor 2 (FGFR2) mRNA expression in mouse cranial tissues, beginning with the period of initiation of posterior frontal cranial suture fusion (postnatal day 22) and extending through completion of posterior frontal suture fusion (postnatal day 45). Expression of FGF-2 was significantly greater in posterior frontal suture mesenchyme and dura compared with sagittal suture mesenchyme and dura during the period of initiation of posterior frontal suture fusion, localizing this cytokine's expression to posterior frontal suture mesenchyme and dura during the process of cranial suture fusion. TGF-beta1 and FGFR2 mRNA expression was found to be up-regulated in posterior frontal suture mesenchyme and dura relative to the underlying brain tissue throughout the study period, whereas TGF-betaR1 and FGF-2 mRNA expression was significantly elevated relative to the underlying brain only at time points corresponding to the initiation of posterior frontal suture fusion (between postnatal days 22 and 31). These results indicate that there is tissue-specific mRNA expression of TGF-beta1, FGF-2, and their receptors between suture mesenchyme and dura and the underlying brain, which correlates with the period of posterior frontal suture fusion in the mouse model. Differences in gene expression between suture mesenchyme and dura relative to the underlying brain may be an important regulator of cranial suture biology. Understanding these differences may eventually help to identify possible targets and time windows by which to most effectively modulate cranial suture fusion.

Frog decline, frog malformations, and a comparison of frog and human health

The decline in frog populations and the increase in the frequency of frog malformations are discussed. Topics considered for analysis include chytridiomycosis, retinoids, UV-B radiation, chemical contaminants, environmental threats, introduced invasive species and predation, unsustainable use, and enigmatic decline. Care must be taken to distinguish between hypotheses, laboratory experiments, and the findings in feral frog populations. Clearly, the causes of population decline and malformations are heterogeneous. The subject of frogs and humans is addressed under three subheadings: the importance of frogs to human societies, medical implications of frog studies, and a comparison of frog and human disease factors.