Weill Cornell Researchers Report Development and Use of New Mouse Model That Could Show the Way to New Treatments and Prevention Strategies for Cleft Lip and Cleft Palate in Humans
Scientists at Weill Cornell Medical College used genetic methods to successfully repair cleft lips in mice embryos specially engineered for the study of cleft lip and cleft palate. The research breakthrough may show the way to prevent or treat the conditions in humans.
Cleft lip and cleft palate are among the most common birth defects, with treatment requiring multiple cycles of surgery, speech therapy and orthodontics. To date, there have been very few pre-clinical methods that allow researchers to study the molecular causes of these malformations. In particular, there has been a lack of animal models that accurately reflect the contribution of multiple genes to these congenital deformities in humans.
In a report in a recent issue of the journal Developmental Cell, Dr. Licia Selleri, associate professor of cell and developmental biology at Weill Cornell Medical College, and her co-authors report the first multigenic mouse model of cleft lip with or without cleft palate. The researchers uncovered the role of genes for (Pre-B Cell Leukemia Transcription Factor) proteins in coordinating cellular signaling behaviors crucial for the development of these abnormalities.
Dr. Selleri has studied Pbx proteins for many years and has previously demonstrated their involvement in organ and skeletal development. In her latest study, she and her collaborators, including postdoctoral fellows Drs. Elisabetta Ferretti and Bingsi Li, tested whether these proteins also play a role in facial development by using mutant mice that lacked various combinations of three Pbx genes in the ectoderm, the embryonic cell layer that gives rise to the lip and nose.
The researchers found that only mutations affecting multiple Pbx genes resulted in complete cleft lip, with or without cleft palate, in all of the mouse embryos with these compound mutations. This finding differs from those of previous studies using other mammal models of these conditions, in which a mutation in a single gene produced defects in only some of the animals, Dr. Selleri says. “The role of Pbx genes in the development of the shape of the face is a new and surprising finding“, she adds.
Moreover, the mouse embryos with multiple Pbx mutations also had reduced or absent Wnt activity, which plays a prominent role in embryo development, within the ectoderm. Dr. Ferretti, the first author of this study, found that Pbx genes regulate a chain of signaling molecules implicated in cleft lip with or without cleft palate, including Wnt, fibroblast growth factors (FGFs), p63, and interferon regulatory factor 6 (Irf6) — signaling pathways that exist across mammal species.
When Dr. Li, the second author of this study, used genetic methods to restore Wnt activity in the ectoderm of mouse embryos with compound Pbx mutations, the cleft lips in all of these animals completely disappeared. “To my knowledge, this is the first time that anyone has corrected this defect in embryos, and we really show here that Wnt is a critical factor,” Dr. Selleri says. “This is a very provocative result because it opens a completely new avenue of strategies for tissue repair.”
The research was supported by a Marie Curie Fellowship, the Medical Research Council in the U.K., the Royal Society, King’s College London, March of Dimes and Birth Defects Foundation, the National Institutes of Health, the Cleft Palate Foundation, and the Alice Bohmfalk Trust.