Generation of mice carrying a knockout-first and conditional-ready allele of transforming growth factor beta2 gene

Transforming growth factor beta2 (TGFβ2) is a multifunctional protein which is expressed in several embryonic and adult organs. TGFB2 mutations can cause Loeys Dietz syndrome, and its dysregulation is involved in cardiovascular, skeletal, ocular, and neuromuscular diseases, osteoarthritis, tissue fibrosis, and various forms of cancer. TGFβ2 is involved in cell growth, apoptosis, cell migration, cell differentiation, cell-matrix remodeling, epithelial-mesenchymal transition, and wound healing in a highly context-dependent and tissue-specific manner. Tgfb2(-/-) mice die perinatally from congenital heart disease, precluding functional studies in adults. Here, we have generated mice harboring Tgfb2(βgeo) (knockout-first lacZ-tagged insertion) gene-trap allele and Tgfb2(flox) conditional allele. Tgfb2(βgeo/βgeo) or Tgfb2(βgeo/-) mice died at perinatal stage from the same congenital heart defects as Tgfb2(-/-) mice. β-galactosidase staining successfully detected Tgfb2 expression in the heterozygous Tgfb2(βgeo) fetal tissue sections. Tgfb2(flox) mice were produced by crossing the Tgfb2(+/βgeo) mice with the FLPeR mice. Tgfb2(flox/-) mice were viable. Tgfb2 conditional knockout (Tgfb2(cko/-) ) fetuses were generated by crossing of Tgfb2(flox/-) mice with Tgfb2(+/-) ; EIIaCre mice. Systemic Tgfb2(cko/-) embryos developed cardiac defects which resembled the Tgfb2(βgeo/βgeo) , Tgfb2(βgeo/-) , and Tgfb2(-/-) fetuses. In conclusion, Tgfb2(βgeo) and Tgfb2(flox) mice are novel mouse strains which will be useful for investigating the tissue specific expression and function of TGFβ2 in embryonic development, adult organs, and disease pathogenesis and cancer. genesi

Role of Transforming Growth Factor Beta2 in Congenital Heart Disease

poster abstractCongenital heart disease (CHD) represents the largest class of birth defects in the US and affects about 0.8% of all babies born. As a result of remarkable advances in the medical and surgical management of CHD, more than 75% of children born with CHD now live into adulthood. As such, discovery of the causes for CHD is not only a fundamental research endeavor, but is vital to the health care of this growing community. Inherited genetic mutations in Transforming Growth Factor Beta (TGFB) gene are found in the patients of Loeys-Dietz syndrome. Several cardiac (endocardial, myocardial) and extra-cardiac (second heart field, neural crest) cell lineages that express Tgfb2 contribute to heart development. To study the role of Tgfb2 in different cell types involved in heart development, we have generated Tgfb2 conditional knockout mice. These mice harbor Tgfb2 LacZ-tagged conditional-ready allele (also called tm1a). By using long range PCR (LR-PCR) we have confirmed the germline transmission of Tgfb2tm1a allele. Histological examination shows that Tgfb2tm1a/tm1a embryos develop several congenital heart defects. This indicates that Tgfb2tm1a allele is a knockout-first allele, which is consistent with the original design of our conditional gene targeting scheme. Next, by crossing to Flp recombinase mice we can generate mice with a Tgfb2 conditional-ready allele (also called tm1c). The presence of Tgfb2tm1c allele in the mice is confirmed by genomic PCR. In the future, we plan to use Tgfb2tm1c mice to conditionally delete Tgfb2 in different cardiac or extra-cardiac cell types using well-characterized Cre recombinase transgenic mice. Collectively, we have produced, generated, and validated mice harboring the Tgfb2 LacZ tagged knockout-first and conditional-ready allele. Our results from embryos carrying homozygous Tgfb2tm1a allele indicate that TGFβ2 is required for heart development. Future research will be crucial in expanding knowledge of the unknown cellular etiology of cardiac malformations in patients with TGFB2 mutations

Mandibular and Neural Crest Cell Deficits Seen in TsDn65 Down Syndrome Mouse Model Rescued By Green Tea Polyphenol, EGCG

poster abstractDown Syndrome (DS) is caused by trisomy of the human chromosome 21 (Hsa21) and occurs in ~1 of every 700 births. DS is distinguished by over 80 phenotypic abnormalities including skeletal deficits and craniofacial phenotypes characterized by a flattened skull, slanted eyes, and a smaller mandible. To study these abnormalities, we utilize the Ts65Dn DS mouse model containing a triplication of approximately half of the gene homologues found on Hsa21 and mirrors the skeletal and mandibular phenotypes observed in DS. In Ts65Dn mice, the origin of the mandibular deficits were traced to a reduction in size of the 1st branchial arch (BA1), the developmental precursor to the mandible, occurring at embryonic day 9.5 (E9.5). At E9.5, we observe a lack of proliferation and migration of neural crest cells (NCC) from the neural tube (NT) into the BA1, causing a reduced BA1. We hypothesize that an overexpression of Dyrk1a, a Hsa21 homologue, contributes to the mandibular deficit seen in E9.5 Ts65Dn embryos. We propose that EGCG, a green tea polyphenol, will inhibit DYRK1a activity, rescuing the BA1 deficit. To test our hypothesis, Ts65Dn mothers were treated with EGCG from E0-E9.5 and sacrificed to retrieve the E9.5 embryos. Our results from unbiased stereological assessments show that E0-E9.5 EGCG in vivo treatment has the potential to increase NCC number, BA1 volume, and embryo volume of trisomic embryos. This data provide preclinical testing for a potential therapy of DS craniofacial disorders, which may extend to treating bone deficits in DS and osteoporosis

Treatment with a Green Tea Polyphenol Corrects Craniofacial Deficits Associated with Down Syndrome

poster abstractDown syndrome (DS) is caused by trisomy of human chromosome 21 (HSA21). Individuals with DS present craniofacial abnormalities including an undersized, dismorphic mandible leading to difficulty with eating, breathing, and swallowing. Using the Ts65Dn DS mouse model (three copies of ~50% HSA21 homologs), we have traced the mandibular deficit to a neural crest cell (NCC) deficiency and reduction in first pharyngeal arch (PA1 or mandibular precursor) size at embryonic day 9.5. At E9.5, Dyrk1A, a triplicated DS candidate gene, is overexpressed and may cause the NCC and PA1 deficits. We hypothesize that treatment of pregnant Ts65Dn mothers with Epigallocatechin gallate (EGCG), a known Dyrk1A inhibitor, will correct NCC deficits and rescue the undersized PA1 in trisomic E9.5 embryos. To test our hypothesis, we treated pregnant Ts65Dn mothers with EGCG from either E7-E8 or E0-E9.5. Our preliminary study found an increase in PA1 volume and NCC number in trisomic E9.5 embryos after treatment, but observed differences between treatment regimens. Differential gene expression was also quantified in trisomic treated embryos. This preliminary data suggests EGCG treatment has the potential to rescue the mandibular phenotype caused by trisomy. These findings provide preclinical testing for a potential therapy for craniofacial disorders linked to DS