Loss of Tbx3 in Mouse Eye Causes Retinal Angiogenesis Defects Reminiscent of Human Disease.

Purpose: Familial exudative vitreoretinopathy (FEVR) and Norrie disease are examples of genetic disorders in which the retinal vasculature fails to fully form (hypovascular), leading to congenital blindness. While studying the role of a factor expressed during retinal development, T-box factor Tbx3, we discovered that optic cup loss of Tbx3 caused the retina to become hypovascular. The purpose of this study was to characterize how loss of Tbx3 affects retinal vasculature formation. Methods: Conditional removal of Tbx3 from both retinal progenitors and astrocytes was done using the optic cup-Cre recombinase driver BAC-Dkk3-Cre and was analyzed using standard immunohistochemical techniques. Results: With Tbx3 loss, the retinas were hypovascular, as seen in patients with retinopathy of prematurity (ROP) and FEVR. Retinal vasculature failed to form the stereotypic tri-layered plexus in the dorsal-temporal region. Astrocyte precursors were reduced in number and failed to form a lattice at the dorsal-temporal edge. We next examined retinal ganglion cells, as they have been shown to play a critical role in retinal angiogenesis. We found that melanopsin expression and Islet1/2-positive retinal ganglion cells were reduced in the dorsal half of the retina. In previous studies, the loss of melanopsin has been linked to hyaloid vessel persistence, which we also observed in the Tbx3 conditional knockout (cKO) retinas, as well as in infants with ROP or FEVR. Conclusions: To the best of our knowledge, these studies are the first demonstration that Tbx3 is required for normal mammalian eye formation. Together, the results provide a potential genetic model for retinal hypovascular diseases.

Use of Cre-adenovirus and CAR transgenic mice for efficient deletion of genes in post-thymic T cells.

Conditional gene deletion using lineage-specific transgenic expression of Cre has been useful for defining the role of specific gene products in mice in vivo. However, this technology has had limitations for studies of peripheral T cell biology, since the T-lineage promoters commonly used are active early in thymic development. As such, T cell development can be altered by the resulting genetic alterations, thus limiting the interpretation of the data in post-thymic T cell studies. Thus, new strategies are needed to delete targeted genes directly in peripheral T lymphocytes. The availability of transgenic mice expressing the CAR in the T cell compartment enabled testing of Cre-mediated recombination using an adenoviral vector in naïve peripheral T cells in vitro, even without cellular activation. Using Rosa26R reporterxCAR transgenic mice, we describe conditions by which Cre-mediated deletion of targeted genes can be achieved with primary T cells in vitro. These cells can also be adoptively transferred into defined recipient mice for study in vivo. We use conditional PTEN-deficient mice as proof of concept to confirm the value of this technique for deleting a negative regulator of T cell activation. This technology should be broadly applicable for studies of T cell-specific gene deletion to gain understanding of function in the post-thymic T cell compartment.

Echocardiographic diagnosis of clinically silent congenital coronary artery anomalies.

BACKGROUND: The incidence of congenital coronary anomalies is mainly derived from autopsy series and pre-participation exams in athletes. Limited data exist regarding the spectrum of coronary anomalies that can be detected in asymptomatic patients. We sought to describe echocardiographically detected congenital coronary artery anomalies in asymptomatic children after implementing a screening protocol mandating identification of coronary artery origin and proximal course in all initial studies. METHODS: Our database was searched from 1/1/1993 to 3/31/2006 and all echocardiograms coded for coronary anomalies were identified. Clinically "silent" congenital coronary anomalies were culled from that group. RESULTS: Of the 168 "silent" coronary anomalies detected, 111 were anomalies of aortic origin, including 59 patients with "high coronary takeoff" and 30 patients with "wrong sinus" origin of either the left or right coronary artery. Small coronary fistulas were seen in 57. Associated congenital heart defects were found in 53% of individuals with coronary anomalies. CONCLUSIONS: This study comprises the largest group of echocardiographically detected, "silent" but potentially clinically significant, congenital coronary anomalies in children. Prospective echocardiographic diagnosis of "high coronary takeoff", a risk factor for injury during cardio-pulmonary bypass, and asymptomatic intraseptal coronary stenosis are described for the first time.