Microarray expression profiling of tissues from mice with uniparental duplications of chromosomes 7 and 11 to identify imprinted genes.

Microarray analysis allows the screening of thousands of identifiable genes in a single experiment. The challenge of this approach is to combine the new technology with established genetic tools to associate genes with specific biological function. In this study we have designed a screen to identify imprinted genes from mice with uniparental duplications of proximal Chromosomes (Chrs) 7 and 11, using microarray analysis. By comparing the expression patterns in embryonic and newborn tissues of maternally versus paternally inherited proximal Chrs 7 and 11, we have correctly identified four out of five known imprinted genes represented on a microarray. We have additionally identified two novel imprinted candidate genes as well as a differentially expressed clone that is a potential downstream target. Interpretation of the microarray data requires careful preparation of age- and strain-matched samples and attention to detail in tissue dissection technique.

The expression of Jagged1 in the developing mammalian heart correlates with cardiovascular disease in Alagille syndrome.

The establishment of the cardiovascular system represents an early, critical event essential for normal embryonic development, and defects in cardiovascular development are a frequent cause of both in utero and neonatal demise. Congenital cardio-vascular malformations, the most frequent birth defect, can occur as isolated events, but are frequently presented clinically within the context of a constellation of defects that involve multiple organs and that define a specific syndrome. In addition, defects can be a primary effect of gene mutations or result from secondary effects of altered cardiac physiology. Alagille syndrome (AGS) is an autosomal dominant disorder characterized by developmental abnormalities of the heart, liver, eye, skeleton and kidney. Congenital heart defects, the majority of which affect the right-sided or pulmonary circulation, contribute significantly to mortality in AGS patients. Recently, mutations in Jagged1 ( JAG1 ), a conserved gene of the Notch intercellular signaling pathway, have been found to cause AGS. In order to begin to delineate the role of JAG1 in normal heart development we have studied the expression pattern of JAG1 in both the murine and human embryonic heart and vascular system. Here, we demonstrate that JAG1 is expressed in the developing heart and multiple associated vascular structures in a pattern that correlates with the congenital cardiovascular defects observed in AGS. These data are consistent with an important role for JAG1 and Notch signaling in early mammalian cardiac development.