Sleeping giants: emerging roles for the fat cadherins in health and disease

The vertebrate Fat cadherins comprise a small gene family of four members, Fat1-Fat4, all closely related in structure to Drosophila ft and ft2. Over the past decade, knock-out mouse studies, genetic manipulation, and large sequencing projects has aided our understanding of the function of vertebrate Fat cadherins in tissue development and disease. The majority of studies of this family have focused on Fat1, with evidence now showing it can bind enable (ENA)/Vasodilator-stimulated phosphoprotein (VASP), β-catenin and Atrophin proteins to influence cell polarity and motility; HOMER-1 and HOMER-3 proteins to regulate actin accumulation in neuronal synapses; and scribble to influence the Hippo signaling pathway. Fat2 and Fat3 can regulate cell migration in a tissue specific manner and Fat4 appears to influence both planar cell polarity and Hippo signaling recapitulating the activity of Drosophila ft. Knowledge about the exact downstream signaling pathways activated by each family member remains in its infancy, but it is becoming clearer that they have tissue specific and redundant roles in development and may be lost or gained in cancer. In this review, we summarize the recent progress on understanding the role of the Fat cadherin family, integrating the current knowledge of molecular interactions and tissue distributions, together with the accumulating evidence of their changed expression in human disease. The latter is now beginning to promote interest in these molecules as both biomarkers and new targets for therapeutic intervention.

Narrowing and genomic annotation of the commonly deleted region of the 5q- syndrome

The 5q- syndrome is the most distinct of the myelodysplastic syndromes, and the molecular basis for this disorder remains unknown. We describe the narrowing of the common deleted region (CDR) of the 5q- syndrome to the approximately 1.5-megabases interval at 5q32 flanked by D5S413 and the GLRA1 gene. The Ensembl gene prediction program has been used for the complete genomic annotation of the CDR. The CDR is gene rich and contains 24 known genes and 16 novel (predicted) genes. Of 40 genes in the CDR, 33 are expressed in CD34(+) cells and, therefore, represent candidate genes since they are expressed within the hematopoietic stem/progenitor cell compartment. A number of the genes assigned to the CDR represent good candidates for the 5q- syndrome, including MEGF1, G3BP, and several of the novel gene predictions. These data now afford a comprehensive mutational/expression analysis of all candidate genes assigned to the CDR.