Gene Expression Patterns 7 (2007) 381–388 www.elsevier.com/locate/modgep 1567-133X/$ - see front matter  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.modgep.2006.12.001 Spatiotemporal distribution of Fras1/Frem proteins during mouse embryonic development Rena Chiotaki a , Petros Petrou a,1 , Elsa Giakoumaki a , Evangelos Pavlakis a , Cassian Sitaru b , Georges Chalepakis a,¤ a Department of Biology, University of Crete, 71409 Heraklion, Crete, Greece b Department of Dermatology, University of Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany Received 25 September 2006; received in revised form 6 December 2006; accepted 10 December 2006 Available online 16 December 2006 Abstract The Fras1/Frem gene family encodes for structurally similar, developmentally regulated extracellular matrix proteins. Mutations in Fras1, Frem1 and Frem2 have been identiWed in diVerent classes of mouse bleb mutants, while defects in the human orthologs FRAS1 and FREM2 are causative for Fraser syndrome. The hallmark phenotypic feature of bleb mice is embryonic skin blistering due to dermal–epi- dermal detachment. The similarity of the phenotypic characteristics among the bleb mouse mutants, together with the fact that Fras1/ Frem proteins are co-localized in embryonic epithelial basement membranes, suggest that they operate in a common pathway. Here, we report for the Wrst time the immunoXuorescence pattern of Frem3 and provide a comparative analysis of the spatiotemporal localization of all Fras1/Frem proteins during mouse embryonic development. We demonstrate their overall co-localization in embryonic epithelial basement membranes, with emphasis on areas of phenotypic interest such as eyelids, limbs, kidneys, lungs and organs of the gastrointesti- nal tract and the central nervous system. We further studied collagen VII, impairment of which produces dystrophic epidermolysis bull- osa, a postnatal skin blistering disorder. We show that basement membrane levels of collagen VII rise at late embryonic life, concomitant with descending Fras1/Frem immunolabeling.  2006 Elsevier B.V. All rights reserved. Keywords: Fras1; Frem1; Frem2; Frem3; Collagen VII; Bleb mutants; Fraser syndrome; Mouse embryo; Development; Immunohistochemistry; Base- ment membrane 1. Results and discussion Fraser syndrome is a rare genetic disorder mainly char- acterized by cryptophthalmos, syndactyly and renal defects (Slavotinek and TiVt, 2002; McGregor et al., 2003; Smyth and Scambler, 2005). Analogous phenotypic mal- formations are featured by a group of Wve mouse mutants referred to as bleb mice, which represent the murine mod- els for the aforementioned disease (Winter, 1990; Darling and Gossler, 1994; Smyth and Scambler, 2005). Recently, the genes responsible for four out of the Wve bleb muta- tions have been identi Wed. These include Fras1 (Fraser syndrome protein 1), Frem1, Frem2 (Fras1-Related Extra- cellular Matrix proteins) and Grip1. Mutations in the above genes are causative for the blebbed (bl: McGregor et al., 2003; Vrontou et al., 2003), head-bleb (heb: Smyth et al., 2004), myelencephalic-bleb (my: Jadeja et al., 2005; Timmer et al., 2005) and eye-blebs (eb: Takamiya et al., 2004) phenotype in mouse, respectively. So far, mutations in Fraser syndrome patients have been identiWed only in FRAS1 and FREM2 (McGregor et al., 2003; Jadeja et al., 2005). Fras1/Frem genes encode for structurally related basement membrane proteins, whereas Grip1, a PDZ- domain cytoplasmic protein, interacts with Fras1 and Frem2 and targets them to the basolateral site of epithelia * Corresponding author. Tel.: +30 2810 394359; fax: +30 2810 394408. E-mail address: chalepak@imbb.forth.gr (G. Chalepakis). 1 Present address: Department of Biological Sciences, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.