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Teneurin‐2 is expressed in tissues that regulate limb and somite pattern formation and is induced in vitro and in situ by FGF8

Teneurin‐2 is a member of a novel family of transmembrane proteins characterized to date in fish, birds, mammals, and Drosophila (e.g., the pair‐rule gene product Ten‐m). We have shown that teneurin‐2 is expressed by neurons in the developing avian visual system in a pattern complementary to the expression of teneurin‐1 and that recombinant teneurin‐2 induces morphologic changes in neuronal cells in culture (Rubin et al., 1999 ). Here we have used cRNA probes to two newly identified splice variants and a teneurin‐2‐specific antibody to determine whether teneurin‐2 is also expressed outside the nervous system. Both reverse transcriptase‐polymerase chain reaction and in situ hybridization indicate that the three splice variants known so far are coexpressed at sites of pattern formation during development. Teneurin‐2 mRNAs and protein are found in the developing limbs, somites, and craniofacial mesenchyme. In addition to expression of teneurin‐2 by the apical ectodermal ridge, teneurin‐2 transcripts also appear transiently at sites of tendon development. Teneurin‐2 expression patterns were strikingly similar to those of fibroblast growth factor 8 (FGF8). In agreement with the overlapping expression pattern, FGF8‐coated beads implanted into chicken limb buds induced the ectopic expression of teneurin‐2 and soluble FGF8 induced teneurin‐2 in limb explant cultures. Thus, teneurin‐2 could act downstream of FGF8 during morphogenesis. © 2001 Wiley‐Liss, Inc.