Expression patterns of the Tmem16 gene family during cephalic development in the mouse

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Abstract

Tmem16a, Tmem16c, Tmem16f, Tmem16h and Tmem16k belong to the newly identified Tmem16 gene family encoding eight-pass transmembrane proteins. We have analyzed the expression patterns of these genes during mouse cephalic development. In the central nervous system, Tmem16a transcripts were abundant in the ventricular neuroepithelium, whereas the other Tmem16 family members were readily detectable in the subventricular zone and differentiating fields. In the rostral spinal cord, Tmem16f expression was highest in the motor neuron area. In the developing eye, the highest amounts of Tmem16a transcripts were detected in the lens epithelium, hyaloid plexus and outer layer of the retina, while the other family members were abundant in the retinal ganglionic cell layer. Interestingly, throughout development, Tmem16a expression in the inner ear was robust and restricted to a subset of cells within the epithelium, which at later stages formed the organ of Corti. The stria vascularis was particularly rich in Tmem16a and Tmem16f mRNA. Other sites of Tmem16 expression included cranial nerve and dorsal root ganglia, meningeal precursors and the pituitary. Tmem16c and Tmem16f transcripts were also patent in the submandibular autonomic ganglia. A conspicuous feature of Tmem16a was its expression along the walls of blood vessels as well as in cells surrounding the trigeminal and olfactory nerve axons. In organs developing through epithelial–mesenchymal interactions, such as the palate, tooth and tongue, the above five Tmem16 family members showed interesting dynamic expression patterns as development proceeded. Finally and remarkably, osteoblasts and chondrocytes were particularly loaded with Tmem16a, Tmem16c and Tmem16f transcripts.

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Results and discussion

The Tmem16 genes constitute a large, highly conserved family found in all eukaryotes. The number of homologues in a given species seems to increase in relation to evolutionary complexity (Galindo and Vacquier, 2005). In humans and mice, 10 family members have been identified: TMEM16A/Tmem16a through TMEM16H/Tmem16h and TP53I5/Tp53i5 (Katoh and Katoh, 2004a, Katoh and Katoh, 2004b, Katoh and Katoh, 2004c, Katoh and Katoh, 2005, Galindo and Vacquier, 2005) as well as TMEM16K/Tmem16k (Rock et al.,

Experimental procedures

Mouse embryos were collected from time-mated pregnant females. Noon of the day of evidence of a vaginal plug was considered as embryonic day 0.5 (E0.5). Embryos and heads from fetuses and postnatal mice were fixed in 4% paraformaldehyde in PBS and processed for paraffin embedding. Sections were hybridized with 35S-UTP-labelled riboprobes as previously described (Angerer and Angerer, 1992). The probes were as follows: The Tmem16a antisense probe was generated as previously described (Rock et al,

Acknowledgments

This study was supported by the Swedish Research Council-Medicine (Grants 2789, 4567 and 15181), the Thuréus and the Åke Wiberg Foundations, and the Institute of Odontology to A.G.L and A.L. B.D.H. was supported with start-up funds from the University of Florida College of Medicine.

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