Development of S100B knockout embryos following inhibition of S100A1 protein expression

Abstract

S100A1 and S100B, members of the EF‐hand family of Ca2+‐binding proteins, exist in cells as homo‐ or hetero‐dimers. Our studies on mouse embryos showed that these two proteins shared some common expression sites including skeletal tissues, dorsal root ganglia, trigeminal ganglia and the hindbrain. However, neither S100A1 nor S100B knockout mice exhibit overt structural abnormalities. In the present study, we had examined the development of mouse embryos in which expression of both proteins was inhibited. Small interfering RNAs targeting specific sequences of S100A1 mRNA were microinjected into S100B knockout embryos in utero at E13.5 when S100A1 protein had just started its expression. Two days after microinjection, S100A1 expression was examined by reverse transcription‐PCR and immunohistochemical localization and structural changes determined after serial sectioning. A decrease of S100A1 expression and absence of S100B protein were observed, but no morphological anomalies were found in S100B knockout embryos with a reduction of S100A1 expression. Our observations support the notion that both S100A1 and S100B proteins are not indispensible for embryonic development.The work was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project no. CUHK4421/05M) and a Direct Grant from the Faculty of Medicine, CUHK (Project Ref 2007.1.006, ID 2041322).