We found that the high-pressure-synthesized material LiOsO 3 (see Supplementary Information) shows a structural transition at a temperature T s = 140 K. The room-temperature crystal structure of LiOsO 3 was initially examined using powder X-ray diffraction (XRD). The Goldschmidt diagram predicts that LiOsO 3 crystallizes into a LiNbO 3 -type structure 3,10 , and a preliminary refinement of the structure was carried out in the R-3c space group with Os at the 6b site 0,0,0 and O at the 18e siteTo investigate the position of the Li ion we turned to neutron diffraction, which is much more sensitive to Li than XRD. The neutron diffraction patterns collected above T s could be successfully described in the R-3c space group, in agreement with the XRD refinement, with the Li ion at the 6a position 0,0,1/4. Atomic absorption spectrometry (see Supplementary Information) indicated that the average Li mass was 2.77%, which corresponds to the composition Li 0.98 OsO 3 . We have used the stoichiometric composition throughout the structural analysis. The refinement indicated highly anisotropic thermal displacements of the Li ions with considerable extension along the c-axis (Table 1 and Fig. 1), which might indicate that the Li ions are distributed equally among equivalent 12c sites 0,0,z and 0,0,1/2-z either side of the oxygen layer at z = 1/4, as reported for LiNbO 3 and LiTaO 3 (refs 3, 11).The thermal variation of the structure of LiOsO 3 was studied by neutron diffraction for temperatures between 10 and 300 K. Figure 1a-d shows structural data obtained from refinements in the R-3c space group. The lattice parameters ( Fig. 1a) decrease uniformly from 300 K until T s = 140 K, below which the parameter c increases and a decreases with only a small variation in the unit-cell volume. Just below T s , the non-symmetry-breaking strain components e xx + e yy and e zz vary almost linearly (Fig. 1b). These 4 results show that the phase transition is continuous and the strain components behave like a secondary order parameter coupled to a primary one via a linear-quadratic free energy invariant 12 . The primary order parameter must necessarily be symmetry-breaking according to Landau's theory of second-order phase transitions 12 . Furthermore, the anisotropic thermal parameter  33 , which describes Li displacements along the c-axis, increases markedly below T s (Fig. 1c). This indicates that the primary structural instability involves the position of the Li ions along the c-axis (Fig. 1d).Given that the phase transition involves a change in symmetry, we find from representation theory 13 that there are three isotropy subgroups, R-3, R32 and R3c, which maintain the translational invariance of the R-3c space group and allow the transition to be continuous. These space groups were tested by refinement against the neutron diffraction data at 10 K. Note that R-3 and R32 should generate additional reflections below T s which were not observed in the experiment. The refinement in the non-centrosymmetric R3c space group gave the best de...

Mutations in SALL4, the human homolog of the Drosophila homeotic gene spalt (sal), cause the autosomal dominant disorder known as Okihiro syndrome. In this study, we show that a targeted null mutation in the mouse Sall4 gene leads to lethality during peri-implantation. Growth of the inner cell mass from the knockout blastocysts was reduced, and Sall4-null embryonic stem (ES) cells proliferated poorly with no aberrant differentiation. Furthermore, we demonstrated that anorectal and heart anomalies in Okihiro syndrome are caused by Sall4 haploinsufficiency and that Sall4/Sall1 heterozygotes exhibited an increased incidence of anorectal and heart anomalies, exencephaly and kidney agenesis. Sall4 and Sall1 formed heterodimers, and a truncated Sall1 caused mislocalization of Sall4 in the heterochromatin; thus, some symptoms of Townes-Brocks syndrome caused by SALL1 truncations could result from SALL4 inhibition.

Methods for the site-specific incorporation of extra components into nucleic acids can be powerful tools for creating DNA and RNA molecules with increased functionality. We present an unnatural base pair system in which DNA containing an unnatural base pair can be amplified and function as a template for the site-specific incorporation of base analog substrates into RNA via transcription. The unnatural base pair is formed by specific hydrophobic shape complementation between the bases, but lacks hydrogen bonding interactions. In replication, this unnatural base pair exhibits high selectivity in combination with the usual triphosphates and modified triphosphates, gamma-amidotriphosphates, as substrates of 3' to 5' exonuclease-proficient DNA polymerases, allowing PCR amplification. In transcription, the unnatural base pair complementarity mediates the incorporation of these base substrates and their analogs, such as a biotinylated substrate, into RNA by T7 RNA polymerase (RNAP). With this system, functional components can be site-specifically incorporated into a large RNA molecule.

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