Dorsal-ventral limb patterning in vertebrates is thought to be controlled by the LIM-homeodomain protein Lmx1b which is expressed in a spatially and temporally restricted manner along the dorsal-ventral limb axis. Here we describe the phenotype resulting from targeted disruption of Lmx1b. Our results demonstrate that Lmx1b is essential for the specification of dorsal limb fates at both the zeugopodal and autopodal level with prominent phenotypes including an absence of nails and patellae. These features are similar to those present in a dominantly inherited human condition called nail patella syndrome (NPS), which also has renal involvement. Mouse Lmx1b maps to a region syntenic to that of the NPS gene, and kidneys of Lmx1b mutant mice exhibit pathological changes similar to that observed in NPS (refs 5,6). Our results demonstrate an essential function for Lmx1b in mouse limb and kidney development and suggest that NPS might result from mutations in the human LMX1B gene.

We identified the LIM homeodomain transcription factor Lmx1b in the mesencephalic dopamine (mesDA) systems of embryos and adults. Analysis of spatiotemporal expression in Lmx1b null mutants and wild-type mice implicated a cascade involving Lmx1b in the early development of mesDA neurons. Although disruption of this cascade did not block induction of tyrosine hydroxylase (TH), a key enzyme in DA synthesis, or Nurr1, a nuclear hormone receptor, Lmx1b knockout mice failed to induce the mesDA-specific homeodomain gene Ptx3 in TH-positive neurons. Eventually, this small set of TH-positive neurons was lost during embryonic maturation. The data suggest that at least two molecular cascades operate during the specification of the mesDA system, one specifying neurotransmitter phenotype and another essential for other aspects of mesDA neuron differentiation.

Cancer-associated mesenchymal stem cells (MSCs) play a pivotal role in modulating tumor progression. However, the interactions between liver cancer-associated MSCs (LC-MSCs) and hepatocellular carcinoma (HCC) remain unreported. Here, we identified the presence of MSCs in HCC tissues. We also showed that LC-MSCs significantly enhanced tumor growth in vivo and promoted tumor sphere formation in vitro. LC-MSCs also promoted HCC metastasis in an orthotopic liver transplantation model. Complementary DNA (cDNA) microarray analysis showed that S100A4 expression was significantly higher in LC-MSCs compared with liver normal MSCs (LN-MSCs) from adjacent cancer-free tissues. Importantly, the inhibition of S100A4 led to a reduction of proliferation and invasion of HCC cells, while exogenous S100A4 expression in HCC cells resulted in heavier tumors and more metastasis sites. Our results indicate that S100A4 secreted from LC-MSCs can promote HCC cell proliferation and invasion. We then found the expression of oncogenic micro-RNA (miR)-155 in HCC cells was significantly up-regulated by coculture with LCMSCs and by S100A4 ectopic overexpression. The invasion-promoting effects of S100A4 were significantly attenuated by a miR-155 inhibitor. These results suggest that S100A4 exerts its effects through the regulation of miR-155 expression in HCC cells. We demonstrate that S100A4 secreted from LC-MSCs promotes the expression of miR-155, which mediates the down-regulation of suppressor of cytokine signaling 1, leading to the subsequent activation of STAT3 signaling. This promotes the expression of matrix metalloproteinases 9, which results in increased tumor invasiveness. Conclusion: S100A4 secreted from LC-MSCs is involved in the modulation of HCC progression, and may be a potential therapeutic target. (HEPATOLOGY 2013;57:2274-2286 T he tumor microenvironment plays an important role in modulating cancer and cancer stem cell progression. 1,2 Recently, mesenchymal stem cells (MSCs), as a pivotal part of the tumor stroma, have attracted great attention for their ability to participate in tumor proliferation 3 and metastasis. 4 Although several lines of evidence demonstrate that MSCs can be activated by cancer cells and contribute to tumor progression, the Abbreviations:: cDNA, complementary DNA; ELISA, enzyme-linked immunosorbent assay; HCC, hepatocellular carcinoma; IHC, immunohistochemistry; LCMSCs, liver cancer-associated MSCs; LN-MSCs, liver normal MSCs; miRNA, microRNA; miR-155, microRNA-155; MMP9, matrix metalloproteinases 9; MSCs, mesenchymal stem cells; qRT-PCR, quantitative real time polymerase chain reaction; siRNA, small interfering RNA; SOCS1, suppressor of cytokine signaling 1; STAT, signal transducer and activator of transcription.From the

Secreted factors FGF8 and WNT1 are essential either for the inductive activity of the isthmus organizer or for the regionalization of the midbrain-hindbrain boundary (MHB). However, transcriptional regulation of these secreted factors during development remains to be elucidated. Here we show that the LIM homeobox gene Lmx1b is expressed in the anterior embryo as early as E7.5 and its expression becomes progressively restricted to the isthmus at E9.0. Analysis of gene expression in the MHB of the mutant embryos showed that many genes were lost by E9.5. In the MHB of Lmx1b -/-embryos, the expression of Fgf8, which normally occurs at the 4-somite stage, was completely absent, whereas Wnt1 was downregulated before the 4-somite stage. Moreover, transcription factors En1 and Pax2 were also downregulated prior to the 4-somite stage, whereas Gbx2 downregulation occurred at the 4-somite stage. By contrast, Otx2 and Pax6 expression was not affected in Lmx1b -/-embryos. The requirement of specific Lmx1b expression in the MHB was further confirmed by Wnt1-Cre-mediated region-specific conditional knockout of Lmx1b. As a result of these molecular defects, the development of the tectum and cerebellum was severely impaired in Lmx1b -/-mice. Taken together, our results indicate that Lmx1b plays an essential role in the development of the tectum and cerebellum by regulating expression of Fgf8, Wnt1 and several isthmus-related transcription factors in the MHB, and is a crucial component of a cross-regulatory network required for the induction activity of the isthmic organizer in the MHB.

Background Despite the prevalence and recurrence of polyploidization in the speciation of flowering plants, its impacts on crop intraspecific genome diversification are largely unknown. Brassica rapa is a mesopolyploid species that is domesticated into many subspecies with distinctive morphotypes. Results Herein, we report the consequences of the whole-genome triplication (WGT) on intraspecific diversification using a pan-genome analysis of 16 de novo assembled and two reported genomes. Among the genes that derive from WGT, 13.42% of polyploidy-derived genes accumulate more transposable elements and non-synonymous mutations than other genes during individual genome evolution. We denote such genes as being “flexible.” We construct the Brassica rapa ancestral genome and observe the continuing influence of the dominant subgenome on intraspecific diversification in B. rapa. The gene flexibility is biased to the more fractionated subgenomes (MFs), in contrast to the more intact gene content of the dominant LF (least fractionated) subgenome. Furthermore, polyploidy-derived flexible syntenic genes are implicated in the response to stimulus and the phytohormone auxin; this may reflect adaptation to the environment. Using an integrated graph-based genome, we investigate the structural variation (SV) landscapes in 524 B. rapa genomes. We observe that SVs track morphotype domestication. Four out of 266 candidate genes for Chinese cabbage domestication are speculated to be involved in the leafy head formation. Conclusions This pan-genome uncovers the possible contributions of allopolyploidization on intraspecific diversification and the possible and underexplored role of SVs in favorable trait domestication. Collectively, our work serves as a rich resource for genome-based B. rapa improvement.