Project description:Development of the complex structure of the vertebrate limb requires carefully orchestrated interactions between multiple regulatory pathways and proteins. Among these, precise regulation of 5’ Hox transcription factor expression is essential for proper limb bud patterning and development. Here, we identified Geminin (Gmnn) as a novel regulator of this process. A conditional model of Gmnn deficiency resulted in loss or severe reduction of forelimb skeletal elements, while both the forelimb autopod and hindlimb were unaffected. 5’ Hox gene expression expanded into more proximal and anterior regions of embryonic forelimb buds in this Gmnn-deficient model. A second conditional model of Gmnn deficiency instead caused a similar but less severe reduction of hindlimb skeletal elements and hindlimb polydactyly, while not affecting the forelimb. An ectopic posterior Shh signaling center was evident in the anterior hindlimb bud of Gmnn-deficient embryos in this model. This center ectopically expressed Hoxd13, the Hoxd13 target Shh, and the Shh target Ptch1, while these mutant hindlimb buds also had reduced levels of the cleaved, repressor form of Gli3, a Shh pathway antagonist. Together, this work delineates a new role for Gmnn in modulating Hox expression to pattern the vertebrate limb.
Project description:Vertebrate appendage patterning is programmed by Hox-TALE factors-bound regulatory elements. However, it remains enigmatic which cell lineages are commissioned by Hox-TALE factors to generate regional specific pattern and whether other Hox-TALE co-factors exist. In this study, we investigated the transcriptional mechanisms controlled by the Shox2 transcriptional regulator in limb patterning. Harnessing an osteogenic lineage-specific Shox2 inactivation approach we show that despite widespread Shox2 expression in multiple cell lineages, lack of the stylopod observed upon Shox2 deficiency is a specific result of Shox2 loss of function in the osteogenic lineage. ChIP-Seq revealed robust interaction of Shox2 with cis-regulatory enhancers clustering around skeletogenic genes that are also bound by Hox-TALE factors, supporting a lineage autonomous function of Shox2 in osteogenic lineage fate determination and skeleton patterning. Pbx ChIP-Seq further allowed the genome-wide identification of cis-regulatory modules exhibiting co-occupancy of Pbx, Meis, and Shox2 transcriptional regulators. Integrative analysis of ChIP-Seq and RNA-Seq data and transgenic enhancer assays indicate that Shox2 patterns the stylopod as a repressor via interaction with enhancers active in the proximal limb mesenchyme and antagonizes the repressive function of TALE factors in osteogenesis. RNA sequencing profiling the transcriptome of Shox2+ in the developing limb
Project description:Vertebrate appendage patterning is programmed by Hox-TALE factors-bound regulatory elements. However, it remains enigmatic which cell lineages are commissioned by Hox-TALE factors to generate regional specific pattern and whether other Hox-TALE co-factors exist. In this study, we investigated the transcriptional mechanisms controlled by the Shox2 transcriptional regulator in limb patterning. Harnessing an osteogenic lineage-specific Shox2 inactivation approach we show that despite widespread Shox2 expression in multiple cell lineages, lack of the stylopod observed upon Shox2 deficiency is a specific result of Shox2 loss of function in the osteogenic lineage. ChIP-Seq revealed robust interaction of Shox2 with cis-regulatory enhancers clustering around skeletogenic genes that are also bound by Hox-TALE factors, supporting a lineage autonomous function of Shox2 in osteogenic lineage fate determination and skeleton patterning. Pbx ChIP-Seq further allowed the genome-wide identification of cis-regulatory modules exhibiting co-occupancy of Pbx, Meis, and Shox2 transcriptional regulators. Integrative analysis of ChIP-Seq and RNA-Seq data and transgenic enhancer assays indicate that Shox2 patterns the stylopod as a repressor via interaction with enhancers active in the proximal limb mesenchyme and antagonizes the repressive function of TALE factors in osteogenesis.
Project description:Diseases caused by mutations in components of the minor spliceosome frequently result in primordial dwarfism, where the limbs are stunted in size but retain pattern. We therefore sought to determine the role of the minor splieceosome in limb development by ablating an essential component, Rnu11, which encodes the U11 snRNA, in the mouse limb bud through Prrx1-Cre. We found that loss of U11 results in severe reduction in limb size at birth. However, mutant limbs retain proximo-distal patterning. Thus, we performed total RNAseq at E10.5 and E11.5 for both WT and mutant forelimb and hindlimb to determine the underlying molecular consequence of U11 loss and its effect on gene expression in the developing limb.
Project description:We used microarray technology to investigate the transcriptional consequences of loss of Gli3 from the anterior mesenchyme of the developing mouse limb bud at both E11.5 and E12.5. Comparisons were made between RNA derived from the anterior margin of Gli3Xt/Xt limb buds and that derived from wild type littermates Keywords: genetic modification
Project description:Transcriptomes of mouse embryonic autopods were generated detecting expression of approximately 26179 transcripts in the developing forelimb or hindlimb autopods, representing about 58 % of the probe sets on MOE-430 A/B GeneChip. Three biological replicate array experiments were finished for each condition and MAS5.0 signal were used to do data analysis. Forty-four transcripts with expression differences higher than 2-fold were detected(T test, P<0.05), including Tbx4, Tbx5, Hoxc10 and Pitx1 which were previously shown to be differentially expressed in developing forelimb and hindlimb bud by in situ hybridization and SAGE study (Margulies 2001). RTPCR and in situ experiments confirmed several top differentially expressed genes which were newly discovered by our experiments. Vast amount of transcripts and its family members such as Bmp, Fgf, Epha, Wnt, T-box and Hox families detected to be highly expressed or differentially expressed in developing autopods, suggesting that the complexity of transcriptomes of developing autopods and dynamic differential expression and differential combinations of gene expression signals in the developing limb tissue contributes to differences in forelimb versus hindlimb patterning. The differentially expressed genes are the essential factors for morphological diversification of developing limb structures. Keywords = microarray Keywords = mouse Keywords = autopod Keywords = limb Keywords = development Keywords = gene expression Keywords = transcriptome Keywords: repeat sample
Project description:The analysis of differentially expressed genes is a powerful approach to elucidate the genetic mechanisms underlying the morphological and evolutionary diversity among serially homologous structures, both within the same organism (e.g., hand vs. foot) and between different species (e.g., hand vs. wing). In the developing embryo, limb-specific expression of Pitx1, Tbx4, and Tbx5 regulates the determination of limb identity. However, numerous lines of evidence, including the fact that these three genes encode transcription factors, indicate that additional genes are involved in the Pitx1-Tbx hierarchy. To examine the molecular distinctions coded for by these factors, and to identify novel genes involved in the determination of limb identity, we have used Serial Analysis of Gene Expression (SAGE) to generate comprehensive gene expression profiles from intact, developing mouse forelimbs and hindlimbs. To minimize the extraction of erroneous SAGE tags from low-quality sequence data, we used a new algorithm to extract tags from -analyzed sequence data and obtained 68,406 and 68,450 SAGE tags from forelimb and hindlimb SAGE libraries, respectively. We also developed an improved method for determining the identity of SAGE tags that increases the specificity of and provides additional information about the confidence of the tag-UniGene cluster match. The most differentially expressed gene between our SAGE libraries was Pitx1. The differential expression of Tbx4, Tbx5, and several limb-specific Hox genes was also detected; however, their abundances in the SAGE libraries were low. Because numerous other tags were differentially expressed at this low level, we performed a 'virtual' subtraction with 362,344 tags from six additional nonlimb SAGE libraries to further refine this set of candidate genes. This subtraction reduced the number of candidate genes by 74%, yet preserved the previously identified regulators of limb identity. This study presents the gene expression complexity of the developing limb and identifies candidate genes involved in the regulation of limb identity. We propose that our computational tools and the overall strategy used here are broadly applicable to other SAGE-based studies in a variety of organisms. Keywords: other
Project description:Transcriptomes of mouse embryonic autopods were generated detecting expression of approximately 26179 transcripts in the developing forelimb or hindlimb autopods, representing about 58 % of the probe sets on MOE-430 A/B GeneChip. Three biological replicate array experiments were finished for each condition and MAS5.0 signal were used to do data analysis. Forty-four transcripts with expression differences higher than 2-fold were detected(T test, P<0.05), including Tbx4, Tbx5, Hoxc10 and Pitx1 which were previously shown to be differentially expressed in developing forelimb and hindlimb bud by in situ hybridization and SAGE study (Margulies 2001). RTPCR and in situ experiments confirmed several top differentially expressed genes which were newly discovered by our experiments. Vast amount of transcripts and its family members such as Bmp, Fgf, Epha, Wnt, T-box and Hox families detected to be highly expressed or differentially expressed in developing autopods, suggesting that the complexity of transcriptomes of developing autopods and dynamic differential expression and differential combinations of gene expression signals in the developing limb tissue contributes to differences in forelimb versus hindlimb patterning. The differentially expressed genes are the essential factors for morphological diversification of developing limb structures.