The analysis of the publicly available Hox gene sequences from the sea lamprey Petromyzon marinus provides evidence that the Hox clusters in lampreys and other vertebrate species arose from independent duplications. In particular, our analysis supports the hypothesis that the last common ancestor of agnathans and gnathostomes had only a single Hox cluster which was subsequently duplicated independently in the two lineages.

No description available.

Yes / Background: The HOX genes are a family of transcription factors that help to determine cell and tissue identity during early development, and which are also over-expressed in a number of malignancies where they have been shown to promote cell proliferation and survival. The purpose of this study was to evaluate the expression of HOX genes in prostate cancer and to establish whether prostate cancer cells are sensitive to killing by HXR9, an inhibitor of HOX function. Methods: HOX function was inhibited using the HXR9 peptide. HOX gene expression was assessed by RNA extraction from cells or tissues followed by quantitative PCR, and siRNA was used to block the expression of the HOX target gene, cFos. In vivo modelling involved a mouse flank tumour induced by inoculation with LNCaP cells. Results: In this study we show that the expression of HOX genes in prostate tumours is greatly increased with respect to normal prostate tissue. Targeting the interaction between HOX proteins and their PBX cofactor induces apoptosis in the prostate cancer derived cell lines PC3, DU145 and LNCaP, through a mechanism that involves a rapid increase in the expression of cFos, an oncogenic transcription factor. Furthermore, disrupting HOX/PBX binding using the HXR9 antagonist blocks the growth of LNCaP tumours in a xenograft model over an extended period. Conclusion: Many HOX genes are highly over-expressed in prostate cancer, and prostate cancer cells are sensitive to killing by HXR9 both in vitro and in vivo. The HOX genes are therefore a potential therapeutic target in prostate cancer. / The authors gratefully acknowledge the support of the Prostate Project charity (UK).

Hox transcription factors are extensively investigated in diverse fields of molecular and evolutionary biology. Hox genes belong to the family of homeobox transcription factors characterised by a 60 amino acids region called homeodomain. These genes are evolutionary conserved and play crucial roles in the development of animals. In particular, they are involved in the specification of segmental identity, and in the tetrapod limb differentiation. In vertebrates, this family of genes can be divided into 14 groups of homology. Common methods to classify Hox proteins focus on the homeodomain. Classification is however hampered by the high conservation of this short domain. Since phylogenetic tree reconstruction is time-consuming, it is not suitable to classify the growing number of Hox sequences. The first goal of this thesis is therefore to design an automated approach to classify vertebrate Hox proteins in their groups of homology. This approach classifies Hox proteins on the basis of their scores for a combination of protein generalised profiles. The resulting program, HoxPred, combines predictive accuracy and time efficiency. We used this program to detect and classify Hox genes in several teleost fish genomes. In particular, it allowed us to clarify the evolutionary history of the HoxC1a genes in teleosts. Overall, HoxPred could efficiently contribute to the bioinformatics toolbox commonly used to annotate vertebrate Hox sequences. This program was then evaluated in non-vertebrate species. Although not intended for the classification of Hox proteins in distantly related species, HoxPred showed a high accuracy in bilaterians. It has also given insights into the evolutionary relationships between bilaterian posterior Hox genes, which are notoriously difficult to classify with phylogenetic trees. As transcription factors, Hox proteins regulate target genes by specifically binding DNA on cis-regulatory elements. Only a few of these target genes have been identified so far. The second goal of this work was to evaluate whether it is possible to apply computational approaches to detect Hox cis-regulatory elements in genomic sequences. Regulatory Sequence Analysis Tools (RSAT) is a suite of bioinformatics tools dedicated to the detection of cis-regulatory elements in genomes. We participated to the development of matrix-based pattern matching approaches in RSAT. After having performed a statistical validation of the pattern-matching scores, we focused on a study case based on the vertebrate HoxB1 protein, which binds DNA with its cofactors Pbx and Meis. This study aimed at predicting combinations of cis-regulatory elements for these three transcription factors.

Hox genes are evolutionarily conserved transcription factors which act to control important developmental pathways involved in morphogenesis of the embryo. Hoxa2 is expressed in the developing CNS in rhombomeres 2-7 in the presumptive hindbrain. During development Hoxa2 expression extends caudally throughout the spinal cord and persists into adulthood.</p><p> Although previous analysis of Hoxa2 expression indicates its possible role in neuronal circuit specification and/or dorsal-ventral patterning within the spinal cord, the precise genetic pathways through which Hoxa2 affects spinal cord development have not been characterized. We have used immunoprecipitation of Hoxa2-target DNA complexes from chromatin preparations of E18 mouse spinal cord and hindbrain tissue to isolate in vivo downstream target genes of Hoxa2. Seven DNA fragments were isolated, sequenced and were shown to exhibit in vitro DNA binding by Hoxa2. A search of sequence databases for the target sequences revealed that of these, two displayed high identity with novel mouse genes: toll-associated serine protease (Tasp) and the murine homolog of the human dual specificity tyrosine phosphorylation regulated kinase 4 (Dyrk4). Also, two of the isolated clones are presumably bacterial sequences containing the canonical homeodomain binding site TAAT, and the remaining three clones have not yet been mapped in the mouse genome. A potential core Hoxa2 binding motif consisting of 5' CCATCA/T 3', which is based on a previously characterized Hoxa2-Pbx consensus sequence (Lampe et al., 2004), has been identified in both the Tasp and Dyrk4 intronic elements. Both Dyrk4 and Tasp mRNA have been detected within the developing mouse from E10-18 and in the adult CNS. Analysis by RT-PCR of Tasp expression in Hoxa2-/- newborn mice hindbrain and spinal cord tissues showed an upregulation of Tasp, and transient transfection experiments indicated that Hoxa2 may act as a transcriptional repressor of Tasp through an intronic regulatory element. Transfection studies using the intronic sequence of Dyrk4 indicated that it may function as an enhancer of transcription of Dyrk4 in the presence of Hoxa2. Both Dyrk4 and Tasp belong to large protein subfamilies whose members play a role in numerous developmental pathways in several organisms. Tasp, also known as HtrA3, interacts with TGFâ signaling molecules which are known to be key regulators of development, dorsoventral patterning and are involved in various neuronal pathways. Although the function of Dyrk4 is not known, many of its family members are involved in the regulation of transcription factors and signaling molecules via phosphorylation that are involved in neuronal pathways also. Hoxa2 may act in specifying neuronal subtypes and dorsoventral patterning in the CNS through down and upregulation of its downstream targets Dyrk4 and Tasp, respectively.

Los genes homeóticos (Hox) codifican factores de transcripción involucrados en la especificación de la identidad segmental a lo largo del eje anteroposterior en el embrión de los metazoos. Estos genes se presentan habitualmente agrupados y organizados en el mismo orden en el que se expresan a lo largo del eje anteroposterior del cuerpo. La conservación de esta organización genómica a lo largo de la filogenia ha sugerido la existencia de constricciones funcionales actuando sobre ella, pero la desestructuración del complejo en Caenorhabditis elegans y las tres roturas descritas en el género Drosophila ponen en cuestión que esta organización sea realmente necesaria para su correcto funcionamiento en algunos linajes. En este trabajo se han estudiado las consecuencias genómicas y funcionales de las dos reorganizaciones del complejo de genes Hox presentes en Drosophila buzzatii, especie perteneciente al grupo repleta. En la primera parte del trabajo se han clonado y secuenciado las regiones codificantes del gen labial (lab) en D. buzzatii y D. virilis. Se han comparado las secuencias de estas dos especies y la de D. melanogaster para comprobar si el cambio de posición del gen lab ocurrido en el linaje de D. buzzatii había producido algún cambio en la estructura del gen o en la evolución de su secuencia. Los resultados muestran una tasa de cambio heterogénea a lo largo del gen pero homogénea a lo largo de la filogenia. La tasa de cambio nucleotídico de lab se ha mantenido constante a pesar del cambio de posición. En la segunda parte del trabajo se han secuenciado dos regiones del genoma de D. buzzatii, una contiene los genes lab y abdominal A (abdA) y la otra incluye el gen proboscipedia (pb), y se ha comparado su organización génica con D. melanogaster y D. pseudoobscura para localizar con precisión los puntos de rotura. También se han comparado las secuencias no codificantes de estas regiones, se ha observado una elevada presencia de bloques conservados en los intrones y regiones adyacentes de los genes Hox. La comparación de los bloques conservados con las regiones reguladoras conocidas de los genes Hox (lab, pb y abdA) en D. melanogaster muestra que la posición y orientación de las regiones reguladoras está conservada entre las tres especies, con excepciones menores. Finalmente se analizó el patrón de expresión de los tres genes Hox en embriones y discos imaginales de D. buzzatii, D. repleta, D. virilis, y D. melanogaster, cuatro especies con diferentes organizaciones de los genes Hox. Las dos roturas estudiadas se produjeron mediante inversiones paracéntricas, con los puntos de rotura respetando las regiones reguladoras de ambos genes. De manera que las regiones reguladoras y patrones de expresión de los genes Hox adyacentes se han conservado a pesar de las reorganizaciones. En Drosophila el complejo parece tener una estructura formada por módulos (que incluyen los genes y las regiones reguladoras) independientes, cuya agrupación no es necesaria para su correcto funcionamiento. La organización de estos genes es modular y su agrupación parece ser el resultado de la inercia filogenética más que de la necesidad funcional. El descubrimiento de más reorganizaciones en otros linajes y la importancia de la colinealidad temporal en algunos organismos sugieren que la causa funcional de la conservación de la organización genómica podría ser la colinealidad temporal. Las reorganizaciones serían consecuencia de la pérdida de colinealidad temporal en organismos con desarrollo rápido por modificación de la embriogénesis. / Homeotic (Hox) genes code for transcription factors involved in the specification of segmental identity in the anteroposterior axis of the early metazoan embryo. These genes are usually clustered and arranged in the same order as they are expressed along the anteroposterior body axis. The conservation of this Hox gene organization along the phylogeny has suggested the existence of functional constraints. However, the partial disassembly of the Caenorhabditis elegans complex and the three splits observed in the Drosophila genus question whether this organization is an absolute necessity for proper function in some lineages. In this work, I analysed the genomic and functional consequences of the two splits present in Drosophila buzzatii, a member of the repleta species group. In the first part, the coding regions of the labial (lab) gene were cloned in D. buzzatii and D. virilis. The sequences of these two species were compared with that of D. melanogaster to test whether the change in position of lab in de D. buzzatii lineage produced any change in gene structure or sequence evolution. The results show that the substitution rate is heterogeneous along the gene but homogeneous along the phylogeny. The nucleotide substitution rate of lab has been constant in spite of the positional change. In the second part, two regions of the D. buzzatii genome have been sequenced, one including the lab y abdominal A (abdA) genes and the other containing the proboscipedia (pb) gene, and compared with the genic organization of D. melanogaster and D. pseudoobscura to precisely locate the breakpoints. The noncoding sequences of these regions have also been compared, and a high presence of conserved blocks has been observed in the introns and surrounding regions of Hox genes. The comparison of these conserved blocks with the known regulatory regions of the Hox genes (lab, pb and abdA) in D. melanogaster shows that the position and order of the regulatory regions is conserved between the three species, with minor exceptions. Finally the expression pattern of the three Hox genes has been analysed in embryos and imaginal discs of D. buzzatii, D. repleta, D. virilis, and D. melanogaster, four species with different Hox gene arrangements. The two splits took place through two paracentric inversions, with their breakpoints between the regulatory regions of adjacent genes. So that the regulatory regions and expression patterns of these Hox genes have been conserved in spite of the reorganizations. In Drosophila the Hox gene complex seems to be composed by independent modules (including the gene and its regulatory regions), whose association is not required for proper function. The organization of these genes is modular and their clustering seems de result of phylogenetic inertia more than of functional necessity. The discovery of more rearrangements in other lineages and the significance of temporal colinearity in some organisms suggest that the functional cause of the conservation of this genomic organization would be temporal colinearity. Rearrangements would be the consequence of the loss of temporal colinearity in organisms with a very rapid mode of embriogenesis.

Hox genes are evolutionarily conserved transcription factors which act to control important developmental pathways involved in morphogenesis of the embryo. Hoxa2 is expressed in the developing CNS in rhombomeres 2-7 in the presumptive hindbrain. During development Hoxa2 expression extends caudally throughout the spinal cord and persists into adulthood.</p><p> Although previous analysis of Hoxa2 expression indicates its possible role in neuronal circuit specification and/or dorsal-ventral patterning within the spinal cord, the precise genetic pathways through which Hoxa2 affects spinal cord development have not been characterized. We have used immunoprecipitation of Hoxa2-target DNA complexes from chromatin preparations of E18 mouse spinal cord and hindbrain tissue to isolate in vivo downstream target genes of Hoxa2. Seven DNA fragments were isolated, sequenced and were shown to exhibit in vitro DNA binding by Hoxa2. A search of sequence databases for the target sequences revealed that of these, two displayed high identity with novel mouse genes: toll-associated serine protease (Tasp) and the murine homolog of the human dual specificity tyrosine phosphorylation regulated kinase 4 (Dyrk4). Also, two of the isolated clones are presumably bacterial sequences containing the canonical homeodomain binding site TAAT, and the remaining three clones have not yet been mapped in the mouse genome. A potential core Hoxa2 binding motif consisting of 5' CCATCA/T 3', which is based on a previously characterized Hoxa2-Pbx consensus sequence (Lampe et al., 2004), has been identified in both the Tasp and Dyrk4 intronic elements. Both Dyrk4 and Tasp mRNA have been detected within the developing mouse from E10-18 and in the adult CNS. Analysis by RT-PCR of Tasp expression in Hoxa2-/- newborn mice hindbrain and spinal cord tissues showed an upregulation of Tasp, and transient transfection experiments indicated that Hoxa2 may act as a transcriptional repressor of Tasp through an intronic regulatory element. Transfection studies using the intronic sequence of Dyrk4 indicated that it may function as an enhancer of transcription of Dyrk4 in the presence of Hoxa2. Both Dyrk4 and Tasp belong to large protein subfamilies whose members play a role in numerous developmental pathways in several organisms. Tasp, also known as HtrA3, interacts with TGFâ signaling molecules which are known to be key regulators of development, dorsoventral patterning and are involved in various neuronal pathways. Although the function of Dyrk4 is not known, many of its family members are involved in the regulation of transcription factors and signaling molecules via phosphorylation that are involved in neuronal pathways also. Hoxa2 may act in specifying neuronal subtypes and dorsoventral patterning in the CNS through down and upregulation of its downstream targets Dyrk4 and Tasp, respectively.

Long non-coding RNAs (lncRNAs) are often defined as transcripts >200nts that have no discernable protein-coding ability (Quinn and Chang, 2016). Although relatively little is understood about the molecular mechanisms of lncRNA function, they have established roles in regulation of gene expression during development, cell differentiation and pluripotency (Fatica and Bozzoni, 2014; Luo et al., 2016; Quinn and Chang, 2016; Rinn and Chang, 2012) across vastly diverse organisms ranging from plants to humans (Ulitsky and Bartel, 2013). LncRNAs have also been associated with numerous pathological conditions, such as cancers (Brunner et al., 2012), cardiovascular disease and neurodegeneration (Chen et al., 2013). Investigations into lncRNAs in wide ranging organisms, have revealed that many influence gene activity by forming ribonucleoprotein complexes that affect the conformational state of chromatin (Rinn and Chang, 2012). A genomic region that has revealed several functional lncRNAs in diverse organisms is the Hox complex (Pauli et al., 2011; Pettini, 2012; Rinn et al., 2007). The Hox complex encodes a set of transcription factors (TFs), physically clustered in the genome, which provide morphological identity along the anterior to posterior axis of developing embryos (Mallo and Alonso, 2013), throughout the majority of bilatarian animals (Moreno et al., 2011). Misexpression or mutation of Hox genes causes morphological and pathophysiological defects (Quinonez and Innis, 2014). We investigated clustering of lncRNAs throughout the D. melanogaster genome using available annotations and carried out RNA-seq in D. virilis to expand the repertoire of lncRNAs and identify clusters of lncRNAs. We found the Hox complex to be heavily enriched with lncRNAs in both organisms, and syntenic transcripts from D. melanogaster could be identified in D. pseudoobscura and D. virilis. Several lncRNAs aligned with polycomb response elements (PREs); transcription of PREs has previously been linked to a switch in their activity (Herzog et al., 2014). However, we found that transcribed PREs in D. melanogaster move positions relative to the protein-coding genes in other drosophilids, whilst the transcriptional units remain in the same syntenic region. Conservation of syntenic transcripts without evidence of remaining a PRE suggest that the transcription is not linked to PRE function, agreeing with recent findings that transcription of PREs does not affect their function (Kassis and Muller, 2015). We investigated functions of a novel lncRNA and adjacent PRE in the Hox complex by ectopic expression and utilization of other genetic manipulation tools. Overexpression of either the lncRNA or PRE and partial duplication of the lncRNA caused phenotypes such as missing halteres and/or T3 legs, misshaped T3 legs or malformed abdominal segments. The observations that ectopic expression of this lncRNA and an adjacent regulatory element from the Hox complex causes phenotypes that can be linked to adjacent Hox gene misregulation, Antp and Ubx, suggest that they are likely to have roles in the regulation of at least one of these Hox genes.

Whole genome transcriptome analysis has revealed that a large proportion of the genome in higher metazoa is transcribed, yet only a small proportion of this transcription is protein-coding. One possible function of non-coding transcription is that it enables complex and diverse body plans to evolve through variation in deployment of a relatively common set of protein-coding genes. Functional studies suggest that long non-coding RNAs (lncRNAs) regulate gene expression via diverse mechanisms, operating in both cis and trans to activate or repress target genes. An emerging theme common to lncRNA function is interaction with proteins that modify chromatin and mediate epigenetic regulation. The Hox gene complexes are particularly rich in lncRNAs and require precise and fine-tuned expression to deploy Hox transcription factors throughout development. Here we identify and functionally characterize two novel lncRNAs within the D. melanogaster Hox complex, in the interval between Scr and Antp. We use nascent transcript fluorescent in-situ hybridization (ntFISH) to characterize the embryonic expression patterns of each lncRNA with respect to flanking Hox genes, and to analyze co-transcription within individual nuclei. We find that the transcription of one lncRNA, ncX, is an initial response to early transcription factors and may activate Scr expression, while transcription of the other lncRNA, ncPRE is consistent with activation and/or maintenance of Scr expression. ntFISH performed in D.virilis embryos revealed the presence of a lncRNA ortholog with highly similar expression to ncX, indicating functional conservation of lncRNA transcription across ~60 million years of evolution. We identify the ncPRE lncRNA locus as a binding site for multiple proteins associated with Polycomb/Trithorax response elements (PREs/TREs) and show that DNA encoding the ncPRE lncRNA functions as a bona fide PRE, mediating trans-interactions between chromosomes and silencing of nearby genes. We find that transcription through the ncPRE DNA relieves silencing, suggesting a role for endogenous transcription of the ncPRE lncRNA in relieving Polycomb-silencing and enabling Scr activation. We demonstrate that both lncRNA transcripts are required for proper Scr expression, and over-expression of either lncRNAs from ectopic genomic loci has no effect on Scr expression, but ectopic expression at the endogenous locus is associated with ectopic Scr activation, indicating that the lncRNA-mediated regulation functions locally at the site of transcription on the chromosome. ncX may mediate transvection effects previously observed at the Scr locus, independent of the protein Zeste. Together our results support a model of competing mechanisms in the regulation of Scr expression - a background of Polycomb repression acting from the ncPRE locus, which in the first thoracic segment is counteracted by lncRNA transcription and Trithorax binding to ncPRE, enabling activation and maintenance of Scr expression. This work provides a functional insight into the complex regulatory interactions between lncRNAs and epigenetic mechanisms, essential to establish and maintain the precise expression pattern of Hox genes through development.

Despite their homology and analogous function, the Hox gene clusters of vertebrates and invertebrates are subject to different constraints on their structural organization. This is demonstrated by a drastically different distribution of repetitive DNA elements in the Hox cluster regions. While gnathostomes have a strong tendency to exclude repetitive DNA elements from the inside of their Hox clusters, no such trend can be detected in the Hox gene clusters of protostomes. Repeats “invade” the gnathostome Hox clusters from the 5′ and 3′ ends while the core of the clusters remains virtually free of repetitive DNA. This invasion appears to be correlated with relaxed constraints associated with gene loss after cluster duplications.