Stromal Hoxa5 function controls the growth and differentiation of mammary alveolar epithelium

Polymorphism and association study of lactoferrin (LF) gene with milk yield, milk composition, and somatic cell count in Beetal goats

The sequence analysis of PCR product exhibited four novel SNPs in the promoter region of the LF gene at loci g.98T>C, g.143T>A, g.189AC>A, and g.346A>G. Each SNP yielded three genotypes; the genotypes TT (SNP1), AA (SNP3), and GG (SNP4) decreased SCC and increase milk quality traits such as density, protein, and milk yield (P < 0.01). The genotype CC (SNP2) and CA (SNP4) significantly (P < 0.01) decreased the milk quality parameters, while genotypes TC (SNP2) and GG (SNP4) showed significantly (P < 0.01) less SCC and increase lactose % in milk. Furthermore, screening of the LF promoter sequence explored the gain of four TF binding sites at locus g.98T˃C and three TF binding sites at g.346A˃G. However, the loss of four and two TF binding sites was seen at locus g.143T˃A and g.189C˃A, respectively. We can conclude from the present study that the GG, TT, and AA genotype might be utilized as genetic markers in marker-assisted selection for the breed improvement program of Beetal goats.

HOXA5: A crucial transcriptional factor in cancer and a potential therapeutic target

HOX genes occupy a significant role in embryogenesis, hematopoiesis, and oncogenesis. HOXA5, a member of the A cluster of HOX genes, is essential for establishing the skeleton and normal organogenesis. As previously reported, aberrant HOXA5 expression contributes to anomalies and dysfunction of various organs, as well as affecting proliferation, differentiation, invasion, apoptosis, and other biological processes of tumor cells. Different cancers showed both downregulated and upregulated HOXA5 expression. The most common strategy for controlling HOXA5 downregulated expression may be CpG island hypermethylation. Additionally, current research demonstrated the regulatory network of HOXA5 and its connection with cancer stem cell progression and the immune microenvironment. Epigenetic modulators and upstream regulators, such as DNMTi and retinoic acid, may be beneficial for anti-tumor effects targeting HOXA5. Here, we summarize current knowledge about the HOXA5 gene, its role in various cancers, and its potential therapeutic value.

HOXA1, a breast cancer oncogene

More than 25 years ago, the first literature records mentioned HOXA1 expression in human breast cancer. A few years later, HOXA1 was confirmed as a proper oncogene in mammary tissue. In the following two decades, molecular data about the mode of action of the HOXA1 protein, the factors contributing to activate and maintain HOXA1 gene expression and the identity of its target genes have accumulated and provide a wider view on the association of this transcription factor to breast oncogenesis. Large-scale transcriptomic data gathered from wide cohorts of patients further allowed refining the relationship between breast cancer type and HOXA1 expression. Several recent reports have reviewed the connection between cancer hallmarks and the biology of HOX genes in general. Here we take HOXA1 as a paradigm and propose an extensive overview of the molecular data centered on this oncoprotein, from what its expression modulators, to the interactors contributing to its oncogenic activities, and to the pathways and genes it controls. The data converge to an intricate picture that answers questions on the multi-modality of its oncogene activities, point towards better understanding of breast cancer aetiology and thereby provides an appraisal for treatment opportunities.

High expression of HOXB7 is an unfavorable prognostic factor for solid malignancies: A meta-analysis

BACKGROUND

HOXB7 is abnormally expressed in a variety of tumors, but its prognostic value remains unclear due to sample size limitation and outcome inconsistency in previous studies. This meta-analysis was performed to explore the effect of HOXB7 expression on prognoses and clinicopathological factors in range of the whole solid tumors.

METHODS

PubMed, EMBASE, and Web of Science databases were searched to identify included studies. Hazard ratios (HR) with its 95% confidence interval (CI) and clinicopathological factors were extracted. Subgroup analyses were performed according to histopathological type, tumor occurrence systems, and HOXB7 detection methods.

RESULTS

A total of 3430 solid tumors patients from 20 studies (21 cohorts) were included in the meta-analysis. The results showed that high HOXB7 expression was significantly associated with worse survival (overall survival: HR = 1.98, 95%CI: 1.74-2.26, P < .001 and disease-free survival: HR = 1.59, 95%CI: 1.21-2.09, P = .001), more advanced tumor-node-metastasis (TNM) stage (odds ratio [OR] = 2.14, 95%CI: 1.68-2.73, P < .001), positive lymph node metastasis (OR = 2.16, 95%CI: 1.74-2.70, P < .001), more distant metastasis (OR = 1.63, 95%CI: 1.01-2.63, P = .048), poorer differentiation (OR = 1.48, 95%CI: 1.14-1.91, P = .003), and higher Ki-67 expression (OR = 2.53, 95%CI: 1.68-3.84, P < .001). Subgroup analysis showed that survival of patients with HOXB7 high expression was worse in either squamous cell carcinomas or non-squamous cell carcinomas, digestive tumors or non-digestive tumors, and protein level or mRNA level.

CONCLUSION

High HOXB7 expression might be a valuable biomarker of poor prognosis for solid tumors. HOXB7 promotes tumor proliferation and metastasis, and is associated with poorer differentiation, more advanced stage, even the chemotherapy resistance, suggesting that HOXB7 is a potential therapeutic target for solid tumors.

HINT1 (Histidine Triad Nucleotide-Binding Protein 1) Attenuates Cardiac Hypertrophy Via Suppressing HOXA5 (Homeobox A5) Expression

BACKGROUND

Cardiac hypertrophy is an important prepathology of, and will ultimately lead to, heart failure. However, the mechanisms underlying pathological cardiac hypertrophy remain largely unknown. This study aims to elucidate the effects and mechanisms of HINT1 (histidine triad nucleotide-binding protein 1) in cardiac hypertrophy and heart failure.

METHODS

HINT1 was downregulated in human hypertrophic heart samples compared with nonhypertrophic samples by mass spectrometry analysis. Hint1 knockout mice were challenged with transverse aortic constriction surgery. Cardiac-specific overexpression of HINT1 mice by intravenous injection of adeno-associated virus 9 (AAV9)-encoding Hint1 under the cTnT (cardiac troponin T) promoter were subjected to transverse aortic construction. Unbiased transcriptional analyses were used to identify the downstream targets of HINT1. AAV9 bearing shRNA against Hoxa5 (homeobox A5) was administrated to investigate whether the effects of HINT1 on cardiac hypertrophy were HOXA5-dependent. RNA sequencing analysis was performed to recapitulate possible changes in transcriptome profile.Coimmunoprecipitation assays and cellular fractionation analyses were conducted to examine the mechanism by which HINT1 regulates the expression of HOXA5.

RESULTS

The reduction of HINT1 expression was observed in the hearts of hypertrophic patients and pressure overloaded-induced hypertrophic mice, respectively. In Hint1-deficient mice, cardiac hypertrophy deteriorated after transverse aortic construction. Conversely, cardiac-specific overexpression of HINT1 alleviated cardiac hypertrophy and dysfunction. Unbiased profiler polymerase chain reaction array showed HOXA5 is 1 target for HINT1, and the cardioprotective role of HINT1 was abolished by HOXA5 knockdown in vivo. Hoxa5 was identified to affect hypertrophy through the TGF-β (transforming growth factor β) signal pathway. Mechanically, HINT1 inhibited PKCβ1 (protein kinase C β type 1) membrane translocation and phosphorylation via direct interaction, attenuating the MEK/ERK/YY1 (mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/yin yang 1) signal pathway, downregulating HOXA5 expression, and eventually attenuating cardiac hypertrophy.

CONCLUSIONS

HINT1 protects against cardiac hypertrophy through suppressing HOXA5 expression. These findings indicate that HINT1 may be a potential target for therapeutic interventions in cardiac hypertrophy and heart failure.

Phosphorylation of Msx1 promotes cell proliferation through the Fgf9/18-MAPK signaling pathway during embryonic limb development

Msh homeobox (Msx) is a subclass of homeobox transcriptional regulators that control cell lineage development, including the early stage of vertebrate limb development, although the underlying mechanisms are not clear. Here, we demonstrate that Msx1 promotes the proliferation of myoblasts and mesenchymal stem cells (MSCs) by enhancing mitogen-activated protein kinase (MAPK) signaling. Msx1 directly binds to and upregulates the expression of fibroblast growth factor 9 (Fgf9) and Fgf18. Accordingly, knockdown or antibody neutralization of Fgf9/18 inhibits Msx1-activated extracellular signal-regulated kinase 1/2 (Erk1/2) phosphorylation. Mechanistically, we determined that the phosphorylation of Msx1 at Ser136 is critical for enhancing Fgf9 and Fgf18 expression and cell proliferation, and cyclin-dependent kinase 1 (CDK1) is apparently responsible for Ser136 phosphorylation. Furthermore, mesenchymal deletion of Msx1/2 results in decreased Fgf9 and Fgf18 expression and Erk1/2 phosphorylation, which leads to serious defects in limb development in mice. Collectively, our findings established an important function of the Msx1-Fgf-MAPK signaling axis in promoting cell proliferation, thus providing a new mechanistic insight into limb development.

Hoxd10 Is Required Systemically for Secretory Activation in Lactation and Interacts Genetically with Hoxd9

Targeted disruption of the murine Hoxd10 gene (ΔHoxd10) leads to a high frequency of localized (gland-to-gland or regionally within a gland) lactation impairment in homozygous mutant mice as a single gene mutation. The effect of Hoxd10 disruption was enhanced by simultaneous disruption of Hoxd9 (ΔHoxd9/d10), a mutation shown previously to have no effect on mammary function as a single gene alteration. Mammary glands of homozygous ΔHoxd10 and ΔHoxd9/d10 females were indistinguishable from those of wild type littermate and age-matched control mice in late pregnancy. However, in lactation, 47% of homozygous ΔHoxd10 females, and 100% of homozygous ΔHoxd9/d10 females, showed localized or complete failure of two or more glands to undergo lactation-associated morphological changes and to secrete milk. Affected regions of ΔHoxd10 and ΔHoxd9/d10 mutants showed reduced prolactin receptor expression, reduced signal transducer and activator transcription protein 5 (STAT5) phosphorylation, reduced expression of downstream milk proteins, mislocalized glucose transporter 1 (GLUT1), increased STAT3 expression and phosphorylation, recruitment of leukocytes, altered cell cycle status, and increased apoptosis relative to unaffected regions and wild type control glands. Despite these local effects on alveolar function, transplantation results and hormone analysis indicate that Hoxd10 primarily has systemic functions that confer attenuated STAT5 phosphorylation on both wild type and ΔHoxd10 transplants when placed in ΔHoxd10 hosts, thereby exacerbating an underlying propensity for lactation failure in C57Bl/6 mice.

HOX genes function in Breast Cancer development

Breast cancer develops in the mammary glands during mammalian adulthood and is considered the second most common type of human carcinoma and the most incident and mortal in the female population. In contrast to other human structures, the female mammary glands continue to develop after birth, undergoing various modifications during pregnancy, lactation and involution under the regulation of hormones and transcription factors, including those encoded by the HOX clusters (A, B, C, and D). Interestingly, HOX gene deregulation is often associated to breast cancer development. Within the HOXB cluster, 8 out of the 10 genes present altered expression levels in breast cancer with an impact in its aggressiveness and resistance to hormone therapy, which highlights the importance of HOXB genes as potential therapeutic targets used to overcome the limitations of tamoxifen-resistant cancer treatments. Here, we review the current state of knowledge on the role of HOX genes in breast cancer, specially focus on HOXB, discussing the causes and consequences of HOXB gene deregulation and their relevance as prognostic factors and therapeutic targets.

HOXA5 and p53 cooperate to suppress lung cancer cell invasion and serve as good prognostic factors in non-small cell lung cancer

Lung cancer is the leading cause of cancer mortality worldwide and tumor metastasis is the major cause of cancer-related death. Our previous study suggested that Homeobox A5 (HOXA5) could inhibit lung cancer cell invasion via regulating cytoskeletal remodeling and involved in tumor metastasis. Recently, consensus HOX binding sites was found in the p53 gene promoter region. However, whether the HOXA5 could cooperate with p53 and contribute the inhibition of lung cancer cell invasion is still unclear. The aim of the current study is to elucidate the correlation of HOXA5 and p53 in tumor invasion and its prognostic influence in lung cancer patient specimens. Totally 71 cases of primary non-small cell lung cancer (NSCLC) were collected. The median follow-up period is 6.8 years. Immunohistochemical stain for p53 and HOXA5 were performed. Kaplan-Meier plot was done for overall survival analysis. In addition, lung cancer cell lines transfected with wild-type or mutated p53 constructs were overexpressed with HOXA5 for invasion assay. In human specimens, HOXA5 expressed mainly in the cytoplasm (54.1%) rather than nuclei (14.6%) of the NSCLC tumor part. The HOXA5 expression is higher in adenocarcinoma than in squamous cell carcinoma (P < 0.001). In addition, poor prognosis is seen in group with both non-immunoreactive for p53 and HOXA5. HOXA5 and p53 could cooperate to inhibit tumor cell invasion significantly partly by decreasing MMP2 activity in a concentration-dependent manner. Our studies provide new insights into how HOXA5 and p53 cooperate to contribute to the suppression of lung cancer cell invasion and play good prognostic roles in NSCLC.

Control of Hoxd gene transcription in the mammary bud by hijacking a preexisting regulatory landscape

Vertebrate Hox genes encode transcription factors operating during the development of multiple organs and structures. However, the evolutionary mechanism underlying this remarkable pleiotropy remains to be fully understood. Here, we show that Hoxd8 and Hoxd9, two genes of the HoxD complex, are transcribed during mammary bud (MB) development. However, unlike in other developmental contexts, their coexpression does not rely on the same regulatory mechanism. Hoxd8 is regulated by the combined activity of closely located sequences and the most distant telomeric gene desert. On the other hand, Hoxd9 is controlled by an enhancer-rich region that is also located within the telomeric gene desert but has no impact on Hoxd8 transcription, thus constituting an exception to the global regulatory logic systematically observed at this locus. The latter DNA region is also involved in Hoxd gene regulation in other contexts and strongly interacts with Hoxd9 in all tissues analyzed thus far, indicating that its regulatory activity was already operational before the appearance of mammary glands. Within this DNA region and neighboring a strong limb enhancer, we identified a short sequence conserved in therian mammals and capable of enhancer activity in the MBs. We propose that Hoxd gene regulation in embryonic MBs evolved by hijacking a preexisting regulatory landscape that was already at work before the emergence of mammals in structures such as the limbs or the intestinal tract.

Hoxa5: A Key Player in Development and Disease

A critical position in the developmental hierarchy is occupied by the Hox genes, which encode transcription factors. Hox genes are crucial in specifying regional identity along the embryonic axes and in regulating morphogenesis. In mouse, targeted mutations of Hox genes cause skeletal transformations and organ defects that can impair viability. Here, we present the current knowledge about the Hoxa5 gene, a paradigm for the function and the regulation of Hox genes. The phenotypic survey of Hoxa5-/- mice has unveiled its critical role in the regional specification of the skeleton and in organogenesis. Most Hoxa5-/- mice die at birth from respiratory distress due to tracheal and lung dysmorphogenesis and impaired diaphragm innervation. The severity of the phenotype establishes that Hoxa5 plays a predominant role in lung organogenesis versus other Hox genes. Hoxa5 also governs digestive tract morphogenesis, thyroid and mammary glands development, and ovary homeostasis. Deregulated Hoxa5 expression is reported in cancers, indicating Hoxa5 involvement in tumor predisposition and progression. The dynamic Hoxa5 expression profile is under the transcriptional control of multiple cis-acting sequences and trans-acting regulators. It is also modulated by epigenetic mechanisms, implicating chromatin modifications and microRNAs. Finally, lncRNAs originating from alternative splicing and distal promoters encompass the Hoxa5 locus.

Cellular and molecular insights into Hox protein action

Hox genes encode homeodomain transcription factors that control morphogenesis and have established functions in development and evolution. Hox proteins have remained enigmatic with regard to the molecular mechanisms that endow them with specific and diverse functions, and to the cellular functions that they control. Here, we review recent examples of Hox-controlled cellular functions that highlight their versatile and highly context-dependent activity. This provides the setting to discuss how Hox proteins control morphogenesis and organogenesis. We then summarise the molecular modalities underlying Hox protein function, in particular in light of current models of transcription factor function. Finally, we discuss how functional divergence between Hox proteins might be achieved to give rise to the many facets of their action.

Upregulation of HOXB7 promotes the tumorigenesis and progression of gastric cancer and correlates with clinical characteristics

Several examples of aberrant homeobox gene expression have been found across a range of cancers, and it is also confirmed that homeobox genes play a critical roles in tumorigenesis and progression. Notwithstanding homeobox B7 (HOXB7) has been documented that its deregulation promotes carcinogenesis and development in gastrointestinal tract, its function in gastric cancer has not been investigated. In this study, HOXB7 expression was examined to be distinctly upregulated in gastric carcinoma GC cell lines and in the tumor relative to normal gastric tissue. High HOXB7 expression was correlated with tumor differentiation (P = 0.025) and TNM stage (P = 0.008). HOXB7 knockdown in BGC-823 and SGC-7901 resulted in decreased migration and invasion with alteration of epithelial-mesenchymal transition (EMT) proteins and influenced proliferation, apoptosis, and cell cycle. Furthermore, complementary DNA (cDNA) microarray, qPCR, and Western blotting were performed to explore potential downstream target genes of HOXB7. HOXB7 is generally overexpressed in GC, associated with patient clinical characteristics, and specifically promotes GC cell malignant biological properties through PIK3R3/AKT signaling pathways, indicating HOXB7 as a causal factor in promoting tumor progression.

Sustained endothelial expression of HoxA5 in vivo impairs pathological angiogenesis and tumor progression

HoxA5 is expressed in quiescent endothelial cells (EC), but absent in activated angiogenic EC. To examine the efficacy of targeting HoxA5 therapeutically to quell pathologic or tumor angiogenesis, we generated an inducible, transgenic mouse model of sustained HoxA5 expression in ECs. During pathologic angiogenesis, sustained HoxA5 regulates expression several angiogenic effector molecules, notably increased expression of TSP-2 and reduced expression of VEGF, thus leading to inhibition of pathological angiogenesis in tissues. To evaluate if this impressive reduction of vascularization could also impact tumor angiogenesis, HoxA5 mice were bred with a mouse model of de novo squamous carcinogenesis, e.g., K14-HPV16 mice. Activation of EC-HoxA5 significantly reduced infiltration by mast cells into neoplastic skin, an early hallmark of progression to dysplasia, reduced angiogenic vasculature, and blunted characteristics of tumor progression. To evaluate HoxA5 as a therapeutic, topical application of a HoxA5 transgene onto early neoplastic skin of K14-HPV16 mice similarly resulted in a significant impairment of angiogenic vasculature and progression to dysplasia to a similar extent as observed with genetic delivery of HoxA5. Together these data indicate that HoxA5 represents a novel molecule for restricting pathological and tumorigenic angiogenesis.

miR-337 regulates the proliferation and invasion in pancreatic ductal adenocarcinoma by targeting HOXB7

Background

miRNAs are involved in coordinating a variety of cellular processes by regulating their target genes. Aberrant expression of miRNAs is correlated with various cancers. Previous studies have shown that miR-337 is significantly down-regulated in pancreatic ductal adenocarcinoma (PDAC) and that its expression is negatively correlated to the expression of HOXB7. Both miR-337 and HOXB7 are associated with the prognosis of PDAC patients. The purpose of this study was to identify the molecular mechanisms by which miR-337 acts as a tumor suppressor in PDAC.

Methods

Synthetic miR-337 mimics were transfected into PANC-1 and As-PC-1 cells using Lipofectamine™ 2000. The expression of HOXB7 protein was analyzed by Western blot. Luciferase reporter plasmids were constructed to confirm that HOXB7 3′UTR was the target of miR-337. The effect of miR-337 on cell proliferation was evaluated by CCK8 assay and colony formation assay, and cell invasion was evaluated by wound healing assay and transwell assay.

Results

Western blot and luciferase activity assays identified HOXB7 as the target of miR-337. A CCK-8 assay showed the absorbance of cells transfected with miR-337 mimics to be less than that of control cells, and that the number of cell clones was significantly decreased by miR-337 expression. A wound healing assay showed the invasion rate of cells transfected with miR-337 mimics at 36 h to be markedly lower than in controls. The average number of cells penetrating the Matrigel was significantly lower than the controls.

Conclusion

These findings suggest that miR-337 targets HOXB7 and effects significant suppression of PDAC cell proliferation and invasion.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_171

Hox protein interactions: screening and network building

Understanding the mode of action of Hox proteins requires the identification of molecular and cellular pathways they take part in. This includes to characterize the networks of protein-protein interactions involving Hox proteins. In this chapter we propose a strategy and methods to map Hox interaction networks, from yeast two-hybrid and high-throughput yeast two-hybrid interaction screening to bioinformatic analyses based on the software platform Cytoscape.

YY1 acts as a transcriptional activator of Hoxa5 gene expression in mouse organogenesis

The Hox gene family encodes homeodomain-containing transcriptional regulators that confer positional information to axial and paraxial tissues in the developing embryo. The dynamic Hox gene expression pattern requires mechanisms that differentially control Hox transcription in a precise spatio-temporal fashion. This implies an integrated regulation of neighbouring Hox genes achieved through the sharing and the selective use of defined enhancer sequences. The Hoxa5 gene plays a crucial role in lung and gut organogenesis. To position Hoxa5 in the regulatory hierarchy that drives organ morphogenesis, we searched for cis-acting regulatory sequences and associated trans-acting factors required for Hoxa5 expression in the developing lung and gut. Using mouse transgenesis, we identified two DNA regions included in a 1.5-kb XbaI-XbaI fragment located in the Hoxa4-Hoxa5 intergenic domain and known to control Hoxa4 organ expression. The multifunctional YY1 transcription factor binds the two regulatory sequences in vitro and in vivo. Moreover, the mesenchymal deletion of the Yy1 gene function in mice results in a Hoxa5-like lung phenotype with decreased Hoxa5 and Hoxa4 gene expression. Thus, YY1 acts as a positive regulator of Hoxa5 expression in the developing lung and gut. Our data also support a role for YY1 in the coordinated expression of Hox genes for correct organogenesis.

Hoxa5/Cre transgenic mice: novel tools for regional deletion along the anterior-posterior axis

The Hoxa5 homeobox gene encodes a transcription factor that plays a critical role in specifying the identity of the cervico-thoracic region along the anterior-posterior embryo axis and in orchestrating organ morphogenesis. The loss of Hoxa5 function results in skeletal transformations, lethality at birth due to lung defects, and organ anomalies affecting the digestive tract, the mammary gland and the ovary. Study of Hoxa5 gene regulation has revealed the interplay of several control regions that direct Hoxa5 developmental expression. Enhancers targeting expression in the CNS, the paraxial and lateral plate mesoderm at the cervico-thoracic level, and in the mesenchymal compartment of the respiratory and digestive tracts have been identified. Using these molecular tools, we have generated two Hoxa5/Cre transgenic mouse lines carrying different combinations of Hoxa5 regulatory enhancers and allowing site-specific recombination in subsets of Hoxa5 expression sites as tested with the Rosa26/lacZ reporter mice. Further validation of the recombination efficiency of the Hoxa5/Cre transgenic lines was performed with mice carrying a Hoxa5 conditional allele. Hoxa5 deletion with the Hoxa5/Cre mouse lines recapitulates Hoxa5 mutant phenotypes, such as skeletal defects, neonatal lethality, and lung malformations. Hoxa5/Cre mouse lines provide novel genetic tools for gene function analysis in defined tissues along the anterior-posterior axis.

Partial functional redundancy between Hoxa5 and Hoxb5 paralog genes during lung morphogenesis

Hox genes encode transcription factors governing complex developmental processes in several organs. A subset of Hox genes are expressed in the developing lung. Except for Hoxa5, the lack of overt lung phenotype in single mutants suggests that Hox genes may not play a predominant role in lung ontogeny or that functional redundancy may mask anomalies. In the Hox5 paralog group, both Hoxa5 and Hoxb5 genes are expressed in the lung mesenchyme whereas Hoxa5 is also expressed in the tracheal mesenchyme. Herein, we generated Hoxa5;Hoxb5 compound mutant mice to evaluate the relative contribution of each gene to lung development. Hoxa5;Hoxb5 mutants carrying the four mutated alleles displayed an aggravated lung phenotype, resulting in the death of the mutant pups at birth. Characterization of the phenotype highlighted the role of Hoxb5 in lung formation, the latter being involved in branching morphogenesis, goblet cell specification, and postnatal air space structure, revealing partial functional redundancy with Hoxa5. However, the Hoxb5 lung phenotypes were less severe than those seen in Hoxa5 mutants, likely because of Hoxa5 compensation. New specific roles for Hoxa5 were also unveiled, demonstrating the extensive contribution of Hoxa5 to the developing respiratory system. The exclusive expression of Hoxa5 in the trachea and the phrenic motor column likely underlies the Hoxa5-specific trachea and diaphragm phenotypes. Altogether, our observations establish that the Hoxa5 and Hoxb5 paralog genes shared some functions during lung morphogenesis, Hoxa5 playing a predominant role.

The loss of Hoxa5 function promotes Notch-dependent goblet cell metaplasia in lung airways

Hox genes encode transcription factors controlling complex developmental processes in various organs. Little is known, however, about how HOX proteins control cell fate. Herein, we demonstrate that the goblet cell metaplasia observed in lung airways from Hoxa5^−/− mice originates from the transdifferentiation of Clara cells. Reduced CC10 expression in Hoxa5^−/− embryos indicates that altered cell specification occurs prior to birth. The loss of Hoxa5 function does not preclude airway repair after naphthalene exposure, but the regenerated epithelium presents goblet cell metaplasia and less CC10-positive cells, demonstrating the essential role of Hoxa5 for correct differentiation. Goblet cell metaplasia in Hoxa5^−/− mice is a FOXA2-independent process. However, it is associated with increased Notch signaling activity. Consistent with these findings, expression levels of activated NOTCH1 and the effector gene HEY2 are enhanced in patients with chronic obstructive pulmonary disease. In vivo administration of a γ-secretase inhibitor attenuates goblet cell metaplasia in Hoxa5^−/− mice, highlighting the contribution of Notch signaling to the phenotype and suggesting a potential therapeutic strategy to inhibit goblet cell differentiation and mucus overproduction in airway diseases. In summary, the loss of Hoxa5 function in lung mesenchyme impacts on epithelial cell fate by modulating Notch signaling.

The loss of Hoxa5 function causes estrous acyclicity and ovarian epithelial inclusion cysts

Hox genes encode transcription factors that play essential roles during embryo morphogenesis and organogenesis. Expression of several Hox members persists at the adult age, indicating a wide spectrum of action from embryonic to postnatal life. In the present study, we reported that in adult mice, the Hoxa5 gene shows a dynamic expression profile in the ovary that depends on the estrous cycle, the gestational status, and the age of the female, suggesting that Hoxa5 may have distinct physiological functions in the ovary. Consistent with a role for Hoxa5 in ovarian function, Hoxa5(-/-) nulliparous females exhibit precocious puberty and an early onset of estrous acyclicity. They show a prolonged estrous cycle with increased metestrus-diestrus length, a phenotype that worsens with age. Older mutant females also develop ovarian epithelial inclusion cysts reminiscent of human endosalpingiosis. Immunolabeling studies suggest that these cysts originate from the ovarian surface epithelium, a source of epithelial ovarian carcinomas. Staining of the Hoxa5(-/-) ovarian cysts by the ovarian cancer markers paired box gene 8 (PAX8) and Wilms' tumor 1 (WT1) further strengthens the notion that these cysts may constitute preneoplastic lesions. Moreover, the deregulation of the estrous cycle and the presence of ovarian epithelial cysts in Hoxa5(-/-) older females correlate with a reduced expression of specific epidermal growth factor receptor signaling components, namely Egfr, Areg, and Btc. Altogether, our data unveil that Hoxa5, a stroma-specific gene, plays a significant role in ovarian biology and may be involved in ovarian cancer predisposition.

Transplantation of a mammary stromal cell line into a mammary fat pad: development of the site-specific in vivo analysis system for mammary stromal cells

The interaction between mammary epithelial and stromal tissue is considered to be important in breast tissue development. In this study, we developed a transplantation procedure for the mammary stromal fibroblastic cell line (MSF) to examine its life in vivo. First we established MSF cells which stably expressed lacZ (lacZ/MSF) and had characteristics of mammary stromal cells. The lacZ/MSF cells were then transplanted into a cleared mammary fat pad of syngenic mice with and without mammary primary epithelial organoids. Whole mount X-gal and carmine staining of the transplants revealed that a number of undifferentiated lacZ/MSF cells survived around the mammary epithelial tissue when transplanted with organoids. These results indicate that transplantation of MSF cells into mammary fat pad was accomplished by co-transplantation with primary mammary organoids. Finally, we discuss the application of transplantation procedure for in vivo studies of the mammary stromal tissue development and stromal-epithelial interactions.

QDMR: a quantitative method for identification of differentially methylated regions by entropy

DNA methylation plays critical roles in transcriptional regulation and chromatin remodeling. Differentially methylated regions (DMRs) have important implications for development, aging and diseases. Therefore, genome-wide mapping of DMRs across various temporal and spatial methylomes is important in revealing the impact of epigenetic modifications on heritable phenotypic variation. We present a quantitative approach, quantitative differentially methylated regions (QDMRs), to quantify methylation difference and identify DMRs from genome-wide methylation profiles by adapting Shannon entropy. QDMR was applied to synthetic methylation patterns and methylation profiles detected by methylated DNA immunoprecipitation microarray (MeDIP-chip) in human tissues/cells. This approach can give a reasonable quantitative measure of methylation difference across multiple samples. Then DMR threshold was determined from methylation probability model. Using this threshold, QDMR identified 10 651 tissue DMRs which are related to the genes enriched for cell differentiation, including 4740 DMRs not identified by the method developed by Rakyan et al. QDMR can also measure the sample specificity of each DMR. Finally, the application to methylation profiles detected by reduced representation bisulphite sequencing (RRBS) in mouse showed the platform-free and species-free nature of QDMR. This approach provides an effective tool for the high-throughput identification of potential functional regions involved in epigenetic regulation.

A preliminary study of differentially expressed genes in expanded skin and normal skin: implications for adult skin regeneration

In adults, severely damaged skin heals by scar formation and cannot regenerate to the original skin structure. However, tissue expansion is an exception, as normal skin regenerates under the mechanical stretch resulting from tissue expansion. This technique has been used clinically for defect repair and organ reconstruction for decades. However, the phenomenon of adult skin regeneration during tissue expansion has caused little attention, and the mechanism of skin regeneration during tissue expansion has not been fully understood. In this study, microarray analysis was performed on expanded human skin and normal human skin. Significant difference was observed in 77 genes, which suggest a network of several integrated cascades, including cytokines, extracellular, cytoskeletal, transmembrane molecular systems, ion or ion channels, protein kinases and transcriptional systems, is involved in the skin regeneration during expansion. Among these, the significant expression of some regeneration related genes, such as HOXA5, HOXB2 and AP1, was the first report in tissue expansion. Data in this study suggest a list of candidate genes, which may help to elucidate the fundamental mechanism of skin regeneration during tissue expansion and which may have implications for postnatal skin regeneration and therapeutic interventions in wound healing.

Repression of Lim only protein 4-activated transcription inhibits proliferation and induces apoptosis of normal mammary epithelial cells and breast cancer cells

Lim only protein (LMO) 4 acts as a transcriptional adapter and modulates mammary gland morphogenesis as well as breast oncogenesis in transgenic mice. Yet, the molecular and cellular mechanisms of these effects remain to be fully elucidated. Engrailed LMO4 fusion protein is a powerful dominant repressor of LMO4 activated transcription that was successfully used to discover the role of LMO4 as a transcriptional activator in mammary gland development in our previous studies using mouse models. In this manuscript, we investigated the cellular effects of LMO4 in human normal mammary epithelial cells (HMECs) and breast cancer cell lines using the Engrailed-LMO4 fusion protein. HMEC cell growth was inhibited by the expression of the Engrailed-LMO4 fusion protein. The decrease in cell number was due to both decreased cell proliferation and enhanced apoptosis, suggesting that LMO4 promotes proliferation and survival of normal mammary epithelial cells. The expression of the Engrailed-LMO4 fusion protein also suppressed cell growth, and induced apoptosis in two breast cancer cell lines, MDA-MB-231 and T47D, suggesting that LMO4 contributes to oncogenesis by similar mechanisms of enhanced cell survival and proliferation. Taken together, our data indicate that LMO4 has similar cellular effects in normal mammary epithelial cells and breast cancer cells, and also provide direct evidence for the idea that normal development and carcinogenesis share conserved molecular mechanisms.

Multiple promoters and alternative splicing: Hoxa5 transcriptional complexity in the mouse embryo

Background

The genomic organization of Hox clusters is fundamental for the precise spatio-temporal regulation and the function of each Hox gene, and hence for correct embryo patterning. Multiple overlapping transcriptional units exist at the Hoxa5 locus reflecting the complexity of Hox clustering: a major form of 1.8 kb corresponding to the two characterized exons of the gene and polyadenylated RNA species of 5.0, 9.5 and 11.0 kb. This transcriptional intricacy raises the question of the involvement of the larger transcripts in Hox function and regulation.

Methodology/Principal Findings

We have undertaken the molecular characterization of the Hoxa5 larger transcripts. They initiate from two highly conserved distal promoters, one corresponding to the putative Hoxa6 promoter, and a second located nearby Hoxa7. Alternative splicing is also involved in the generation of the different transcripts. No functional polyadenylation sequence was found at the Hoxa6 locus and all larger transcripts use the polyadenylation site of the Hoxa5 gene. Some larger transcripts are potential Hoxa6/Hoxa5 bicistronic units. However, even though all transcripts could produce the genuine 270 a.a. HOXA5 protein, only the 1.8 kb form is translated into the protein, indicative of its essential role in Hoxa5 gene function. The Hoxa6 mutation disrupts the larger transcripts without major phenotypic impact on axial specification in their expression domain. However, Hoxa5-like skeletal anomalies are observed in Hoxa6 mutants and these defects can be explained by the loss of expression of the 1.8 kb transcript. Our data raise the possibility that the larger transcripts may be involved in Hoxa5 gene regulation.

Significance

Our observation that the Hoxa5 larger transcripts possess a developmentally-regulated expression combined to the increasing sum of data on the role of long noncoding RNAs in transcriptional regulation suggest that the Hoxa5 larger transcripts may participate in the control of Hox gene expression.

Influence of Hoxa5 on p53 tumorigenic outcome in mice

Hox genes encode transcription factors of crucial importance in the pattern formation of a large spectrum of species. Several studies have now proposed a role for these developmental genes in cancer biology. It has been suggested that HOXA5 possesses growth-suppressive properties through activation of p53 expression in human breast tissue. To assess the genetic cooperation that may exist between Hoxa5 and p53 in tumorigenesis, we generated Hoxa5/p53 compound mutant mice. The presence of Hoxa5 null alleles increased the susceptibility of p53(-/-) mice to develop tumors with a high prevalence for thymic lymphoma, suggesting that the loss of function of the two genes collaborate in tumor formation. To extend our analysis to mammary tumorigenesis, we performed Hoxa5/p53 whole mammary gland transplantations into wild-type hosts. In the p53(-/-) background, the presence of one Hoxa5 mutant allele had no impact on mammary tumor formation. In contrast, the complete loss of Hoxa5 function influenced the tumorigenic outcome of p53(+/-) mammary glands. However, the collaborative nature of this interaction did not depend on the transcriptional regulation of p53 by Hoxa5. Altogether, our data establish that Hoxa5 and p53 cooperate in mammary tumorigenesis in vivo.

[Hoxa5: a master gene with multifaceted roles]

The Hox gene family occupies a central position in the control of body patterning by regulating the transcription of downstream effectors that, in turn, direct the morphogenetic events leading to the complex body forms along the axes. Analysis of Hox mutant mouse lines has revealed a panoply of phenotypes indicative of the broad range of Hox genes action throughout embryonic and postnatal life. Although Hox genes have been the subject of extensive research in the last two decades, the comprehension of the mechanisms involved in their regulation and function still remains elusive. Here, we present an overview of our current knowledge about one Hox gene family member, Hoxa5. The phenotypic survey of Hoxa5 mutant mice has unveiled the crucial role of this gene in regulating morphogenesis and specifying regional identity along the embryo. A majority of Hoxa5 mutant pups die at birth from defective respiratory tract. Surviving mutants present deficient alveolar septation revealing the importance of Hoxa5 during formation and maturation of the lung. Hoxa5 also participates in the morphogenesis of the digestive tract as well as that of the thyroid and mammary glands. Hoxa5 expression is restricted to the mesenchyme, and its action appears to be mediated through the control of mesenchymal-epithelial interactions during organogenesis. The implication of Hoxa5 in tumorigenesis has also been documented. In breast cancer, Hoxa5 down-regulation may impact on p53 gene expression, contributing to the oncogenic process. In contrast, the loss of Hoxa5 function limits leukaemia associated with specific chromosomal translocations. Thus, inappropriate Hoxa5 gene expression may disrupt normal growth and differentiation programs causing neoplasia. Hox gene function is intimately linked to its correct expression. Regulation of Hoxa5 expression requires multiple cis-acting regions, some encompassing coding sequences from neighboring genes. Moreover, it is complicated by the presence of several transcription units. Together these data enlighten the importance of Hox cluster organization in Hoxa5 function.

HoxA5 stabilizes adherens junctions via increased Akt1

Normal vascular development and angiogenesis is regulated by coordinated changes in cell-cell and cell-extracellular matrix (ECM) interactions. The Homeobox (Hox) family of transcription factors coordinately regulate expression of matrix degrading proteinases, integrins and ECM components and profoundly impact vascular remodeling. Whereas HoxA5 is down regulated in active angiogenic endothelial cells (EC), sustained expression of HoxA5 induces TSP-2 and blocks angiogenesis. Since HoxA5 is also lacking in EC in proliferating hemangiomas, we investigated whether restoring expression of HoxA5 could normalize hemangioma cell morphology and/or behavior. Sustained expression of HoxA5 in the murine hemangioma cell line (EOMA) reduced their growth in vivo and promoted branching morphogenesis in 3D BM cultures. Moreover, restoring HoxA5 expression increased the retention of beta-catenin in adherens junctions and reduced permeability. In addition we also show that the HoxA5 mediated increase in stability of adherens junctions requires Akt1 activity and introduction of constitutively active myr-Akt in EOMA cells also increased retention of beta-catenin in adherens junctions. Finally we show that HoxA5 increases Akt1 mRNA, protein expression and further enhances Akt activity via a coordinate down regulation of PTEN. Together these results demonstrate a central role for HoxA5 in coordinating a stable vascular phenotype.

Comparative analysis of Hoxa5 allelic series

Analysis of the Hoxa5(-/-) mutants has revealed the critical role of Hoxa5 in survival, specification of axial identity, and ontogeny of organs, including the respiratory tract. The presence of the selection cassette in the original Hoxa5(-/-) mutation may interfere with the interpretation of the phenotypes. To circumvent this aspect and to bypass the lethality of the Hoxa5 mutation, we have designed a conditional approach and generated Hoxa5 allelic variants. The conditional allele (Hoxa5(floxed)) behaves as a wild-type allele. In contrast, both the Hoxa5(Delta) and the Hoxa5(floxneo) alleles are characterized by the loss of the functional transcript and protein, the lethality due to lung defects and the skeletal homeotic transformations similar to those of the Hoxa5(-/-) mutants. Analysis of neighboring Hox gene expression patterns in the Hoxa5 mutants produced further confirmed that the Hoxa5 allelic variants are true null alleles.

All-trans retinoic acid induces proliferation of an irradiated stem cell supporting stromal cell line AFT024

OBJECTIVE

We have previously shown that all-trans retinoic acid (ATRA) enhanced the maintenance of early human hematopoietic progenitor cells (HPCs) in the presence of an irradiated stromal cell line AFT024. In this study, we examined the effects of ATRA on the stromal cell component with particular reference to cellular proliferation and gene expression.

METHODS

Irradiated AFT024 cells were cultured in Dulbecco's Modified Eagle's Medium supplemented with fetal bovine serum and were incubated with ATRA at 1 mumol/L up to 21 days. The cells were examined in terms of immunostaining for proliferative cell nuclear antigen (PCNA) and BrdU incorporation, apoptosis assay, cell cycle analysis, and gene expression using semiquantitative reverse-transcriptase polymerase chain reaction.

RESULTS

In the control experiments, AFT024 cells lost their confluence in culture after 15-Gy irradiation and were arrested in G2/M phase on days 7 and 21. ATRA restored the cellular confluence with an increase in proliferation on day 21 (BrdU incorporation: 20.6-fold; PCNA staining: 51.7-fold) with reversal of cell cycle arrest (S phase: 2.7-fold increase; G2/M phase: 2.0-fold decrease). There was no effect on apoptosis as shown by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. ATRA significantly upregulated the expression of cell cycle genes for checkpoint transition, including cyclin A2, B2, and aurora kinase B, as well as genes associated with a putative role in HPC maintenance, including osteopontin, HoxA5, enhancer of zeste homolog 2, and peroxisome proliferator-activated receptor gamma.

CONCLUSION

We concluded that ATRA induced cellular proliferation of irradiated AFT024 cells and expression of a number of genes whose relevance to HPC homeostasis would have to be further examined.

Impact of the loss of Hoxa5 function on lung alveogenesis

The involvement of genes controlling embryonic processes in the etiology of diseases often escapes attention because of the focus given to their inherent developmental role. Hoxa5 belongs to the Hox gene family encoding transcription factors known for their role in skeletal patterning. Hoxa5 is required for embryonic respiratory tract morphogenesis. We now show that the loss of Hoxa5 function has severe repercussions on postnatal lung development. Hoxa5-/- lungs present an emphysema-like morphology because of impaired alveogenesis. Chronic inflammation characteristics, including goblet cell hyperplasia, mucus hypersecretion, and recruitment of inflammatory cells, were also observed. Altered cell specification during lung morphogenesis triggered goblet cell anomalies. In addition, the defective motility of alveolar myofibroblast precursors in the embryonic lung led to the mispositioning of the alveolar myofibroblasts and to abnormal elastin deposition postnatally. Both goblet cell hyperplasia and elastic fiber abnormalities contributed to the chronic physiopathological features of Hoxa5-/- lungs. They constituted an attractive stimulus to recruit activated macrophages that in turn generated a positive feedback loop that perpetuated macrophage accumulation in the lung. The present work corroborates the notion that altered Hox gene expression may predispose to lung pathologies.