Pax in development

PAX2 induces vascular‑like structures in normal ovarian cells and ovarian cancer

In adult tissue, the paired box 2 (PAX2) protein is expressed in healthy oviductal, but not normal ovarian surface epithelial cells. PAX2 is expressed in a subset of cases of serous ovarian carcinoma; however, the role of PAX2 in the initiation and progression of ovarian cancer remains unknown. The aim of the present study was to determine the biological effects of PAX2 expression in normal and cancerous epithelial cells. By culturing the normal and cancerous ovarian cells that express PAX2 in 3D culture and staining the cells with vasculogenic mimicry markers such as CD31 and PAS, it was shown that PAX2 overexpression in both normal and cancerous ovarian epithelial cells induced formation of vascular-like structures both in vitro and in vivo. These results indicated a potential role of PAX2 in ovarian cancer progression by increasing the presence of vascular-like structures to promote the supply of nutrients to tumor cells and facilitate cancer cell proliferation and invasion.

Human spinal cord in vitro differentiation pace is initially maintained in heterologous embryonic environments

Species-specific differentiation pace in vitro indicates that some aspects of neural differentiation are governed by cell intrinsic properties. Here we describe a novel in vitro human neural-rosette assay that recapitulates dorsal spinal cord differentiation but proceeds more rapidly than in the human embryo, suggesting that it lacks endogenous signalling dynamics. To test whether in vitro conditions represent an intrinsic differentiation pace, human iPSC-derived neural rosettes were challenged by grafting into the faster differentiating chicken embryonic neural tube iso-chronically, or hetero-chronically into older embryos. In both contexts in vitro differentiation pace was initially unchanged, while long-term analysis revealed iso-chronic slowed and hetero-chronic conditions promoted human neural differentiation. Moreover, hetero-chronic conditions did not alter the human neural differentiation programme, which progressed to neurogenesis, while the host embryo advanced into gliogenesis. This study demonstrates that intrinsic properties limit human differentiation pace, and that timely extrinsic signals are required for progression through an intrinsic human neural differentiation programme.

Effect of NTN and Lmx1α on the Notch Signaling Pathway during the Differentiation of Human Bone Marrow Mesenchymal Stem Cells into Dopaminergic Neuron-Like Cells

Human bone marrow mesenchymal stem cells (h-BMSCs) have the potential to differentiate into dopaminergic neuron-like cells to treat Parkinson's disease. The Notch signaling pathway has been implicated in the regulation of cell fate decisions such as differentiation of BMSCs. This study investigated changes in the expression of Notch-related genes in the differentiation of BMSCs in vitro into dopaminergic (DA) neuron-like cells. BMSCs transfected with empty lentiviral vectors served as the control group and those transfected with NTN and Lmx1α recombinant lentiviral vectors served as the experimental group. After induction and culture of NTN and Lmx1α-transfected h-BMSCs for 21 days, the cells exhibited features of dopaminergic neuron-like cells, which were observed by transmission and scanning electron microscopy and verified by immunofluorescence of tyrosine hydroxylase (TH) and dopamine transporter (DAT). These induced cells could secrete dopamine and had basic action potentials. Expression of the neural stem cell (NSC) markers, including octamer-binding protein (Oct4), paired box gene 6 (Pax6), and sex determining region Y-box 1 (SOX1), increased on day 14 of induction and decreased on day 21 of induction during differentiation. The human Notch signaling pathway PCR array showed a differential expression of Notch-related genes during the differentiation of h-BMSCs into DA neuron-like cells in vitro relative to that in the control group. In conclusion, h-BMSCs overexpressing NTN and Lmx1α can successfully be induced to differentiate into dopaminergic neuron-like cells with a neuronal phenotype exhibiting fundamental biological functions in vitro, and NTN and Lmx1α may affect the expression of Notch-related genes during differentiation.

Dynamic Molecular Evolution of Mammalian Homeobox Genes: Duplication, Loss, Divergence and Gene Conversion Sculpt PRD Class Repertoires

The majority of homeobox genes are highly conserved across animals, but the eutherian-specific ETCHbox genes, embryonically expressed and highly divergent duplicates of CRX, are a notable exception. Here we compare the ETCHbox genes of 34 mammalian species, uncovering dynamic patterns of gene loss and tandem duplication, including the presence of a large tandem array of LEUTX loci in the genome of the European rabbit (Oryctolagus cuniculus). Despite extensive gene gain and loss, all sampled species possess at least two ETCHbox genes, suggesting their collective role is indispensable. We find evidence for positive selection and show that TPRX1 and TPRX2 have been the subject of repeated gene conversion across the Boreoeutheria, homogenising their sequences and preventing divergence, especially in the homeobox region. Together, these results are consistent with a model where mammalian ETCHbox genes are dynamic in evolution due to functional overlap, yet have collective indispensable roles.

Pax3 and Pax7 Exhibit Distinct and Overlapping Functions in Marking Muscle Satellite Cells and Muscle Repair in a Marine Teleost, Sebastes schlegelii

Pax3 and Pax7 are members of the Pax gene family which are essential for embryo and organ development. Both genes have been proved to be markers of muscle satellite cells and play key roles in the process of muscle growth and repair. Here, we identified two Pax3 genes (SsPax3a and SsPax3b) and two Pax7 genes (SsPax7a and SsPax7b) in a marine teleost, black rockfish (Sebastes schlegelii). Our results showed SsPax3 and SsPax7 marked distinct populations of muscle satellite cells, which originated from the multi-cell stage and somite stage, respectively. In addition, we constructed a muscle injury model to explore the function of these four genes during muscle repair. Hematoxylin–eosin (H–E) of injured muscle sections showed new-formed myofibers occurred at 16 days post-injury (dpi). ISH (in situ hybridization) analysis demonstrated that the expression level of SsPax3a and two SsPax7 genes increased gradually during 0–16 dpi and peaked at 16 dpi. Interestingly, SsPax3b showed no significant differences during the injury repair process, indicating that the satellite cells labeled by SsPax3b were not involved in muscle repair. These results imply that the muscle stem cell populations in teleosts are more complicated than in mammals. This lays the foundation for future studies on the molecular mechanism of indeterminant growth and muscle repair of large fish species.

Immunohistochemical expression of PAX-8 in Sudanese patients diagnosed with malignant female reproductive tract tumors

Objectives

Paired box protein-8 (PAX-8) immunohistochemical expression can be used as a diagnostic marker for epithelial cells tumors. This study aimed at investigating the immunohistochemical expression of PAX-8 among Sudanese females diagnosed with cervical, endometrial, and ovarian cancers between December 2017 and May 2019 by studying their Formalin-fixed paraffin embedded blocks.

Results

Sixty patients diagnosed with female reproductive tract cancers were included who aged 58.7 ± 6.9 years (range, 43—71). Cervix was the most common cancer site in 51/60 (85%) patients. Regarding cancer stage, there was 17 (28%) and 14 (23%) of the study population had stage 3B and 2B, respectively. The histopathological diagnosis included 20 (44%), 13 (29%), and 12 (27%) poorly, moderately, and well differentiated cervical squamous cell carcinoma (SCC) as well as 11 (73%), 2 (13%), 1 (7%), and 1 (7%) endometrial adenocarcinoma, metastatic adenocarcinoma, endocervical adenocarcinoma, and ovarian mucinous cyst adenocarcinoma, respectively. PAX-8 was positively expressed in 9 endometrial adenocarcinoma, 1 endocervical adenocarcinoma and 1 ovarian mucinous cyst adenocarcinoma, 2 poorly, and 1 moderately differentiated SCC. All patients diagnosed with well differentiated SCC and metastatic adenocarcinoma showed no expression of PAX-8. A statistically significant was seen for PAX-8 expression and the different histopathological diagnosis, P value < 0.001.

Activating PAX gene family paralogs to complement PAX5 leukemia driver mutations

PAX5, one of nine members of the mammalian paired box (PAX) family of transcription factors, plays an important role in B cell development. Approximately one-third of individuals with pre-B acute lymphoblastic leukemia (ALL) acquire heterozygous inactivating mutations of PAX5 in malignant cells, and heterozygous germline loss-of-function PAX5 mutations cause autosomal dominant predisposition to ALL. At least in mice, Pax5 is required for pre-B cell maturation, and leukemic remission occurs when Pax5 expression is restored in a Pax5-deficient mouse model of ALL. Together, these observations indicate that PAX5 deficiency reversibly drives leukemogenesis. PAX5 and its two most closely related paralogs, PAX2 and PAX8, which are not mutated in ALL, exhibit overlapping expression and function redundantly during embryonic development. However, PAX5 alone is expressed in lymphocytes, while PAX2 and PAX8 are predominantly specific to kidney and thyroid, respectively. We show that forced expression of PAX2 or PAX8 complements PAX5 loss-of-function mutation in ALL cells as determined by modulation of PAX5 target genes, restoration of immunophenotypic and morphological differentiation, and, ultimately, reduction of replicative potential. Activation of PAX5 paralogs, PAX2 or PAX8, ordinarily silenced in lymphocytes, may therefore represent a novel approach for treating PAX5-deficient ALL. In pursuit of this strategy, we took advantage of the fact that, in kidney, PAX2 is upregulated by extracellular hyperosmolarity. We found that hyperosmolarity, at potentially clinically achievable levels, transcriptionally activates endogenous PAX2 in ALL cells via a mechanism dependent on NFAT5, a transcription factor coordinating response to hyperosmolarity. We also found that hyperosmolarity upregulates residual wild type PAX5 expression in ALL cells and modulates gene expression, including in PAX5-mutant primary ALL cells. These findings specifically demonstrate that osmosensing pathways may represent a new therapeutic target for ALL and more broadly point toward the possibility of using gene paralogs to rescue mutations driving cancer and other diseases.

Paired box 7 (Pax7) gene: molecular characterisation, polymorphism and its association with growth performance in goose (Anser cygnoides)

1. Paired box (Pax7) gene is a member of the paired box family and plays a critical role in animal growth and muscle development. However, the molecular characterisation of the goose Pax7 gene is unknown. 2. The open-reading frame of goose Pax7 is composed of 1509 bp, which encodes a protein of 503 amino acids and shares high homology with Pax7 of other birds. 3. Ten single-nucleotide polymorphisms were identified in the genomic DNA sequence, 8 located in the intron region and two located in the exon region. 4. Association analysis showed the C122T locus was significantly associated with the body weight of Zhedong-White geese in week 4, 6, 8, 10 and 12. 5. It was concluded that the goose Pax7 gene may be an important candidate gene for goose growth traits and marker-assisted selection.

PAX6 aniridia syndrome: clinics, genetics, and therapeutics

PURPOSE OF REVIEW

Aniridia is a rare and panocular disorder affecting most of the ocular structures which may have significant impact on vision. The purpose of this review is to describe the clinical features, genetics, and therapeutic options for this disease and to provide an update of current knowledge and latest research findings.

RECENT FINDINGS

Aside from the ocular features, a variety of associated systemic abnormalities, including hormonal, metabolic, gastrointestinal, genitourinary, and neurologic pathologies have been reported in children with aniridia. Although mutations in PAX6 are a major cause of aniridia, genetic defects in nearby genes, such as TRIM44 or ELP4, have also been reported to cause aniridia. Recent improvement in genetic testing technique will help more rapid and precise diagnosis for aniridia. A promising therapeutic approach called nonsense suppression therapy has been introduced and successfully used in an animal model.

SUMMARY

Aniridia is a challenging disease. The progressive nature of this condition and its potential complications require continuous and life-long ophthalmologic care. Genetic diagnosis for aniridia is important for establishing definitive molecular characterization as well as identifying individuals at high risk for Wilms tumor. Recent advancement in understanding the genetic pathogenesis of this disease offers promise for the approaches to treatment.

PAX2 maintains the differentiation of mouse oviductal epithelium and inhibits the transition to a stem cell-like state

Recent studies have provided evidence that the secretory cells of the fallopian tube (oviduct) are a probable origin for high-grade serous ovarian carcinoma. In addition to secretory cells, the fallopian tube epithelium consists of ciliated cells and CD44+ undifferentiated stem-like cells. Loss of PAX2 expression is recognized as an early event in epithelial transformation, but the specific role of PAX2 in this transition is unknown. The aim of this study was to define the role of PAX2 in oviductal epithelial (OVE) cells and its response to transforming growth factor β1 (TGFβ), characterizing specifically its potential involvement in regulating stem cell-like behaviors that may contribute to formation of cancer-initiating cells. Treatment of primary cultures of mouse OVE cells with TGFβ induced an epithelial-mesenchymal transition (EMT) associated with decreased expression of PAX2 and an increase in the fraction of cells expressing CD44. PAX2 knockdown in OVE cells and overexpression in ovarian epithelial cells confirmed that PAX2 inhibits stem cell characteristics and regulates the degree of epithelial differentiation of OVE cells. These results suggest that loss of PAX2, as occurs in serous tubal intraepithelial carcinomas, may shift secretory cells to a more mesenchymal phenotype associated with stem-like features.

Genetic association between PAX2 and mullerian duct anomalies in Han Chinese females

PURPOSE

The study aims to investigate the genetic association between paired box gene 2 (PAX2) and mullerian duct anomalies (MDA) in Chinese Han females.

METHODS

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to identify the genotypes of three tag single nucleotide polymorphisms (SNPs) in PAX2 in 362 MDA cases and 406 controls.

RESULTS

We found that one tag SNP (rs12266644) of PAX2 was associated with susceptibility to MDA. The genotype distributions of the SNP rs12266644 have a statistically significant difference in the MDA patients and controls with a p value = 0.008. In the dominant model, we also observed that the GT + TT genotype increased the risk for MDA (p = 0.015, OR = 1.637, 95 % CI = 1.096-2.443).

CONCLUSION

The polymorphism rs12266644 of PAX2 might be a risk factor for MDA in Chinese Han females.

PAX8 is transcribed aberrantly in cervical tumors and derived cell lines due to complex gene rearrangements

The transcription factor PAX8, a member of the paired box-containing gene family with an important role in embryogenesis of the kidney, thyroid gland and nervous system, has been described as a biomarker in tumors of the thyroid, parathyroid, kidney and thymus. The PAX8 gene gives rise to four isoforms, through alternative mRNA splicing, but the splicing pattern in tumors is not yet established. Cervical cancer has a positive expression of PAX8; however, there is no available data determining which PAX8 isoform or isoforms are present in cervical cancer tissues as well as in cervical carcinoma-derived cell lines. Instead of a differential pattern of splicing isoforms, we found numerous previously unreported PAX8 aberrant transcripts ranging from 378 to 542 bases and present in both cervical carcinoma-derived cell lines and tumor samples. This is the first report of PAX8 aberrant transcript production in cervical cancer. Reported PAX8 isoforms possess differential transactivation properties; therefore, besides being a helpful marker for detection of cancer, PAX8 isoforms can plausibly exert differential regulation properties during carcinogenesis.

PAX6: 25th anniversary and more to learn

The DNA-binding transcription factor PAX6 was cloned 25 years ago by multiple teams pursuing identification of human and mouse eye disease causing genes, cloning vertebrate homologues of pattern-forming regulatory genes identified in Drosophila, or abundant eye-specific transcripts. Since its discovery in 1991, genetic, cellular, molecular and evolutionary studies on Pax6 mushroomed in the mid 1990s leading to the transformative thinking regarding the genetic program orchestrating both early and late stages of eye morphogenesis as well as the origin and evolution of diverse visual systems. Since Pax6 is also expressed outside of the eye, namely in the central nervous system and pancreas, a number of important insights into the development and function of these organs have been amassed. In most recent years, genome-wide technologies utilizing massively parallel DNA sequencing have begun to provide unbiased insights into the regulatory hierarchies of specification, determination and differentiation of ocular cells and neurogenesis in general. This review is focused on major advancements in studies on mammalian eye development driven by studies of Pax6 genes in model organisms and future challenges to harness the technology-driven opportunities to reconstruct, step-by-step, the transition from naïve ectoderm, neuroepithelium and periocular mesenchyme/neural crest cells into the three-dimensional architecture of the eye.

PAX transcription factors in neural crest development

The nine vertebrate PAX transcription factors (PAX1-PAX9) play essential roles during early development and organogenesis. Pax genes were identified in vertebrates using their homology with the Drosophila melanogaster paired gene DNA-binding domain. PAX1-9 functions are largely conserved throughout vertebrate evolution, in particular during central nervous system and neural crest development. The neural crest is a vertebrate invention, which gives rise to numerous derivatives during organogenesis, including neurons and glia of the peripheral nervous system, craniofacial skeleton and mesenchyme, the heart outflow tract, endocrine and pigment cells. Human and mouse spontaneous mutations as well as experimental analyses have evidenced the critical and diverse functions of PAX factors during neural crest development. Recent studies have highlighted the role of PAX3 and PAX7 in neural crest induction. Additionally, several PAX proteins - PAX1, 3, 7, 9 - regulate cell proliferation, migration and determination in multiple neural crest-derived lineages, such as cardiac, sensory, and enteric neural crest, pigment cells, glia, craniofacial skeleton and teeth, or in organs developing in close relationship with the neural crest such as the thymus and parathyroids. The diverse PAX molecular functions during neural crest formation rely on fine-tuned modulations of their transcriptional transactivation properties. These modulations are generated by multiple means, such as different roles for the various isoforms (formed by alternative splicing), or posttranslational modifications which alter protein-DNA binding, or carefully orchestrated protein-protein interactions with various co-factors which control PAX proteins activity. Understanding these regulations is the key to decipher the versatile roles of PAX transcription factors in neural crest development, differentiation and disease.

Transcriptional and epigenetic mechanisms of early cortical development: An examination of how Pax6 coordinates cortical development

The development of the cortex is an elaborate process that integrates a plethora of finely tuned molecular processes ranging from carefully regulated gradients of transcription factors, dynamic changes in the chromatin landscape, or formation of protein complexes to elicit and regulate transcription. Combined with cellular processes such as cell type specification, proliferation, differentiation, and migration, all of these developmental processes result in the establishment of an adult mammalian cortex with its typical lamination and regional patterning. By examining in-depth the role of one transcription factor, Pax6, on the regulation of cortical development, its integration in the regulation of chromatin state, and its regulation by cis-regulatory elements, we aim to demonstrate the importance of integrating each level of regulation in our understanding of cortical development.

Characterization of Pax3 and Pax7 genes and their expression patterns during different development and growth stages of Japanese pufferfish Takifugu rubripes

Pax3 and Pax7 are the regulators and markers of muscle progenitors and satellite cells that contribute to the embryonic development and postembryonic growth of skeletal muscle in vertebrates, as well as to its repair and regeneration. However, information regarding them in vertebrate genome model, torafugu Takifugu rubripes, has remained unknown. Therefore, as an initial step, here we characterized Pax3 and Pax7 from torafugu and investigated their expression patterns during different developmental stages by RT-PCR. In silico analysis with the Fugu genome database (ver. 4.0) yielded two distinct genes each for Pax3 (Pax3a and Pax3b) and Pax7 (Pax7a and Pax7b). The 75th amino acid, glutamine (Gln75), from the N-terminus was replaced by proline in the paired box domain (PD) of Pax3a. One single cDNA clone encoding Pax3a had deletion of Gln75 in PD, suggesting the presence of alternatively spliced variants (Q+/Q-). This was further supported by identification of two adjacent alternative 3' splice acceptor sites which produce Pax3b Q+ (aagCAGGGA) and Q- (aagcagGGA) variants. Interestingly, torafugu Pax7a, but not Pax7b, had an insert encoding five amino acid residues (SGEAS) in a C-terminal region of PD in two out of three cDNA clones. Genomic analysis showed two alternate splice donor sites at exon 4 of Pax7a. In synteny analysis, torafugu Pax3a showed syntenic relationship with the corresponding regions in other teleosts only, whereas Pax3b and Pax7b showed high syntenic relationship with the corresponding regions of both mammals and other teleosts. RT-PCR revealed that expression of Pax3a and Pax3b transcripts was restricted to embryonic stages only, whereas those of Pax7a and Pax7b was continued to be expressed in larvae and importantly those of Pax7a were found in adult skeletal muscles. Therefore, Pax3 appears to be most important for primary myogenesis and Pax7 for secondary myogenesis and growth by hyperplasia in fish. In this regard, the transcripts of torafugu Pax3 and Pax7 genes might be used for further investigation as a marker for identification of muscle precursor cells during different phases of growth, and this ambiguity is the next target of our research.

The duplicated paired box protein 7 (pax7) genes differentially transcribed during Japanese flounder (Paralichthys olivaceus) embryogenesis

PAX are important regulators of developmental processes. PAX7 plays crucial roles in patterning of the dorsal central nervous system (CNS), neural crest (NC), and skeletal muscle. Here, we identified six spliced isoforms of pax7a and one pax7b and characterized their expression patterns. All of flounder Pax7a-1, Pax7a-2, Pax7a-3, and Pax7b contain a conserved paired domain (PD), an octapeptide motif (OP), and a paired type homeodomain (HD). However, the PD of Pax7a-4 and the HD of Pax7a-5 are not intact, and there is no HD in Pax7a-4 and Pax7a-6. pax7a and pax7b show distinct spatiotemporal expression patterns during embryogenesis. Whole-mount in situ hybridization demonstrates that the expression patterns of pax7a and pax7b are overlapping but distinguishable in the dorsal central nervous system. pax7a is expressed in most part of the brain and the neural tube, while pax7b is expressed exclusively in the diencephalon and the midbrain. In addition, pax7a is also expressed in the cranial NC and the trunk NC. RT-PCR results show that there were different expression patterns between the different isoforms. These results indicate subfunction partitioning of the duplicated pax7 genes. The duplicated pax7 may provide additional flexibility in fine-tuning neurogenesis and somitogenesis.

Regulation of cerebral cortical neurogenesis by the Pax6 transcription factor

Understanding brain development remains a major challenge at the heart of understanding what makes us human. The neocortex, in evolutionary terms the newest part of the cerebral cortex, is the seat of higher cognitive functions. Its normal development requires the production, positioning, and appropriate interconnection of very large numbers of both excitatory and inhibitory neurons. Pax6 is one of a relatively small group of transcription factors that exert high-level control of cortical development, and whose mutation or deletion from developing embryos causes major brain defects and a wide range of neurodevelopmental disorders. Pax6 is very highly conserved between primate and non-primate species, is expressed in a gradient throughout the developing cortex and is essential for normal corticogenesis. Our understanding of Pax6’s functions and the cellular processes that it regulates during mammalian cortical development has significantly advanced in the last decade, owing to the combined application of genetic and biochemical analyses. Here, we review the functional importance of Pax6 in regulating cortical progenitor proliferation, neurogenesis, and formation of cortical layers and highlight important differences between rodents and primates. We also review the pathological effects of PAX6 mutations in human neurodevelopmental disorders. We discuss some aspects of Pax6’s molecular actions including its own complex transcriptional regulation, the distinct molecular functions of its splice variants and some of Pax6’s known direct targets which mediate its actions during cortical development.

A novel duplication in the PAX6 gene in a North Indian family with aniridia

Mutations in paired box gene 6 (PAX6) are the major cause of aniridia that may be associated with several other developmental anomalies of the eye, including microcornea in rare cases. Therefore, the purpose of this study was to identify the underlying genetic cause in a two-generation North Indian family diagnosed with aniridia. All the participants enrolled in the study, including the aniridia family and 20 healthy individuals (controls), underwent a comprehensive ophthalmic examination. Mutation screening was performed for the PAX6 gene by direct sequencing of the polymerase chain reaction products. A novel PAX6 duplication in exon 5 at position c.474dupC was identified in all three affected individuals from the family but not in the unaffected family members or unrelated controls. We reported a novel duplication in the PAX6 gene capable of causing the classic aniridia phenotype. This is the first report on the duplication in a North Indian family with autosomal dominant aniridia.

The olive flounder (Paralichthys olivaceus) Pax3 homologues are highly conserved, encode multiple isoforms and show unique expression patterns

Pax genes encode a highly conserved family of transcription factors that play crucial roles in the formation of tissues and organs during development. Pax3 plays crucial roles in patterning of the dorsal central nervous system (CNS), neural crest and skeletal muscle. Here, we identified two spliced isoforms of Pax3a and three spliced isoforms of Pax3b and characterized their expression patterns. Both of flounder Pax3a-1 and Pax3b-1 contain the conserved paired domain (PD), an octapeptide motif (OP), and a paired type homeodomain (HD). But the PD domain in Pax3a-2 and Pax3b-3 is not intact and there is no HD in Pax3b-2 and Pax3b-3. Pax3a and Pax3b show distinct temporal expression patterns during embryogenesis. Whole-mount in situ hybridization demonstrates that Pax3a and Pax3b are expressed in overlapping patterns in the dorsal central nervous system, with some subtle regional differences between the two genes. In addition, Pax3a is scattered in the somites while Pax3b is specifically expressed in the newly forming somites. RT-PCR results have shown that there were different expression patterns between the different isoforms. These results indicate subfunction partitioning of the duplicated Pax3 genes. The duplicated Pax3 may provide additional flexibility in fine-tuning neurogenesis and somitogenesis.

Temporospatial gene expression of Prx1 and Prx2 is involved in morphogenesis of cranial placode-derived tissues through epithelio-mesenchymal interaction during rat embryogenesis

Paired-related homeobox transcription factors, PRX1 and PRX2, are verified to play essential roles in limb, heart and craniofacial development by analyses of knockout animals. Their gene expression in the embryonic primordia derived from the mesoderm and neural crest is confirmed by in situ hybridization. Nevertheless, a detailed localization of PRX1 and PRX2 was not carried out because of a lack of specific antibodies for each factor. We have previously confirmed the presence of PRX proteins in rat embryonic pituitary by using an antibody that recognizes both PRX1 and PRX2. However, the pituitary originates in the cranial placodes, not the mesoderm or neural crest. In this study, we analyze the temporospatial distribution of PRX1 and PRX2 with novel antibodies specific for each factor, together with a stem/progenitor marker SOX2 (sex-determining region Y-box 2) in the primordia formed by epithelio-mesenchymal interaction. We observe immunoreactive signals of both PRX proteins in rat embryo, showing a similar pattern to that obtained by in situ hybridization. In early embryogenesis, PRX proteins are not co-localized with SOX2 but PRX2 and/or PRX1-positive cells are present in the border or periphery of SOX2-positive primordia originating in the cranial placode. During advanced embryogenesis, either PRX2-positive cells become condensed in the border of SOX2-positive cells or PRX1 and/or PRX2 become co-localized with SOX2. Our results suggest that PRX proteins, especially PRX2, play a role in the morphogenesis of the primordial tissues formed by the epithelio-mesenchymal interaction and that neural crest cells contribute to the morphogenesis of tissues derived from the cranial placode.

Expressional alterations in functional ultra-conserved non-coding RNAs in response to all-trans retinoic acid--induced differentiation in neuroblastoma cells

Background

Ultra-conserved regions (UCRs) are segments of the genome (≥ 200 bp) that exhibit 100% DNA sequence conservation between human, mouse and rat. Transcribed UCRs (T-UCRs) have been shown to be differentially expressed in cancers versus normal tissue, indicating a possible role in carcinogenesis. All-trans-retinoic acid (ATRA) causes some neuroblastoma (NB) cell lines to undergo differentiation and leads to a significant decrease in the oncogenic transcription factor MYCN. Here, we examine the impact of ATRA treatment on T-UCR expression and investigate the biological significance of these changes.

Methods

We designed a custom tiling microarray to profile the expression of 481 T-UCRs in sense and anti-sense orientation (962 potential transcripts) in untreated and ATRA-treated neuroblastoma cell lines (SH-SY5Y, SK-N-BE, LAN-5). Following identification of significantly differentially expressed T-UCRs, we carried out siRNA knockdown and gene expression microarray analysis to investigate putative functional roles for selected T-UCRs.

Results

Following ATRA-induced differentiation, 32 T-UCRs were differentially expressed (16 up-regulated, 16 down-regulated) across all three cell lines. Further insight into the possible role of T-UC.300A, an independent transcript whose expression is down-regulated following ATRA was achieved by siRNA knockdown, resulting in the decreased viability and invasiveness of ATRA-responsive cell lines. Gene expression microarray analysis following knockdown of T-UC.300A revealed a number of genes whose expression was altered by changing T-UC.300A levels and that might play a role in the increased proliferation and invasion of NB cells prior to ATRA-treatment.

Conclusions

Our results indicate that significant numbers of T-UCRs have altered expression levels in response to ATRA. While the precise roles that T-UCRs might play in cancer or in normal development are largely unknown and an important area for future study, our findings strongly indicate that the function of non-coding RNA T-UC.300A is connected with proliferation, invasion and the inhibition of differentiation of neuroblastoma cell lines prior to ATRA treatment.

Value of PAX8, PAX2, claudin-4, and h-caldesmon immunostaining in distinguishing peritoneal epithelioid mesotheliomas from serous carcinomas

Distinguishing between peritoneal epithelioid mesotheliomas and papillary serous carcinomas involving the peritoneum can be difficult on routine histological preparations, but this differential diagnosis can be facilitated by the use of immunohistochemistry. Recent investigations have indicated that PAX8, PAX2, claudin-4, and h-caldesmon are immunohistochemical markers that can assist in distinguishing between these two malignancies; however, much of the information published on the value of these markers is either insufficient or contradictory. The purpose of this study is to resolve some of the existing controversies and to fully determine the practical value of these markers for assisting in the differential diagnosis between peritoneal mesotheliomas and serous carcinomas. In order to do so, a total of 40 peritoneal epithelioid mesotheliomas and 45 serous carcinomas (15 primary, 30 metastatic to the peritoneum) were investigated. PAX8 and PAX2 nuclear positivity was demonstrated in 42 (93%) and 25 (56%) of the serous carcinomas, respectively, whereas none of the mesotheliomas expressed either marker. Forty-four (98%) of the serous carcinomas exhibited claudin-4 reactivity along the cell membrane, whereas none of the mesotheliomas were positive for this marker. All of the serous carcinomas and mesotheliomas were negative for h-caldesmon. Based on these results, it is concluded that PAX8 and claudin-4 have a higher sensitivity and specificity for assisting in discriminating between peritoneal epithelioid mesotheliomas and serous carcinomas when compared with all of the other positive carcinoma markers that are, at present, recommended to be included in the immunohistochemical panels used in this differential diagnosis. Even though it is highly specific, PAX2 has little practical value in the diagnosis of peritoneal epithelioid mesotheliomas as its sensitivity is low. The h-caldesmon is not useful.

Ontogenesis of gonadotropin-releasing hormone neurons: a model for hypothalamic neuroendocrine cell development

The vertebrate hypothalamo-pituitary-gonadal axis is the anatomical framework responsible for reproductive competence and species propagation. Essential to the coordinated actions of this three-tiered biological system is the fact that the regulatory inputs ultimately converge on the gonadotropin-releasing hormone (GnRH) neuronal system, which in rodents primarily resides in the preoptic/hypothalamic region. In this short review we will focus on: (1) the general embryonic temporal and spatial development of the rodent GnRH neuronal system, (2) the origin(s) of GnRH neurons, and (3) which transcription - and growth factors have been found to be critical for GnRH neuronal ontogenesis and cellular fate-specification. Moreover, we ask the question whether the molecular and cellular mechanisms involved in GnRH neuronal development may also play a role in the development of other hypophyseal secreting neuroendocrine cells in the hypothalamus.

PAX2 loss by immunohistochemistry occurs early and often in endometrial hyperplasia

Immunohistochemical markers to assist in the diagnosis and classification of hyperplastic endometrial epithelial proliferations would be of diagnostic use. To examine the possible use of PAX2 as a marker of hyperplastic endometrium, cases of normal endometrium, simple and complex hyperplasia without atypia, atypical hyperplasia, and International Federation of Gynecology and Obstetrics (FIGO) grade 1 endometrioid carcinomas were stained for PAX2. Two hundred and six endometrial samples were available for interpretation of PAX2 staining. The percentage of cases with complete PAX2 loss (0% of cells staining) increased with increasing severity of hyperplasia: 0% of normal proliferative and secretory endometrium (n=28), 17.4% of simple hyperplasia (n=23), 59.0% of complex hyperplasia (n=83), 74.1% of atypical hyperplasia (n=54), and 73.3% of FIGO grade 1 endometrioid cancers (n=15). Partial loss of PAX2 expression did occur in normal endometrium (17.9%) but in smaller proportions of tissue and was less frequent than in simple hyperplasia (47.8% with partial loss), complex hyperplasia (32.5%), atypical hyperplasia (22.2%), and FIGO grade 1 carcinomas (20.0%). Uniform PAX2 expression was rare in complex (8.4%) and atypical hyperplasia (3.7%) and carcinoma (6.7%). When evaluating loss of PAX2 in histologically normal endometrium adjacent to lesional endometrium in a given case, statistically significant differences in staining were observed for simple hyperplasia (P=0.011), complex hyperplasia (P<0.001), atypical hyperplasia (P<0.001), and FIGO grade 1 endometrioid cancer (P=0.003). In summary, PAX2 loss seems to occur early in the development of endometrial precancers and may prove useful in some settings as a diagnostic marker in determining normal endometrium from complex and atypical hyperplasia and low-grade carcinomas. However, it is not useful in distinguishing between these diagnostic categories.

Value of PAX 8 immunostaining in tumor diagnosis: a review and update

PAX 8 is a transcription factor involved in the regulation of organogenesis of the thyroid gland, kidney, and Müllerian system. Recent studies have shown that, among tumors, PAX 8 is commonly expressed in epithelial tumors of the thyroid and parathyroid glands, kidney, thymus, and female genital tract. Although PAX 8 expression has also been reported in certain neuroendocrine tumors, including well-differentiated pancreatic neuroendocrine tumors, and duodenal and rectal carcinoids, as well as in B-cell lymphomas, it has recently been shown that the PAX 8 positivity reported in these tumors was due to a cross-reactivity of the antibody used with the N-terminal region of PAX 6 and PAX 5, respectively. Owing to its restricted expression, PAX 8 has proved to be a useful immunohistochemical marker with a wide range of diagnostic applications in surgical pathology, some of which are briefly reviewed.

PAX2 in 192 Chinese women with Müllerian duct abnormalities: mutation analysis

The paired box gene 2 (PAX2) has been proven to be a crucial gene during organogenesis of the urogenital system in mice models. This study was aimed to explore the relationship between PAX2 mutations and human Müllerian duct abnormalities (MDA). A total of 192 Chinese MDA patients (15 cases of uterine aplasia and 177 of incomplete Müllerian fusion) and 192 ethnic-matched controls were recruited from 2009 to 2011. Coding regions of PAX2 of MDA cases were amplified and sequenced. One rare novel synonymous variant (c.320G>A) was discovered in one patient with uterus didelphys, whereas this variant was not found in the control group. Mutations in PAX2 may be not a common cause of MDA.

Homeodomain subtypes and functional diversity

The homeodomain is a protein domain of about 60 amino acids that is encoded by homeobox genes. The homeodomain is a DNA binding domain, and hence homeodomain proteins are essentially transcription factors (TFs). They have been shown to play major roles in many developmental processes of animals, as well as fungi and plants. A primary function of homeodomain proteins is to regulate the expression of other genes in development and differentiation. Thousands of homeobox genes have been identified, and they can be grouped into many different classes. Often other conserved protein domains are found linked to a homeodomain. Several particular types of homeobox genes are organized into chromosomal clusters. The best-known cluster, the HOX cluster, is found in all bilaterian animals. Tetrapods contain four HOX clusters that arose through duplication in early vertebrate evolution. The genes in these clusters are called Hox genes. Lower chordates, insects and nematodes tend to have only one HOX cluster. Of particular interest is that many of the HOX cluster genes function in the process of pattern formation along the anterior-posterior body axis. Many other types of homeodomain proteins play roles in the determination of cell fates and cell differentiation. Homeobox genes thus perform key roles for all aspects of the development of an organism.

Pax3 induces differentiation of juvenile skeletal muscle stem cells without transcriptional upregulation of canonical myogenic regulatory factors

Pax3 is an essential myogenic regulator of fetal and embryonic development, but its role in postnatal myogenesis remains a topic of debate. We show that constitutive expression of Pax3 in postnatal, juvenile mouse skeletal muscle stem cells, a subset of the heterogeneous satellite cell pool highly enriched for myogenic activity, potently induces differentiation. This differentiation-promoting activity stands in contrast to the differentiation-inhibiting effects of Pax3 in the commonly used mouse myoblast cell line C2C12. Pax3 mRNA levels in distinct muscles correlate with the rate of myogenic differentiation of their muscle stem cells. Although Pax3 controls embryonic myogenesis through regulation of the canonical myogenic regulatory factors (MRFs) Myf-5, MyoD, myogenin and Mrf4, we find that in postnatal muscle stem cells, ectopic Pax3 expression fails to induce expression of any of these factors. Unexpectedly, overexpression of neither Myf-5 nor myogenin is sufficient to induce differentiation of juvenile stem cells; and knockdown of Myf-5, rather than inhibiting differentiation, promotes it. Taken together, our results suggest that there are distinct myogenic regulatory pathways that control the embryonic development, juvenile myogenesis and adult regeneration of skeletal myofibers.

PAX2 distinguishes benign mesonephric and mullerian glandular lesions of the cervix from endocervical adenocarcinoma, including minimal deviation adenocarcinoma

Mesonephric remnants of the cervix are vestiges of the embryonic mesonephric system which typically regresses during female development. Uncommonly, hyperplasia of the mesonephric remnants may occur. The differential diagnosis of exuberant mesonephric hyperplasia includes minimal deviation adenocarcinoma of the cervix, a tumor with deceptively bland morphology for which no reliable diagnostic biomarkers currently exist. PAX2 encodes a transcription factor necessary in the development of the Wolffian duct system, and the protein is expressed in several tumors of mesonephric origin, including renal cell carcinoma, Wilm tumor, and nephrogenic adenoma. We hypothesized that PAX2 may also be expressed in mesonephric lesions of the cervix and may distinguish mesonephric hyperplasia from minimal deviation adenocarcinoma of the cervix. We demonstrated that PAX2 was strongly and diffusely expressed in mesonephric remnants (6 of 6) and in mesonephric hyperplasia (18 of 18); however, no expression was noted in mesonephric adenocarcinoma (0 of 1). PAX2 was expressed in normal endocervical glands (including tunnel clusters and Nabothian cysts) (86 of 86), lobular endocervical glandular hyperplasia (5 of 5), tubal/tuboendometrioid metaplasia (8 of 8), and cervical endometriosis (13 of 14). In contrast, only 2 cases of endocervical adenocarcinoma were positive for PAX2 [invasive adenocarcinoma of the minimal deviation type (0 of 5), usual type (1 of 22), and endometrioid type (1 of 1)]. Adjacent adenocarcinoma in situ, as well as cases of pure adenocarcinoma in situ (0 of 6), were also PAX2 negative. PAX2 expression in the 2 positive endocervical adenocarcinomas was patchy and weak. Most (11 of 15) stage II endometrial endometrioid adenocarcinomas lacked PAX2 expression but 1 of 10 grade 1 tumors and 3 of 5 grade 2 tumors did express PAX2. These results suggest that PAX2 immunoreactivity may be useful to (1) distinguish mesonephric hyperplasia from minimal deviation adenocarcinoma, (2) to distinguish lobular endocervical glandular hyperplasia from minimal deviation adenocarcinoma, and (3) to distinguish endocervical tubal metaplasia or cervical endometriosis from endocervical adenocarcinoma in situ. Overall, a strong, diffuse nuclear PAX2 expression pattern in a cervical glandular proliferation predicts a benign diagnosis (positive predictive value 90%, negative predictive value 98%; P<0.001); however, PAX2 should not be interpreted in isolation from the architectural and cytologic features of the lesion as it may be expressed in some stage II endometrial adenocarcinomas involving the cervix.

The Pax3 and Pax7 paralogs cooperate in neural and neural crest patterning using distinct molecular mechanisms, in Xenopus laevis embryos

Pax3 and Pax7 paralogous genes have functionally diverged in vertebrate evolution, creating opportunity for a new distribution of roles between the two genes and the evolution of novel functions. Here we focus on the regulation and function of Pax7 in the brain and neural crest of amphibian embryos, which display a different pax7 expression pattern, compared to the other vertebrates already described. Pax7 expression is restricted to the midbrain, hindbrain and anterior spinal cord, and Pax7 activity is important for maintaining the fates of these regions, by restricting otx2 expression anteriorly. In contrast, pax3 displays broader expression along the entire neuraxis and Pax3 function is important for posterior brain patterning without acting on otx2 expression. Moreover, while both genes are essential for neural crest patterning, we show that they do so using two distinct mechanisms: Pax3 acts within the ectoderm which will be induced into neural crest, while Pax7 is essential for the inducing activity of the paraxial mesoderm towards the prospective neural crest.

Diabetes and apoptosis: neural crest cells and neural tube

Birth defects resulting from diabetic pregnancy are associated with apoptosis of a critical mass of progenitor cells early during the formation of the affected organ(s). Insufficient expression of genes that regulate viability of the progenitor cells is responsible for the apoptosis. In particular, maternal diabetes inhibits expression of a gene, Pax3, that encodes a transcription factor which is expressed in neural crest and neuroepithelial cells. As a result of insufficient Pax3, cardiac neural crest and neuroepithelial cells undergo apoptosis by a process dependent on the p53 tumor suppressor protein. This, then provides a cellular explanation for the cardiac outflow tract and neural tube and defects induced by diabetic pregnancy.

Oxidative stress during diabetic pregnancy disrupts cardiac neural crest migration and causes outflow tract defects

BACKGROUND

Maternal diabetes increases risk for congenital malformations, particularly cardiac outflow tract defects. Maternal diabetes inhibits expression of Pax3 in neuroepithelium through hyperglycemia-induced oxidative stress. The neuroepithelium gives rise to the neural crest, and Pax3 expression in cardiac neural crest (CNC) is required for CNC migration to the heart and for outflow tract septation. Here we tested whether maternal diabetes, through hyperglycemia-induced oxidative stress, before the onset of CNC delamination, impairs CNC migration and cardiac outflow tract septation.

METHODS

CNC migration was mapped in mouse embryos whose mothers were diabetic, or transiently hyperglycemic, or in which oxidative stress was transiently induced, using reporters linked to Pax3 expression. CNC apoptosis was examined by TUNEL assay. Outflow tract septation was examined histologically and by gross inspection.

RESULTS

Few, if any, migrating CNC cells were observed in embryos of diabetic mice, and this was associated with increased apoptosis along the path of CNC migration. Outflow tract defects were significantly increased in fetuses of diabetic mice. Notably, induction of hyperglycemia or oxidative stress on the day prior to the onset of Pax3 expression and CNC migration also impaired CNC migration, increased apoptosis, and caused outflow tract defects. However, antioxidants administered on the day prior to the onset of Pax3 expression and CNC migration prevented these effects of hyperglycemia or oxidative stress.

CONCLUSIONS

In diabetic pregnancy, oxidative stress, which inhibits expression of genes required for CNC viability, causes subsequent CNC depletion by apoptosis during migration, which leads to outflow tract defects.

Cis-regulatory organization of the Pax6 gene in the ascidian Ciona intestinalis

The Pax6 gene has attracted intense research interest due to its apparently important role in the development of eyes and the central nervous system (CNS) in many animal groups. Pax6 is also of interest for comparative genomics since it has not been duplicated in tetrapods, making for a direct orthology between the Ciona intestinalis gene CiPax6 and Pax6 in mammals. CiPax6 has been shown to be expressed in the anterior brain, caudal nerve cord, and in parts of the brain associated with the photoreceptive ocellus. This information was extended here using in-situ hybridization, and shows that CiPax6 transcripts mark the lateral regions of the nerve cord, remarkably similar to Pax6 expression in the mouse. As a means of dissecting the cis-regulation of CiPax6 we tested 8 kb of sequence using transient reporter transgene assays. Three separate regions were found that work together to drive the overall CiPax6 expression pattern. A 211 bp sequence 2 kb upstream of the first exon was found to be a major enhancer driving expression in the sensory vesicle (the anterior portion of the ascidian brain). Other upstream sequences were shown to work with the sensory vesicle enhancer to drive expression in the remainder of the CNS. An "eye enhancer" was localized to the first intron, which controls specific expression in the central portion of the sensory vesicle, including photoreceptor cells. The fourth intron was found to repress ectopic expression of the reporter gene in middle portions of the embryonic brain. Aspects of this overall regulatory organization are similar to the organization of the Pax6 homologs in mice and Drosophila, particularly the presence of intronic elements driving expression in the eye, brain and nerve cord.

Molecular basis for skeletal variation: insights from developmental genetic studies in mice

Skeletal variations are common in humans, and potentially are caused by genetic as well as environmental factors. We here review molecular principles in skeletal development to develop a knowledge base of possible alterations that could explain variations in skeletal element number, shape or size. Environmental agents that induce variations, such as teratogens, likely interact with the molecular pathways that regulate skeletal development.

Expression of PAX2 in papillary serous carcinoma of the ovary: immunohistochemical evidence of fallopian tube or secondary Müllerian system origin?

PAX2 is a urogenital developmental transcription factor expressed in the Wolffian ducts, developing kidneys, and Müllerian ducts during embryonic stage. Its function in renal development is well documented and its clinical application in the diagnosis of lesions of renal origin has been reported recently. However, information on its role in the Müllerian-derived genital tract is sparse. In this study, we investigated the expression of PAX2 in human female genital tract using immunohistochemistry. We demonstrated that PAX2 was expressed specifically in the epithelial cells of fallopian tube, endometrial and endocervical glands, but not in the stromal tissues in these areas. PAX2 was detected in secondary Müllerian structures in the ovary, such as endometriotic and endosalpingiotic glands and rete ovarii, but not in ovarian surface epithelium, surface epithelium-derived inclusion cysts, stroma, or sex-cord-derived structures such as follicles, oocytes, and corpus luteum. In addition, PAX2 was detected in 67% of ovarian papillary serous carcinomas (N=36) but rarely in peritoneal malignant mesotheliomas, with two exceptions (N=54). Interestingly, the two PAX2-positive 'peritoneal malignant mesotheliomas' were from female patients and were positive for estrogen receptor. The significance of expression of PAX2 and estrogen receptor in these cases is under investigation. Taken together, we suggest that PAX2 is a novel Müllerian-specific epithelial marker when used in proper clinical settings. Identification of PAX2 in the majority of papillary serous carcinomas of the ovary but not in the ovarian surface epithelium or epithelium-derived inclusion cysts suggests that this malignant epithelial tumor may be directly derived from the primary or secondary Müllerian epithelium in or surrounding the ovary, rather than from the surface epithelium or its derivatives.

Functional anthology of intrinsic disorder. 2. Cellular components, domains, technical terms, developmental processes, and coding sequence diversities correlated with long disordered regions

Biologically active proteins without stable ordered structure (i.e., intrinsically disordered proteins) are attracting increased attention. Functional repertoires of ordered and disordered proteins are very different, and the ability to differentiate whether a given function is associated with intrinsic disorder or with a well-folded protein is crucial for modern protein science. However, there is a large gap between the number of proteins experimentally confirmed to be disordered and their actual number in nature. As a result, studies of functional properties of confirmed disordered proteins, while helpful in revealing the functional diversity of protein disorder, provide only a limited view. To overcome this problem, a bioinformatics approach for comprehensive study of functional roles of protein disorder was proposed in the first paper of this series (Xie, H.; Vucetic, S.; Iakoucheva, L. M.; Oldfield, C. J.; Dunker, A. K.; Obradovic, Z.; Uversky, V. N. Functional anthology of intrinsic disorder. 1. Biological processes and functions of proteins with long disordered regions. J. Proteome Res. 2007, 5, 1882-1898). Applying this novel approach to Swiss-Prot sequences and functional keywords, we found over 238 and 302 keywords to be strongly positively or negatively correlated, respectively, with long intrinsically disordered regions. This paper describes approximately 90 Swiss-Prot keywords attributed to the cellular components, domains, technical terms, developmental processes, and coding sequence diversities possessing strong positive and negative correlation with long disordered regions.

Sulf1 expression pattern and its role in cartilage and joint development

A very dynamic and localised spatiotemporal expression pattern of Sulf1 was observed in axial structures and different regions of developing quail somites that included myotomal and sclerotomal regions at specific levels. Sulf1 expression was also observed in not only the scapular and pelvic girdle forming regions of the quail limb that connect the appendicular skeleton to the body trunk but also the cartilage templates of the appendicular skeleton. The highest expression level of Sulf1 was observed in condensing mesenchyme, during the early differentiation stage of chondrogenesis, and highly dynamic expression was observed in the perichondrial and joint-forming regions. Overexpression of Sulf1 in quail micromass cultures enhanced aggregation and differentiation of prechondrocytes into chondrogenic lineage supporting its role in mesenchymal condensation and early differentiation of cartilaginous elements. The exposure of digital explants to high levels of Sulf1 expression in vitro led to increased growth of the original 1st phalange but complete inhibition of joint formation and generation of any further phalanges. Sulf1 thus plays a key role during multiple stages of cartilage development and joint formation.

Current perspectives on the genetic causes of neural tube defects

Neural tube defects (NTDs) are a group of severe congenital abnormalities resulting from the failure of neurulation. The pattern of inheritance of these complex defects is multifactorial, making it difficult to identify the underlying causes. Scientific research has rapidly progressed in experimental embryology and molecular genetics to elucidate the basis of neurulation. Crucial mechanisms of neurulation include the planar cell polarity pathway, which is essential for the initiation of neural tube closure, and the sonic hedgehog signaling pathway, which regulates neural plate bending. Genes influencing neurulation have been investigated for their contribution to human neural tube defects, but only genes with well-established role in convergent extension provide an exciting new set of candidate genes. Biochemical factors such as folic acid appear to be the greatest modifiers of NTDs risk in the human population. Consequently, much research has focused on genes of folate-related metabolic pathways. Variants of several such genes have been found to be significantly associated with the risk of neural tube defects in more studies. In this manuscript, we reviewed the current perspectives on the causes of neural tube defects and highlighted that we are still a long way from understanding the etiology of these complex defects.

Aberrant DNA demethylation in promoter region and aberrant expression of mRNA of PAX4 gene in hematologic malignancies

The PAX4 gene, a member of the paired box (PAX) gene family, is thought to be involved in regulating the fate of beta-cells in the mammalian pancreas. We observed the aberrant expression of PAX4 mRNA in 10 of 15 hematologic cell lines analyzed by RT-PCR. The restoration of PAX4 gene expression after treatment with the demethylating agent 5-aza-2'-deoxycitidine, as well as bisulfite sequencing analysis, indicated that gene overexpression was caused by DNA demethylation at the promoter region. Such DNA demethylation also was observed in primary lymphoma (20 out of 45 patients) on combined bisulfite restriction assay (COBRA). Forced expression of the PAX4 gene in the HEK293 and SHSY/610 cell lines conferred positive effects on cell growth. This profile of PAX4 thus corresponds to that of a candidate oncogene in hematologic malignancies.

Properties of growth and molecular profiles of rat progenitor cells from ciliary epithelium

Recent studies have demonstrated that multipotent retinal stem or progenitor cells can be isolated from the ciliary epithelium (CE) of the eye using a neurosphere culture. In this study, we investigated the properties of growth and differentiation, and molecular profiles of rat adult ciliary epithelium (CE)-derived retinal progenitors and forebrain (FB) derived neurospheres. Under clonogenic culture conditions, we found that the CE-derived neurospheres contained fewer undifferentiated cells compared with the FB-derived neurospheres, and that CE-derived neurospheres initially expressed the set of Notch pathway molecules genes including Notch 1 and Delta 1, HES-1 and HES-5, but partially lose their expression after passaging. Furthermore, we found that the CE-derived neurospheres did not express several markers for in vivo embryonic retinal progenitors. Additionally, when the eye was divided into four subregions along its dorsoventral and nasotemporal axes and progenitor cells were obtained from the subregions, the progenitor cells did not express the subregion specific transcription factors, suggesting that subregional specificity is not maintained in vitro. Together, our results demonstrate that CE-derived progenitor cells may have intrinsic limitations in the production of cell types.

Ciona intestinalis: chordate development made simple

Thanks to their transparent and rapidly developing mosaic embryos, ascidians (or sea squirts) have been a model system for embryological studies for over a century. Recently, ascidians have entered the postgenomic era, with the sequencing of the Ciona intestinalis genome and the accumulation of molecular resources that rival those available for fruit flies and mice. One strength of ascidians as a model system is their close similarity to vertebrates. Literature reporting molecular homologies between vertebrate and ascidian tissues has flourished over the past 15 years, since the first ascidian genes were cloned. However, it should not be forgotten that ascidians diverged from the lineage leading to vertebrates over 500 million years ago. Here, we review the main similarities and differences so far identified, at the molecular level, between ascidian and vertebrate tissues and discuss the evolution of the compact ascidian genome.