The human hepatocyte nuclear factor 3/fork head gene FKHL13: genomic structure and pattern of expression

Rno_circRNA_008646 regulates formaldehyde induced lung injury through Rno-miR-224 mediated FOXI1/CFTR axis

Formaldehyde (FA) serves as a prevailing air pollutant, which has seriously threatened public health in recent years. Of all the known health effects, lung injury is one of the most severe risks. However, little is known about the circRNAs related molecular mechanism in the development of lung injury induced by FA. This study was designed to explore the potential roles of dysregulated circRNAs as well as its mechanism in FA-induced lung injury. In the present study, 24 male SD rats were exposed to formaldehyde (control, 0.5, 2.46 and 5 mg/m³) for 8 h per day for 8 weeks to induce lung injury. We used H&E staining to evaluate the histopathological changes of lung injury indifferent groups. The expression of circRNAs in lung tissue was detected by real-time PCR. Meanwhile, circRNA/miRNA/mRNA interaction networks were predicted by bioinformatics analysis. Our study revealed that formaldehyde exposure resulted in abnormal histopathological changes in lung tissues. Moreover, the expression of rno_circRNA_008646 was significantly higher in lung tissues of formaldehyde exposure rats than in control. Bioinformatics analysis showed that one potential target miRNA/mRNA for rno_circRNA_008646 was rno-miR-224/Forkhead Box I1 (FOXI1). Besides, luciferase report gene confirmed that there was targeted binding relationship between rno_circRNA_008646 and rno-miR-224, rno-miR-224 and FOXI1. Further verification experiments indicated that the expression of rno_circRNA_008646 was negatively correlated rno-miR-224, while it was positively correlated with FOXI1. JASPAR database showed transcription factor FOXI1 located in promotor of CF Transmembrane Conductance Regulator (CFTR). Both FOXI1 and CFTR were up-regulated in lung tissues after formaldehyde exposure. In conclusion, our findings suggested that formaldehyde may induce lung injury, and this may be caused by up-regulatedrno_circRNA_008646, which medicated rno-miR-224/FOXI1/CFTR axis.

Construction of a Suite of Computable Biological Network Models Focused on Mucociliary Clearance in the Respiratory Tract

Mucociliary clearance (MCC), considered as a collaboration of mucus secreted from goblet cells, the airway surface liquid layer, and the beating of cilia of ciliated cells, is the airways’ defense system against airborne contaminants. Because the process is well described at the molecular level, we gathered the available information into a suite of comprehensive causal biological network (CBN) models. The suite consists of three independent models that represent (1) cilium assembly, (2) ciliary beating, and (3) goblet cell hyperplasia/metaplasia and that were built in the Biological Expression Language, which is both human-readable and computable. The network analysis of highly connected nodes and pathways demonstrated that the relevant biology was captured in the MCC models. We also show the scoring of transcriptomic data onto these network models and demonstrate that the models capture the perturbation in each dataset accurately. This work is a continuation of our approach to use computational biological network models and mathematical algorithms that allow for the interpretation of high-throughput molecular datasets in the context of known biology. The MCC network model suite can be a valuable tool in personalized medicine to further understand heterogeneity and individual drug responses in complex respiratory diseases.

Paratubal Cyst Size Correlates With Obesity and Dysregulation of the Wnt Signaling Pathway

STUDY OBJECTIVE

Paratubal cysts (PTCs) occur in 7%-10% of women, regardless of age. Although common, PTCs often are found incidentally because of the potential for these cysts to be asymptomatic. The specific aims of the study were to determine if PTC number and size correlated with signs of hyperandrogenism and obesity, as well as to investigate the molecular profiles of these PTCs in samples derived from female adolescents. DESIGN, SETTING, PARTICIPANTS, INTERVENTIONS, AND MAIN OUTCOME MEASURES: A prospective cohort study was performed in a single children's hospital. Girls 18 years of age or younger who underwent surgery for PTC suspected on the basis of the presence of a persistent adnexal cyst on imaging or a concern for adnexal torsion involving a cyst were consented to participate in the study.

RESULTS

Nineteen patients met enrollment criteria with a mean age at menarche of 11.2 ± 1.3 years. Most of the patients (84%; n = 16/19) had adnexal torsion at the time of diagnosis of PTC. Irregular menses and hirsutism was found in 52.6% (n = 10/19) of the patients, among whom 36.8% (n = 7/19) were obese. The mean PTC size was 10.4 ± 4.3 cm with 57.9% (n = 11/19) of the cohort having more than 1 PTC. When patients were compared on the basis of their body mass index, the size of PTCs was significantly larger in the overweight/obese group. The wingless-type (WNT) signaling members catenin beta 1 (CTNBB1) and wingless-type MMTV integration site family, member 7A (WNT7A) were upregulated in 86% (n = 12/14) and 79% (n = 11/14) of the patients, respectively. WNT7A was significantly upregulated in girls with 1 cyst and low body mass index.

CONCLUSION

A correlation exists between obesity, cyst size, and hyperandrogenism. Activation of the WNT/CTNBB1 pathway via WNT7A might play a role in PTC development.

GemC1 controls multiciliogenesis in the airway epithelium

Multiciliated cells are terminally differentiated, post-mitotic cells that form hundreds of motile cilia on their apical surface. Defects in multiciliated cells lead to disease, including mucociliary clearance disorders that result from ciliated cell disfunction in airways. The pathway controlling multiciliogenesis, however, remains poorly characterized. We showed that GemC1, previously implicated in cell cycle control, is a central regulator of ciliogenesis. GemC1 is specifically expressed in ciliated epithelia. Ectopic expression of GemC1 is sufficient to induce early steps of multiciliogenesis in airway epithelial cells ex vivo, upregulating McIdas and FoxJ1, key transcriptional regulators of multiciliogenesis. GemC1 directly transactivates the McIdas and FoxJ1 upstream regulatory sequences, and its activity is enhanced by E2F5 and inhibited by Geminin. GemC1-knockout mice are born with airway epithelia devoid of multiciliated cells. Our results identify GemC1 as an essential regulator of ciliogenesis in the airway epithelium and a candidate gene for mucociliary disorders.

Switching on cilia: transcriptional networks regulating ciliogenesis

Cilia play many essential roles in fluid transport and cellular locomotion, and as sensory hubs for a variety of signal transduction pathways. Despite having a conserved basic morphology, cilia vary extensively in their shapes and sizes, ultrastructural details, numbers per cell, motility patterns and sensory capabilities. Emerging evidence indicates that this diversity, which is intimately linked to the different functions that cilia perform, is in large part programmed at the transcriptional level. Here, we review our understanding of the transcriptional control of ciliary biogenesis, highlighting the activities of FOXJ1 and the RFX family of transcriptional regulators. In addition, we examine how a number of signaling pathways, and lineage and cell fate determinants can induce and modulate ciliogenic programs to bring about the differentiation of distinct cilia types.

RFX3 modulation of FOXJ1 regulation of cilia genes in the human airway epithelium

Background

Ciliated cells play a central role in cleansing the airways of inhaled contaminants. They are derived from basal cells that include the airway stem/progenitor cells. In animal models, the transcription factor FOXJ1 has been shown to induce differentiation to the ciliated cell lineage, and the RFX transcription factor-family has been shown to be necessary for, but not sufficient to induce, correct cilia development.

Methods

To test the hypothesis that FOXJ1 and RFX3 cooperatively induce expression of ciliated genes in the differentiation process of basal progenitor cells toward a ciliated cell linage in the human airway epithelium, primary human airway basal cells were assessed under conditions of in vitro differentiation induced by plasmid-mediated gene transfer of FOXJ1 and/or RFX3. TaqMan PCR was used to quantify mRNA levels of basal, secretory, and cilia-associated genes.

Results

Basal cells, when cultured in air-liquid interface, differentiated into a ciliated epithelium, expressing FOXJ1 and RFX3. Transfection of FOXJ1 into resting basal cells activated promoters and induced expression of ciliated cell genes as well as both FOXJ1 and RFX3, but not basal cell genes. Transfection of RFX3 induced expression of RFX3 but not FOXJ1, nor the expression of cilia-related genes. The combination of FOXJ1 + RFX3 enhanced ciliated gene promoter activity and mRNA expression beyond that due to FOXJ1 alone. Corroborating immunoprecipitation studies demonstrated an interaction between FOXJ1 and RFX3.

Conclusion

FOXJ1 is an important regulator of cilia gene expression during ciliated cell differentiation, with RFX3 as a transcriptional co-activator to FOXJ1, helping to induce the expression of cilia genes in the process of ciliated cell differentiation of basal/progenitor cells.

Wt1a, Foxc1a, and the Notch mediator Rbpj physically interact and regulate the formation of podocytes in zebrafish

Podocytes help form the glomerular blood filtration barrier in the kidney and their injury or loss leads to renal disease. The Wilms' tumor suppressor-1 (Wt1) and the FoxC1/2 transcription factors, as well as Notch signaling, have been implicated as important regulators of podocyte fate. It is not known whether these factors work in parallel or sequentially on different gene targets, or as higher-order transcriptional complexes on common genes. Here, we use the zebrafish to demonstrate that embryos treated with morpholinos against wt1a, foxc1a, or the Notch transcriptional mediator rbpj develop fewer podocytes, as determined by wt1b, hey1 and nephrin expression, while embryos deficient in any two of these factors completely lack podocytes. From GST-pull-downs and co-immunoprecipitation experiments we show that Wt1a, Foxc1a, and Rbpj can physically interact with each other, whereas only Rbpj binds to the Notch intracellular domain (NICD). In transactivation assays, combinations of Wt1, FoxC1/2, and NICD synergistically induce the Hey1 promoter, and have additive or repressive effects on the Podocalyxin promoter, depending on dosage. Taken together, these data suggest that Wt1, FoxC1/2, and Notch signaling converge on common target genes where they physically interact to regulate a podocyte-specific gene program. These findings further our understanding of the transcriptional circuitry responsible for podocyte formation and differentiation during kidney development.

Lentiviral transfection of ependymal primary cultures facilitates the characterisation of kinocilia-specific promoters

Ependymal primary cultures (EPCs) are an established model for studying ependymal cell biochemistry and the biology of kinocilia-bearing cells. However, the difficulty in causing them to express transgenes at high efficiency has been an important drawback of the system. Indeed plasmid-based transfection attempts remain at an efficiency below 1% and fail to elicit reporter gene expression, namely green fluorescent protein (GFP) synthesis, in any of the kinocilia-bearing cells of the cultures. Human immunodeficiency virus pseudotyped with the vesicular stomatitis virus envelope glycoprotein (HIV/VSV-G) and encoding GFP under the control of the ubiquitously recognised promoter of elongation factor 1 alpha (EF1alpha) also does not cause transgene expression in the kinocilia-bearing cells of an EPC when applied at multiplicities of infection (MOIs) of up to 40 and destroys the culture when the MOI is increased further. In contrast, HIV/VSV-G encoding GFP under the control of a promoter specifically active in kinocilia-bearing cells leads to transgene expression in up to 79% of the kinociliated cells of an EPC when applied at an MOI of 20. This has permitted the initial characterisation of the promoter for the gene specifically transcribed in kinocilia-bearing cells, wdr16. The results have identified two regions of 100 nucleotides length each, which are critical for promoter activity and contain putative binding sites for the transcription factors Foxd1, Sox17 and Spz1. It appears that wdr16 is controlled by a bidirectional promoter also responsible for regulating the syntaxin 8 gene.

Deletion of Dicer in somatic cells of the female reproductive tract causes sterility

Dicer is an evolutionarily conserved ribonuclease III that is necessary for microRNA (miRNA) processing and the synthesis of small interfering RNAs from long double-stranded RNA. Although it has been shown that Dicer plays important roles in the mammalian germline and early embryogenesis, the functions of Dicer-dependent pathways in the somatic cells of the female reproductive tract are unknown. Using a transgenic line in which Cre recombinase is driven by the anti-Müllerian hormone receptor type 2 promoter, we conditionally inactivated Dicer1 in the mesenchyme of the developing Müllerian ducts and postnatally in ovarian granulosa cells and mesenchyme-derived cells of the oviducts and uterus. Deletion of Dicer in these cell types results in female sterility and multiple reproductive defects including decreased ovulation rates, compromised oocyte and embryo integrity, prominent bilateral paratubal (oviductal) cysts, and shorter uterine horns. The paratubal cysts act as a reservoir for spermatozoa and oocytes and prevent embryos from transiting the oviductal isthmus and passing the uterotubal junction to enter the uterus for implantation. Deep sequencing of small RNAs in oviduct revealed down-regulation of specific miRNAs in Dicer conditional knockout females compared with wild type. The majority of these differentially expressed miRNAs are predicted to regulate genes important for Müllerian duct differentiation and mesenchyme-derived structures, and several of these putative target genes were significantly up-regulated upon conditional deletion of Dicer1. Thus, our findings reveal diverse and critical roles for Dicer and its miRNA products in the development and function of the female reproductive tract.

Tissue expression patterns identify mouse cilia genes

In mammals, cilia are critical for development, sensation, cell signaling, sperm motility, and fluid movement. Defects in cilia are causes of several congenital syndromes, providing additional reasons to identify cilia-related genes. We hypothesized that mRNAs selectively abundant in tissues rich in highly ciliated cells encode cilia proteins. Selective abundance in olfactory epithelium, testes, vomeronasal organ, trachea, and lung proved to be an expression pattern uniquely effective in identifying documented cilia-related genes. Known and suspected cilia-related genes were statistically overrepresented among the 99 genes identified, but the majority encoded proteins of unknown function, thereby predicting new cilia-related proteins. Evidence of expression in a highly ciliated cell, the olfactory sensory neuron, exists for 73 of the genes. In situ hybridization for 17 mRNAs confirmed expression of all 17 in olfactory sensory neurons. Most were also detected in vomeronasal sensory neurons and in neighboring tissues rich in ciliated cells such as respiratory epithelium. Immunoreactivity for one of the proteins identified, Spa17, colocalized with acetylated tubulin in the cilia layer of the olfactory epithelium. In contrast, the ciliary rootlet protein, Crocc, was located in discrete structures whose position was consistent with the dendritic knobs of the olfactory sensory neurons. A compilation of >2,000 mouse genes predicted to encode cilia-related proteins revealed a strong correlation (R = 0.99) between the number of studies predicting a gene's involvement in cilia and documented evidence of such involvement, a fact that simplifies the selection of genes for further study of the physiology of cilia.

Expression of CFTR from a ciliated cell-specific promoter is ineffective at correcting nasal potential difference in CF mice

Successful gene therapy will require that the therapeutic gene be expressed at a sufficient level in the correct cell type(s). To improve the specificity of gene transfer for cystic fibrosis (CF) and other airway diseases, we have begun to develop cell-type specific promoters to target the expression of transgenes to specific airway cell types. Using a FOXJ1 promoter construct previously shown to direct transgene expression specifically to ciliated cells, we have generated transgenic mice expressing human cystic fibrosis transmembrane conductance regulator (CFTR) in the murine tracheal and nasal epithelia. RNA analysis demonstrated levels of CFTR expression is greater than or equal to the level of endogenous mouse CFTR. Immunoprecipitation and western blotting demonstrated the production of human CFTR protein, and immunochemistry confirmed that CFTR was expressed in the apical region of ciliated cells. The transgenic animals were bred to CFTR null mice (Cftr(tm1Unc)) to determine if expression of CFTR from the FOXJ1 promoter is capable of correcting the airway defects in Cl(-) secretion and Na(+) absorption that accompany CF. Isolated trachea from neonatal CF mice expressing the FOXJ1/CFTR transgene demonstrated a correction of forskolin-stimulated Cl(-) secretion. However, expression of human CFTR in ciliated cells of the nasal epithelia failed to significantly change the nasal bioelectrics of the CF mice.

A transgenic FOXJ1-Cre system for gene inactivation in ciliated epithelial cells

Ciliated airway epithelial cells are critical for mucosal barrier function, including host defense against pathogens. This cell population is often the primary target and thereby the first line of defense against many common respiratory viruses. It is also the precursor for mucous cells and thereby promotes mucociliary clearance of infectious and other noxious agents. Cells with motile cilia in other organs (e.g., brain and reproductive organs) may also have roles in development and reproduction. However, definitive proof of ciliated cell function is hampered by the lack of strategies to specifically target this cell population for loss of function in vivo. To this end, cell type-specific gene promoters have been combined with the Cre/LoxP system to disrupt genes in airway and alveolar epithelial cell populations expressing surfactant protein C (SP-C) or Clara cell secretory protein (CCSP). By contrast, an analogous system to disrupt gene function in ciliated airway epithelial cells was still needed. Here we report the generation and analysis of mouse lines with a FOXJ1 promoter driving the Cre recombinase and show that this system mediates genomic recombination specifically in ciliated cells. The pattern of recombination recapitulates endogenous FOXJ1 promoter function, being restricted to ciliated cells present in pulmonary airways as well as choroid plexus, ependyma, oviduct, and testis. This transgenic mouse system thereby offers a new strategy for specific knockouts of genes in ciliated cells. It should prove extremely useful for defining ciliated cell function in airway mucosal immunity as well as development and reproduction.

Absent inner dynein arms in a fetus with familial hydrocephalus-situs abnormality

We report a family in which a healthy, unrelated couple had a male fetus with bilateral ventriculomegaly, a normal liveborn girl, a hydatidiform molar pregnancy, a female fetus with ventriculomegaly and situs abnormalities, and a male fetus with hydrocephalus, a three-lobed left lung, and defective tracheal cilia with absent inner dynein arms and a single centriole. A mutation analysis of FOXJ1 and POLL in the last fetus with ciliary defect revealed no mutation within their coding regions. The presence of three affected fetuses of both sexes in a family with phenotypically normal parents suggests that the condition was inherited as an autosomal recessive trait. A thorough evaluation of the thoracic and abdominal situs is recommended before counseling a family of a child with hydrocephalus, because the recognition of situs defects may point to the diagnosis of primary ciliary defect and recurrence risk of 25% for siblings. This figure is much higher than the general risk of 1-2% for siblings of a patient with isolated hydrocephalus.

Gene expression changes in the course of neural progenitor cell differentiation

The molecular changes underlying neural progenitor differentiation are essentially unknown. We applied cDNA microarrays with 13,627 clones to measure dynamic gene expression changes during the in vitro differentiation of neural progenitor cells that were isolated from the subventricular zone of postnatal day 7 mice and grown in vitro as neurospheres. In two experimental series in which we withdrew epidermal growth factor and added the neurotrophins Neurotrophin-4 or BDNF, four time points were investigated: undifferentiated cells grown as neurospheres, and cells 24, 48, and 96 hr after differentiation. Expression changes of selected genes were confirmed by semiquantitative RT-PCR. Ten different groups of gene expression dynamics obtained by cluster analysis are described. To correlate selected gene expression changes to the localization of respective proteins, we performed immunostainings of cultured neurospheres and of brain sections from adult mice. Our results provide new insights into the genetic program of neural progenitor differentiation and give strong hints to as yet unknown cellular communications within the adult subventricular zone stem cell niche.

Characterization of newly established clonal oviductal cell lines and differential hormonal regulation of gene expression

Oviductal functions have been studied mainly in primary epithelial cell culture and organ culture. However, secretory cells and ciliated cells coexist in the epithelium, and the small size of the oviduct limits the sources of both epithelial and stromal cells. To circumvent the limits, we attempted to establish clonal cell lines from an oviduct of a p53-deficient mouse. An oviduct was enzymatically digested and cultured in medium containing 10% fetal calf serum supplemented with estradiol-17beta. Morphologically distinct clones (10 epithelial and 4 fibroblastic clones) were established, and all clones expressed estrogen receptor alpha and progesterone receptor. Expression of a mouse oviduct-specific glycoprotein gene as a marker of secretory cells was limited in one clone and was stimulated by estrogens and suppressed by progesterone. Expression of helix factor hepatocyte nuclear factor/forkhead homologue-4 gene as a marker of ciliated cells was limited in two clones and was suppressed by estrogens. The two genes were never coexpressed in any clones. The results strongly suggest that the oviductal epithelium consists of two functionally determined populations. To our knowledge, this is the first establishment of functional clonal cell lines of the oviduct and makes it possible to study independently two oviductal functions, secretion and ciliogenesis.

Differential gene expression in ovarian carcinoma: identification of potential biomarkers

Ovarian cancer remains the fifth leading cause of cancer death for women in the United States. In this study, the gene expression of 20 ovarian carcinomas, 17 ovarian carcinomas metastatic to the omentum, and 50 normal ovaries was determined by Gene Logic Inc. using Affymetrix GeneChip HU_95 arrays containing approximately 12,000 known genes. Differences in gene expression were quantified as fold changes in gene expression in ovarian carcinomas compared to normal ovaries and ovarian carcinoma metastases. Genes up-regulated in ovarian carcinoma tissue samples compared to more than 300 other normal and diseased tissue samples were identified. Seven genes were selected for further screening by immunohistochemistry to determine the presence and localization of the proteins. These seven genes were: the beta8 integrin subunit, bone morphogenetic protein-7, claudin-4, collagen type IX alpha2, cellular retinoic acid binding protein-1, forkhead box J1, and S100 calcium-binding protein A1. Statistical analyses showed that the beta8 integrin subunit, claudin-4, and S100A1 provided the best distinction between ovarian carcinoma and normal ovary tissues, and may serve as the best candidate tumor markers among the seven genes studied. These results suggest that further exploration into other up-regulated genes may identify novel diagnostic, therapeutic, and/or prognostic biomarkers in ovarian carcinoma.

An evidence of stromal cell populations functionally linked with epithelial cell populations in the mouse oviduct

The oviductal epithelium consists of two major cell populations, secretory cells and cilial cells. In a previous report, we established clonal cell lines from the epithelium and stroma of an oviduct which allowed us to analyze stromal contribution to epithelial functions. Three stromal cell lines were co-cultured in separated apparatus with 3 epithelial cell lines, respectively. Two stromal cell lines preferentially stimulated mogp-1 expression on secretory cells and the stimulation was additive with estrogen. The lines had no effect on cilial cells. One stromal cell line preferentially stimulated foxj1 expression on cilial cells and the stimulation relieved suppression by estrogen. The line had no effect on secretory cells. Experiments with conditioned media of the stromal cells confirmed the results of co-culture experiments, suggesting that the oviductal stroma contains multiple cell populations preferentially regulating or modulating specific cell populations of the epithelium via diffusible factors.

Bases moléculaires des dyskinésies ciliaires primitives

INTRODUCTION

The primary ciliary dyskinesias (PCD) are rare diseases characterised by infection of the airways due to impaired muco-ciliary clearance. Half the patients have situs inversus making up Kartagener's syndrome.

STATE OF THE ART

Primary cilia play a role in development. In the adult ciliated cells occur mainly in the airways and the genital tract. The axoneme, the internal structure of the cilia, is made up of a central pair of microtubules surrounded by peripheral doublets carrying the inner and outer dynein arms. These multiprotein complexes are composed of chains of dynein whose ATPase activity is the basis of ciliary movement. Structural and functional abnormalities of the respiratory ciliated cells are the cause of PCD, diseases that are heterogeneous at both the genetic and ultrastructural levels.

PERSPECTIVES

There are more than two hundred axonemal proteins. The synthesis and assembly of these proteins are controlled by transcription factors and intraflagellar transport molecules respectively. The genes that code for these proteins are as numerous as candidate genes for PCD.

CONCLUSIONS

To date only two dynein genes, DNA11 and DNAH5, have been implicated and only in individuals suffering from PCD with absence of outer dynein arms.

Targeting expression of a transgene to the airway surface epithelium using a ciliated cell-specific promoter

Many of the vectors being investigated for gene therapy utilize viral promoters or promoters from ubiquitously expressed genes (e.g., CMV, beta-actin). These promoters are active in many cell types and generally result in high levels of transgene expression. However, the use of these promoters for gene therapy of cystic fibrosis (CF) may produce undesirable effects by directing high levels of CFTR expression in cells that normally do not synthesize this protein. In contrast, a vector containing a ciliated cell-specific promoter and delivered to the lung would be active only in the ciliated cells that line the surface of the airways. Ciliated cells express CFTR and are in direct contact with the airway surface liquid normally regulated by CFTR. To develop a ciliated cell-specific promoter for CF gene therapy, we have characterized the promoter region of the FOXJ1 gene, a transcription factor required for ciliated cell differentiation. A fragment of the human FOXJ1 promoter region was inserted into an EGFP expression cassette and used to produce transgenic mice. Transgene-positive animals demonstrated strong EGFP expression in the ciliated cells of tracheal, bronchial, and nasal epithelium. Our results demonstrate that elements within the FOXJ1 promoter region are sufficient to target expression of transgenes to ciliated cells and may be useful for gene therapy of CF.

Cell Biology of Normal and Abnormal Ciliogenesis in the Ciliated Epithelium

Ciliogenesis is divided into four stages: (1) generation of centrioles, (2) migration of duplicated centrioles, (3) formation of the basal body-associated structures, and (4) elongation of cilia. The ultrastructural profile of ciliogenesis is fundamentally the same among various kinds of animal species. In acentriolar centriologenesis, centrioles are generated around deuterosomes by the use of fibrous granules. Components of the centriolar precursor structures, and genes that regulate the differentiation of ciliated cells, have been revealed. Ciliary abnormalities are classified into two categories: specific congenital defects of ciliary structure and acquired nonspecific anomalies of the ciliary apparatus. When ciliogenesis is disturbed, various nonspecific ciliary abnormalities develop in the cell. Inhibition of centriole migration results in the development of intracytoplasmic axonemes, cilia within periciliary sheaths, and intracellular ciliated vacuoles. Swollen cilia and the bulging type of compound cilia are formed during ciliary budding and elongation. Primary cilia can also develop from one of a pair of centrioles. They lack dynein arms and are immobile, but work as a mechanosensor and play a role during morphogenesis of the kidney. Abnormal function or structure of primary cilia results in the development of polycystic kidney disease. The axonemes of primary cilia or monocilia in the embryonic node cells are associated with dynein arms and move vortically. They have a role in determining the left-right (L-R) asymmetry of the fetus. This review also discusses the ciliogenesis of a primary cilium in the cell.

Ciliogenesis and left-right axis defects in forkhead factor HFH-4-null mice

Cilia have been classified as sensory or motile types on the basis of functional and structural characteristics; however, factors important for regulation of assembly of different cilia types are not well understood. Hepatocyte nuclear factor-3/forkhead homologue 4 (HFH-4) is a winged helix/forkhead transcription factor expressed in ciliated cells of the respiratory tract, oviduct, and ependyma in late development through adulthood. Targeted deletion of the Hfh4 gene resulted in defective ciliogenesis in airway epithelial cells and randomized left-right asymmetry so that half the mice had situs inversus. In HFH-4-null mice, classic motile type cilia with a 9 + 2 microtubule ultrastructure were absent in epithelial cells, including those in the airways. In other organs, sensory cilia with a 9 + 0 microtubule pattern, such as those on olfactory neuroepithelial cells, were present. Ultrastructural analysis of mutant cells with absent 9 + 2 cilia demonstrated that defective ciliogenesis was due to abnormal centriole migration and/or apical membrane docking, suggesting that HFH-4 functions to direct basal body positioning or anchoring. Evaluation of wild-type embryos at gestational days 7.0 to 7.5 revealed Hfh4 expression in embryonic node cells that have monocilium, consistent with a function for this factor at the node in early determination of left- right axis. Analysis of the node of HFH-4 mutant embryos revealed that, in contrast to absent airway cilia, node cilia were present. These observations indicate that there are independent regulatory pathways for node ciliogenesis compared with 9 + 2 type ciliogenesis in airways, and support a central role for HFH-4 in ciliogenesis and left-right axis formation.

A new locus for late-onset, progressive, hereditary hearing loss DFNA20 maps to 17q25

We report the localization of DFNA20, a gene causing dominant, nonsyndromic, progressive hearing loss in a three-generation Midwestern family, to chromosome 17q25. Affected family members show a bilateral, sloping, progressive, sensorineural hearing loss, first evident at 6000 and 8000 Hz, that can be identified in some family members in the early teens and is clearly evident by the early twenties. As age increases, the degree of hearing loss increases with threshold shifts seen at all frequencies. Linkage to known hereditary hearing loss loci was excluded. A genome-wide screen detected positive linkage to D17S784 (LOD(Z) = 6.62; θ = 0). Haplotype analysis refines the DFNA20 critical region to 12 cM between D17S1806 and D17S668. Radiation hybrid mapping with Stanford G3 and TNG panels was used to evaluate the genes ACTG1, GRIN2C, FKHL13, P4HB, SPARC, and ARHGDIA as candidates for DFNA20.

HNF-3/forkhead homologue-4 influences lung morphogenesis and respiratory epithelial cell differentiation in vivo

HNF-3/forkhead homologue 4 (HFH-4), a transcription factor of the winged helix/forkhead family, is expressed in various tissues including lung, brain, oviduct, testis, and embryonic kidney. In order to test whether the temporospatial expression of HFH-4 influences lung morphogenesis, HFH-4 was expressed in lungs of transgenic mice under control of the surfactant protein C (SP-C) promoter. The morphology of the lungs from SP-C/HFH-4 embryos (day 18 postconception) was distinctly abnormal, and the severity of the alterations correlated with the level of transgene expression as detected by in situ hybridization. At high levels of expression, HFH-4 altered epithelial cell differentiation and inhibited branching morphogenesis. Atypical cuboidal or columnar cells lined the lung periphery of SP-C/HFH-4 transgenic mice. The atypical epithelial cells seen in the SP-C/HFH-4 mice expressed thyroid transcription factor-1 and hepatocyte nuclear factor 3beta (HNF-3beta). However, surfactant proteins SP-B, SP-C, and Clara cell secretory protein, normally produced by nonciliated epithelial cells in lung parenchyma were lacking. beta-Tubulin IV, a marker of ciliated cells, stained the atypical columnar cells produced by expression of high levels of the SP-C/HFH-4 transgene. Ectopic expression of HFH-4 in developing mouse lung altered epithelial cell differentiation and morphology, restricting the expression of markers typical of nonciliated cells of the distal lung parenchyma.

Forkhead transcription factor HFH-4 expression is temporally related to ciliogenesis

Members of the forkhead/winged-helix family of transcription factors are expressed in tissue-specific patterns and play critical roles in development and cell differentiation. The expression of forkhead family member hepatocyte nuclear factor-3/forkhead homologue 4 (HFH-4) has been localized by RNA-blot analysis and in situ hybridization to the proximal airway of the lung (trachea, bronchi, and bronchioles) with onset at mouse embryonic day (E) 14.5 and is present in the choroid plexus, ependymal cells, oviduct, and testis. We hypothesized that the restricted expression of HFH-4 messenger RNA suggests a function common to these tissues and therefore a cell-specific role for HFH-4. Accordingly, an anti-HFH-4 antibody was generated and used for cell-specific localization of protein expression to begin to identify the functions of HFH-4. We found HFH-4 expression in proximal airway ciliated epithelial cells, but not Clara cells or alveolar epithelial cells. HFH-4 was also expressed in ciliated epithelial cells of the nose and paranasal sinuses, choroid plexus, ependyma, and oviduct. In developing mouse lung, HFH-4 expression was initially detected in airway epithelial cells at E15.5, before the appearance of cilia, and at later stages was localized to epithelial cells with cilia. In the testis, HFH-4 expression in spermatids was coincident with stage-specific generation of flagella. The temporal relationship of HFH-4 expression to the development of cilia and flagella, and the restricted expression in ciliated epithelial cells, suggest that this transcription factor has a role in regulation and maintenance of the ciliated cell phenotype in epithelial cells.

HNF-3/forkhead homologue-4 (HFH-4) is expressed in ciliated epithelial cells in the developing mouse lung

HNF-3/forkhead homologue-4 (HFH-4), a transcription factor of the winged-helix/forkhead family, was detected by immunohistochemistry in tissue of the developing mouse. HFH-4 protein was present in epithelial cells of the lung, trachea, oviduct, and embryonic esophagus, and in ependymal cells lining the spinal column and ventricles of the brain. In lung, trachea, and nose, HFH-4 was expressed in a distinct subset of epithelial cells that also expressed beta-tubulin IV, a ciliated cell marker. Cellular sites of HFH-4 and beta-tubulin IV expression were distinct from that of Clara cell secretory protein (CCSP), which was detected in nonciliated epithelial cells in the conducting airway of the lung. HFH-4 and beta-tubulin IV, but not CCSP, were detected in the respiratory epithelium of thyroid transcription factor-1 (TTF-1) gene-targeted mice. The presence of HFH-4 and beta-tubulin IV in TTF-1 gene-targeted mice demonstrates that differentiation of ciliated epithelium does not require TTF-1. Co-localization of HFH-4 and beta-tubulin IV staining in various tissues during mouse development supports a role for HFH-4 in the differentiation of ciliated cell lineages.

Molecular cloning of FKHRL1P2, a member of the developmentally regulated fork head domain transcription factor family

Here we report the expression of a fork head domain protein in human T helper cells. We cloned and characterized a fork head cDNA from human T helper cell mRNA using differential display RT-PCR. The cDNA contains a 546-nucleotide (nt) open reading frame (ORF) that codes for the carboxyl-terminal 180 amino acids (aa) of the recently identified fkhrl1 gene. This ORF does not contain the characteristic DNA-binding domain found in members of the forkhead protein family. In-vitro transcription/translation of this cDNA expressed a protein of approximately 20 kDa. We have generated antibodies that specifically immunoprecipitated the in-vitro-translated 20-kDa protein. This antibody also recognizes in human T lymphocytes a 70-kDa protein corresponding in size to that predicted for the fkhrl1 gene product. The mRNA levels for fkhrl1 is elevated in T helper-induced lymphocytes in comparison to PHA-stimulated T lymphocytes. Further characterization of FKHRL1 and its related family members should shed light on the transcriptional mechanisms of this fork head gene subfamily and their role in T helper cell differentiation and regulation of cell growth.

Mouse HNF-3/fork head homolog-1-like gene: structure, chromosomal location, and expression in adult and embryonic kidney

Screening of a mouse kidney cDNA library with a HNF-3/fork head domain probe revealed cDNA Hfh-1L containing the highly conserved fork head DNA-binding domain. The Hfh1L cDNA shows 92.7% homology at the nucleic acid level with the fork head gene HFH-1 from rat. Southern blot analyses demonstrated that the Hfh-1L gene is highly conserved in a wide variety of species, including goldfish and frog. Sequencing the corresponding genomic clone, we found that the Hfh-1L gene is most likely intronless. By interspecific back-cross analysis, the Hfh-1L gene was localized to mouse chromosome 13. In order to analyze the expression pattern of Hfh-1L, we performed Northern blot analyses and revealed a 2.7-kb transcript in adult kidney and stomach. In situ hybridization experiments of adult mouse kidney showed Hfh-1L expression in the outer medulla of the kidney and the transitional epithelium. In light of the significance of a number of fork head genes in early embryonic development, the pattern of expression during murine embryogenesis was examined by reverse transcriptase-polymerase chain reaction (RT-PCR), and Hfh-1L transcripts were detected in mouse embryos at every stage tested from day 10.5 to 16.5 postconception (p.c.) and in the developing metanephros of 14.5- and 15.5-day p.c. embryos. This expression pattern suggests that the Hfh-1L gene is involved in the development of the kidney.

The human TRIDENT/HFH-11/FKHL16 gene: structure, localization, and promoter characterization

We recently identified the winged-helix/fork head transcription factor Trident in mouse and described its expression in cycling cells. Here we report the isolation and characterization of the human TRIDENT (HGMW-approved symbol FKHL16) cDNA and gene. Homology between the human and the mouse Trident proteins was 79%. The gene consists of 10 exons and is located on chromosome 12 band p13. The winged-helix DNA-binding domain is encoded on three exons. Analysis of the promoter in synchronized Rat-1 fibroblasts revealed a fragment of 300 bases responsible for the cell cycle-specific expression of the TRIDENT gene.