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The chemokine SDF-1 (CXCL12) and its receptor CXCR4 control several processes during embryonic development such as the regulation of stem cell proliferation, differentiation, and migration. However, the role of this pathway in the formation of the pituitary gland is not understood. We sought to characterise the expression patterns of CXCR4, SDF-1 and CXCR7 at different stages of pituitary gland development. Our expression profiling revealed that SDF-1 is expressed in progenitor-rich regions of the pituitary anterior lobe, that CXCR4 and CXCR7 have opposite expression domains and that CXCR4 expression is conserved between mice and human embryos. We then assessed the importance of this signalling pathway in the development and function of the murine pituitary gland through conditional deletion of CXCR4 in embryonic pituitary progenitors. Successful and specific ablation of CXCR4 expression in embryonic pituitary progenitors did not lead to observable embryonic nor postnatal defects but allowed the identification of stromal CXCR4+ cells not derived from HESX1+ progenitors. Further analysis of constitutive SDF-1, CXCR7 and CXCR4 mutants of the pathway indicates that CXCR4 expression in HESX1+ cells and their descendants is not essential for normal pituitary development in mice., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Gonzalez-Meljem et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Cxcl12-null embryos have dysplastic, misaligned, and hyperplastic semilunar valves (SLVs). In this study, we show that CXCL12 signaling via its receptor CXCR4 fulfills distinct roles at different stages of SLV development, acting initially as a guidance cue to pattern cellular distribution within the valve primordia during the endocardial-to-mesenchymal transition (endoMT) phase and later regulating mesenchymal cell proliferation during SLV remodeling. Transient, anteriorly localized puncta of internalized CXCR4 are observed in cells undergoing endoMT. In vitro, CXCR4 + cell orientation in response to CXCL12 requires phosphatidylinositol 3-kinase (PI3K) signaling and is inhibited by suppression of endocytosis. This dynamic intracellular localization of CXCR4 during SLV development is related to CXCL12 availability, potentially enabling activation of divergent downstream signaling pathways at key developmental stages. Importantly, Cxcr7 -/- mutants display evidence of excessive CXCL12 signaling, indicating a likely role for atypical chemokine receptor CXCR7 in regulating ligand bioavailability and thus CXCR4 signaling output during SLV morphogenesis., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objectives: Objective measurements of asthma impairment could aid teens in recognition of changes in asthma status over time. Ready access to a conventional spirometer is not realistic outside of the clinical setting. In this proof-of-concept study, we compared the performance of the VitalFlo mobile spirometer to the nSpire KoKo® sx1000 spirometer for accuracy in measuring Forced Expiratory Volume in one second (FEV 1 ) and Forced Vital Capacity (FVC) in adolescents with asthma., Methods: Two hundred forty pulmonary function measurements were collected from 48 adolescents with persistent asthma from the University of North Carolina's pediatric allergy and pulmonology subspecialty clinics. Participants performed spirometry with the nSpireKoKo® sx1000 spirometer and the VitalFlo spirometer during their clinic visits. 119 simulated FVC maneuvers were conducted on both devices to standardize measurements. Pearson correlations, Bland-Altman procedure, and two-sample comparison tests were performed to assess the relationship between the two spirometers., Results: VitalFlo measurements were significantly highly correlated with nSpireKoKo® spirometer values for FEV 1, ( r 2 =0.721, [95% CI, 0.749 ± 0.120], P  < 0.001) and moderately for FVC ( r 2 = 0.617, [95% CI, 0.640 ± 0.130], P  < 0.001) measurements. There were no statistically significant differences of the mean FEV 1 ( M  = 0.00764, SD = 0.364, t(59)=0.16, P  = 0.87) and FVC measurements ( M  = 0.00261, SD = 0.565, t(59)=0.036, P  = 0.97.) between the VitalFlo and nSpireKoKo® systems. Both devices demonstrated significantly high correlation when comparing the automated FVC ( r 2 = 0.997, [95% CI, 1.00 ± 0.00974], P  < 0.001) measurements. Bland-Altman plots did not demonstrate significant bias between devices for both FEV 1 (0.00764 L) and FVC (0.00261 L) measurements., Conclusions: Lung function measurements from the VitalFlo mobile spirometer were comparable to a commercially-available spirometer commonly used in clinical settings. This validated app-based spirometer for home use has the potential to improve asthma self-management.

The CXCL12-CXCR4 pathway has crucial roles in stem cell homing and maintenance, neuronal guidance, cancer progression, inflammation, remote-conditioning, cell migration and development. Recently, work in chick suggested that signalling via CXCR4 in neural crest cells (NCCs) has a role in the 22q11.2 deletion syndrome (22q11.2DS), a disorder where haploinsufficiency of the transcription factor TBX1 is responsible for the major structural defects. We tested this idea in mouse models. Our analysis of genes with altered expression in Tbx1 mutant mouse models showed down-regulation of Cxcl12 in pharyngeal surface ectoderm and rostral mesoderm, both tissues with the potential to signal to migrating NCCs. Conditional mutagenesis of Tbx1 in the pharyngeal surface ectoderm is associated with hypo/aplasia of the 4th pharyngeal arch artery (PAA) and interruption of the aortic arch type B (IAA-B), the cardiovascular defect most typical of 22q11.2DS. We therefore analysed constitutive mouse mutants of the ligand (CXCL12) and receptor (CXCR4) components of the pathway, in addition to ectodermal conditionals of Cxcl12 and NCC conditionals of Cxcr4. However, none of these typical 22q11.2DS features were detected in constitutively or conditionally mutant embryos. Instead, duplicated carotid arteries were observed, a phenotype recapitulated in Tie-2Cre (endothelial) conditional knock outs of Cxcr4. Previous studies have demonstrated genetic interaction between signalling pathways and Tbx1 haploinsufficiency e.g. FGF, WNT, SMAD-dependent. We therefore tested for possible epistasis between Tbx1 and the CXCL12 signalling axis by examining Tbx1 and Cxcl12 double heterozygotes as well as Tbx1/Cxcl12/Cxcr4 triple heterozygotes, but failed to identify any exacerbation of the Tbx1 haploinsufficient arch artery phenotype. We conclude that CXCL12 signalling via NCC/CXCR4 has no major role in the genesis of the Tbx1 loss of function phenotype. Instead, the pathway has a distinct effect on remodelling of head vessels and interventricular septation mediated via CXCL12 signalling from the pharyngeal surface ectoderm and second heart field to endothelial cells., Competing Interests: The authors have declared that no competing interests exist.

Background: The Asthma Control Test (ACT) is widely used to assess asthma control, yet the validity and reliability of the test have not been specifically evaluated in adolescents or African-Americans. We conducted a prospective psychometric study of the ACT in African-American (AA) and non-African-American (nAA) adolescents with persistent asthma, with emphasis on the clinical utility of the test for medical decision making., Methods: Participants completed the ACT and performed spirometry. A physician conducted a guidelines-based assessment of asthma control, blinded to the ACT score. Study procedures were repeated 6-8 weeks later. The ACT-based asthma control assessment was compared to physician assessment., Results: For baseline and follow-up visits, internal consistency, as measured using Cronbach's alpha, was 0.80 and 0.81 in AA teens and 0.80 and 0.83 in nAA teens. Intraclass correlation coefficients were 0.59 and 0.76 in AA and nAA teens, respectively, with stable asthma control over time. Agreement between ACT and physician assessment was moderate in AA teens and fair in nAA teens. An ACT score of ≤19 showed reduced sensitivity for not well controlled asthma in both groups, while a score of ≤21 had the greatest area under the ROC curve. ACT scores were marginally responsive to change in control status., Conclusions: Concerns for the ACT's ability to detect uncontrolled asthma in adolescents emphasizes the need for a more comprehensive evaluation of asthma control in clinical settings. A higher threshold ACT score to define not well controlled asthma may be needed if the ACT is to be used for medical decision making., Trial Registration: ClinicalTrials.gov: NCT02671643 , NCT02662413 .

Whole mount visualization of the embryonic coronary plexus from which the capillary and arterial networks will form is rendered problematic using standard microscopy techniques, due to the scattering of imaging light by the thick heart tissue, as these vessels are localized deep within the walls of the developing heart. As optical clearing of tissues using organic solvents such as BABB (1 part benzyl alcohol to 2 parts benzyl benzoate) has been shown to greatly improve the optical penetration depth that can be achieved, we combined clearance of whole, PECAM1-immunostained hearts, with laser-scanning confocal microscopy, in order to obtain high-resolution images of vessels throughout the entire heart. BABB clearance of embryonic hearts takes place rapidly and also acts to preserve the fluorescent signal for several weeks; in addition, samples can be imaged multiple times without loss of signal. This straightforward method is also applicable to imaging other types of blood vessels in whole embryos.

We previously observed greater ozone-induced lung function decrements in obese than non-obese women. Animal models suggest that obesity enhances ozone-induced airway reactivity and inflammation. In a controlled exposure study, we compared the acute effect of randomized 0.4ppm ozone and air exposures (2 h with intermittent light exercise) in obese (N = 20) (30

The chemokine CXCL12 and its receptor CXCR4 have many functions during embryonic and post-natal life. We used murine models to investigate the role of CXCL12/CXCR4 signaling in cardiac development and found that embryonic Cxcl12-null hearts lacked intra-ventricular coronary arteries (CAs) and exhibited absent or misplaced CA stems. We traced the origin of this phenotype to defects in the early stages of CA stem formation. CA stems derive from the peritruncal plexus, an encircling capillary network that invades the wall of the developing aorta. We showed that CXCL12 is present at high levels in the outflow tract, while peritruncal endothelial cells (ECs) express CXCR4. In the absence of CXCL12, ECs were abnormally localized and impaired in their ability to anastomose with the aortic lumen. We propose that CXCL12 is required for connection of peritruncal plexus ECs to the aortic endothelium and thus plays a vital role in CA formation., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

22q11.2 Deletion Syndrome (22q11DS) arises from an interstitial chromosomal microdeletion encompassing at least 30 genes. This disorder is one of the most significant known cytogenetic risk factors for schizophrenia, and can also cause heart abnormalities, cognitive deficits, hearing difficulties, and a variety of other medical problems. The Df1/+ hemizygous knockout mouse, a model for human 22q11DS, recapitulates many of the deficits observed in the human syndrome including heart defects, impaired memory, and abnormal auditory sensorimotor gating. Here we show that Df1/+ mice, like human 22q11DS patients, have substantial rates of hearing loss arising from chronic middle ear infection. Auditory brainstem response (ABR) measurements revealed significant elevation of click-response thresholds in 48% of Df1/+ mice, often in only one ear. Anatomical and histological analysis of the middle ear demonstrated no gross structural abnormalities, but frequent signs of otitis media (OM, chronic inflammation of the middle ear), including excessive effusion and thickened mucosa. In mice for which both in vivo ABR thresholds and post mortem middle-ear histology were obtained, the severity of signs of OM correlated directly with the level of hearing impairment. These results suggest that abnormal auditory sensorimotor gating previously reported in mouse models of 22q11DS could arise from abnormalities in auditory processing. Furthermore, the findings indicate that Df1/+ mice are an excellent model for increased risk of OM in human 22q11DS patients. Given the frequently monaural nature of OM in Df1/+ mice, these animals could also be a powerful tool for investigating the interplay between genetic and environmental causes of OM.

Elucidating the gene regulatory networks that govern pharyngeal arch artery (PAA) development is an important goal, as such knowledge can help to identify new genes involved in cardiovascular disease. The transcription factor Tbx1 plays a vital role in PAA development and is a major contributor to cardiovascular disease associated with DiGeorge syndrome. In this report, we used various genetic approaches to reveal part of a signalling network by which Tbx1 controls PAA development in mice. We investigated the crucial role played by the homeobox-containing transcription factor Gbx2 downstream of Tbx1. We found that PAA formation requires the pharyngeal surface ectoderm as a key signalling centre from which Gbx2, in response to Tbx1, triggers essential directional cues to the adjacent cardiac neural crest cells (cNCCs) en route to the caudal PAAs. Abrogation of this signal generates cNCC patterning defects leading to PAA abnormalities. Finally, we showed that the Slit/Robo signalling pathway is activated during cNCC migration and that components of this pathway are affected in Gbx2 and Tbx1 mutant embryos at the time of PAA development. We propose that the spatiotemporal control of this tightly orchestrated network of genes participates in crucial aspects of PAA development.

Cyp26a1, a gene required for retinoic acid (RA) inactivation during embryogenesis, was previously identified as a potential Tbx1 target from a microarray screen comparing wild-type and null Tbx1 mouse embryo pharyngeal arches (pa) at E9.5. Using real-time PCR and in situ hybridization analysis of Cyp26a1 and its two functionally related family members Cyp26b1 and c1, we demonstrate reduced and/or altered expression for all three genes in pharyngeal tissues of Tbx1 null embryos. Blockade of Cyp26 function in the chick embryo using R115866, a specific inhibitor of Cyp26 enzyme function, resulted in a dose-dependent phenocopy of the Tbx1 null mouse including loss of caudal pa and pharyngeal arch arteries (paa), small otic vesicles, loss of head mesenchyme and, at later stages, DiGeorge Syndrome-like heart defects, including common arterial trunk and perimembranous ventricular septal defects. Molecular markers revealed a serious disruption of pharyngeal pouch endoderm (ppe) morphogenesis and reduced staining for smooth muscle cells in paa. Expression of the RA synthesizing enzyme Raldh2 was also up-regulated and altered Hoxb1 expression indicated that RA levels are raised in R115866-treated embryos as reported for Tbx1 null mice. Down-regulation of Tbx1 itself was observed, in accordance with previous observations that RA represses Tbx1 expression. Thus, by specifically blocking the action of the Cyp26 enzymes we can recapitulate many elements of the Tbx1 mutant mouse, supporting the hypothesis that the dysregulation of RA-controlled morphogenesis contributes to the Tbx1 loss of function phenotype.

22q11-deletion (DiGeorge/velocardiofacial) syndrome (22q11DS) is modeled by mutation of murine transcription factor Tbx1. As part of efforts to identify transcriptional targets of Tbx1, we analyzed the transcriptome of the pharyngeal region of Df1/+;Tbx1+/- embryos at 9.5 days of embryonic development using two independent microarray platforms. In this model, embryos are null for Tbx1, with hemizygosity of genes in cis with Tbx1 on one chromosome providing a positive control for array sensitivity. Reduced mRNA levels of genes deleted from Df1 were detected on both platforms. Expression level filtering and statistical analysis identified several genes that were consistently differentially expressed between mutant and wild type embryos. Real-time quantitative PCR and in situ hybridization validated diminished expression of Pax9 and Gcm2, genes known to be required for normal thymus and parathyroid gland morphogenesis, whereas Pax1, Hoxa3, Eya1, and Foxn1, which are similarly required, were not down-regulated. Gbx2, a gene required for normal arch artery development, was down-regulated specifically in the pharyngeal endoderm and the posterior part of pharyngeal arch 1, and is a potential point of cross talk between the Tbx1 and Fgf8 controlled pathways. These experiments highlight which genes and pathways potentially affected by lack of Tbx1, and whose role may be explored further by testing for epistasis using mouse mutants.

Histone acetyltransferase (HAT) activities of proteins such as p300, CBP, and P/CAF play important roles in activation of gene expression. We now show that the HAT activity of p300 can also be required for down-regulation of transcription by a DNA binding repressor protein. Promyelocytic leukemia zinc finger (PLZF), originally identified as a fusion with retinoic acid receptor alpha in rare cases of all-trans-retinoic acid-resistant acute promyelocytic leukemia, is a transcriptional repressor that recruits histone deacetylase-containing corepressor complexes to specific DNA binding sites. PLZF associates with p300 in vivo, and its ability to repress transcription is specifically dependent on HAT activity of p300 and acetylation of lysines in its C-terminal C2-H2 zinc finger motif. An acetylation site mutant of PLZF does not repress transcription and is functionally deficient in a colony suppression assay despite retaining its abilities to interact with corepressor/histone deacetylase complexes. This is due to the fact that acetylation of PLZF activates its ability to bind specific DNA sequences both in vitro and in vivo. Taken together, our results indicate that a histone deacetylase-dependent transcriptional repressor can be positively regulated through acetylation and point to an unexpected role of a coactivator protein in transcriptional repression.

The 22q11 deletion syndrome (22q11DS; DiGeorge/velo-cardio-facial syndrome) primarily affects the structures comprising the pharyngeal arches and pouches resulting in arch artery, cardiac, parathyroid, thymus, palatal and craniofacial defects. Tbx1 haploinsufficiency is thought to account for the main structural anomalies observed in the 22q11DS. The Df1 deleted mouse provides a model for 22q11DS, the deletion reflecting Tbx1 haploinsufficiency in the context of the deletion of 21 adjacent genes. We examined the expression of genes in Df1 embryos at embryonic day (E) 10.5, a stage when the arch-artery phenotype is fully penetrant. Our aims were threefold, with our primary aim to identify differentially regulated genes. Second, we asked whether any of the genes hemizygous in Df1 were dosage compensated to wild type levels, and third we investigated whether genes immediately adjacent to the deletion were dysregulated secondary to a position effect. Utilisation of oligonulceotide arrays allowed us to achieve our aims with 9 out of 12 Df1 deleted genes passing the stringent statistical filtering applied. Several genes involved in vasculogenesis and cardiogenesis were validated by real time quantitative PCR (RTQPCR), including Connexin 45, a gene required for normal vascular development, and Dnajb9 a gene implicated in microvascular differentiation. There was no evidence of any dosage compensation of deleted genes, suggesting this phenomenon is rare, and no dysregulation of genes mapping immediately adjacent to the deletion was detected. However Crkl, another gene implicated in the 22q11DS phenotype, was found to be downregulated by microarray and RTQPCR.

The development of pharyngeal arch derivatives in mouse and zebrafish embryos depends on the activity of the transcription factor Tbx1. We cloned the Xenopus laevis orthologue of Tbx1 (XTbx1) and show that the pattern of expression is similar to that in other vertebrate species. Zygotic transcripts are first detected shortly after the mid-blastula transition and are localized to the presumptive mesoderm at mid-gastrula stages. XTbx1 expression persists in the lateral plate mesoderm at neurula stages and is found in the pharyngeal arches and otic vesicles from early tail bud stages onward. We demonstrate that XTbx1 is a transcriptional activator and that this trans-activation requires the C-terminal region of the protein. A dominant interfering mutant of XTbx1 disrupts the development of Xenopus head structures and pharyngeal arch derivatives. Lineage labeling reveals a requirement for XTbx1 function in cells that contribute to the pharyngeal mesoderm and for fgf8 expression., (Copyright 2005 Wiley-Liss, Inc.)

The PLZF gene is translocated in a subset of all-trans-retinoic acid resistant acute promyelocytic leukaemia (APL) cases, encodes a DNA binding transcription factor and is expressed highly in haematopoietic progenitor cells as well-developing central nervous system (CNS). The spatially restricted and temporally dynamic pattern of PLZF expression in the developing CNS suggested that it might play a role in the circuitry regulating hindbrain segmentation. We have now identified a PLZF binding site (PLZF-RE) in an enhancer region of Hoxb2 that itself is required for directing high-level expression in rhombomers 3 and 5 of the developing hindbrain. The wild-type r3/r5 enhancer linked to a heterologous promoter was responsive to regulation by PLZF, and this activity was lost in variants containing a mutated PLZF-RE. Compared with the wild-type protein, the binding of the APL-associated reciprocal RARalpha-PLZF fusion to PLZF-RE was much stronger, suggesting that the N-terminal PLZF sequences missing from the fusion may play a role in the regulation of DNA binding. Consistent with this, the N-terminal POZ domain was required for cooperative binding of PLZF to a multimerized PLZF-RE. In the context of the r3/r5 enhancer, the PLZF-RE cooperated for PLZF binding with an additional A/T-rich motif positioned downstream of the PLZF-RE. This A/T motif was previously shown to be essential for the regulation of Hoxb2 expression in r3 and r5 in cooperation with another Krüppel-like zinc finger protein Krox 20. The presence of both the PLZF-RE and the A/T-rich motif was required for a maximal effect of PLZF on a heterologous promoter and was essential in vivo to direct the expression of a lacZ reporter in the chick neural tube. Hence, both PLZF and Krox20 cooperate with a common A/T motif in mediating in vivo activity of the Hoxb2 enhancer. Our findings indicate that Hoxb2 is a direct target for regulation by PLZF in the developing CNS and suggest that deregulation of Hox gene expression may contribute to APL pathogenesis.

Acute promyelocytic leukemia (APL) is associated with chromosomal translocations that always involve the RARalpha gene, which variably fuses to one of several distinct loci, including PML or PLZF (X genes). Due to the reciprocity of the translocation, X-RARalpha and RARalpha-X fusion proteins coexist in APL blasts. PLZF-RARalpha transgenic mice (TM) develop leukemia that lacks the differentiation block at the promyelocytic stage that characterizes APL. We generated TM expressing RARalpha-PLZF and PLZF-RARalpha in their promyelocytes. RARalpha-PLZF TM do not develop leukemia. However, PLZF-RARalpha/RARalpha-PLZF double TM develop leukemia with classic APL features. We demonstrate that RARalpha-PLZF can interfere with PLZF transcriptional repression and that this is critical for APL pathogenesis, since leukemias in PLZF(-/-)/PLZF-RARalpha mutants and in PLZF-RARalpha/RARalpha-PLZF TM are indistinguishable. Thus, both products of a cancer-associated translocation are crucial in determining the distinctive features of the disease.

The Wilms' tumour suppressor gene, WT1, encodes a zinc finger transcription factor that has been shown to repress a variety of cellular promoters via binding to cognate DNA elements. Our earlier work identified an antisense WT1 promoter that contains WT1 consensus sites, but is transcriptionally activated by WT1. In this study, we demonstrate that, unlike previous reports of transcriptional regulation by WT1, transactivation of the antisense promoter is unique to a single isoform of WT1. Of the four alternatively spliced isoforms in which exon 5 (at splice I) or amino acid residues KTS (at splice II) are inserted or omitted, only the WT1 isoform containing splice I and omitting splice II (WT1[+/-]) displays transactivation. We demonstrate that transregulation variations observed with WT1 isoforms are not solely attributable to differential DNA binding by [+KTS] or [-KTS] isoforms. Thus, the transactivation of the antisense promoter displays an absolute requirement for exon 5, suggesting that interaction between WT1 and other cellular factors is necessary for this regulatory function.

The promyelocytic leukemia zinc finger (PLZF) gene, which is disrupted in therapy-resistant, t(11;17)(q23;q21)-associated acute promyelocytic leukemia (APL), is expressed in immature hematopoietic cells and is down-regulated during differentiation. To determine the role of PLZF in myeloid development, we engineered expression of PLZF in murine 32Dcl3 cells. Expression of PLZF had a dramatic growth-suppressive effect accompanied by accumulation of cells in the G0/G1 compartment of the cell cycle and an increased incidence of apoptosis. PLZF-expressing pools also secreted a growth-inhibitory factor, which could explain the severe growth suppression of PLZF-expressing pools that occurred despite the fact that only half of the cells expressed high levels of PLZF. PLZF overexpression inhibited myeloid differentiation of 32Dcl3 cells in response to granulocyte and granulocyte-macrophage colony-stimulating factors. Furthermore, cells that expressed PLZF appeared immature as demonstrated by morphology, increased expression of Sca-1, and decreased expression of Gr-1. These findings suggest that PLZF is an important regulator of cell growth, death, and differentiation. Disruption of PLZF function associated with t(11;17) may be a critical event leading to APL.

Typical acute promyelocytic leukemia (APL) is associated with expression of the PML-RARalpha fusion protein and responsiveness to treatment with all-trans retinoic acid (ATRA). A rare, but recurrent, APL has been described that does not respond to ATRA treatment and is associated with a variant chromosomal translocation and expression of the PLZF-RARalpha fusion protein. Both PML- and PLZF-RARalpha possess identical RAR sequences and inhibit ATRA-induced gene transcription as well as cell differentiation. We now show that the above-mentioned oncogenic fusion proteins interact with the nuclear receptor corepressor N-CoR and, in comparison with the wild-type RARalpha protein, their interactions display reduced sensitivities to ATRA. Although pharmacologic concentration of ATRA could still induce dissociation of N-CoR from PML-RARalpha, it had a very little effect on its association with the PLZF-RARalpha fusion protein. This ATRA-insensitive interaction between N-CoR and PLZF-RARalpha was mediated by the N-terminal PLZF moiety of the chimera. It appears that N-CoR/histone deacetylase corepressor complex interacts directly in an ATRA-insensitive manner with the BTB/POZ-domain of the wild-type PLZF protein and is required, at least in part, for its function as a transcriptional repressor. As the above-noted results predict, histone deacetylase inhibitors antagonize oncogenic activities of the PML-RARalpha fusion protein and partially relieve transcriptional repression by PLZF as well as inhibitory effect of PLZF-RARalpha on ATRA response. Taken together, our results demonstrate involvement of nuclear receptor corepressor/histone deacetylase complex in the molecular pathogenesis of APL and provide an explanation for differential sensitivities of PML- and PLZF-RARalpha-associated leukemias to ATRA.

Expression of the Wilms' tumour suppressor gene, WT1, is tightly regulated during nephrogenesis, and loss of function of its gene product correlates with malignancy. By using luciferase reporter gene constructs containing DNA sequences from the first intron of the WT1 gene, we have identified an antisense WT1 promoter operational in the opposite direction relative to the 5' promoter. Transcription directed by the promoter is negatively regulated by upstream elements, but is activated by expression of WT1. This effect of WT1 is reciprocal to that observed on the 5' promoter, suggesting that antisense promoter activity is involved in WT1 gene regulation. By mimicking expression of the transcript regulated by the antisense promoter, we demonstrate that cellular levels of WT1 can be effectively down-regulated by antisense mRNA complementary to sequences in the first exon of WT1.

In a study of 159 school-age children whose histories of outpatient visits for lower respiratory illness (LRI) had been documented from early infancy, we observed lower mean levels of small airway function in boys who had experienced two or more episodes of wheezing-associated LRI before 6 yr of age. To determine whether allergy was an important factor influencing this result, we examined relationships among the results of RAST tests for seven common inhalant allergens and concurrent lung function in 126 subjects who consented to venipuncture. Increasing values for the sum of scores for the seven RAST tests were associated with progressively lower mean levels of small airways function in boys with histories of recurrent wheezing LRI during the preschool years. The association of allergy with lower levels of lung function was largely accounted for by dust mite allergy. RAST results were not correlated with lung function in boys who had experienced zero or 1 wheezing LRI before 6 yr of age or in girls. A history of recurrent wheezing LRI during the preschool years was also associated with significantly lower mean levels of small airways function in boys who had negative RAST tests. A subset of 49 boys was reevaluated after an average interval of 4 yr with RAST tests, spirometry, and methacholine challenge. Dust mite allergy was associated with an increased prevalence of bronchial hyperreactivity independent of early childhood wheezing LRI history.(ABSTRACT TRUNCATED AT 250 WORDS)

We examined the relationship between patterns of mild lower respiratory illness (LRI) experienced in early childhood and lung function in 89 boys and 70 girls 6 to 18 yr of age. The children's histories of outpatient visits for wheezing and nonwheezing LRI during the first 6 yr of life had been documented by physicians in a single pediatric practice. Most children were reported by their parents to have been free of recurrent respiratory symptoms during the 2 yr prior to lung function testing. In sex-specific analyses, average lung function assessed by spirometry was similar in children who had made zero or one physician visit for wheezing LRI during the preschool years. Boys who had experienced two or more episodes of wheezing LRI during the preschool years had lower average FEV1, FEV1/FVC, FEF25-75, Vmax50, and Vmax75 than did boys who had zero or one preschool wheezing illness. The association between recurrent preschool wheezing LRI and later lung function remained after exclusion of data from seven boys who were reported to have wheezed in the 2 yr prior to study. Girls who had experienced two or more preschool wheezing LRI had lower average FEF25-75 and Vmax50 than girls with a history of zero or one such illness, but differences were not statistically significant. Recurrent nonwheezing LRI during the preschool years was not significantly associated with subsequent lung function in either sex, regardless of preschool wheezing LRI history. Detailed information concerning early childhood LRI experience is valuable in epidemiologic studies of factors influencing lung function in children.