Mouse Otx2 functions in the formation and patterning of rostral head

The anterior part of the vertebrate head expresses a group of homeo box genes in segmentally restricted patterns during embryogenesis. Among these, Otx2 expression covers the entire fore- and midbrains and takes place earliest. To examine its role in development of the rostral head, a mutation was introduced into this locus. The homozygous mutants did not develop structures anterior to rhombomere 3, indicating an essential role of Otx2 in the formation of the rostral head. In contrast, heterozygous mutants displayed craniofacial malformations designated as otocephaly; affected structures appeared to correspond to the most posterior and most anterior domains of Otx expression where Otx1 is not expressed. The homo- and heterozygous mutant phenotypes suggest Otx2 functions as a gap-like gene in the rostral head where Hox code is not present. The evolutionary significance of Otx2 mutant phenotypes was discussed for the innovation of the neurocranium and the jaw.

twist is required in head mesenchyme for cranial neural tube morphogenesis

To understand the role of twist during mammalian development, we generated twist-null mice. twist-null embryos died at embryonic day 11.5. Their most prominent phenotype was a failure of the cranial neural folds to fuse. Mutant embryos also had defects in head mesenchyme, somites, and limb buds. Chimera analysis suggested that head mesenchyme was required for cranial neural tube closure and that twist acted in a cell-autonomous manner in this tissue. In addition, in the head mesenchyme region of chimeras, twist-null cells were segregated from wild-type cells, and in the forebrain they lacked mesenchymal characteristics. These results suggest that twist regulates the cellular phenotype and behavior of head mesenchyme cells that are essential for the subsequent formation of the cranial neural tube.

Concept and application of limbal stem cells

Cumulative reported evidence indicates that some fraction of limbal basal epithelial cells are the stem cells for corneal epithelial cell proliferation and differentiation. Limbal epithelium is therefore crucial in maintaining the cell mass of corneal epithelium under normal conditions and plays an important role in corneal epithelial wound healing. Deficiency or absence of limbal stem cells explains well the pathogenesis of several ocular surface disorders characterised by defective conjunctival transdifferentiation or conjunctivalisation of cornea. This paper reviews and updates the basic concept of stem cells, the reported findings of limbal stem cells for corneal epithelium, and their therapeutic applications. Through this review, one hopes to gain a more complete understanding and increase proficiency in treating these diseases.

Lymphoid enhancer factor 1 directs hair follicle patterning and epithelial cell fate

T cell-specific transcription factor (TCF-1) and lymphoid enhancer factor 1 (LEF-1) have been implicated exclusively in the regulation of T cell-specific genes. The only adult tissue other than thymus known to express these factors is spleen and lymph node, which contain low levels of LEF-1 and no TCF-1. We noticed that genes involved in hair-specific gene expression possess LEF-1/TCF-1 consensus motifs located in similar positions relative to their TATA box. We show that of the two factors only LEF-1 is expressed in hair follicles; it can be cloned in both splice forms from human skin keratinocytes and it can bind to these sites in the hair promoters. We show that LEF-1 mRNA is present in pluripotent ectoderm, and it is up-regulated in a highly restricted pattern just before the formation of underlying mesenchymal condensates and commitment of overlying ectodermal cells to invaginate and become hair follicles. New waves of ectodermal LEF-1 spots appear concomitant with new waves of follicle morphogenesis. To test whether LEF-1 patterning might be functionally important for hair patterning and morphogenesis, we used transgenic technology to alter the patterning and timing of LEF-1 over the surface ectoderm. Striking abnormalities arose in the positioning and orientation of hair follicles, leaving a marked disruption of this normally uniform patterning. This provides the first direct evidence that ectodermal cues are critical in establishing these developmental processes, which at later stages are known to be influenced by underlying mesenchyme. Remarkably, elevated LEF-1 in the lip furrow epithelium of developing transgenic animals triggered these cells to invaginate, sometimes leading to the inappropriate adoption of hair follicle and tooth cell fates. Collectively, our findings demonstrate that ectodermal expression of LEF-1 plays a central role in gene expression, pattern formation, and other developmental processes involving epithelial-mesenchymal associations.

Gene targeting of BPAG1: abnormalities in mechanical strength and cell migration in stratified epithelia and neurologic degeneration

BPAG1 is the major antigenic determinant of autoimmune sera of bullous pemphigoid (BP) patients. It is made by stratified squamous epithelia, where it localizes to the inner surface of specialized integrin-mediated adherens junctions (hemidesmosomes). To explore the function of BPAG1 and its relation to BP, we targeted the removal of the BPAG1 gene in mice. Hemidesmosomes are otherwise normal, but they lack the inner plate and have no cytoskeleton attached. Though not affecting cell growth or substratum adhesion, this compromises mechanical integrity and influences migration. Unexpectedly, the mice also develop severe dystonia and sensory nerve degeneration typical of dystonia musculorum (dt/dt) mice. We show that in at least one other strain of dt/dt mice, BPAG1 gene is defective.

Dicer function is essential for lung epithelium morphogenesis

DICER is a key enzyme that processes microRNA and small interfering RNA precursors into their short mature forms, enabling them to regulate gene expression. Only a single Dicer gene exists in the mouse genome, and it is broadly expressed in developing tissues. Dicer-null mutants die before gastrulation. Therefore, to study Dicer function in the later event of lung formation, we inactivated it in the mouse lung epithelium using a Dicer conditional allele and the Sonic Hedgehogcre (Shhcre) allele. Branching arrests in these mutant lungs, although epithelial growth continues in distal domains that are expanded compared with normal samples. These defects result in a few large epithelial pouches in the mutant lung instead of numerous fine branches present in a normal lung. Significantly, the initial phenotypes are apparent before an increase in epithelial cell death is observed, leading us to propose that Dicer plays a specific role in regulating lung epithelial morphogenesis independent of its requirement in cell survival. In addition, we found that the expression of Fgf10, a key gene involved in lung development, is up-regulated and expanded in the mesenchyme of Dicer mutant lungs. Previous studies support the hypothesis that precise localization of FGF10 in discrete sites of the lung mesenchyme serves as a chemoattractant for the outgrowth of epithelial branches. The aberrant Fgf10 expression may contribute to the Dicer morphological defects. However, the mechanism by which DICER functions in the epithelium to influence Fgf10 expression in the mesenchyme remains unknown.

Defects of urogenital development in mice lacking Emx2

The homeobox gene Emx2 is a mouse homologue of a Drosophila head gap gene empty spiracles (ems) and is essential for the development of dorsal telencephalon (Yoshida, M., Suda, Y., Matsuo, I., Miyamoto, N., Takeda, N., Kuratani, S. and Aizawa, S. (1997) Development 124, 101–111). At the same time, Emx2 is expressed in the epithelial components of the developing urogenital system and, in Emx2 mutant mice, the kidneys, ureters, gonads and genital tracts were completely missing. Pax-2 and c-ret expressions in the Wolffian duct and WT-1 and GDNF expressions in the metanephric blastema were initially normal in the mutant. The ureteric bud grew and invaded the metanephric mesenchyme where Pax-2 expression was normally induced. Subsequently, however, Pax-2, c-ret and Lim1 expressions in the ureteric bud and GDNF expression in the mesenchyme were greatly reduced. Wnt-4 expression was never found in the mesenchyme. The tip of the ureteric bud never dilated and branching of the bud did not occur. Neither pretubular cell aggregates nor epithelialization were found in the mesenchyme. Instead the ureteric bud soon degenerated and apoptotic figures were prominent in mesenchymal cells. In explant culture, the mutant ureteric bud did not induce the epithelial transformation of the wild-type mesenchyme, and branching of the mutant ureteric bud was not induced by wild-type mesenchyme. In contrast, defects were not apparent in the mutant mesenchyme by co-culture with wild-type ureteric bud or spinal cord. These results suggest that, in metanephrogenesis, Emx2 is essential for the ureteric bud functions subsequent to Pax-2 induction in the metanephric mesenchyme. Degeneration of the Wolffian duct and mesonephric tubules was also abnormally accelerated without the formation of the Mullerian duct.

A role for MEK kinase 1 in TGF-beta/activin-induced epithelium movement and embryonic eyelid closure

MEKK1-deficient mice show an eye open at birth phenotype caused by impairment in embryonic eyelid closure. MEK kinase 1 (MEKK1) is highly expressed in the growing tip of the eyelid epithelium, which displays loose cell-cell contacts and prominent F-actin fibers in wild-type mice, but compact cell contacts, lack of polymerized actin and a concomitant impairment in c-Jun N-terminal phosphorylation in MEKK1-deficient mice. In cultured keratinocytes, MEKK1 is essential for JNK activation by TGF-beta and activin, but not by TGF-alpha. MEKK1-driven JNK activation is required for actin stress fiber formation, c-Jun phosphorylation and cell migration. However, MEKK1 ablation does not impair other TGF-beta/activin functions, such as nuclear translocation of Smad4. These results establish a specific role for the MEKK1-JNK cascade in transmission of TGF-beta and activin signals that control epithelial cell movement, providing the mechanistic basis for the regulation of eyelid closure by MEKK1. This study also suggests that the signaling mechanisms that control eyelid closure in mammals and dorsal closure in Drosophila are evolutionarily conserved.

LET-413 is a basolateral protein required for the assembly of adherens junctions in Caenorhabditis elegans

Epithelial cells are polarized, with apical and basal compartments demarcated by tight and adherens junctions. Proper establishment of these subapical junctions is critical for normal development and histogenesis. We report the characterization of the gene let-413 which has a critical role in assembling adherens junctions in Caenorhabditis elegans. In let-413 mutants, adherens junctions are abnormal and mislocalized to more basolateral positions, epithelial cell polarity is affected and the actin cytoskeleton is disorganized. The LET-413 protein contains one PDZ domain and 16 leucine-rich repeats with high homology to proteins known to interact with small GTPases. Strikingly, LET-413 localizes to the basolateral membrane. We suggest that LET-413 acts as an adaptor protein involved in polarizing protein trafficking in epithelial cells.

Combined loss of Hey1 and HeyL causes congenital heart defects because of impaired epithelial to mesenchymal transition

Congenital heart defects affect almost 1% of human newborns. Recently, mutations in Notch ligands and receptors have been found to cause a variety of heart defects in rodents and humans. However, the molecular effects downstream of Notch are still poorly understood. Here we report that combined inactivation of Hey1 and HeyL, two primary target genes of Notch, causes severe heart malformations, including membranous ventricular septal defects and dysplastic atrioventricular and pulmonary valves. These defects lead to congestive cardiac failure with high lethality. We found both genes to be coexpressed with Notch1, Notch2 and the Notch ligand Jagged1 in the endocardium of the atrioventricular canal, representing the primary source of mesenchymal cells forming membraneous septum and valves. Atrioventricular explants from Hey1/HeyL deficient mice exhibited impaired epithelial to mesenchymal transition. Although epithelial to mesenchymal transition was initiated regularly, full transformation into mesenchymal cells failed. This was accompanied by reduced levels of matrix metalloproteinase-2 expression and reduced cell density in endocardial cushions in vivo. We further show that loss of Hey2 leads to very similar deficiencies, whereas a Notch1 null mutation completely abolishes epithelial to mesenchymal transition. Thus, the Hey gene family shows overlap in controlling Notch induced endocardial epithelial to mesenchymal transition, a process critical for valve and septum formation.

Lack of pendrin expression leads to deafness and expansion of the endolymphatic compartment in inner ears of Foxi1 null mutant mice

Mice that lack the winged helix/forkhead gene Foxi1 (also known as Fkh10) are deaf and display shaker/waltzer behavior, an indication of disturbed balance. While Foxi1 is expressed in the entire otic vesicle at E9.5, it becomes gradually restricted to the endolymphatic duct/sac epithelium and at E16.5 Foxi1 expression in the inner ear is confined to this epithelium. Histological sections, paintfill experiments and whole-mount hybridizations reveal no abnormality in inner ear development of Foxi1(-/-) mice before E13.5. Between E13.5 and E16.5 the membranous labyrinth of inner ears from null mutants starts to expand as can be seen in histological sections, paint-fill experiments and three-dimensional reconstruction. Postnatally, inner ears of Foxi1(-/-) mice are extremely expanded, and large irregular cavities, compressing the cerebellum and the otherwise normal middle ear, have replaced the delicate compartments of the wild-type inner ear. This phenotype resembles that of the human sensorineural deafness syndrome Pendred syndrome, caused by mutations in the PDS gene. In situ hybridization of Foxi1(-/-) endolymphatic duct/sac epithelium shows a complete lack of the transcript encoding the chloride/iodide transporter pendrin. Based on this, we would like to suggest that Foxi1 is an upstream regulator of pendrin and that the phenotype seen in Foxi1 null mice is, at least in part, due to defective pendrin-mediated chloride ion resorption in the endolymphatic duct/sac epithelium. We show that this regulation could be mediated by absence of a specific endolymphatic cell type--FORE (forkhead related) cells--expressing Foxi1, Pds, Coch and Jag1. Thus, mutations in FOXI1 could prove to cause a Pendred syndrome-like human deafness.

Gliotactin, a novel marker of tricellular junctions, is necessary for septate junction development in Drosophila

Septate junctions (SJs), similar to tight junctions, function as transepithelial permeability barriers. Gliotactin (Gli) is a cholinesterase-like molecule that is necessary for blood-nerve barrier integrity, and may, therefore, contribute to SJ development or function. To address this hypothesis, we analyzed Gli expression and the Gli mutant phenotype in Drosophila epithelia. In Gli mutants, localization of SJ markers neurexin-IV, discs large, and coracle are disrupted. Furthermore, SJ barrier function is lost as determined by dye permeability assays. These data suggest that Gli is necessary for SJ formation. Surprisingly, Gli distribution only colocalizes with other SJ markers at tricellular junctions, suggesting that Gli has a unique function in SJ development. Ultrastructural analysis of Gli mutants supports this notion. In contrast to other SJ mutants in which septa are missing, septa are present in Gli mutants, but the junction has an immature morphology. We propose a model, whereby Gli acts at tricellular junctions to bind, anchor, or compact SJ strands apically during SJ development.

Epithelial and ectomesenchymal role of the type I TGF-beta receptor ALK5 during facial morphogenesis and palatal fusion

Transforming growth factor beta (TGF-beta) proteins play important roles in morphogenesis of many craniofacial tissues; however, detailed biological mechanisms of TGF-beta action, particularly in vivo, are still poorly understood. Here, we deleted the TGF-beta type I receptor gene Alk5 specifically in the embryonic ectodermal and neural crest cell lineages. Failure in signaling via this receptor, either in the epithelium or in the mesenchyme, caused severe craniofacial defects including cleft palate. Moreover, the facial phenotypes of neural crest-specific Alk5 mutants included devastating facial cleft and appeared significantly more severe than the defects seen in corresponding mutants lacking the TGF-beta type II receptor (TGFbetaRII), a prototypical binding partner of ALK5. Our data indicate that ALK5 plays unique, non-redundant cell-autonomous roles during facial development. Remarkable divergence between Tgfbr2 and Alk5 phenotypes, together with our biochemical in vitro data, imply that (1) ALK5 mediates signaling of a diverse set of ligands not limited to the three isoforms of TGF-beta, and (2) ALK5 acts also in conjunction with type II receptors other than TGFbetaRII.

Requirement for chitin biosynthesis in epithelial tube morphogenesis

Many organs are composed of branched networks of epithelial tubes that transport vital fluids or gases. The proper size and shape of tubes are crucial for their transport function, but the molecular processes that govern tube size and shape are not well understood. Here we show that three genes required for tracheal tube morphogenesis in Drosophila melanogaster encode proteins involved in the synthesis and accumulation of chitin, a polymer of N-acetyl-beta-D-glucosamine that serves as a scaffold in the rigid extracellular matrix of insect cuticle. In all three mutants, developing tracheal tubes bud and extend normally, but the epithelial walls of the tubes do not expand uniformly, and the resultant tubes are grossly misshapen, with constricted and distended regions all along their lengths. The genes are expressed in tracheal cells during the expansion process, and chitin accumulates in the lumen of tubes, forming an expanding cylinder that we propose coordinates the behavior of the surrounding tracheal cells and stabilizes the expanding epithelium. These findings show that chitin regulates epithelial tube morphogenesis, in addition to its classical role protecting mature epithelia.

Incidence of ocular surface epithelial dysplasia in metropolitan Brisbane. A 10-year survey

The ocular histologic records of all hospital and private pathologic laboratories in metropolitan Brisbane, Australia, were surveyed from 1980 through 1989. One hundred thirty-nine cases of histologically proven dysplasia, carcinoma in situ, and invasive carcinoma of the cornea and conjunctiva were identified. The incidence of these conditions in the area surveyed is estimated to be 1.9 per 100,000 per year averaged for 10 years.

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.

ErbB2 is required for ductal morphogenesis of the mammary gland

The ERBB2/HER2/NEU receptor tyrosine kinase gene is amplified in up to 30% of human breast cancers. The frequent and specific selection of this receptor kinase gene for amplification in breast cancer implies that it has important normal functions in the mammary gland. To investigate the functions of ErbB2 during normal mouse mammary gland development, we transplanted mammary buds from genetically rescued ErbB2(-/-) embryos that express ErbB2 in the cardiac muscle. ErbB2(-/-) mammary buds transplanted to a wild-type mammary fat pad support outgrowth of an epithelial tree that advances only slowly through the mammary fat pad at puberty. This penetration defect is associated with structural defects in terminal end buds, characterized by a decrease in body cell number, an increased presence of cap-like cells in the prelumenal compartment, and the presence of large luminal spaces. Lobuloalveolar development was not affected in glands that developed from ErbB2(-/-) transplanted tissue. The results may have implications for the aggressive phenotypes associated with ERBB2-overexpressing mammary carcinomas.

Abnormal epidermal differentiation and impaired epithelial-mesenchymal tissue interactions in mice lacking the retinoblastoma relatives p107 and p130

The functions of p107 and p130, members of the retinoblastoma family, include the control of cell cycle progression and differentiation in several tissues. Our previous studies suggested a role for p107 and p130 in keratinocyte differentiation in vitro. We now extend these data using knockout animal models. We found impaired terminal differentiation in the interfollicular keratinocytes of p107/p130-double-null mice epidermis. In addition, we observed a decreased number of hair follicles and a clear developmental delay in hair, whiskers and tooth germs. Skin grafts of p107/p130-deficient epidermis onto NOD/scid mice showed altered differentiation and hyperproliferation of the interfollicular keratinocytes, thus demonstrating that the absence of p107 and p130 results in the deficient control of differentiation in keratinocytes in a cell-autonomous manner. Besides normal hair formation, follicular cysts, misoriented and dysplastic follicles, together with aberrant hair cycling, were also observed in the p107/p130 skin transplants. Finally, the hair abnormalities in p107/p130-null skin were associated with altered Bmp4-dependent signaling including decreased DeltaNp63 expression. These results indicate an essential role for p107 and p130 in the epithelial-mesenchimal interactions.

The hairless gene of the mouse: relationship of phenotypic effects with expression profile and genotype

Various mutations of the hairless (hr) gene of mice result in hair loss and other integument defects. To examine the role of the hr gene in mouse development, the expression profile of hr has been determined by in situ hybridisation and correlated to the nature of genetic changes and morphological abnormalities in different mutant animals. Four variant alleles have been characterised at the molecular level. hr/hr mice produce reduced, but significant, levels of hr mRNA whereas other alleles contain mutations which would be expected to preclude the synthesis of functional product, demonstrating a correlation between allelic variation at the hr locus and phenotypic severity. hr expression was shown to be widespread and temporally regulated. It was identified in novel tissues such as cartilage, developing tooth, inner ear, retina, and colon as well as in skin and brain. Analysis of mice homozygous for the rhino allele of hairless revealed that, although no morphological defects were detectable in many tissues normally expressing hr, previously undescribed abnormalities were present in several tissues including inner ear, retina, and colon. These findings indicate that the hairless gene product plays a wider role in development than previously suspected. Dev Dyn 1999;216:113-126.

Upper beak truncation in chicken embryos with the cleft primary palate mutation is due to an epithelial defect in the frontonasal mass

In this study, we used the chicken mutant strain known as cleft primary palate (cpp) to study the mechanisms of beak outgrowth. cpp mutants have complete truncation of the upper beak with normal development of the lower beak. Based on structural analysis and grafts of facial prominences, we localized the defect to the frontonasal mass and its derivatives. Several explanations that would account for the outgrowth defect were investigated, including abnormal expression of genes in the frontonasal epithelium, intrinsic defects in epithelium and/or mesenchyme defects in epithelial-mesenchymal signalling, a localized decrease in cell proliferation or a localized increase in programmed cell death. One of the genes expressed in the frontonasal epithelial growth zone, Fgf8, failed to down-regulate and was maintained for at least 48 hr beyond the time when down-regulation normally occurs. Recombination experiments further illustrated that the frontonasal mass epithelium was abnormal in the cpp mutants, whereas mutant mesenchyme was capable of normal outgrowth when combined with wild-type epithelium. Cell proliferation was not decreased in mutant embryos nor was cell death initially increased. Later, at stages 31-32, when the prenasal cartilage begins directed outgrowth, there was an increase in cell death within the mutant upper but not lower beak cartilage. The cpp beak truncation, therefore, is due to an epithelial defect in the frontonasal mass that is coincident with a failure to down-regulate expression of Fgf8.

Epithelial abnormalities and precancerous lesions of anterior urethra in patients with penile carcinoma: a report of 89 cases

Urethral and penile tissues and their neoplasms are considered anatomically and pathogenetically different. Since we observed urethral dysplastic lesions and some similarities between noninvasive and invasive lesions of the anterior urethra and glans, we designed this study to document epithelial urethral abnormalities in patients with penile squamous cell carcinoma. We examined urethral epithelia from 170 penectomies with invasive squamous cell carcinoma finding a variety of primary epithelial abnormalities in 89 cases (52%) and secondary invasion of penile carcinoma to urethra in 42 cases (25%). Patients' average age was 68 years. Primary tumors measured 4 cm in average diameter and the majority were squamous cell carcinoma of the usual (67%) or verrucous type (15%). Primary epithelial abnormalities found were squamous intraepithelial lesions, metaplasias and microglandular hyperplasias. Urethral squamous intraepithelial lesions of high grade was found in six patients and of low grade in eight cases. Squamous metaplasia, seen in 69 cases, was the most frequent finding. Metaplasias were classified as nonkeratinizing and keratinizing. Nonkeratinizing metaplasias (57 cases) were variegated in morphology: simplex (26 cases), hyperplastic (12 cases), clear cell (11 cases) and spindle (8 cases). Keratinizing metaplasias (12 cases) showed hyperkeratosis and were more frequently associated with verrucous than nonverrucous penile squamous cell carcinoma. Microglandular hyperplasia was present in eight cases. Lichen sclerosus was associated with simplex squamous metaplasia in four cases. Despite the large size of the primary tumors, direct urethral invasion by penile carcinoma was present in only 25% of the cases. The presence of precancerous lesions in urethra of patients with penile carcinoma indicates urethral participation in the pathogenesis of penile cancer. Simplex squamous metaplasia is a common finding probably related to chronic inflammation. Keratinizing and hyperplastic squamous metaplasias may be important in the pathogenesis of special types of penile carcinomas such as verrucous carcinoma.

Alveolar epithelial composition and architecture of the late fetal pulmonary acinus: an immunocytochemical and morphometric study in a rat model of pulmonary hypoplasia and congenital diaphragmatic hernia

The aim of the present study was to compare the architecture and alveolar epithelial cell composition of the pulmonary acinus in hypoplastic and normal fetal rat lungs. For this purpose, a rat model of pulmonary hypoplasia in association with congenital diaphragmatic hernia (CDH) induced by Nitrofen (100 mg on day 10 of pregnancy) was studied. Sections (5 microns) from lungs of control and Nitrofen-exposed fetal Sprague Dawley rats with or without CDH aged 18-22 days (vaginal plug on day 1, birth on day 23) were stained with hematoxylin and eosin. To identify developing alveolar epithelial cells, sections were incubated with anti-surfactant protein A (SP-A; rabbit anti-mouse) or preimmunization serum (indirect immunofluorescence). On days 18 and 19, control lungs and exposed lungs from fetuses with and without CDH looked similar (pseudoglandular stage of lung development). The prospective pulmonary acinus consisted of acinar tubules with small round lumens, lined by cuboid, fluorescent type II cells. Morphometric analysis on day 19 showed significantly smaller lung volumes and lung tissue volumes after Nitrofen exposure. On day 20 (canalicular stage), some tubules were slightly dilated and lined by cuboid and thinner fluorescent cells; these dilated tubules were less numerous in lungs from exposed fetuses with CDH. On days 21 and 22 (saccular stage), the saccular lining consisted of cuboid to thin fluorescent cells in exposed lungs from fetuses with and without CDH, and fluorescent (low) cuboid cells interspersed with dark zones (type I cell areas) in control lungs. In the exposed lungs from fetuses with CDH, the lumens of all airspaces were frequently slit-like, and the septa were thicker. These phenomena gave the lungs a primitive, compact aspect. Morphometric analysis on day 22 showed smaller lung volumes and lung tissue volumes, smaller airspace/tissue ratios, smaller epithelial surface areas, and more type II cells per surface area in Nitrofen-exposed lungs than in normal control lungs. The results suggest that Nitrofen-exposed, and thus hypoplastic, fetal rat lungs are retarded with respect to the differentiation of cuboid type II cells into squamous type I cells whether or not CDH is present, and with respect to the development of the future airspaces between days 20 and 22 if CDH is present.

Lack of Expression of EGF and TGF- in the Fetal Mouse Alters Formation of Prostatic Epithelial Buds and Influences the Response to TCDD

In utero, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure causes abnormal ventral, dorsolateral, and anterior prostate development in C57BL/6J mice. Androgens, mesenchymal-epithelial interactions, and growth factor expression all have roles in initiating and regulating development and growth of the prostate. Epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha), both of which bind the EGF receptor (EGFR), are expressed in human and rodent developing prostate. This study examines the influence of null expression of EGF and/or TGF-alpha on prostatic bud development and on the ability of TCDD to inhibit prostatic budding. Growth factor knockout (-/-) and wild-type (WT) mice were exposed either to vehicle or to TCDD (0, 0.2, 1, 5, 10, 50, 100, or 150 microg/kg) on gestation day (GD) 12. The number of anterior, dorsal, and lateral prostatic buds (ADLB) and ventral buds (VB) were counted on GD 17.5. Control WT and EGF (-/-) fetuses had similar numbers of ADLB and VB. In control TGF-alpha (-/-) fetuses, the number of ADLBs was higher relative to the C57BL/6J. Control EGF + TGF-alpha (-/-) had poor bud outgrowth, especially in the ADL region. TCDD induced a dose-related decrease in bud formation in all strains with the formation of VBs being more sensitive than ADLBs. The severity of the response depended on growth factor expression, with the most severe effects on VBs in the EGF (-/-) and on ADLBs in the EGF + TGF-alpha (-/-) fetuses. TGF-alpha (-/-) and C57BL/6J fetuses responded to TCDD similarly. In conclusion, EGF and TGF-alpha expression are important for the formation of ADLBs and VBs, and expression of EGF and TGF-alpha affects the ability of TCDD to inhibit prostatic bud formation in a region-specific manner.

Bartsocas-Papas syndrome with internal anomalies: evidence for a more generalized epithelial defect or new syndrome?

We report on two Dutch sibs with external anomalies compatible with Bartsocas-Papas syndrome, who also had internal anomalies: bilateral renal agenesis in one, and esophageal atresia, hypoplastic diaphragma, unilateral renal agenesis, agenesis of the shaft of the penis, and anal atresia in the other patient. Several possible patterns for the pathogenesis of this combination of anomalies are discussed. We propose a generalized epithelial defect, affecting both epidermis and other lining epithelia, as the most probable cause in the present patients.

Extension of the cleft lip phenotype: the subepithelial cleft

We present a previously undescribed occult malformation of the upper lip manifest by discontinuity of the orbicularis oris muscle. The relationship of this defect to our current concept of abnormal maxillary process development is discussed along with a proposal to extend the cleft lip phenotype.