Accumulation of different shapes of microplastics initiates intestinal injury and gut microbiota dysbiosis in the gut of zebrafish

Different shapes of microplastics are widely detected in the environment and organisms and most of them remain in the gut. However, the influences of shapes on the bioaccumulation and toxicity of microplastics in the gut are largely unknown. Three shapes (bead, fragment, and fiber) of microplastics of comparable size in one dimension were prepared to exposure to zebrafish. The accumulation and toxicities of microplastics in the gut were detected. Shape-dependent accumulation in the gut was observed with the order of fibers (8.0 μg/mg) > fragments (1.7 μg/mg) > beads (0.5 μg/mg). The accumulation of microplastics caused multiple toxic effects in fish intestine, including mucosal damage, and increased permeability, inflammation and metabolism disruption. Based on these toxic effects, microplastic fibers resulted in more severe intestinal toxicity than microplastic fragments and beads did. Furthermore, microplastics also induced gut microbiota dysbiosis and specific bacteria alterations, which will provide novel insights into the potential mechanism of microplastics causing intestinal toxicities in fish. Our results also suggested that shape-depended effects should not be ignored in the health risk assessment of microplastics.

Ablation of the CDK inhibitor p57Kip2 results in increased apoptosis and delayed differentiation during mouse development

p57(Kip2) is a paternally imprinted gene that encodes a potent inhibitor of several cyclin/Cdk complexes. p57(Kip2) is primarily expressed in terminally differentiated cells, associates with G1 Cdks, and can cause cell cycle arrest in G1 phase. To investigate the role of p57(Kip2) in vivo, we have ablated the p57(Kip2) gene by homologous recombination in ES cells and generated mice devoid of p57(Kip2) expression. Most p57(Kip2) null mice die after birth and display severe developmental defects with varying degrees of penetrance. As expected, heterozygous mice that inherit a maternal, but not a paternal, targeted allele exhibit similar deficiencies and neonatal death. Developmental defects of p57(Kip2) mutant mice include cleft palate and gastrointestinal abnormalities ranging from an inflated GI tract to loss of the jejunum and ileum. These tissues display a significant increase of apoptotic cells in the absence of p57(Kip2). Most p57(Kip2) mutant mice have short limbs, a defect attributable to abnormal endochondral ossification caused by delayed cell cycle exit during chondrocyte differentiation. A similar defect has been observed in mice lacking p107 and p130, thus suggesting that p57(Kip2) might be an upstream regulator of these Rb-related proteins. The p57(Kip2) locus has been implicated in the Beckwith-Wiedemann syndrome and in the development of sporadic Wilms' tumors and lung carcinomas. To date, we have not observed neoplastic development even in those p57(Kip2) mutant mice that have survived for >5 months of age. These findings indicate that p57(Kip2) has an important role during mouse development that cannot be compensated by other Cdk inhibitors.

Nutritional and other postoperative management of neonates with short bowel syndrome correlates with clinical outcomes

OBJECTIVE

To determine correlates of clinical outcomes in patients with short bowel syndrome (SBS).

METHODS

Retrospective medical record review of neonates treated between 1986 and 1998 who met our criteria for SBS: dependence on parenteral nutrition (PN) for at least 90 days after surgical therapy for congenital or acquired intestinal diseases.

RESULTS

Thirty subjects with complete data were identified; 13 (43%) had necrotizing enterocolitis, and 17 (57%)had intestinal malformations. Mean (SD) residual small bowel length was 83 (67) cm. Enteral feeding with breastmilk (r = -0.821) or an amino acid-based formula (r = -0.793) was associated with a shorter duration of PN, as were longer residual small bowel length (r = -0.475) and percentage of calories received enterally at 6 weeks after surgery(r = -0.527). Shorter time without diverting ileostomy or colostomy (r = 0.400), enteral feeding with a protein hydrolysate formula (r = -0.476), and percentage of calories received enterally at 6 weeks after surgery (r = -0.504) were associated with a lower peak direct bilirubin concentration. Presence of an intact ileocecal valve and frequency of catheter-related infections were not significantly correlated with duration of PN. In multivariate analysis, only residual small bowel length was a significant independent predictor of duration of PN, and only less time with a diverting ostomy was an independent predictor of peak direct bilirubin concentration.

CONCLUSIONS

Although residual small bowel length remains an important predictor of duration of PN use in infants with SBS, other factors, such as use of breast milk or amino acid-based formula, may also play a role in intestinal adaptation. In addition, prompt restoration of intestinal continuity is associated with lowered risk of cholestatic liver disease. Early enteral feeding after surgery is associated both with reduced duration of PN and less cholestasis.

Mutations affecting the cardiovascular system and other internal organs in zebrafish

In a screen for early developmental mutants of the zebrafish, we have identified mutations specifically affecting the internal organs. We identified 53 mutations affecting the cardiovascular system. Nine of them affect specific landmarks of heart morphogenesis. Mutations in four genes cause a failure in the fusion of the bilateral heart primordia, resulting in cardia bifida. In lonely atrium, no heart venticle is visible and the atrium is directly fused to the outflow tract. In the overlooped mutant, the relative position of the two heart chambers is distorted. The heart is enormously enlarged in the santa mutant. In two mutants, scotch tape and superglue, the cardiac jelly between the two layers of the heart is significantly reduced. We also identified a number of mutations affecting the function of the heart. The mutations affecting heart function can be subdivided into two groups, one affecting heart contraction and another affecting the rhythm of the heart beat. Among the contractility group of mutants are 5 with no heart beat at all and 15 with a reduced heart beat of one or both chambers. 6 mutations are in the rhythmicity group and specifically affect the beating pattern of the heart. Mutations in two genes, bypass and kurzschluss, cause specific defects in the circulatory system. In addition to the heart mutants, we identified 23 mutations affecting the integrity of the liver, the intestine or the kidney. In this report, we demonstrate that it is feasible to screen for genes specific for the patterning or function of certain internal organs in the zebrafish. The mutations presented here could serve as an entry point to the establishment of a genetic hierarchy underlying organogenesis.

Congenital cardiac disease associated with polysplenia. A developmental complex of bilateral "left-sidedness"

The well-recognized association of congenital cardiac disease with asplenia has been termed "bilateral right-sidedness" or dextro-isomerism, since the spleen is absent, the liver is symmetrical, and each lung has three lobes and an epiarterial bronchus. In a study of pathological material from 12 patients with congenital cardiac disease associated with multiple spleens (as contrasted to accessory spleen), we found a definite tendency for the symmetrical development of organs but with a tendency for bilateral left-sidedness or levo-isomerism.

The abnormalities assumed one of three forms as follows: (1) absence of a normal right-sided structure, (2) bilateral organs, each with the structure of a left-sided organ, or (3) excessive tissue of a left-sided organ. Thus, in polysplenia we observed a tendency for (1) absence of the hepatic segment of the inferior vena cava and absence of the gallbladder, (2) two lobes in each lung with hyparterial bronchi, and (3) multiple spleens. Other noncardiac abnormalities were partial or complete abdominal heterotaxia and partial malrotation of the bowel. The cardiac malformations included dextrocardia, bilateral superior venae cavae, anomalous pulmonary venous connection with malposition of the atrial septum, and defects in the atrial septum and in the ventricular septum.

Our study suggests that the developmental complex of multiple spleens is closely related to the asplenic syndrome, with the important difference being left-sided symmetry rather than right-sided symmetry.

Genetic control of single lumen formation in the zebrafish gut

Most organs consist of networks of interconnected tubes that serve as conduits to transport fluid and cells and act as physiological barriers between compartments. Biological tubes are assembled through very diverse developmental processes that generate structures of different shapes and sizes. Nevertheless, all biological tubes invariably possess one single lumen. The mechanisms responsible for single lumen specification are not known. Here we show that zebrafish mutants for the MODY5 and familial GCKD gene tcf2 (also known as vhnf1) fail to specify a single lumen in their gut tube and instead develop multiple lumens. We show that Tcf2 controls single lumen formation by regulating claudin15 and Na+/K+-ATPase expression. Our in vivo and in vitro results indicate that Claudin15 functions in paracellular ion transport to specify single lumen formation. This work shows that single lumen formation is genetically controlled and appears to be driven by the accumulation of fluid.

Dwarfism and impaired gut development in insulin-like growth factor II mRNA-binding protein 1-deficient mice

Insulin-like growth factor II mRNA-binding protein 1 (IMP1) belongs to a family of RNA-binding proteins implicated in mRNA localization, turnover, and translational control. Mouse IMP1 is expressed during early development, and an increase in expression occurs around embryonic day 12.5 (E12.5). To characterize the physiological role of IMP1, we generated IMP1-deficient mice carrying a gene trap insertion in the Imp1 gene. Imp1(-/-) mice were on average 40% smaller than wild-type and heterozygous sex-matched littermates. Growth retardation was apparent from E17.5 and remained permanent into adult life. Moreover, Imp1(-/-) mice exhibited high perinatal mortality, and only 50% were alive 3 days after birth. In contrast to most other organs, intestinal epithelial cells continue to express IMP1 postnatally, and Imp1(-/-) mice exhibited impaired development of the intestine, with small and misshapen villi and twisted colon crypts. Analysis of target mRNAs and global expression profiling at E12.5 indicated that Igf2 translation was downregulated, whereas the postnatal intestine showed reduced expression of transcripts encoding extracellular matrix components, such as galectin- 1, lumican, tenascin-C, procollagen transcripts, and the Hsp47 procollagen chaperone. Taken together, the results demonstrate that IMP1 is essential for normal growth and development. Moreover, IMP1 may facilitate intestinal morphogenesis via regulation of extracellular matrix formation.

Foxf1andFoxf2control murine gut development by limiting mesenchymal Wnt signaling and promoting extracellular matrix production

Development of the vertebrate gut is controlled by paracrine crosstalk between the endodermal epithelium and the associated splanchnic mesoderm. In the adult, the same types of signals control epithelial proliferation and survival, which account for the importance of the stroma in colon carcinoma progression. Here, we show that targeting murine Foxf1 and Foxf2, encoding forkhead transcription factors, has pleiotropic effects on intestinal paracrine signaling. Inactivation of both Foxf2alleles, or one allele each of Foxf1 and Foxf2, cause a range of defects, including megacolon, colorectal muscle hypoplasia and agangliosis. Foxf expression in the splanchnic mesoderm is activated by Indian and sonic hedgehog secreted by the epithelium. In Foxf mutants, mesenchymal expression of Bmp4 is reduced, whereas Wnt5a expression is increased. Activation of the canonical Wnt pathway – with nuclear localization of β-catenin in epithelial cells – is associated with over-proliferation and resistance to apoptosis. Extracellular matrix,particularly collagens, is severely reduced in Foxf mutant intestine, which causes epithelial depolarization and tissue disintegration. Thus, Foxf proteins are mesenchymal factors that control epithelial proliferation and survival, and link hedgehog to Bmp and Wnt signaling.

BMP5 and the molecular, skeletal, and soft-tissue alterations in short ear mice

Mutations at the mouse short ear (se) locus alter the formation and repair of skeletal structures and the development of several soft tissues. Most of the developmental effects of the gene have been studied using a spontaneous mutation reported over 70 years ago. Here we show that this mutation consists of a nonsense mutation in a secreted signaling molecule called bone morphogenetic protein 5 (BMP5). This small sequence alteration, in combination with previously reported translocation and deletion mutations, provides strong genetic evidence that BMP5 is the normal product of the se locus. Transcripts from the Bmp5 gene are expressed at the earliest stages of normal skeletal development in patterns that closely resemble the shapes of forming skeletal elements. The gene is also expressed at several sites of soft tissue abnormalities previously reported in se animals, including lungs, liver, ureter, bladder, and intestines. The combined genetic, biochemical, and expression data suggest that BMP5 is a key signal used to initiate formation of particular skeletal elements and is required for normal development of several soft tissues as well.

Urethral obstruction malformation complex: a cause of abdominal muscle deficiency and the "prune belly"

Abdominal muscle deficiency with a "prune belly" abdomen as been a major feature of the so-called prune belly syndrome, which has been regarded as a specific entity, although the etiology and developmental pathology are not understood. We present evidence that abdominal muscle deficiency is an etiologically nonspecific anatomic defect which is secondary to fetal abdominal distention of various causes. One of the more common causes is urethral obstruction with consequent early bladder distention, causing abdominal distention and other anomalies, a constellation of findings which we have termed the urethral obstruction malformation complex. This interpretation of the etiology of most cases of prune belly syndrome accounts for the male predominance, the observed variability in severity, and the lack of a defined mode of inheritance. Recurrence risk figures need to be redefined for each specific obstructing lesion of the urethra. The possibility of early prenatal diagnosis and management of fetuses with urethral obstruction needs further study.

Smooth-muscle contraction without smooth-muscle myosin

Here we have used gene-targeting to eliminate expression of smooth-muscle myosin heavy chain. Elimination of this gene does not affect expression of non-muscle myosin heavy chain, and knockout individuals typically survive for three days. Prolonged activation, by KCl depolarisation, of intact bladder preparations from wild-type neonatal mice produces an initial transient state (phase 1) of high force generation and maximal shortening velocity, which is followed by a sustained state (phase 2) characterized by low force generation and maximal shortening velocity. Similar preparations from knockout neonatal mice do not undergo phase 1, but exhibit a normal phase 2. We propose that, in neonatal smooth muscle phase 1 is generated by recruitment of smooth-muscle myosin heavy chain, whereas phase 2 can be generated by activation of non-muscle myosin heavy chain. We conclude that phase 1 becomes indispensable for survival and normal growth soon after birth, particularly for functions such as homeostasis and circulation.

Intestinal malrotation in children: a problem-solving approach to the upper gastrointestinal series

Intestinal malrotation, which is defined by a congenital abnormal position of the duodenojejunal junction, may lead to midgut volvulus, a potentially life-threatening complication. An evaluation for malrotation is part of every upper gastrointestinal (GI) tract examination in pediatric patients, particularly neonates and infants. Although the diagnosis of malrotation is often straightforward, the imaging features in approximately 15% of upper GI tract examinations are equivocal and lead to a false-positive or false-negative interpretation. The clinical manifestations and upper GI tract findings of malrotation in older children and adults are less specific than are those in younger patients, and for this reason diagnosis of the condition may be more difficult. Successful differentiation between a normal variant and malrotation requires the use of optimal techniques in acquiring and interpreting the upper GI series. Familiarity with the upper GI series appearance of both normal and abnormal anatomic variants allows the radiologist to increase both diagnostic accuracy and confidence in the diagnosis of malrotation.

Zebra fish Dnmt1 and Suv39h1 regulate organ-specific terminal differentiation during development

DNA methylation and histone methylation are two key epigenetic modifications that help govern heterochromatin dynamics. The roles for these chromatin-modifying activities in directing tissue-specific development remain largely unknown. To address this issue, we examined the roles of DNA methyltransferase 1 (Dnmt1) and the H3K9 histone methyltransferase Suv39h1 in zebra fish development. Knockdown of Dnmt1 in zebra fish embryos caused defects in terminal differentiation of the intestine, exocrine pancreas, and retina. Interestingly, not all tissues required Dnmt1, as differentiation of the liver and endocrine pancreas appeared normal. Proper differentiation depended on Dnmt1 catalytic activity, as Dnmt1 morphants could be rescued by active zebra fish or human DNMT1 but not by catalytically inactive derivatives. Dnmt1 morphants exhibited dramatic reductions of both genomic cytosine methylation and genome-wide H3K9 trimethyl levels, leading us to investigate the overlap of in vivo functions of Dnmt1 and Suv39h1. Embryos lacking Suv39h1 had organ-specific terminal differentiation defects that produced largely phenocopies of Dnmt1 morphants but retained wild-type levels of DNA methylation. Remarkably, suv39h1 overexpression rescued markers of terminal differentiation in Dnmt1 morphants. Our results suggest that Dnmt1 activity helps direct histone methylation by Suv39h1 and that, together, Dnmt1 and Suv39h1 help guide the terminal differentiation of particular tissues.

Wnt5a is essential for intestinal elongation in mice

Morphogenesis of the mammalian small intestine entails extensive elongation and folding of the primitive gut into a tightly coiled digestive tube. Surprisingly, little is known about the cellular and molecular mechanisms that mediate the morphological aspects of small intestine formation. Here, we demonstrate that Wnt5a, a member of the Wnt family of secreted proteins, is essential for the development and elongation of the small intestine from the midgut region. We found that the small intestine in mice lacking Wnt5a was dramatically shortened and duplicated, forming a bifurcated lumen instead of a single tube. In addition, cell proliferation was reduced and re-intercalation of post-mitotic cells into the elongating gut tube epithelium was disrupted. Thus, our study demonstrates that Wnt5a functions as a critical regulator of midgut formation and morphogenesis in mammals.

Malrotation presenting beyond the neonatal period

The diagnosis of malrotation is easily made in the neonatal period, but is often delayed in older patients. Among 82 patients treated for malrotation in this institution, 45 patients presented with symptoms related to their malrotation, seven were diagnosed at exploration for concomitant intrinsic duodenal obstruction, and 30 patients had malrotations discovered as incidental findings at laparotomy or autopsy. Among the 45 symptomatic patients, 25 (56%) underwent surgery in the first month of life, whereas 20 patients (44%) underwent surgery at an older age. In this last group, the mean age at surgery was 51.5 months (range, 2 months to 16 years), the mean age of onset of symptoms was 2 years (range, 0 to 15 years) and the mean delay in diagnosis was 1.7 years. Although bilious vomiting was the presenting symptom among all patients undergoing surgery in the neonatal period, clinical features of older patients included intestinal obstruction (7), chronic abdominal pain (4), malabsorption/diarrhea (3), peritonitis/septic shock (2), solid food intolerance (1), common bile duct obstruction (1), abdominal distention (1), and delayed transit postappendectomy (1). The frequency of midgut volvulus was equal among both groups. Unusual forms of malrotation were more frequent in patients undergoing surgery beyond the neonatal period. In this group there was evidence of chronic venous and lymphatic obstruction with one case of superior mesenteric vein thrombosis and two cases of intestinal gangrene. A Ladd's procedure was performed in all cases and the most frequent postoperative complication was adhesive intestinal obstruction. There were no deaths. Awareness of the unusual presentation in patients who present beyond the neonatal period may help reduce delays in diagnosis and surgical treatment. We believe that laparotomy is indicated in all patients with malrotation, even if they are asymptomatic.

MRI of the fetal gastrointestinal tract

OBJECTIVE

To determine the MRI patterns of the gastrointestinal (GI) tract in normal fetuses and some GI tract abnormalities.

MATERIALS AND METHODS

A retrospective (1996-1998) and prospective (1999-2000) study of 48 fetal abdominal MRI scans was performed between 23 and 38 weeks of gestation. T1-weighted (T1-W) fast gradient-echo (Flash 2D) and T2-weighted (T2-W) HASTE sequences were obtained on a 1.5-T unit, in frontal and sagittal planes, after maternal premedication. Fresh meconium was also studied.

RESULTS

Normal patterns (40 cases): the rectum was seen in all cases and exhibited meconium-like high signal on T1-W images and low signal on T2-W images. It was close to the bladder whatever the fetal gender with its cul-de-sac being at least 10 mm below the bladder neck. The large bowel had a same signal; the distal colon was demonstrated more frequently than the proximal colon. The small bowel was transiently hyperintense on TI-W images early in gestation and then hyperintense on T2-W images. Normal measurements were obtained. GI tract abnormalities (eight cases): cysts close to normal bowel ( n=2), atresias ( n=5; microcolon, dilated small bowel with abnormal signal, one with a meconium cyst) and a cloacal malformation with midgut malrotation ( n=1; abnormal liquid signal in the rectum separated from the bladder wall and colon located on the left side).

CONCLUSIONS

MRI provided complete visualisation of the fetal GI tract, showed specific signal intensities, identified the level of an obstruction, detected a microcolon, and demonstrated communication between urinary and GI tracts. It shows great potential.

Bmp signaling is required for intestinal growth and morphogenesis

Intestinal growth, morphogenesis, differentiation, and homeostasis are regulated by reciprocal interactions between the epithelium and the underlying mesenchymal stroma. The identification of BMPR1A mutations in patients with Juvenile Polyposis implicates Bmp signaling as an important mediator of these interactions. To test this hypothesis, we inhibited Bmp signaling in the mouse proximal intestine by transgenic misexpression of the BMP antagonist, noggin, using regulatory elements of the fatty acid binding protein (Fabp1) gene. This leads to abnormal villus morphogenesis, stromal and epithelial hyperplasia, and ectopic crypt formation. The resulting intestinal histopathology resembles that seen in human Juvenile Polyposis. Misexpression of noggin in the large intestine gives a similar abnormal phenotype in this region of the gut. Analysis of gene expression in the transgenic small intestine raises the possibility that Hedgehog and Pdgf signaling play a role in the development of the Juvenile Polyposis-like phenotype.

Embryology and pathology of the intestinal tract: presentation of 40 cases of malrotation

Images

Acute and chronic presentation of intestinal nonrotation in adults

Intestinal nonrotation has been recognized as a cause of obstruction in neonates and children and may be complicated by volvulus and intestinal necrosis. It is very rarely seen in the adult and may present acutely as a bowel obstruction and intestinal ischemia associated with midgut or ileocecal volvulus, or chronically as vague intermittent abdominal pain. The purpose of this communication is to reveal the pathogenesis and the surgical significance of intestinal nonrotation in adults and to review the English and German language literature since 1923 to establish the optimal therapeutic management. Between 1983 and 1992, we have managed and observed prospectively 10 adults with intestinal nonrotation. In four patients the nonrotation has been detected at emergency laparotomy owing to midgut or ileocecal volvulus. Four patients suffered from chronic symptoms of intermittent volvulus or small bowel obstruction and in two patients the nonrotation has been noted as an incidental finding at laparotomy for another condition. A survey of the literature from 1923 to 1992 revealed 40 adults with symptomatic intestinal nonrotation to which we contribute nine patients. We establish that in the acute symptomatic pattern, only emergency laparotomy can provide the correct diagnosis and decrease the risk of bowel disturbance. In the chronic situation, barium studies of the upper and lower gastrointestinal tract reveal varying degrees of midgut malrotation and confirm the nonrotation in each case. Also, in these forms the explorative laparotomy with a consequent staging of the abdominal situs is to be recommended. All reported cases at our institutions are without complaints after surgery. Adult patients with intestinal nonrotation and acute or chronic obstructive symptoms or those detected incidentally at laparotomy for other conditions should undergo a Ladd procedure because of the risk of midgut volvulus. In this operation, the nonrotation is left in place and the ascending colon is sutured at the colon descendens and sigmoideum. After this procedure the mesenteric pedicle is fixed and the risk of midgut torsion remains minimal.

Clockwise whirlpool sign at color Doppler US: an objective and definite sign of midgut volvulus

PURPOSE

To evaluate the clockwise whirlpool sign at color Doppler ultrasound (US) in the diagnosis of midgut volvulus.

MATERIALS AND METHODS

Pediatric patients (160 boys, 76 girls; age range, 0 day to 14 years) with possible midgut volvulus underwent abdominal gray-scale US and color Doppler US. Midgut volvulus was diagnosed by recognition of the whirlpool sign (wrapping of the superior mesenteric vein and the mesentery around the superior mesenteric artery). If the whirlpool rotated clockwise with caudal movement of the transducer, the direction of the whirlpool was defined as clockwise.

RESULTS

Color Doppler US showed a whirlpool sign that was clockwise in 12 of 13 patients with surgically confirmed midgut volvulus and counterclockwise in three patients without midgut volvulus. Sensitivity, specificity, and positive predictive value of clockwise whirlpool sign for midgut volvulus were 92%, 100%, and 100%.

CONCLUSION

The clockwise whirlpool sign is diagnostic of midgut volvulus. Color Doppler US should be performed as an initial imaging study in children suspected of having midgut volvulus.

Neoplastic change in duplications of the alimentary tract

Two cases of adenocarcinoma arising in sequestrated duplications of the bowel in adults are reported. The literature is reviewed and a tendency for duplications to present in early childhood is noted. Although relatively few of these anomalies persist into adult life 8 cases of neoplastic change have now been reported. The histological features of many of the duplications undergoing malignant degeneration suggest the presence of underlying epithelial instability in this condition. It is postulated that duplications of the large bowel have malignant potential.

The Pitx2 protein in mouse development

The Rieger syndrome, an autosomal dominant disorder involving ocular, dental, and umbilical defects is caused by mutations in PITX2, a Bicoid-type homeobox protein. Mouse Pitx2 mRNA is expressed in eye, tooth and umbilicus consistent with the human Riegers phenotype. Moreover, Pitx2 is involved in the Nodal/Sonic hedgehog pathway that determines left/right polarity. In this report we demonstrate a 32-kDa polypeptide on Western blots of nuclear extracts from a rat pituitary cell line, using a Pitx2 specific antibody (designated P2R10). We describe also for the first time expression of the Pitx2 protein in mouse. Pitx2 protein immunostaining was detectable during the development of the eye, tooth, umbilicus, and also in the pituitary, heart, gut, and limb. We demonstrate for the first time directly that Pitx2 is asymmetrically expressed in early heart, gut, and lung development.