Prenatal diagnosis in a cystic fibrosis family: a combined molecular strategy for a precise diagnosis

INTRODUCTION

The high genetic heterogeneity in populations with a wide spectrum of mutations in the CF transmembrane conductance regulator gene (CFTR), makes the detection of mutations a very hard and difficult task, thereby limiting the accurate diagnosis of the disease, mainly in patients with uncharacterized mutations.

MATERIAL AND METHODS

Molecular strategies, like targeted identification of the most frequent CFTR mutations in Mexican population combined with linkage analysis using markers, is very useful for carrier detection and for prenatal diagnosis in affected families with CF. In this paper we show that the combination of methodologies was a crucial alternative to reach a precise prenatal CF diagnosis. We documented CF diagnosis in a 14th-week fetus combining the screening of the most common mutations in Mexican population with linkage analysis of two extragenic polymorphisms (XV2C/TaqI and KM19/PstI).

RESULTS

We determined that the fetus inherited the PG542X mutation from its mother and an unknown mutation from its father through the chromosomal phases analysis.

Absent gallbladder on fetal ultrasound: prenatal findings and postnatal outcome

OBJECTIVES

Fetal gallbladder non-visualization on prenatal ultrasound in the second trimester is uncommon and in most cases the gallbladder is detected eventually. Associations of gallbladder non-visualization with cystic fibrosis, aneuploidy, agenesis of the gallbladder and biliary atresia have been reported. We present our experience and review the literature.

METHODS

During the study period from January 2004 to June 2009 we collected prospectively cases of non-visualization of the fetal gallbladder in the second trimester. In each case the fetus was evaluated by two examiners on at least two occasions, at least a week apart. Cases with no additional sonographic malformations were designated as isolated. Further evaluation included follow-up scans and a meticulous search for fetal anomalies. All patients were offered genetic consultation. Cystic fibrosis testing, amniocentesis for karyotyping and analysis of fetal digestive enzymes in the amniotic fluid were offered.

RESULTS

We collected 21 cases of non-visualization of the fetal gallbladder, 16 of which were isolated and five of which had additional malformations. In four of these five, the associated anomalies were severe and the pregnancies were terminated for aneuploidy (two cases of trisomy 18 and one triploidy) or for the severity of the associated anomalies. Associated anomalies included left isomerism with complex cardiac anomaly and intrauterine growth restriction with multisystem anomalies. The fifth fetus had interrupted inferior vena cava with azygos continuation without other anomalies and the child was alive and well at the age of 4 years. In 15 of the 16 isolated cases, antenatal and postnatal development were normal at the last follow-up, ranging from 4 months to 2.5 years. One case of cystic fibrosis was diagnosed prenatally and this pregnancy was terminated. There were no diagnoses of abnormal karyotype or biliary atresia among cases of isolated non-visualization of the gallbladder.

CONCLUSIONS

When prenatal non-visualization of the fetal gallbladder is associated with other severe malformation, aneuploidy should be suspected. When it is isolated, if cystic fibrosis is ruled out, the outcome is good.

[Fetal echogenic bowel by ultrasound: what is the clinical significance?]

Echogenic bowel is diagnosed in 0.2% to 1.4% of second trimester ultrasonographic examinations. This finding occurs as a normal variant in the second trimester but also has been associated with several pathologic conditions that include cystic fibrosis, chromosomal abnormalities and in utero infection with cytomegalovirus and toxoplasmosis. Ultrasound assessment of echogenic bowel is usually subjective by comparing the echogenicity with adjacent bone or liver. The diagnosis of fetal echogenic bowel in the second trimester has significant implications for prenatal management. Fetal echogenic bowel should be considered an important marker of placental damage. This finding in the second trimester is strongly associated with adverse pregnancy outcome due to utero-placental insufficiency, particularly in women with elevated maternal serum alpha-fetoprotein concentration due to severe feto-maternal bleeding. This review focuses on the definition and diagnosis of this entity and problems raised by echogenic bowel due to subjectivity of the diagnosis. It also includes the pathophysiology in the different conditions and the prevalence of each condition. Based on this review, we suggest the evaluation that is needed, as well as the recommendations to follow-up, during the remaining term of pregnancy according to the literature.

Early inflammation in the airways of a cystic fibrosis foetus

In cystic fibrosis patients, inflammation is often considered to be secondary to chronic infections. In the present study, we show increased levels of pro-inflammatory proteins in the lungs of a cystic fibrosis foetus compared to the lungs of two normal foetuses. Our findings suggest therefore the existence of an early intrinsic pro-inflammatory state in cystic fibrosis airways.

CF-Emerging therapies: Modulation inflammation

Persistent and dysregulated inflammation, combined with an exaggerated host response is a major contributor to CF lung disease. As lung disease progresses, neutrophil accumulation in the airways ensues. Modulation of CF airway inflammation may result in either beneficial or deleterious side effects, resulting in more harm than good. Antibiotics, in particular, macrolides which act as a long-term anti-inflammatory agent with an excellent safety profile, and dornase alpha, are very interesting agents; steroids are not indicated in CF except in very special situations, and other promising agents such as leukotriene modifiers, high-dose N-acetylcysteine, anti-elastase and anti-cytokines require further research. Research should focus on early treatment, before lung damage has occurred.

Follow-up of children with isolated fetal echogenic bowel with particular reference to bowel-related symptoms

OBJECTIVES

To determine whether there was any evidence of long-term bowel pathology in children, apparently healthy at birth, who had a prenatal second-trimester diagnosis of isolated grade 2 fetal echogenic bowel.

METHODS

This was a retrospective study using data from the Oxford Congenital Anomaly Register. Fetuses with isolated grade 2 fetal echogenic bowel and date of delivery from 1994 to 2000 inclusive were identified. Information about the health of the children, particularly relating to bowel symptoms, was obtained from hospital records and from a questionnaire sent to the general practitioner.

RESULTS

A total of 109 cases were identified, with delivery details available for 108. There was one unexplained intrauterine death, and additional problems were subsequently diagnosed in four cases (cystic fibrosis (2), Down syndrome (1), and VACTERL (1)). Questionnaires were sent to the GPs of the 103 who had no problems identified at the time of discharge from the maternity hospital. Age at follow-up ranged from one to four years. Responses to the questionnaires were received from 83 (81%). Of these, 74 (89%) had not reported bowel symptoms to the GP, 9 (11%) reported symptoms relating to constipation (6), chronic abdominal pain (1), infantile colic with milk intolerance (1) and gastro-oesophageal reflux (1).

CONCLUSION

This small study provides some reassurance that there was no evidence of any serious long-term bowel pathology associated with isolated fetal echogenic bowel.

Progress toward generating a ferret model of cystic fibrosis by somatic cell nuclear transfer

Mammalian cloning by nuclear transfer from somatic cells has created new opportunities to generate animal models of genetic diseases in species other than mice. Although genetic mouse models play a critical role in basic and applied research for numerous diseases, often mouse models do not adequately reproduce the human disease phenotype. Cystic fibrosis (CF) is one such disease. Targeted ablation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in mice does not adequately replicate spontaneous bacterial infections observed in the human CF lung. Hence, several laboratories are pursuing alternative animal models of CF in larger species such as the pig, sheep, rabbits, and ferrets. Our laboratory has focused on developing the ferret as a CF animal model. Over the past few years, we have investigated several experimental parameters required for gene targeting and nuclear transfer (NT) cloning in the ferret using somatic cells. In this review, we will discuss our progress and the hurdles to NT cloning and gene-targeting that accompany efforts to generate animal models of genetic diseases in species such as the ferret.

Improving clinical preimplantation genetic diagnosis for cystic fibrosis by duplex PCR using two polymorphic markers or one polymorphic marker in combination with the detection of the DeltaF508 mutation

Cystic fibrosis (CF) is an autosomal recessive disease characterized by obstruction and chronic infection of the respiratory tract and pancreatic insufficiency. The first preimplantation genetic diagnosis (PGD) for CF was carried out in 1992. At our centre the first cycle was performed in 1993. However, the number of known CF mutations is >1000, so developing mutation-specific PCR protocols for PGD is unfeasible. This is why a number of marker-based duplex PCRs were developed at the single cell level. A duplex PCR of a mutation and one or two microsatellites is not only a diagnostic tool, but it can also be used as a control for allele drop-out and contamination. During PGD, embryos obtained in vitro are analysed for the presence or absence of a particular genetic disease, after which only embryos shown to be free of this disease are returned to the mother. In total, 22 PGD cycles with duplex PCR (IVS8CA/IVS17BTA, DeltaF508/IVS8CA, DeltaF508/IVS17BTA and D7S486/D7S490) were carried out in 16 couples, which resulted in four ongoing pregnancies and one miscarriage.

Temporal regulation of CFTR expression during ovine lung development: implications for CF gene therapy

The cystic fibrosis transmembrane conductance regulator (CFTR) protein is a small conductance chloride ion channel that may interact directly with other channels including the epithelial sodium channel (ENaC). CFTR is known to be more abundant in the airway epithelium during the second trimester of human development than after birth. This could be a consequence of the change in function of the respiratory epithelium from chloride secretion to sodium absorption near term. Alternatively it might reflect an additional role for CFTR in the developing airway epithelium. Though the lung epithelia of CF fetuses and infants rarely show gross histological abnormalities, there is often evidence of inflammation. Our aim was to establish whether CFTR expression levels correlated with specific developmental stages or differentiated functions in the ovine fetal lung. We evaluated CFTR expression using a quantitative assay of mRNA at 14 time points through gestation and showed highest levels at the start of the second trimester followed by a gradual decline through to term. In contrast, ENaC expression increased from the start of the third trimester. These results support a role for CFTR in differentiation of the respiratory epithelium and suggest that its expression levels are not merely reflecting major changes in the sodium/chloride bulk flow close to term. These observations may have significant implications for the likely success of CF gene therapy in the postnatal lung.

Jejunoileal atresia and associated malformations: correlation with the timing of in utero insult

PURPOSE

Duodenal atresia is associated with a higher incidence of associated congenital malformations than jejunoileal atresia, supporting the hypothesis that the duodenal obstruction occurs early in fetal life. In this study, the authors analyzed the incidence of major associated malformations in jejunal atresia (JA) and ileal atresia (IA) to determine if there is a positive correlation between the proximity of the intestinal atresia and the association of other major anomalies.

METHODS

Records of all patients with jejunoileal atresias treated at the authors' institution between 1980 and 1997 were examined.

RESULTS

There were 83 patients with jejunoileal atresias, 38 with JA, and 45 with IA. Sixteen (42%) of the JA patients had an associated major congenital malformation, whereas only 1 (2%) of the IA patients had an associated malformation. A single atresia was found in 18 (47%) of JA patients and 41 (91%) of IA patients. Twenty (53%) of the JA patients had either multiple or apple-peel atresia. Thirteen patients (16%) died, 11 with JA, and 2 with IA. Of the 11 patients with JA who died, 6 had multiple atresias, 4 had cystic fibrosis, and 1 had small bowel volvulus.

CONCLUSION

The higher incidence of associated major congenital extraintestinal malformations in JA compared with IA patients suggests that some cases of JA may arise from a malformative process.

Inflammation and infection in naive human cystic fibrosis airway grafts

Exacerbated inflammation is now recognized as an important component of cystic fibrosis (CF) airway disease. Whether inflammation is part of the basic defect in CF or a response to persistent infection remains controversial. We addressed this question using human fetal tracheal grafts in severe combined immunodeficient mice. This model yields histologically mature, and most importantly, naive CF and non-CF surrogate airways. Significant inflammatory imbalance was found in naive CF airway grafts, including a highly increased intraluminal interleukin 8 content (CF: 10.1 +/- 2.2 ng/ml; non-CF: 1.2 +/- 0.6 ng/ml; P < 0.05) and consistent accumulation of leukocytes in the subepithelial region (P < 0.001). CF airway grafts were not histologically affected until challenged with Pseudomonas aeruginosa, which provoked: (1) early (before 3 h) and massive leukocyte transepithelial migration, (2) intense epithelial exfoliation, and (3) rapid progression of bacteria toward the lamina propria. In non-CF grafts, these three sets of events were not observed before 6 h. Using a model of naive human airways, we thus demonstrate that before any infection, CF airways are in a proinflammatory state. After infection, the basal inflammatory imbalance contributes to exert severe damage to the mucosa, paving the way for bacterial colonization and subsequent steps of CF airway disease.

Diagnosis of sex and cystic fibrosis status in fetal erythroblasts isolated from cord blood

Diagnosis of fetal cells in the maternal circulation will obviate the need for invasive sampling procedures. It is essential however, before this can be put into wide clinical practice, that a reliable isolation procedure and a simple, robust means of genotyping rare fetal cells be developed. A relatively inexpensive, sensitive diagnostic procedure which can detect single gene defects and/or aneuploidy is fluorescent PCR. This has been used extensively in molecular diagnostics including preimplantation diagnosis but, to our knowledge, has not been applied widely for the diagnosis of isolated fetal erythroblasts. Here we used cord blood as a model system for fetal cells in the maternal circulation: we isolated erythroblasts on a glass slide, employed a simple micromanipulation technique to place them into a PCR tube and then applied fluorescent PCR to diagnose sex and cystic fibrosis status in 10 patients. Nine samples had a normal cystic fibrosis status, one patient, however, had a mutant allele suggesting that this fetus was a carrier for cystic fibrosis. Fluorescent PCR has virtually limitless potential in the genotyping of rare fetal cells isolated from the maternal circulation.

Bioelectric properties of human cystic fibrosis and non-cystic fibrosis fetal tracheal xenografts in SCID mice

We measured, the bioelectric properties of 14 cystic fibrosis (CF) and 33 non-CF human fetal tracheal xenografts in severe combined immunodeficiency (SCID) mice. All xenografts exhibited a mature airway-type epithelium irrespective of their gestational age, duration of engraftment, and genotype. The in vivo potential difference and the in vitro baseline short-circuit current (Isc) were significantly higher in non-CF than in CF xenografts. In non-CF xenografts, sequential addition of amiloride, forskolin, and ATP resulted in a 39.4% decrease, a 24.1% increase, and a 43.6% increase in Isc, respectively. In CF xenografts, forskolin had no significant effect on Isc, whereas amiloride- and ATP-induced changes in Isc were proportionally higher than in non-CF xenografts (-60.0 and +68.8%, respectively). These results indicate that the bioelectric properties of non-CF xenografts are similar to those of postnatal airways and that CF xenografts exhibit lower baseline electrogenic activity than non-CF xenografts but similar regulation of ion transport processes to postnatal CF airways. This model of mature human fetal tracheal mucosa may help gain insight into early CF airway pathogenesis.

Normal vas deferens in fetuses with cystic fibrosis

PURPOSE

Infertility in patients with cystic fibrosis has been attributed to the congenital bilateral absence of the vas deferens. We studied the vas deferens in cystic fibrosis fetuses to determine whether this condition could be related to primary developmental abnormalities or to secondary obstructions.

MATERIALS AND METHODS

Two cystic fibrosis male fetuses, with deltaF508+/+ and deltaF508/G542X genetic mutations, were examined after abortion at 12 and 18 weeks, respectively. The lumens of the vas deferens were measured using histological serial sections in the 2 cystic fibrosis fetuses and in 6 control fetuses.

RESULTS

The vas deferens of cystic fibrosis and control fetuses showed a similar development. The diameters of the lumens were smaller at the extremities than in the medial part of the duct in cystic fibrosis and in control fetuses. No epithelial necrosis, focal dilatation or fibrous stenosis could be detected at any age. Secretions were observed in the lumen of the vas deferens of the homozygous fetus, but no obstruction was detected.

CONCLUSIONS

The normal organogenesis of the vas deferens, the presence of secretions filling the lumen of the deltaF508 +/+ fetus and the high proportion of normal ducts reported in prepubertal male cystic fibrosis patients suggest a mechanism of luminal obstruction resulting in duct atrophy and infertility in male adults with cystic fibrosis. The term "atresia" or "inspissation" should be used in cases of congenital bilateral absence of the vas deferens associated with cystic fibrosis mutations, whereas the term "agenesis" should be used for cases of congenital bilateral absence of the vas deferens associated with urogenital abnormalities in which regional defects occur during organogenesis.

[Prenatal molecular diagnosis of cystic fibrosis. Report of 3 cases]

Cystic Fibrosis (CF) is a severe and relatively common autosomic recessive disease caused by a variety of mutations in the CFTR gene. The most frequent mutation worldwide, consists of the deletion of the phenylalanine codon at position 508 (delta F508). Here we report the first cases of prenatal diagnosis of CF by DNA analysis in couples at risk in Venezuela. The study focused on the detection of delta F508 alleles analyzing DNA recovered directly from amniocytes or from their cultures, using the polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis. Two of three fetuses resulted homozygotic for the delta F508 allele and the third one turned out to be a delta F508 carrier. This information sustained the genetic counseling of the couples and allowed them to take objective reproductive decisions, a direct consequence of the availability of gene analysis at the DNA level.

Mutations in the cystic fibrosis gene in men with congenital bilateral absence of the vas deferens

This paper reviews the relationship between mutations in the cystic fibrosis (CF) gene (CFTR mutations) and congenital bilateral absence of the vas deferens (CBAVD). Two CFTR mutations were identified in 14.5% of the 449 man with CBAVD thus far reported in the literature while one CFTR mutation was found in another 48.1%. CBAVD appears to be a heterogeneous genetic condition, many cases being mild forms of cystic fibrosis, others having no relationship with CF. The 5T allele has also been found in 46% of men with CBAVD, but is not associated by the 'classical' picture of cystic fibrosis. The role of the CFTR gene presumably extends beyond a normal development of the vas deferens, possibly playing a role in spermatogenesis. The detection of CFTR mutations in CBAVD had considerable implications in genetic counselling. Couples requesting microsurgical epididymal sperm aspiration/in-vitro fertilization and those in which the man has CF should be offered CFTR mutations screening if CBAVD is the cause of the male infertility.

Case report: cystic fibrosis and embryonal carcinoma of the testis

The authors describe a patient with cystic fibrosis and a stage III testicular embryonal cell cancer. Because cystic fibrosis occurs in approximately 1 of 2,500 births and embryonal carcinoma in 3 of 100,000, the likelihood of concurrence for both disorders in the same patient is approximately 1 in 80 million. Involvement of the vas deferens in cystic fibrosis raises the possibility of a fundamental embryologic basis that explains the pathogenesis of this association.

Fluorescent PCR: a new technique for PGD of sex and single-gene defects

BACKGROUND

For single-cell diagnosis, particularly preimplantation genetic diagnosis to be successful four main criteria must be achieved: sensitivity, reliability, accuracy, and identification/elimination of contamination.

METHODS AND RESULTS

Fluorescent PCR achieves all four necessary criteria and, in addition, currently allows genes on up to nine chromosomes to be simultaneously investigated. Fluorescent PCR has high sensitivity (approximately 1000 x conventional analysis systems), high reliability (97%), and high accuracy (97%) rates for both sex and CF diagnosis in single somatic cells. The low detection threshold allows allelic dropout (one of the main causes of misdiagnosis) to be easily distinguished from PCR phenomena such as preferential amplification. High reliability (90%) and accuracy (97-100%) have been achieved in sex and CF diagnosis in human blastomeres. Fluorescent PCR can also be used to DNA fingerprint (STR profiling) single cells to identify the source/origin of the cell and determine if contamination has occurred.

CONCLUSIONS

Fluorescent PCR is therefore a suitable method for PGD.

Reduced allele dropout in single-cell analysis for preimplantation genetic diagnosis of cystic fibrosis

BACKGROUND

For couples at risk of transmitting a known single-gene defect, preimplantation genetic diagnosis (PGD) allows the identification and transfer of only unaffected embryos following in vitro fertilisation (IVF), single-cell biopsy at about the eight-cell stage, and genetic analysis by PCR. This technique therefore avoids the risk of terminating an affected pregnancy diagnosed later in gestation.

METHODS AND RESULTS

Using nested PCR, the delta F508 mutation causing cystic fibrosis can be detected in single cells and we previously reported successful PGD in a couple in whom both partners carry the delta F508 mutation. To date we have treated 12 couples in a total of 18 cycles. This resulted in five singleton births confirmed to be homozygous normal. Single blastomeres from disaggregated embryos which had not been transferred were analysed to confirm the original diagnosis and assess reliability in clinical practice. Amplification efficiency and accuracy were high, with blastomeres from embryos diagnosed as homozygous normal or affected. In a proportion of blastomeres from presumed carrier embryos, one of the parental alleles failed to amplify, apparently at random (allele dropout, ADO). A possible explanation is the relative inaccessibility of one of the target allele early in the PCR. To test this we have used single lymphocytes from delta F508 carriers and investigated the effects of various denaturation temperatures in the early cycles of amplification.

CONCLUSIONS

Increasing the denaturation temperature reduced the rate of ADO without affecting amplification efficiency.

Meconium ileus and intestinal atresia in fetuses and neonates

A collaborative study was performed to determine the different types and mechanisms of intestinal abnormalities during gestation. Cases had to fulfill one or more of the following three criteria: (1) meconium ileus, (2) intestinal stenosis or atresia, and (3) meconium peritonitis. Esophageal atresia, anorectal atresia, and abdominal wall defects were excluded. One hundred two cases were reviewed from the autopsies of 42 induced abortions, 22 stillborns, and the surgical findings in 38 neonates. Meconium ileus was detected mainly during the second trimester (28/38), and was associated with cystic fibrosis (15), fetal blood deglutition (4), infection (6), or multiple-abnormalities (10), in which three chromosomal aberrations were found. Intestinal stenosis or atresia was more commonly detected during the third trimester of gestation (46/56). Sixteen of the 30 duodenal malformations were associated with trisomy 21, whereas in the 26 small intestinal atresias, signs of distress or ischemia were most frequently detected. Only 8 of 25 meconium peritonitis cases were isolated. A total of 20 cystic fibrosis cases could be proved. In this series, functional abnormalities were observed predominantly in the second trimester and associated mainly with cystic fibrosis or amniotic fluid abnormalities. Anatomic lesions were commonly detected later on and associated with ischemic conditions, chromosomal aberrations, and even cystic fibrosis.

Gene transfer to human fetal pulmonary tissue developed in immunodeficient SCID mice

Human fetal lung rudiments (8-12 weeks of development) undergo considerable growth upon microsurgical ectopic implantation in the xenograft-tolerant SCID mouse, and differentiate into a lung-like tissue that includes: (i) bronchial structures lined with pseudostratified, secretory, ciliated epithelium surrounded by smooth muscle and cartilage rings, (ii) submucosal glands, and (iii) alveolar sacs. Normal expression of the cystic fibrosis transmembrane conductance regulator (CFTR) protein was detected by immunostaining in those grafts, and similar differentiation was observed from either normal or cystic fibrosis (CF) fetal lung rudiments. Upon microinjection into human CF or normal lung grafts in SCID mice, beta-galactosidase-adenovirus gene constructs were efficiently transduced into epithelial and glandular cells. Such an in vivo replica of the human respiratory tissue may be a useful experimental model to study normal and pathologic lung development, and to assay candidate therapeutic gene constructs preclinically.

Immunohistochemical localization of cystic fibrosis transmembrane conductance regulator in human fetal airway and digestive mucosa

The cellular distribution of the cystic fibrosis transmembrane conductance regulator (CFTR) in human fetal digestive and respiratory mucosa has been studied by immunohistochemistry. The streptavidin-biotin immunoperoxidase method was applied to paraffin-embedded specimens collected from normal fetuses ranging from 7 to 39 wk of gestation. By the 7th wk, CFTR protein was strongly detected in the yolk sack; in contrast, the staining was weak in the undifferentiated epithelium of the intestine and the airways. At 12 wk, the intestine showed strongly and diffusely stained enterocytes and a basal cytoplasmic reactivity in the first secretory cells. During development, only slight changes could be detected in the digestive epithelial distribution of CFTR. In the airways, the CFTR distribution followed the cephalocaudal maturation. In the tracheal ciliated cells, the CFTR protein was diffusely detected in the cytoplasm as early as 7 wk. After 24-25 wk, CFTR was localized at the apical domain of the ciliated cells and was also present in the collecting ducts and in the glands of the airways, predominantly in the periphery of the acini. Our data suggest that the CFTR is present as early as 7 wk during organogenesis and probably plays an important role during fetal life. There is an evolution in the CFTR distribution during airway development, whereas, in the intestine, CFTR is highly expressed through the epithelium as early as 12 wk and keeps the same distribution until birth.

Reliability of polymerase chain reaction (PCR) analysis of single cells for preimplantation genetic diagnosis

PURPOSE

We investigated the reliability of polymerase chain reaction (PCR) genotype analyses performed on single cells for the purposes of preimplantation genetic analysis.

METHODS

We performed blind analysis of 130 single skin fibroblasts heterozygous for the delta-F508 mutation in the cystic fibrosis transmembrane regulator (CFTR) gene and 73 single skin fibroblasts from an individual heterozygous for the XbaI polymorphic site of the Factor VIII gene.

RESULTS

Amplification was successful for 116 cells and 52 cells respectively and in all but one case (a CFTR analysis) both alleles were amplified. The incidence of diagnostic error was 1 out of 203 analyses or 0.0043. We conclude that PCR is a reliable method for determining the genotype of single cells for the purposes of preimplantation genetic analysis.

Developmental expression of mucin genes MUC1 and MUC2

The mucin gene MUC1, is expressed in a number of human ductal epithelia in vivo including those within the pancreas, mammary gland, kidney and genital ducts. Further it is expressed at a high level in certain tumours and tumour-derived cell lines. MUC2 was initially isolated from a human jejunum cDNA library and is thought to be one of the major intestinal mucin genes, though it is also expressed in the trachea. We have examined the developmental expression of these two mucin genes in human tissues. High level expression of MUC1 has been seen by 12.5 weeks of gestation in the epithelial of the distal respiratory tract and the collecting ducts in the kidney. By 18 weeks MUC1 mRNA is detectable in the colon but pancreatic expression of MUC1 is not seen until late in gestation. MUC2 mRNA is seen by 12 weeks of gestation in the jejunum, ileum and colon, and in large bronchioles of the lung by 18 weeks. The pattern of expression of MUC1 suggests that this mucin may not be involved in early ductal obstruction in the CF pancreas, but both MUC1 and MUC2 may play a role in the development of intestinal disease and MUC1 in early respiratory disease associated with CF.

A severe phenotype in mice with a duplication of exon 3 in the cystic fibrosis locus

To develop an animal model for cystic fibrosis (CF), targeted gene disruption in embryonic stem (ES) cells was used to generate a duplication of exon 3 (cftrm1Bay allele) of the mouse CF gene. ES cells containing this mutation were used to generate chimeric animals that transmitted the mutant allele through the germline. Homozygous mutant animals display a severe phenotype, with approximately 40% dying within 1 week from intestinal obstruction. RNAase protection analysis of the cftrm1Bay allele did not detect any normal mRNA (< 1-2% of wild-type) in mutant animals. Pathologic changes in the intestines from mutant mice included mucus accumulation in the crypts and intestinal lumen, dilatation of the bases of the crypts, enlargement of goblet cells, and the presence of concretions in the crypts or between the villi. Changes were also present in the mucosal glands of the pharynx and the minor sublingual glands, where dilatation of acini and accumulation of eosinophilic material were evident. Atrophy of acinar cells that may be secondary to nutritional deficiency and mild inflammation in the main pancreatic duct were present in the pancreas of mutant animals. No changes were noted in the lung, trachea, liver, or male reproductive tract of mutant animals, and mutant males were fertile. Homozygous mutant mice showed defects in cAMP-mediated ion transport both in ileum and in cultured fetal tracheal explants. Thus, an additional mouse model for CF has been generated that should prove useful for the understanding of the pathogenesis and the development of treatments for CF.

Cell-specific localization of CFTR mRNA shows developmentally regulated expression in human fetal tissues

An improved understanding of the expression of the cystic fibrosis gene (CFTR) will assist our approach to preventing the organ damage caused by cystic fibrosis (CF). We have studied the expression of CFTR in human fetal tissues at different gestational ages using in situ hybridization to detect CFTR mRNA. CFTR was principally expressed in less differentiated cells of endodermal origin. The highest levels were seen in specific areas of the developing pancreas, liver, gall bladder and intestine, with lower but significant levels in lung and trachea. Expression was also seen in reproductive tissues, such as epididymis and third trimester uterus and fallopian tubes, and in addition, sweat and salivary glands. No detection of CFTR mRNA was found in many other relevant tissues. The detection of CFTR transcript in these organs is consistent with the clinical manifestations of CF and the function of CFTR as a chloride channel early in development. The localization and levels of expression described have implications regarding the pathogenesis of organ damage and the potential gains that can be achieved by early therapy in the disease.

Localization of expression of the cystic fibrosis gene in human pancreatic development

Cystic fibrosis (CF) is a disease that affects the function of specialized epithelial cells within the lungs, gut, pancreas, sweat glands, and male genital ducts. Following the cloning of the CF gene, it is possible to examine tissue-specific expression of this gene. To investigate the onset of the CF disease process, expression of the CF gene in midtrimester human fetal tissues has been analyzed by in situ hybridization using antisense RNA probes. The major site of CF gene expression at this stage of development is in the pancreas. Within the pancreas, CF mRNA is seen to be largely restricted to the epithelium of intralobular and small interlobular ducts.

Wheat-germ lectin affinity electrophoresis for alkaline phosphatase isoforms in children: age-dependent reference ranges and changes in liver and bone disease

This modified lectin affinity electrophoresis method is suitable for simultaneous measurement of liver, bone, and high-molecular-mass (high-Mr) isoforms of alkaline phosphatase (ALP; EC 3.1.3.1) in children. Age-related isoform reference ranges were derived for 247 children, ages 0-13 years. Liver ALP did not appear in plasma until after six months of age, and remained constant after one year of age. Bone ALP was highest in the youngest age group, and declined to relatively constant activities thereafter. High-MrALP was not detected in normal children. In bone disease, the bone isoform was increased in all age groups. In liver disease, only 5 of 30 infants younger than six months had detectable liver ALP, although half had increased bone ALP. Among children older than six months, 5 patients with biliary atresia and 15 patients with hepatitis A all had increased liver isoform activity. Liver ALP was also a sensitive index of early hepatobiliary complications in 27 nonjaundiced children with cystic fibrosis. Measurement of ALP isoforms therefore yields useful clinical information in children older than six months but is of doubtful value in younger infants.

Expression of CFTR and presence of cAMP-mediated fluid secretion in human fetal lung

We studied the developmental expression of the cystic fibrosis (CF) gene in human lung tissue from normal and CF-affected fetuses. Two unrelated CF fetuses, both homozygous for the delta F508 deletion, were examined. Cystic fibrosis transmembrane conductance regulator (CFTR) mRNA was present in second-trimester CF lung and in first- and second-trimester normal lung as assessed by amplification of reverse transcribed total RNA with the use of the polymerase chain reaction. CFTR protein was identified by immunoprecipitation in normal second-trimester fetal lung explants. To evaluate possible functional consequences of CF in the fetus, lung tissue explants were grown in submersion organ culture. By light and electron microscopy, the CF fetal lung explants appeared normal. When explants from normal fetal lung were exposed to 8-(4-chlorophenylthio) adenosine 3',-5'cyclic monophosphate (CPT-cAMP), and 3-isobutyl-1-methylxanthine (IBMX) for 24 h, the intraluminal fluid content increased, as assessed by a 40 +/- 4% increase in cross-sectional diameter. In contrast, identically treated CF explants showed no significant change in explant diameter (3 +/- 1.6%). The transepithelial potential (psi t) across fetal lung explants was measured with microelectrodes. In normal second-trimester explants, CPT-cAMP and IBMX caused hyperpolarization of psi t (-0.93 +/- 14 mV to -4.3 +/- 1.2 mV); in contrast, CF fetal lung explants showed no significant change in psi t with CPT-cAMP and IBMX (-0.84 +/- 0.07 mV to -1.21 +/- 0.26 mV). This study confirms the presence of CFTR mRNA and protein in human fetal lung and suggests that although the CF fetal lung appears normal morphologically, there is a defect in cAMP-mediated fluid secretion in the lung of the CF fetus.

Abnormal fucosylation of ileal mucus in cystic fibrosis: I. A histochemical study using peroxidase labelled lectins

Peroxidase conjugated lectins were used to analyse the glycoproteins of small intestinal mucins in normal infants and those with cystic fibrosis to ascertain whether there are any detectable histochemical differences in saccharide composition. A significant decrease in Lotus tetragonolobus (LTG) binding fucose was shown in normal small intestinal mucin starting around 36 weeks' gestation with total absence of staining at term and beyond. In contrast, the age matched patients with cystic fibrosis showed persistent and intense LTG binding of fucose. These results provide the first clear histochemical evidence that cystic fibrosis mucin is abnormal and confirm the findings of previous biochemical studies.

Vasoactive intestinal peptide and its receptors in fetuses with cystic fibrosis

Fetuses were investigated to establish whether vasoactive intestinal peptide (VIP) and its receptors are involved in the basic biochemical defect causing cystic fibrosis (CF). The intestine was used as a target for the disease and the liver as control. The immunoreactive and biologically active VIP contents of the colon and lower part of the small intestine were 1.5-2.5 times higher in CF fetuses than in controls. In control and CF intestinal mucosa, there was no change in the Scatchard parameters of the 125I-labeled VIP binding sites (Kd = 4.7-6.1 X 10(-11) M; Bmax = 268-280 fmol/mg protein for the high-affinity sites), in the two molecular components constituting the cross-linked 125I-VIP binding (Mr = 66,000 and 30,000), or in the pharmacological properties and functional characteristics of the VIP receptors activating the G proteins-adenylate cyclase system (Ka = 0.7 X 10(-9) M VIP). Similar results were obtained in liver. These findings suggest that neither VIP nor its receptors are involved in CF intestine. The possible involvement of other effectors related to the VIP pathway in CF intestine, including the release of VIP and adenosine 3',5'-cyclic monophosphate signal-transduction cascade, are presented.

Fetal abnormalities in cystic fibrosis suggest a deficiency in proteolysis of cholecystokinin

Ultrastructural and microvillous enzyme (MVE) histochemical studies of fetuses with cystic fibrosis (CF) and trisomies 13 and 18 identified features in CF which differed from the abnormalities in trisomies 13 and 18. The principal abnormalities in CF were in the tight (occluding) junctions and intracellular organelles, particularly the golgi and mitochondria, of the epithelial cells of the pancreas, respiratory system, intestine, and gallbladder. Abnormalities of amniotic fluid MVE levels in CF and trisomy 13 occur because of disruption of the pathways by which the MVE reach the amniotic fluid. Trisomy 18 shows hypoplasia and deficiency of epithelial cell microvilli. It is postulated that the basic defect in CF is due to the deficiency of an enzyme that cleaves the Arg-Asp peptide bond in cholecystokinin to produce the active octapeptide CCK-8, which normally stimulates exocrine secretion, especially in pancreas, gallbladder, and intestine, and potentiates the action of other gastrointestinal hormones.

Intestinal obstruction and cystic fibrosis: antenatal ultrasound appearance

The diagnosis of cystic fibrosis in utero is based on amniotic fluid analysis. False negative results of this method underline the importance of antenatal ultrasonography to detect intestinal obstruction in affected fetuses.

Cystic fibrosis of the pancreas in a human fetus

Postmortem examination of a 26 week old (postmenstrual) human fetus delivered by Cesarean section revealed meconium ileus and many swollen mucus-secreting cells in the gastro-intestinal mucosa. The pancreas showed extensive fibrosis, acinar destruction and dilatation of ducts containing eosinophilic casts. Mucous glands of the lungs also revealed mucous cells swollen and distended with their secretory products. The patient is believed to have cystic fibrosis of the pancreas, suggesting that the pathologic manifestations of the disease may begin early in fetal life.

Congenital mesonephric defects in male infants with mucoviscidosis

Reports that men with mucoviscidosis were sterile and that portions of their genital tracts were atretic prompted us to investigate the genital tracts of 15 male infants with mucoviscidosis who died within the first year of life and came to necropsy. The genital tracts of all of these infants were abnormal, the abnormalities being confined to mesonephric derivatives. Hypoplastic or absent ducti efferentia, ducti epididymides, or ducti deferentia were found in all 28 specimens of epididymides, and the ducti deferentia were missing from 25 of 27 examples of spermatic cord. The seminal vesicles and the ejaculatory ducts were less frequently hypoplastic or absent. Because these abnormalities of mesonephric derivatives were present so early in life and inflammatory and obstructive changes were absent we believe that they resulted from a failure of development.