Maternal isodisomy for chromosome 9 causing homozygosity for a novel FOXE1 mutation in syndromic congenital hypothyroidism

Identification of Germline FOXE1 and Somatic MAPK Pathway Gene Alterations in Patients with Malignant Struma Ovarii, Cleft Palate and Thyroid Cancer

Germline variants in the FOXE1 transcription factor have been associated with thyroid ectopy, cleft palate (CP) and thyroid cancer (TC). Here, we aimed to clarify the role of FOXE1 in Portuguese families (F1 and F2) with members diagnosed with malignant struma ovarii (MSO), an ovarian teratoma with ectopic malignant thyroid tissue, papillary TC (PTC) and CP. Two rare germline heterozygous variants in the FOXE1 promoter were identified: F1) c.-522G>C, in the proband (MSO) and her mother (asymptomatic); F2) c.9C>T, in the proband (PTC), her sister and her mother (CP). Functional studies using rat normal thyroid (PCCL3) and human PTC (TPC-1) cells revealed that c.9C>T decreased FOXE1 promoter transcriptional activity in both cell models, while c.-522G>C led to opposing activities in the two models, when compared to the wild type. Immunohistochemistry and RT-qPCR analyses of patients' thyroid tumours revealed lower FOXE1 expression compared to adjacent normal and hyperplastic thyroid tissues. The patient with MSO also harboured a novel germline AXIN1 variant, presenting a loss of heterozygosity in its benign and malignant teratoma tissues and observable β-catenin cytoplasmic accumulation. The sequencing of the F1 (MSO) and F2 (PTC) probands' tumours unveiled somatic BRAF and HRAS variants, respectively. Germline FOXE1 and AXIN1 variants might have a role in thyroid ectopy and cleft palate, which, together with MAPK pathway activation, may contribute to tumours' malignant transformation.

The length of FOXE1 polyalanine tract in congenital hypothyroidism: Evidence for a pathogenic role from familial, molecular and cohort studies

INTRODUCTION

FOXE1 is required for thyroid function and its homozygous mutations cause a rare syndromic form of congenital hypothyroidism (CH). FOXE1 has a polymorphic polyalanine tract whose involvement in thyroid pathology is controversial. Starting from genetic studies in a CH family, we explored the functional role and involvement of FOXE1 variations in a large CH population.

METHODS

We applied NGS screening to a large CH family and a cohort of 1752 individuals and validated these results by in silico modeling and in vitro experiments.

RESULTS

A new heterozygous FOXE1 variant segregated with 14-Alanine tract homozygosity in 5 CH siblings with athyreosis. The p.L107V variant demonstrated to significantly reduce the FOXE1 transcriptional activity. The 14-Alanine-FOXE1 displayed altered subcellular localization and significantly impaired synergy with other transcription factors, when compared with the more common 16-Alanine-FOXE1. The CH group with thyroid dysgenesis was largely and significantly enriched with the 14-Alanine-FOXE1 homozygosity.

DISCUSSION

We provide new evidence that disentangle the pathophysiological role of FOXE1 polyalanine tract, thereby significantly broadening the perspective on the role of FOXE1 in the complex pathogenesis of CH. FOXE1 should be therefore added to the group of polyalanine disease-associated transcription factors.

A new FOXE1 homozygous frameshift variant expands the genotypic and phenotypic spectrum of Bamforth-Lazarus syndrome

Bamforth-Lazarus syndrome is a rare autosomal recessive disease caused by biallelic loss-of-function variants in the FOXE1 gene. The condition is characterized by congenital hypothyroidism due to thyroid agenesis or thyroid hypoplasia, cleft palate, spiky hair, with or without choanal atresia, and bifid epiglottis. To date, seven pathogenic variants have been reported in the FOXE1 gene causing Bamforth-Lazarus syndrome. Here we report a novel homozygous loss-of-function variant in the FOXE1 gene NM_004473.4:c.141dupC:p.(Leu49Profs*75) leading to congenital hypothyroidism due to thyroid agenesis, scalp hair abnormalities, cleft palate, small areola, cafe-au-lait spots, mild bilateral hearing loss, skin abnormalities, and facial dysmorphism. We describe the evolving phenotype in the patient with age and review previous variants reported in FOXE1. This report further expands the clinical and molecular spectrum of Bamforth-Lazarus syndrome.

Detection of maternal uniparental disomy 9 in association with low-level mosaic trisomy 9 at amniocentesis in a pregnancy associated with intrauterine growth restriction, abnormal first-trimester screening result (low PAPP-A and low PlGF), maternal preeclampsia and a favorable outcome

OBJECTIVE

We present detection of maternal uniparental disomy (UPD) 9 in association with low-level mosaic trisomy 9 at amniocentesis in a pregnancy associated with intrauterine growth restriction (IUGR), an abnormal first-trimester maternal serum screening result, abnormal non-invasive prenatal testing (NIPT), maternal preeclampsia and a favorable outcome.

CASE REPORT

A 37-year-old, primigravid woman underwent first-trimester maternal serum screening and NIPT at 11 weeks of gestation, which revealed a gene dosage increase in chromosome 9 and low levels of plasma protein-A (PAPP-A) and placental growth factor (PlGF) in maternal blood. The woman underwent amniocentesis at 16 weeks of gestation, which revealed a karyotype of 47,XX,+9[4]/46,XX[35] in cultured amniocytes. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed a result of arr [GRCh37] (9) × 3 [0.14] (X) × 2, compatible with mosaic trisomy 9. The parental karyotypes were normal. Repeat amniocentesis was performed at 20 weeks of gestation. The cultured amniocytes had a karyotype of 47,XX,+9[1]/46,XX[23]. The uncultured amniocytes had a mosaic trisomy 9 level of 10.7% (12/112 cells) by interphase fluorescence in situ hybridization (FISH), a mosaic trisomy 9 level of 10-14% (log₂ ratio = 0.1) by aCGH, and maternal uniparental isodisomy 9 by polymorphic DNA marker analysis. Prenatal ultrasound revealed IUGR, and the mother had preeclampsia. At 29 weeks of gestation, a 1054-g phenotypically normal baby was delivered because of preterm labor. The cord blood and umbilical cord had the karyotype of 46, XX and maternal UPD 9 and isodisomy 9, while the placenta had trisomy 9 of maternal origin. Postnatal FISH anlaysis on 101 buccal mucosal cells and 100 urinary cells at age three months detected no trisomy 9 signals. The baby was doing well at age six months.

CONCLUSION

Pregnancy with low-level mosaic trisomy 9 and maternal UPD 9 at amniocentesis can be associated with IUGR, maternal preeclampsia and a favorable outcome. Fetuses with maternal UPD 9 can be associated with an abnormal NIPT result concerning chromosome 9, an abnormal first-trimester maternal serum screening result (low PAPP-A and low PlGF) and mosaic trisomy 9 at amniocentesis.

An evo-devo perspective of the female reproductive tract

The vertebrate female reproductive tract has undergone considerable diversification over evolution, having become physiologically adapted to different reproductive strategies. This review considers the female reproductive tract from the perspective of evolutionary developmental biology (evo-devo). Very little is known about how the evolution of this organ system has been driven at the molecular level. In most vertebrates, the female reproductive tract develops from paired embryonic tubes, the Müllerian ducts. We propose that formation of the Müllerian duct is a conserved process that has involved co-option of genes and molecular pathways involved in tubulogenesis in the adjacent mesonephric kidney and Wolffian duct. Downstream of this conservation, genetic regulatory divergence has occurred, generating diversity in duct structure. Plasticity of the Hox gene code and wnt signaling, in particular, may underlie morphological variation of the uterus in mammals, and evolution of the vagina. This developmental plasticity in Hox and Wnt activity may also apply to other vertebrates, generating the morphological diversity of female reproductive tracts evident today.

Transcriptional landscape of the embryonic chicken Müllerian duct

Background

Müllerian ducts are paired embryonic tubes that give rise to the female reproductive tract in vertebrates. Many disorders of female reproduction can be attributed to anomalies of Müllerian duct development. However, the molecular genetics of Müllerian duct formation is poorly understood and most disorders of duct development have unknown etiology. In this study, we describe for the first time the transcriptional landscape of the embryonic Müllerian duct, using the chicken embryo as a model system. RNA sequencing was conducted at 1 day intervals during duct formation to identify developmentally-regulated genes, validated by in situ hybridization.

Results

This analysis detected hundreds of genes specifically up-regulated during duct morphogenesis. Gene ontology and pathway analysis revealed enrichment for developmental pathways associated with cell adhesion, cell migration and proliferation, ERK and WNT signaling, and, interestingly, axonal guidance. The latter included factors linked to neuronal cell migration or axonal outgrowth, such as Ephrin B2, netrin receptor, SLIT1 and class A semaphorins. A number of transcriptional modules were identified that centred around key hub genes specifying matrix-associated signaling factors; SPOCK1, HTRA3 and ADGRD1. Several novel regulators of the WNT and TFG-β signaling pathway were identified in Müllerian ducts, including APCDD1 and DKK1, BMP3 and TGFBI. A number of novel transcription factors were also identified, including OSR1, FOXE1, PRICKLE1, TSHZ3 and SMARCA2. In addition, over 100 long non-coding RNAs (lncRNAs) were expressed during duct formation.

Conclusions

This study provides a rich resource of new candidate genes for Müllerian duct development and its disorders. It also sheds light on the molecular pathways engaged during tubulogenesis, a fundamental process in embryonic development.

Clinical significance of copy number variants involving KANK1 in patients with neurodevelopmental disorders

Copy number variants (CNV)s involving KANK1 are generally classified as variants of unknown significance. Several clinical case reports suggest that the loss of KANK1 on chromosome 9p24.3 has potential impact on neurodevelopment. These case studies are inconsistent in terms of patient phenotype and suspected pattern of inheritance. Further complexities arise because these published reports utilize a variety of genetic testing platforms with varying resolution of the 9p region; this ultimately causes uncertainty about the impacted genomic coordinates and gene transcripts. Beyond these case reports, large case-control studies and publicly available databases statistically cast doubt as to whether variants of KANK1 are clinically significant. However, these large data sources are neither easily extracted nor uniformly applied to clinical interpretation. In this report we provide an updated analysis of the data on this locus and its potential clinical relevance. This is based on a review of the literature as well as 28 patients who harbor a single copy number variant involving KANK1 with or without DOCK8 (27 of whom are not published previously) identified by our clinical laboratory using an ultra-high resolution chromosomal microarray analysis. We note that 13 of 16 patients have a documented diagnosis of autism spectrum disorder (ASD) while only two, with documented perinatal complications, have a documented diagnosis of cerebral palsy (CP). A careful review of the CNVs suggests a transcript-specific effect. After evaluation of our case series and reconsideration of the literature, we propose that KANK1 aberrations do not frequently cause CP but cannot exclude that they represent a risk factor for ASD, especially when the coding region of the shorter, alternate KANK1 transcript (termed "transcript 4" in the UCSC Genome Browser) is impacted.

Thyroid transcription factor FOXE1 interacts with ETS factor ELK1 to co-regulate TERT

BACKGROUND

Although FOXE1 was initially recognized for its role in thyroid organogenesis, more recently a strong association has been identified between the FOXE1 locus and thyroid cancer. The role of FOXE1 in adult thyroid, and in particular regarding cancer risk, has not been well established. We hypothesised that discovering key FOXE1 transcriptional partners would in turn identify regulatory pathways relevant to its role in oncogenesis.

RESULTS

In a transcription factor-binding array, ELK1 was identified to bind FOXE1. We confirmed this physical association in heterologously transfected cells by IP and mammalian two-hybrid assays. In thyroid tissue, endogenous FOXE1 was shown to bind ELK1, and using ChIP assays these factors bound thyroid-relevant gene promoters TPO and TERT in close proximity to each other. Using a combination of electromobility shift assays, TERT promoter assays and siRNA-silencing, we found that FOXE1 positively regulated TERT expression in a manner dependent upon its association with ELK1. Treating heterologously transfected thyroid cells with MEK inhibitor U0126 inhibited FOXE1-ELK1 interaction, and reduced TERT and TPO promoter activity.

METHODOLOGY

We investigated FOXE1 interactions within in vitro thyroid cell models and human thyroid tissue using a combination of immunoprecipitation (IP), chromatin IP (ChIP) and gene reporter assays.

CONCLUSIONS

FOXE1 interacts with ELK1 on thyroid relevant gene promoters, establishing a new regulatory pathway for its role in adult thyroid function. Co-regulation of TERT suggests a mechanism by which allelic variants in/near FOXE1 are associated with thyroid cancer risk.

Disorders of thyroid morphogenesis

Developmental anomalies of the thyroid gland, defined as thyroid dysgenesis, underlie the majority of cases of congenital hypothyroidism. Thyroid dysgenesis is predominantly a sporadic disorder although a reported familial enrichment, variation of incidence by ethnicity and the monogenic defects associated mainly with athyreosis or orthotopic thyroid hypoplasia, suggest a genetic contribution. Of note, the most common developmental anomaly, thyroid ectopy, remains unexplained. Ectopy may result from multiple genetic or epigenetic variants in the germline and/or at the somatic level. This review provides a brief overview of the monogenic defects in candidate genes that have been identified so far and of the syndromes which are known to be associated with thyroid dysgenesis.

Update of Thyroid Developmental Genes

Thyroid dysgenesis (TD) is the most common cause of congenital hypothyroidism in iodine-sufficient regions and includes a spectrum of developmental anomalies. The genetic components of TD are complex. Although a sporadic disease, advances in developmental biology have revealed monogenetic forms of TD. Inheritance is not based on a simple Mendelian pattern and additional genetic elements might contribute to the phenotypic spectrum. This article summarizes the key steps of normal thyroid development and provides an update on responsible genes and underlying mechanisms of TD. Up-to-date technologies in genetics and biology will allow us to advance in our knowledge of TD.

Sublingual thyroid ectopy: similarities and differences with Kallmann syndrome

Permanent primary congenital hypothyroidism (CH), the commonest cause of preventable intellectual disability, is due to defects in the embryonic development of the thyroid in the vast majority of cases. These defects are collectively called thyroid dysgenesis. The thyroid may be absent (athyreosis) but, more commonly, a sublingual thyroid ectopy without lateral lobes, is the only thyroid tissue present. Such an ectopy presumably results from an arrest in the downward migration of the median anlage. Thyroid ectopy almost always occurs in a sporadic fashion. However, first-degree relatives are affected more often than chance alone would predict. On the other hand, almost all reported monozygotic twin pairs are discordant for thyroid ectopy. Current research is aimed at reconciling these contradictory epidemiological data. We propose a two-hit mechanism associating a germline predisposing factor with another genetic or epigenetic alteration within the ectopic thyroid tissue itself or, as in some forms of Kallmann syndrome, in the structures surrounding the thyroid during embryogenesis. Thyroid ectopy, a model for sporadic congenital malformations in humans, is also associated with congenital heart disease, and molecular mechanisms common to thyroid and heart development are being unraveled.

European Society for Paediatric Endocrinology consensus guidelines on screening, diagnosis, and management of congenital hypothyroidism

OBJECTIVE

The aim was to formulate practice guidelines for the diagnosis and management of congenital hypothyroidism (CH).

EVIDENCE

A systematic literature search was conducted to identify key articles relating to the screening, diagnosis, and management of CH. The evidence-based guidelines were developed with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system, describing both the strength of recommendations and the quality of evidence. In the absence of sufficient evidence, conclusions were based on expert opinion.

CONSENSUS PROCESS

Thirty-two participants drawn from the European Society for Paediatric Endocrinology and five other major scientific societies in the field of pediatric endocrinology were allocated to working groups with assigned topics and specific questions. Each group searched the literature, evaluated the evidence, and developed a draft document. These papers were debated and finalized by each group before presentation to the full assembly for further discussion and agreement.

RECOMMENDATIONS

The recommendations include: worldwide neonatal screening, approaches to assess the cause (including genotyping) and the severity of the disorder, the immediate initiation of appropriate L-T4 supplementation and frequent monitoring to ensure dose adjustments to keep thyroid hormone levels in the target ranges, a trial of treatment in patients suspected of transient CH, regular assessments of developmental and neurosensory functions, consulting health professionals as appropriate, and education about CH. The harmonization of diagnosis, management, and routine health surveillance would not only optimize patient outcomes, but should also facilitate epidemiological studies of the disorder. Individuals with CH require monitoring throughout their lives, particularly during early childhood and pregnancy.

Maternal uniparental isodisomy causing autosomal recessive GM1 gangliosidosis: a clinical report

Uniparental disomy is a genetic cause of disease that may result in the inheritance of an autosomal recessive condition. A child with developmental delay and hypotonia was seen and found to have severely abnormal myelination. Lysosomal enzyme testing identified an isolated deficiency of beta-galactosidase. Subsequently, homozygous missense mutations in the galactosidase, beta 1 (GLB1) gene on chromosome 3 were found. Parental testing confirmed inheritance of two copies of the same mutated maternal GLB1 gene, and no paternal copy. SNP analysis was also done to confirm paternity. The patient was ultimately diagnosed with autosomal recessive GM1 gangliosidosis caused by maternal uniparental isodisomy. We provide a review of this patient and others in which uniparental disomy (UPD) of a non-imprinted chromosome unexpectedly caused an autosomal recessive condition. This is the first case of GM1 gangliosidosis reported in the literature to have been caused by UPD. It is important for genetic counselors and other health care providers to be aware of the possibility of autosomal recessive disease caused by UPD. UPD as a cause of autosomal recessive disease drastically changes the recurrence risk for families, and discussions surrounding UPD can be complex. Working with families to understand UPD when it occurs requires a secure and trusting counselor-family relationship.

A novel FOXE1 mutation (R73S) in Bamforth-Lazarus syndrome causing increased thyroidal gene expression

BACKGROUND

Homozygous loss-of-function mutations in the FOXE1 gene have been reported in several patients with partial or complete Bamforth-Lazarus syndrome: congenital hypothyroidism (CH) with thyroid dysgenesis (usually athyreosis), cleft palate, spiky hair, with or without choanal atresia, and bifid epiglottis. Here, our objective was to evaluate potential functional consequences of a FOXE1 mutation in a patient with a similar clinical phenotype.

METHODS

FOXE1 was sequenced in eight patients with thyroid dysgenesis and cleft palate. Transient transfection was performed in HEK293 cells using the thyroglobulin (TG) and thyroid peroxidase (TPO) promoters in luciferase reporter plasmids to assess the functional impact of the FOXE1 mutations. Primary human thyrocytes transfected with wild type and mutant FOXE1 served to assess the impact of the mutation on endogenous TG and TPO expression.

RESULTS

We identified and characterized the function of a new homozygous FOXE1 missense mutation (p.R73S) in a boy with a typical phenotype (athyreosis, cleft palate, and partial choanal atresia). This new mutation located within the forkhead domain was inherited from the heterozygous healthy consanguineous parents. In vitro functional studies in HEK293 cells showed that this mutant gene enhanced the activity of the TG and TPO gene promoters (1.5-fold and 1.7-fold respectively vs. wild type FOXE1; p<0.05), unlike the five mutations previously reported in Bamforth-Lazarus syndrome. The gain-of-function effect of the FOXE1-p.R73S mutant gene was confirmed by an increase in endogenous TG production in primary human thyrocytes.

CONCLUSION

We identified a new homozygous FOXE1 mutation responsible for enhanced expression of the TG and TPO genes in a boy whose phenotype is similar to that reported previously in patients with loss-of-function FOXE1 mutations. This finding further delineates the role for FOXE1 in both thyroid and palate development, and shows that enhanced gene activity should be considered among the mechanisms underlying Bamforth-Lazarus syndrome.

European Society for Paediatric Endocrinology consensus guidelines on screening, diagnosis, and management of congenital hypothyroidism

OBJECTIVE

The aim was to formulate practice guidelines for the diagnosis and management of congenital hypothyroidism (CH).

EVIDENCE

A systematic literature search was conducted to identify key articles relating to the screening, diagnosis, and management of CH. The evidence-based guidelines were developed with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system, describing both the strength of recommendations and the quality of evidence. In the absence of sufficient evidence, conclusions were based on expert opinion.

CONSENSUS PROCESS

Thirty-two participants drawn from the European Society for Paediatric Endocrinology and five other major scientific societies in the field of pediatric endocrinology were allocated to working groups with assigned topics and specific questions. Each group searched the literature, evaluated the evidence, and developed a draft document. These papers were debated and finalized by each group before presentation to the full assembly for further discussion and agreement.

RECOMMENDATIONS

The recommendations include: worldwide neonatal screening, approaches to assess the cause (including genotyping) and the severity of the disorder, the immediate initiation of appropriate L-T4 supplementation and frequent monitoring to ensure dose adjustments to keep thyroid hormone levels in the target ranges, a trial of treatment in patients suspected of transient CH, regular assessments of developmental and neurosensory functions, consulting health professionals as appropriate, and education about CH. The harmonization of diagnosis, management, and routine health surveillance would not only optimize patient outcomes, but should also facilitate epidemiological studies of the disorder. Individuals with CH require monitoring throughout their lives, particularly during early childhood and pregnancy.

Mutations in the sarcosine dehydrogenase gene in patients with sarcosinemia

Sarcosinemia is an autosomal recessive metabolic trait manifested by relatively high concentrations of sarcosine in blood and urine. Sarcosine is a key intermediate in 1-carbon metabolism and under normal circumstances is converted to glycine by the enzyme sarcosine dehydrogenase. We encountered six families from two different descents (French and Arab), each with at least one individual with elevated levels of sarcosine in blood and urine. Using the "candidate gene approach" we sequenced the gene encoding sarcosine dehydrogenase (SARDH), which plays an important role in the conversion of sarcosine to glycine, and found four different mutations (P287L, V71F, R723X, R514X) in three patients. In an additional patient, we found a uniparental disomy in the region of SARDH gene. In two other patients, we did not find any mutations in this gene. We have shown for the first time that mutations in the SARDH gene are associated with sarcosinemia. In addition, our results indicate that other genes are most probably involved in the pathogenesis of this condition.

The consequences of uniparental disomy and copy number neutral loss-of-heterozygosity during human development and cancer

UPD (uniparental disomy) describes the inheritance of a pair of chromosomes from only one parent. Mechanisms that lead to UPD include trisomy rescue, gamete complementation, monosomy rescue and somatic recombination. Most of these mechanisms can involve aberrant chromosomes, particularly isochromosomes and Robertsonian translocations. In the last decade, the number of UPD cases reported in the literature has increased exponentially. This is partly due to the advances in genomic technologies that have allowed for high-resolution SNP (single nucleotide polymorphism) studies, which have complemented traditional methods relying on polymorphic microsatellite markers. In this review, we discuss aberrant cellular mechanisms leading to UPD and their impact on gene expression. Special emphasis is placed on the unmasking of mutant recessive alleles and the disruption of imprinted gene dosage, which give rise to specific and recurrent imprinting phenotypes. Finally, we discuss how copy number maps determined from SNP array datasets have helped identify not only deletions and duplications but also recurrent copy number neutral regions of loss-of-heterozygosity, which have been reported in many cancer types and that may constitute an important driving force in cancer. These tiny regions of UPD also alter imprinted gene dosage, which may have cumulative tumourgenic effects in addition to that of unmasking homozygous cancer-associated mutations.

Genetics of nonsyndromic orofacial clefts

With an average worldwide prevalence of approximately 1.2/1000 live births, orofacial clefts are the most common craniofacial birth defects in humans. Like other complex disorders, these birth defects are thought to result from the complex interplay of multiple genes and environmental factors. Significant progress in the identification of underlying genes and pathways has benefited from large populations available for study, increased international collaboration, rapid advances in genotyping technology, and major improvements in analytic approaches. Here we review recent advances in genetic epidemiological approaches to complex traits and their applications to studies of nonsyndromic orofacial clefts. Our main aim is to bring together a discussion of new and previously identified candidate genes to create a more cohesive picture of interacting pathways that shape the human craniofacial region. In future directions, we highlight the need to search for copy number variants that affect gene dosage and rare variants that are possibly associated with a higher disease penetrance. In addition, sequencing of protein-coding regions in candidate genes and screening for genetic variation in noncoding regulatory elements will help advance this important area of research.

Mosaic trisomy 9 at amniocentesis: prenatal diagnosis and molecular genetic analyses

OBJECTIVE

To present prenatal diagnosis and molecular genetic analyses of mosaic trisomy 9.

MATERIALS, METHODS AND RESULTS

A 35-year-old woman, gravida 3, para 1, underwent amniocentesis at 17 weeks of gestation because of her advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+9[3]/46,XX[6]. Repeat amniocentesis at 19 weeks of gestation revealed a karyotype of 47,XX,+9[6]/46,XX[19]. At 22 weeks of gestation, she was referred to a tertiary medical center for genetic counseling, and amniocentesis revealed a karyotype of 47,XX,+9[2]/46,XX[22]. Array comparative genomic hybridization analysis of uncultured amniocytes revealed no genomic imbalance in chromosome 9. However, interphase fluorescence in situ hybridization analysis of uncultured amniocytes showed that nine (18%) of 50 cells were trisomic for chromosome 9. Polymorphic DNA marker analyses also revealed a diallelic pattern with unequal biparental inheritance of chromosome 9 and a dosage ratio of 1:18 (paternal allele:maternal allele) in the uncultured amniocytes and a dosage ratio of 1:36 in the cultured amniocytes, indicating that the euploid cell line had maternal uniparental isodisomy for chromosome 9. Level II ultrasound demonstrated bilateral ventriculomegaly. The pregnancy was subsequently terminated, and a malformed fetus was delivered. Postnatal cytogenetic and polymorphic DNA marker analyses of the fetal and extraembryonic tissues confirmed the prenatal diagnosis.

CONCLUSION

Mosaic trisomy 9 carries a high risk of fetal abnormalities warranting detailed sonographic investigation of congenital malformations. Mosaic trisomy 9 can be associated with maternal uniparental disomy for chromosome 9 in euploid cell lines. Array comparative genomic hybridization is limited for the detection of low-level mosaicism.

MSX1 and TGF-beta3 are novel target genes functionally regulated by FOXE1

FOXE1 mutations cause the Bamforth-Lazarus syndrome characterized by thyroid and craniofacial defects. Although a pioneer activity of FOXE1 in thyroid development has been reported, FOXE1 regulation in other contexts remains unexplored. We pointed to: (i) a role of FOXE1 in controlling the expression of MSX1 and TGF-β3 relevant in craniofacial development and (ii) a causative part of FOXE1 mutations or mice Foxe1(-/-) genotype in the pathogenesis of cleft palate in the Bamforth-Lazarus syndrome. The MSX1 and TGF-β3 up-regulation in response to FOXE1 at both transcriptional and translational levels and the recruitment of FOXE1 to specific binding motifs, together with the transactivation of the promoters of these genes, indicate that MSX1 and TGF-β3 are direct FOXE1 targets. Moreover, we showed that all the known forkhead-domain mutations, but not the polyalanine-stretch polymorphisms, affect the FOXE1 ability to bind to and transactivate MSX1 and TGF-β3 promoters. In 14-day Foxe1(-/-) mice embryos, Tgf-β3 and Msx1 mRNAs were almost absent in palatal shelves compared with Foxe1(+/-) embryos. Our findings give new insights into the genetic mechanisms underlying the Bamforth-Lazarus syndrome-associated facial defects.